Think Snow, Tweet Snow !!!

Saturday, December 29, 2007

2008 Commencement dinner does indeed consist of two courses !!

Finally we can make some progress sorting out this New Years holiday forecast mess. And it certainly seems as if the still pending and adverse January pattern change has been easier to predict and even detail verses the happenings of the next few days.

New Years Eve - A powder day ?
Yes, we have an excellent chance for a few inches anyway. This is the first in a series of two storms that will never come into phase but impact MRG at different times in the New Years holiday period. This first system is generated from the nearly stationary and decaying front which will be draped across the southeast on Sunday. Low pressure will form in the Virginia Tidewater area and proceed northeastward. The track of the storm would seem too far south for any precipitation to reach central and northern Vermont. The area of upward vertical motion with this system however will extend northwestward more than usual allowing the precipitation shield to likewise expand over our beloved location. It is not a guarantee, but snow, assuming my thinking is correct, will begin around midnight on the 31st and continue at a mostly light intensity through mid morning before tapering off. The snow is capable of accumulating 2-5 inches. I am hoping it will be enough for a few freshies at first tracks time but this remains a tricky system capable of producing a few suprises both on the positive and negative side as far as us skiers are concerned.

New Years Day
It will remain dry from late New Years Eve through early New Years Day which means no new snow at first tracks time on January 1st. Snow will not be far away however. The second, in this series of systems appears like an Alberta Clipper on the surface map but is actually a product of this consolidated Pacific Jet talked about at length in the blog. It is also a very dynamic system and is the catylist for this temporary but not insignificant pattern amplification. Synoptic snow from the system arrives in the mid to late morning time frame new years day and should continue for the rest of the ski day. By January 2nd, the system should clear the region but there are indications of a favorable TIS set up allowing for more accumulating snow. Needless to say that January 2nd should be a very winning day since conservatively speaking I can predict 5-10 inches of new snow by opening.

January 2008
Very unfavorable fundamentals continue to loom large starting around January 4th. When looking at the actual behavior of the weather, it has exhibited the ability, at least so far, to fight off the adverse impacts of the prevailing pattern. This is somewhat different than in 2005 where the weather showed zero resistance to the move toward a milder January. The actual weather when compared to expected weather can actually say quite a bit about the seasonal characteristics for what will in this case be the remainder of the winter. The problem however is that the fundamentals such as the consolidated Jet in the Pacific and the unfavorable teleconnection indices have strengthened considerably and the medium range models now suggest that the move toward much above normal temperatures are now less than a week away. My best guess is that the 20 days starting January 4th and ending January 24th are around 10 degrees above normal for interior New England and that the umbrella will be needed on more than one occasion. Although I must say that when it rains in January I refuse to use an umbrella as a protest to mother nature.

Thursday, December 27, 2007

Snow falls heavily a MRG Thursday afternoon leaving no more room for negativity

For all you big city folk that have seen too much snow melt away this Christmas then check out my favorite Vermont weather cam. It is none other than the "Coles Pond Weather Cam" - complete with a snow stick and what appears to be a Christmas Wreath. If your watching Thursday afternoon you should be able to witness some heavy snow as what I referred to as a "weak" or "weakening" system impacts central and northern Vermont. This aforementioned system is in fact a fairly benign one but it does deserve credit for bringing more moisture to the north country than I expected. The accumulating snow will end by 11 pm Thursday evening but 3-6 inches of fresh powder will be the end result and will turn Friday into a winning day. Temperatures Friday afternoon could touch or even exceed freezing during the afternoon at the base so first tracks is the way to go.

Friday Night into Saturday System
The system set to impact the region Friday night into Saturday is a stronger one. It is also a very close call as far as outcomes go. The storm will take the lousy St Lawrence Valley route and when combined with the limited amounts of available cold air it is hard to get too optimistic. The storm will however try and re-center itself along the Maine Coast Saturday morning and will mitigate the push of warm air into northern New England. Furthermore, model cross section temperature profiles leave room for hope. My best stab at the situation is this. At no point during the storm will temperatures be warm enough to allow for plain rain, so long as it is precipitating hard enough (the explanation for this will take too long so I won't try). Instead, precipitation will be mostly snow late Friday night with some sleet mixed in on occasion. Total accumulations will range between 3-6 inches again but temperatures could be too close to freezing to support powder. Usually temperatures need to be 30 F or below to support powder at night and 27 F or below for powder during the daylight. When the snow or snow/sleet ends early Saturday then we could see a period of drizzle Saturday morning into the early afternoon with temperatures hovering around the freezing mark.

The New Years holiday period - forecast still hard to pin down but I will try
Sunday will be slightly colder (14 F during the A.M 28 F P.M) which then brings us to the days surrounding the New Years holiday. Overall it looks good for MRG but its a head-ache for us prognosticators. The three day period beginning on the 31st and ending on the 3rd of January appeared to me like a two course meal for MRG (getting some impact from two separate systems). That interpretation appeared as it would be the incorrect one yesterday although the European model continues to occasionally suggest that as a possibility (including in its most recent run). So the revised outlook will consist of this. There are still two systems - a southern branch system that may or may not bring precipitation (snow or a mixed bag) to MRG New Years Eve followed by a powerful Pacific System which will attack from the west-northwest and bring both synoptic snow and TIS to MRG during the January 1st-3rd time frame. This second system marks the temporary but sizable jet amplification which will occur in this same time frame. It will mean a return to some very wintry weather in Vermont but again its temporary.

No change on the outlook for January

I have no good news for the period after January 4th which means everything in my last post regarding that time frame still applies. The pattern is in fact dangerously similar to January of '06 and like that one could turn out to be one of the milder January's on record. Consistent with the title of the post, I have little to no room for negativity and there is certainly room for excitement regarding the next 7 days which needed and still probably needs some serious clarification.

Tuesday, December 25, 2007

Good news is hard to find on Christmas Day but I am looking

Merry Christmas !!! Sunday's rain knocked the snow depth near the Mt. Mansfield Summit to 48 inches, down 8 from its peak of near 56 inches and still well above average for this time of the year. It is the quality of the snow which took the biggest hit however since crust now plagues the Vermont Woods from Stratton to Jay Peak. The most dominant feature going forward has been, is now and will be the consolidated and very powerful jet in the northeast Pacific Ocean. The valve controlling the flow of arctic air into the U.S. has been temporarily shut as a result and now the longwave pattern is sending storms on a perilous course. La Nina has brought its chickens home to roost and going forward into January looms an uphill pattern as the now marginally unfavoarable pattern has a chance to turn downright awful after January 4th. Until that time we have a chance at scoring some individual victories and we will get a chance to detail those in this post.

Through Saturday
Calm winds and slightly above average temperatures will make for some comfortable weather as far as skiing is concerned both Wednesday and Thursday. Thursday will be the day which features more in the way of clouds and eventually some light snow late in the day. There is a good chance this light snow continues into the night dusting MRG with a very light accumulation (1-3 inches). The disturbance responsible for the light snow is a very weak one but will be followed quickly by more organized weather system which approaches late Friday. This, stronger weather system will take dead aim at Lake Huron which to be blunt is a deplorable track in terms of bringing new snow to Vermont. Consequently, there will be a push of warm air ahead of the passage of this storm and it will be tough to keep precpitation in the frozen variety. Some of this "warming" will get cut off at the pass as this storm will try desperately to re-center itself off the New England coast. This is a very close call with a few very different options still on the table. If the coastal "cyclogenesis" can occur efficiently then precipation would ramain mostly snow even if more of it gets confined to Maine. The other option would involve a period of sleet or freezing rain before a return to snow or flurries occurs Saturday.

What about those individual victories ??
Our best hope for big time new snow comes around the time of New Years as the pattern takes a temporary turn for the more amplfied thanks largely to the Davis Straits blocking which is trying to ease the pain of this regime. It becomes rather complicated because there are two weather systems in this time frame, a very tight temperature gradient and considerable disagreement amongst the computer guidance. The outcome is therefore very up for grabs and extremely sensitive to slight changes in the track of either weather system. Precipitation from the first storm would arrive late on Sunday although the American model suggests there is little if any impact from this system. Assuming we do get an impact (which is about 60%) then precipitation could be snow, mixed, precpitation, rain or all three depending on the track and evolution of this system. The second system will hypothetically impact the region on January 2nd or 3rd and is of the "snow or no" variety which means that the chance for rain is limited. This second system is a product of the clash between La Nina's southeast ridge and the push of colder temeperatures resulting from the temporary pattern amplification. The storm will pass to MRG's south which is a good for keeping precipitation in the form of snow but if the storm were to travel too far south then little or no impact would be the result.

The taste is sour not sweet after January 4th
After January 4th, the pattern has a very ugly and bitter appearance. The taste is not horse radish either which I can eat in large quantities on almost anything but rather some dairy product still sitting in your fridge that has seen better days. Both the european and american ensemble guidance now indicate a very large signal of warmth after January 4th across the eastern U.S. and southeast Canada. The driving force of such a pattern is a combination of of the persistent and very agitating jet in the northeast Pacific and some of the teleconnection indices, specifically the AO, which has turned quite unfavorable in recent days (much more than what was expected just a week ago). Regarding the AO, there is actually a time gap between what the value of the index and the impact of that index on the weather at MRG. For instance the AO was negative for the last half of November and into early December but then turned postive by December 6th. The weather at MRG was was golden from late November to the Winter Solstice. I will therefore offer that the AO index which is currently a positive 2 will ultimately have a much more negative impact on the weather going forward into early January. We can certainly hope for better results verses the one I am suggesting but I am not optimistic as of now.

Merry Christmas again to everybody out there. Be safe this holiday season !!

Friday, December 21, 2007

Borrowed time is running out

It was actually a slight misrepresentation to call this "the last few days of the favorable December pattern". The weather pattern has in fact already turned and evidence of this can be found in Whistler-Blackcomb's snowfall report which shows a new 40 inches over the past 7 days. This is a consequence of the very consolidated Pacific Jet Stream, fueled by the La Nina. The same jet which is working rapidly to erode the remnants of the cold which was produced by the early December negative AO.

Does anybody really want any additional details about Sunday's rain event ? If so then I suppose you can read on but if not feel free to skip down, I won't be offended. The rain will arrive later in the day Sunday and some areas could see a period of freezing rain before southerly winds push temperatures regionally above freezing later Sunday evening. Temperatures will climb to about 40 degrees overnight and rainfall totals will range between a half an inch to eight tenths of an inch.

I did mention in the last post the possibility of some terrain induced snow (TIS) on Christmas Eve and Christmas Day and this is still a likely outcome I am happy to say. The culprit is a fairly tight pocket of favorable upper air dynamics which will produce enough instability over the high terrain of Vermont for a few inches of much needed snow by early X-Mas day (I don't think much falls on Christmas Eve however). Later in the week looms another conundrum however as another storm takes the highway to the danger zone (credit - Kenny Loggins). Its too early to for a specific outcome but I am not encouraged at our chances given the lack of available cold air. I am hoping this system late next week simply doesn't come together and avoids us completely.

If there is a sliver of light in all this looking toward New Years Day and beyond its this. Ensembles are indicating a healthy area of jet stream blocking over the Davis Straits even as we continue to hear the roar of a furious Pacific Jet. What I hope this causes is the Jet Stream to split somewhat across the eastern United States. We won't get any real cold air even in this scenario but it would help to keep the storm track farther south which is one way to sneak through this proverbial thorn-brush.

I got one more update prior to Christmas but if this is your last read then a merry Christmas and a happy Winter Solstice to everyone.

Tuesday, December 18, 2007

Clipper me this ! At least 5-10 more inches of powder for Thursday first tracks

No, those innocent moisture-starved clipper systems are certain short on drama but they do consistently deliver. Powder that is, particularly to the high terrain of Vermont and is what this one will do. This is a system we able to key on fairly early in the ball game but up until now it was a bit uncertain as to which day would feature the most new powder to ski in. The answer is Thursday. Snow from this vigorous upper air disturbance will approach from the northwest and begin falling late in the ski day Wednesday. MRG should see snow much of the night and into Thursday morning and accumulations will be enhanced by the effects of the local oragraphy. Do you want my advice ? Take the day off Thursday and get your rear end to MRG and enjoy the last days of this favorable pattern. 5-10 inches of snow from this clipper atop the already fallen December snow will make Thursday one of the best December ski days at Mad River since 2002.

La Nina is hunting is down

Now I am well aware of our good fortune so far this December. The winter of '07-'08 has begun much the way '06-'07 ended. I am also well aware of my seasonal prediction and I can say one thing regarding that. I am not changing it - The forecast must be judged on its content prior to the season and I will happily taste crow should the prediction go up in a plume of smoke. La Nina, by the way, has maintained its moderate strength and is quite articulate in its speakings to the current weather pattern. The biggest feature across the Western Hemisphere is a large upper air trough in the Gulf of Alaska with a ridge directly underneath it northeast of Hawaii. The two features when put together create a powerful jet which will work quite efficiently at ridding mid-latitude North America of its arctic air. New England, in fact, will be one of the last places in the U.S. to be encompassed by cold weather as early as this Friday. Looking for a silver lining ? I can give you the following. Teleconnection indices are not overwhelmingly unfavorable at face value. The AO is forecast to run Neutral, the NAO is indicated to even go negative (favorable) leaving the PNA as the only major teleconnection index to be consistently working against us (it will be running negative). Translation - We could dodge a few bullets but there will be numerous of them around to avoid.

The Sunday Dilemma

The first effects of this adverse shift in the global pattern will be a bullet that will prove very difficult to avoid. On Sunday the arctic cold will move off the Atlantic Coast and in doing so become quite stale. As this is happening a low pressure center will take dead aim on the St. Lawrence valley and push warm air deep into the northeast U.S. and even into southeast Canada. The result on Sunday will be freezing rain which will develop during the day Sunday and ultimately go to plain rain for a period of time Sunday night. I do not believe temperatures will get especially warm during this event and thus the deep early season base will see little depletion. With freezing rain or rain however comes the crust once a re-freezing occurs and I believe this happens quickly on Christmas Eve as colder air arrives in the wake of the storm. This colder air combined with marginally favorable dynamics may be enough to induce some TIS (Terrain Induced Snow) into X-Mas day but its too early talk accumulations. It is possible that we could see some however and this could bring some serious help to Christmas Day skiing.

X-Mas to New Years

During the last week of December, much of the country will be be covered by Pacific Air and it is my thinking that much of New England will see above average temperatures in spite of any brief intrusion of colder air on December 24th - December 26th. The models are going off on some expected tangents in this time frame with the American GFS model showing a more amplified pattern consisting of a more amplified negative NAO. The results of such a regime would be temperatures which are closer to normal and some new snow. The European however suggests much more in the way of milder weather and much more in the way of rain. All of the ensemble data confirms that it will be a very difficult pattern for us to navigate through with several potential land mines going into early January.

Sunday, December 16, 2007

Heavy snow Sunday Night to bring storm total to near 2 feet

The mixed precipitation or sleet is finished at Mad River and as it turned out, the mountain got rather lucky since the lull coincided well with the warmest part of the storm. How does the saying go ? If you don't have something nice to say don't say anything at all. My saying is more along the lines of "If it isn't cold enough to snow then it might as well not precipitate at all. I don't know about you but the two sayings sound synonymous to me. Our winter storm is intensifying very rapidly having just reached the Maine coast as of 6:30 pm Sunday. As a result, there is a very healthy conveyor of snow pivoting eastward that is set to deliver an additional 10-14 inches to the mountain tonight. No doubt that with all the wind received Sunday and more expected Sunday night, there will be plenty of fresh tracks to be had even late into the day Monday. Snow will taper to flurries by morning but the blustery conditions will continue.

We got another promising clipper system on Wednesday as well. Clipper's are inherently short on moisture but we do happen to be in a fairly good spot to get the most out of this one. Snow will begin during the morning and persist into the evening totaling as much as 6 inches before giving way to a reinforcing shot of colder weather. This reinforcing shot may be the last of the arctic air for a little off as we will be defending against a rather adverse pattern from Christmas Eve forward. More details on that to follow.

Saturday, December 15, 2007

Winter Storm Forecast: Fine Tuned

There are a few important items requiring clarification regarding our upcoming winter storm. First of all, the start time which was advertised in the blog as 8 am needs to be pushed up to 5 am (give or take a few hours). This obviously means that snow accumulations for first tracks time on Sunday which was indicated to an inch or less may turn out to be 2 or 3 inches. Between 8 am and noon we could see some snowfall rates of 2 inches an hour meaning that snow accumulations by early afternoon could approach 10 inches

It will be around the early afternoon when the much talked about winter storm will begin transitioning much of its energy from the original low pressure center which at that time will be over eastern Pennsylvania to what will ultimately be the Maine coast. This time of transition will be the "warm" period of the storm when the critical above freezing layer reaches central and even northern Vermont. The change to sleet at MRG will occur between 12 and 2 pm and will last around 6 hours. It is possible even that precipitation subsides for a time and we get a "lull" within the storm. As the storm "bombs" on the Maine coast Sunday evening, precipitation will go back to snow and it could again get quite heavy before tapering off Sunday night or Monday morning. I am sticking by the total accumulation numbers of 15-30 inches although my feeling is the 6 hours of sleet hurts our chances of getting much over 2 feet.

Friday, December 14, 2007

Whats that I hear ?? The sweet sound of the big dog barking !!! Mad River to get clobbered with 16-30 inches of Snow and some Sleet Sunday/Monday

If that ski jacket you own comes with one of those powder skirts you better make sure it works because you can put it to use this weekend. The ghosts of Valentines Day have been put to work and are producing an event this Sunday which is very analogous to February 14th. Who would've thunk it !! Certainly not me since apparently someone injected with me the "glass-half-empty steroid" prior to that pre-season report I gave last month. But who really cares what was said and when. Without a doubt the best responsibility I have maintaining this blog is to hype a storm such as the likes of this one.

The Storm
Dig back through the archives of the blog or in the recesses of your mind and recall that the Valentines Day Blizzard deepened to about 978 mb and tracked directly over the city of Boston. It was a juicy system also supported with moisture from the gulf, amplifying/digging upper air dynamics and a healthy supply of fresh low level cold air from eastern Canada. This system has about every part of what Valentines Day had including the cold air which will arrive on brisk northwest winds by Saturday morning. The difference would seem small but it does make the forecast a bit trickier. This storm, according to the models will track from Philadelphia, to Hartford to Worcester to Portland, Maine. In other words, if things go according to the plan, the storm tracks west of Boston bringing the above freezing temperatures in the mid-layers of the troposphere closer and eventually over MRG. So recall that the sweet spot for Valentines Day storm was at the base of the Single Chair and I marked the spot with some red tape if anyone wants to take a look (joke). For this event, the sweet spot will probably be closer to Mt. Marcy in the Adirondacks. That is quite alright though because Mt Marcy is really not that far away.

The Details
High clouds from the rapidly strengthening system may arrive as early as the afternoon Saturday which will help to keep temperatures at or below 10. Calm winds and the new snow received throughout this past week will help to make it a pretty good day to ski. Good visibility will do wonders for the view as well (won't be much of a view on Sunday). My guess right now is that the snow commences around 8 am Sunday with a minimal accumulation by first tracks time if any at all. I know a few inches would be nice but the timing here isn't bad since the first 6-8 hours of the storm will be the part which does not feature as much wind thus putting us less at risk for any wind holds. Believe me once this snow starts coming down by mid-morning it will accumulate at a rate of between 2-3 inches an hour and this should persist throughout the end of the day. In other words, it will be all about last tracks since that 3:30 pm run I know everyone plans to take will feature nearly a foot of new powder to ski in. In all seriousness though, please drive safe if your traveling Sunday and consider staying at a lodge and taking the day off Monday. It will be a epic day to ski but a miserable day to travel particularly during the evening when the wind intensifies. The interstates should improve dramatically by late Monday.

Sleet Factor
Some have accused me of sleet-a-phobia and I will argue that I have none. I am just an east coast realist as far as weather is concerned and I have also looked at the temperature cross sections about 10 different ways. The change to sleet will occur during the evening and last for a period of around 3-6 hours Sunday night before we go back to a period snow prior to first tracks Monday. Snow and sleet accumulations will be in the 16-30 inch range with much predicated on the duration of the sleet. We will not get any freezing rain however which means none of that dreaded breakable crust. What I can say is that this storm assuredly puts the mountain in fantastic shape heading into the X-Mas holiday as far as the base is concerned.

Next Week and Beyond

The snow on Monday will taper to snow showers and flurries. It will be blustery and quite chilly as it always is following a big storm such as this. On Tuesday the winds diminish but remains cold with temperatures below zero in the morning and in the teens during the afternoon. On Wednesday, a clipper system will bring limited amounts of moisture to the region which will likely be deposited as a small accumulation of snow and giving us a powder day (either Wednesday or Thursday).

Now I hinted at a potential pattern change of a possible adverse variety late next week and indeed some of the teleconnection indices specifically the PNA will turn unfavorable by the winter solstice. Data however from both the medium range model guidance and the ensembles seems to be delaying the effects of this pattern change in the northeast and is suggesting that the turn to milder weather will be felt most dramatically in the plains. This is certainly encouraging for the time being and we will have to hope that an ample supply of cold air is still available X-Mas weekend prior to the arrival of the next system which still has a zillion possibilities as far as its impacts on MRG are concerned. More will follow on this but for now I will stay focused on the storm and will provide another/shorter update regarding that sometime on Saturday.

Wednesday, December 12, 2007

Thursday storm disappoints but the ghosts of the Valentines Day Blizzard 2007 are brewing up a sequel this Sunday !!!!

I suppose it was very foolish of me to stray from the philosophy which worked so well during the winter of 06-07. There was a disagreement on how the weather would play out this week and the European model said this and the American model said that and in light of some of the recent struggles which plagued the European model through the summer and fall I was baited into fading its reliability during the winter. I like my crow served with cranberry sauce thank you ! Actually I would prefer my crow served with about 2 feet of snow and there and things are in the works to make that a reality if you can believe it.

The European had the right idea all along. It had the right idea Sunday and had the right idea Monday when I issued the last update and now the other model guidance is in the process of jumping on the bandwagon. Wasn't it somewhere that I heard that all the cool people show up late to the party ?? Perhaps that only applies to America and not Europe. Actually us weathergeeks are often joked on for rarely getting invited to the party at all though we can still be fun and festive company, like Phillip Seymour Hoffman in Twister who was great as a tornado-chasing weather weenie in a movie full of bad science.

Thursday event fizzles to a few inches by Friday morning
Thursday's system was a disjointed one to begin and because it is a fast moving, it never had huge potential. As it turns out, the two pieces that were suppose to make up this weather system will never fully align. One storm, containing the bulk of the moisture will move quickly out of the Tennessee Valley early Thursday and be south of Long Island by the evening, too far south for any real impact on MRG. The other is a rather potent Alberta Clipper which marks the leading edge of a re-enforcing shot of cold air which will trail the aforementioned moisture-rich system to the south. Most of central and northern Vermont can expect snow from this trailing system but mainly late on Thursday or Thursday night. The dynamics from the clipper will induce snow showers and snow squalls Friday. Accumulations should be considerably lower than what was advertised in the last update, probably in the 2-6 inch range between Thursday night and Friday.

Sunday contains the real potential
The jet stream will form a nice confluence area over the Canadian Maritimes providing interior New England with a chilly day Saturday including high temperatures which struggle to get past 10 on the mountain although the winds will be relatively calm. This confluence area is a key ingredient for what is to follow on Sunday as a major weather system approaches from the southwest. It is rather incredible actually to look at the upper air and surface maps and see so many things which are strikingly similar to Valentines Day 2007, a day which probably should be memorialized at MRG. In truth, it is dangerous for a prognosticator to make such analogies 4 days from the event and some key details are likely to change over the course of the next few days. With that said, there is very good agreement concerning a big noreaster this weekend, one which will provide the coast with a mix of snow, sleet, freezing rain and ice and one which will deal interior New England and much of northern New York a sizable snow event (and wind) or one that can be measured in feet. I don't want to get carried away here because it is early and hype as a tendency to fizzle. Another update in a day or two can probably zoom in on the details a little closer and we can go to work from there.

The 20th or the 21st continues to be the date of a potential pattern change with two of the three teleconnection indices turning against us. The most dominant feature according to all indications will be a big trough in the northeast Pacific Ocean and over British Columbia. The snow cover which could be fairly deep by then could mitigate any warm-up for a time. Hopefully we can also avoid any X-Mas rain drops.

Monday, December 10, 2007

Is the Airmass Clash leading to a Thursday Winter Storm Bash ??

La Nina often means some serious pain for our skiing friends south of the Mason-Dixon line and the jet stream's southeast ridge this week promises to bring another chapter of mild weather and rain to those locations. There is typically more drama concerning the impacts of the southeast ridge on Vermont and surrounding New England locations since the storm track is often lifted northward with many systems taking direct aim at General Stark and his Green Mountain companions. The arctic air provided courtesy of the negative Arctic Oscillation (AO) will take to the battlefield against La Nina's ultimate weapon (the aforementioned southeast ridge) leading hopefully to some very positive consequences as far as the upcoming weekend is concerned. I realize the drama was poured on a little thick but the Thursday storm threat is real and we should be excited to see winter storm potential such as this so early in the season.

Tuesday Teaser !!
Prior to Thursday, MRG will be impacted by what should be a rather disorganized area of precipitation late Tuesday or Tuesday night. Temperatures, particularly in the valley locations on Tuesday will warm quite significantly and in many cases may exceed the freezing mark. Precipitation in these areas may fall as a mix for a time before going to snow overnight. Aries the higher terrain, such as MRG, precipitation will be all snow and accumulations have a chance to exceed 4 inches. The snow will fall in association with a fast moving arctic cold front which will clear the areas early Wednesday and will end all precipitation by the middle to late morning. The clear skies, snow cover and light winds will set the stage for one of the colder nights of the season Wednesday night before what we hope will be some fun and games for Thursday.

Thursday's Storm !!

The fast-moving aspect of weather systems within this ambient pattern presents a challenge to the prognosticators and the Thursday's situation is no exception. The medium range guidance has been keying on a system in the southern Plains gathering moisture very quickly Wednesday night before speeding northeastward. Although it seems likely this will happen in some variety meaning the increase in clouds and the eventual accumulation of snow, the exact timing will have a big say on the end result. The usually reliable European model has been unusually unreliable for much of the fall and it seems somewhat pessimistic on moisture reaching the central and northern sections of Vermont. The GFS and Canadian model tell a different and much more appealing tale and will be one I will choose to lean to at this time. This solution has the system in question tracking from southern Illinois to southern New England. Snow would develop during the day and would fall heavily during much of the afternoon accumulating 8-16 inches as a conservative guess. Wednesday's update will have to take the more specific step on addressing accumulations and a more smaller window of start times and stop times.

The Weekend
Although this European model seems unwilling to give us any love for Thursday, it does follow up with a humdinger of a noreaster for the weekend. Unfortunately it is not good scientific practice to go buffet style as far as sifting through the model data is concerned and we will not do that here. For now we will stick to the idea that the dynamics and upper air jet stream support stemming from Thursday's storm will linger into the weekend and will keep the opportunity for new snow through Saturday when finally the commencement of a slight warming trend will act as a stabilizer for the atmosphere. Not bad though for a December 14-15 weekend !!

The Xmas week questions are beginning to role my way also. Don't want to get too distracted with that right now since I am exhausted but I will say though that the ensembles are not showing a fundamentally supportive pattern for cold and new snow beginning around the time for the winter solstice with the main axis of the upper air trough shifting in the west. In short, I am expecting a more adverse change in the pattern within a few days of the Solstice and we will have to hope that the arctic cold provided by the negative AO index can hold off such a change as long as possible. Even if the cold does relinquish significantly, we will not see a repeat of 06 when the mild weather completely depleted an already limited base.

Thursday, December 6, 2007

Mad River is off and running - Challenges lay ahead

A fiercely negative Arctic Oscillation (AO) brought some big time love to Vermont and helped give MRG one of the earliest opening day's I can remember this decade. It was also a big slap in the face to the seasonal forecast but I have no problem with that. The prospects for new snow over the next few days including the weekend do not look great as the atmosphere will become fairly stable as a ridge in the jet stream becomes established across the southeast. As I mentioned in the previous post, the southeast ridge is what La Nina does best and it forces the mountain to go on the defensive in terms of protecting its base and keeping temperatures below freezing.

Specifically for the weekend, we do have a the passing of a very benign weather system late Friday. It would obviously nice to squeeze out a few inches prior to first tracks time on Saturday but a dusting to 2 inches is the most reasonable guess I can make. Saturday's temps may approach 30 in the afternoon. On Sunday, we will be blessed with some great visibility (either clear skies or a high overcast) but low level cold will push temps to near zero in the morning while afternoon readings only approach 20.

By early next week, the baraclinic zone will be directly over Mad River Glen and much of Vermont. To put it plainly the baraclinic zone refers to the region where warm air is directly clashing with cold air thus producing a big contrast in temperatures over a relatively narrow region. It also is the region where overrrunning precipitation is often focused. The challenge involves keeping all this precipitation in the form of snow which could prove to be quite difficult. The best I can do in terms of offering out specifics now is to say that precipitation, if we get any, on Monday and Monday night will be in the form of snow. By Wednesday a much more organized area of low pressure will approach along this baraclinic area and threaten to push more warmth into central and northern Vermont. Models are suggesting that we do have a chance at keeping enough low level around to prevent a move to above freezing temperatures and plain rain. It will be tough however to keep precipitation all snow during the middle of next week. Again, we are playing defense.

By late next week and into the weekend, we are back into more widespread cold and also some instability. This means that some accumulating TIS is likely before the weekend of the 14th and 15th. There also is a chance that we are impacted by a more organized weather system. We can't really expand on that however until the next update. Enjoy the snow and the early December skiing !!!

Saturday, December 1, 2007

Negative AO means a strong early December start

Fundamentally, there are few allies more dependable than a negative Arctic Oscilation. Send the cold down to the mid-lattitudes and keep the relative warmth near the poles. A whole winter consisting of such a pattern and there would be no need for a single chair weather blog since every other day would be a powder day. It is encouraging to see the '07-'08 winter begin as the '06-'07 winter ended but the deck remains stacked against us unlike it was last year.

Not only do we have some cold courtesy of the AO index, but we also have a storm. One which should begin as snow late Sunday, change to a period of sleet for a time early Monday and then go back to a longer period of snow later Monday into Tuesday. Much of the snow later Monday into Tuesday will be of the terrain induced variety and I will refer to this as TIS (Terrain induced snow) for the sake of concision. It is a fairly good set-up for TIS actually and I would not be surprised to see MRG tally 10-20 inches in the period beginning late Sunday and ending early Wednesday. No sense in getting more specific with the mountain closed but if new snow totals do indeed fall in this range it could be enough to induce an opening day announcement from the powers that be.

The AO is expected to remain on the negative side of zero for the next 10 days although models are showing a dreaded strengthening of the southeast ridge by next weekend. This is going to be a tough animal to tame this winter as the prevelance of the southeast ridge is correlated to the La Nina. It will be a bullet we will need to dodge next weekend or else its mild weather and perhaps even some rain. I will check back early next week to see if MRG plans an opening and will update the blog accordingly.