Think Snow, Tweet Snow !!!

Tuesday, February 28, 2012

Upcoming storm will produce two powder days late this week

Now I understand town meeting day is a week from now (if I am not mistaken) so perhaps take a day Thursday or Friday and trade it for a few hours next Tuesday. This will be a storm we will want a piece of and not just because it is a nice looking system. The storm will precede a rough stretch of weather at MRG. It is in the best tradition of La Nina to produce an epic day and follow it up a few days later with big trouble.

The upcoming storm is not necessarily a well-organized, particularly intense, or clean looking system. Ultimately, like many garden variety northeast storms, there will be two low pressure center's. One system which intensifies off the Atlantic Coast and another gradually diminishing but nonetheless notable storm in the Great Lakes. The two will work together, kinda, to produce a long west-to-east overrunning zone. This overrunning surface is the key to this storm and it will act as the centerpiece for a moist conveyor which should cover interior New England for an extended period of time.

Radar Wednesday should show snow inching its way toward MRG but it will take its time in getting here. By evening, the flakes should start flying and will gradually intensify to occasionally moderate snow after dark. By Thursday morning we should have 3-5 inches to show for our efforts while snow continues for a good part of the day and even into Thursday evening and Thursday night. By Friday morning Snowfall totals should be in the 10-15 inch range. If I were to pick a day to ski, it would be Friday. Winds are not expected to be particularly strong Thursday but they will be out of the east and historically that has caused some issues on the Single. On Friday winds will diminish and the snow will diminish to a few flurries. I am sure both days will be winners no matter what is open and what isn't.

So I gave the good news first so now here is the rest. We have managed to keep it winter-like across Vermont for the past week even as the rest of the eastern seaboard enjoys a continuation of what has been a very mild winter. On Friday however, a storm will gather strength in the middle Mississippi Valley and make a huge charge northward. Consequently, mild air will also make a huge push northward out ahead of this storm. Temperatures may sneak above freezing Friday afternoon but I am not too worried about that. By Saturday however clouds and precipitation (not the good kind) will return to MRG. We may retain enough surface cold air to produce a period of freezing rain but that's about it. Eventually we are going to see some rain and temperatures that reach the 40's during the day Saturday. The cold front associated with this storm is a sharp one and winter will return Sunday along with snow showers. The instability in the wake of this system could allow for a light terrain induced accumulation Monday and then readings should stay below freezing through Wednesday morning.

Ensembles are starting to key in on a major thaw for the middle and back half of next week. We still have a little time to escape some of this but has the potential to be a real crusher with record breaking temperatures, maybe even 60's. The thaw would then culminate with a rain event later in the week. Also a crusher.

The moral of the story is pretty self explanatory. Get a piece of this storm !!

Sunday, February 26, 2012

More where that came from ?? Maybe a lot more

Sure !! sign me up. Its been a few days since the last update but not much has changed. Two systems will travel from the Rocky Mountains toward New England over the next 5 days or so. Both will be guided by a very typical La Nina upper level pattern. The first system, which should bring 1-2 inches to northern Vermont Monday, will not generate much excitement. This storm does not have significant amounts of moisture and its track up through the St Lawrence Valley is hardly ideal. It will however play an important role in the story and set the stage for a much more potent mid-week storm with lots of potential.

The Monday system, as it passes, will generate a critical confluence area in the jet stream over the Canadian Maritimes. A confluence area can be described as an area in the jet stream where wind speeds accelerate as one moves from west to east. Imagine traveling down a calm river in a kayak and suddenly encountering class 5 rapids. Its more or less like that. The mid-week system will move out of the Rocky Mountains Tuesday and threaten to follow the track of Monday's storm up the St Lawrence Valley. It being a stronger system, such a track would bring the threat of warmer temperatures and rain. The confluence zone will prevent such an occurrence and allow cold and dry Canadian air to establish itself over interior New England in advance of the clouds and the arrival of precipitation Wednesday. The result will thus be snow which should arrive Wednesday and persist through a good period of the day.

There are some questions regarding this storm even though I think the threat for rain and ice is greatly diminished as of Sunday morning. The various models show a varying degree of impact from this so called "right entrance" region of the jet stream. The European shows a profound impact and although it suggests a period of snow Wednesday, the snow is ultimately pushed south Thursday and total snowfalls would be in the lighter 2-5 inch territory. Other indications however show a much more significant period of snow and the possibility for a real "epic" style event. Snow would persist for a 24-hour plus period and could snowfall totals could approach 2-feet. It would be a heck of a way to start March.

Ironically, this is all happening as the teleconnection indices have all turned unfavorable. The pattern for much of the eastern seaboard south of New York city has been in fact very non winter-like. Washington D.C. is reaching 60 degrees it seems every day and parts of Virginia have seen readings approach 80. Much of this will continue through this week with a sharp divide between winter which will be confined to interior New England and spring which will continue to prevail in the Mid-Atlantic States. Looking out beyond the storm, this is shown to generally continue and there are continued threats for "thaws" and bouts of mild weather even across interior New England. So far this pattern has put us on the right side of the battle but we are living on the edge. If we strike gold with this storm Wednesday/Thursday take advantage of it because our good fortune might not hold up.

Thursday, February 23, 2012

Nice 6-12 inch snow event for the weekend

Even in a good year, La Nina can hang Vermont right on the edge. With this storm, like many others it is touch and go all the way to the finish line. Some you win and some you don't. With this one it looks like we come out on top. The storm in question will not intensify the way I thought it might a day or two ago. As a result it will be able to transfer its energy to the coast quicker thus stopping the flow of warm air at key levels of the lower troposphere.

I've looked at some of the latest data from the high resolution models which are shining some light on specifics. Precipitation will arrive in the form of snow and begin as early as noon Friday with temperatures within a few degrees of freezing. The snow could become moderate to fairly heavy for a time during the afternoon and accumulate a few inches before lift closing time. It could make for a decent afternoon of skiing if you can sneak one in. This initial wave of snow will actually taper to flurries during the evening. At this time, temperatures a few thousand feet up might still exceed the freezing mark opening the door for the possibility of some freezing drizzle or light sleet. At the surface however, temperatures will hover between 25 and 29 for much of the evening and the overnight. Around midnight, the second batch of good upward motion associated with the storm will arrive and the threat of freezing rain/sleet will be gone (I don't think we really see too much of that). Snow should re-commence and could become heavy in the pre-dawn hours. In the end, the heaviest snow will only persist for a few hours but it will be enough to blanket MRG with 6-12 inches of relatively dense powder. The critical temperatures for powdery vs wet snow is about 28 or 29 degrees (depending on a few variables) and base temperatures will be right there. Temps at mid-mountain and at the summit will support powder all the way through. Even after the heaviest snow is completed, lingering instability will allow terrain induced snow to persist through much of Saturday. It will be mostly light to occasionally moderate snow and enough for an additional 2-4 inches.

And for those heading up from those southern locales let me say this. Driving to Killington or Okemo may not get it done. Much better chance for a period of sleet or freezing rain in central and southern Vermont. If your going to make the drive, make it to MRG, the best place to be on a powder day without question !!!

The Rocky Mountains will actually spit out two additional weather systems over the next week. The first moves into the Great Lakes and up the St Lawrence Valley Monday night. This is a system that lacks moisture and will lose some of its dynamic support as it presses east which will prove to be a blessing since its track would suggest maybe a rain event if it were stronger. In the end, this has the makings of a light accumulation of snow if at all. The second system will generate a lot of discussion and will arrive Wednesday as a much more potent storm with plenty of moisture. Again, Vermont should be right on the edge and could see an icy mix, maybe some rain or maybe a big winter storm. I will call it the "Leap Year" storm since its arrival will be on Feb 29. We could go back to our 2012 ways and flame out on this event but we have the chance to score big so stay tuned.

Tuesday, February 21, 2012

Friday/Saturday weather system is the strongest to impact the region all month

It has been amazing to look at precipitation totals for the month of February and see many places struggling to reach a half an inch (liquid). If the region doesn't get more precipitation this month, it would certainly rank as one of the driest February's on record. Certainly another in a litany of wrong answers this winter. All of that said, MRG and the surrounding area will get the direct impact of the strongest, most organized system of the month later Friday into Saturday. The specifics remain a little uncertain, the precipitation type remains a little uncertain but we can try and clarify what we do know as of now.

Until Friday, the mountain will have to endure another mild stretch of weather. Both Wednesday and Thursday will feature above freezing temperatures. Thursday's weather however will be cloudy and I would expect a period light to moderate snow most likely in the morning. With temperatures in the low to mid 30's, this is going to be a wet snow, perhaps even rain in the immediate Mad River Valley but on the mountain a few inches is a reasonable expectation.

There will not be much cold air to work with as a storm system gathers strength and gathers moisture in the Midwest Thursday night. Temperatures will drop below freezing on the mountain by Friday morning and will hover a few degrees above freezing during the midday. When precipitation finally begins late in the day it will be pretty marginal. The dry air as the surface will help bring temperatures back below freezing as the precipitation intensity increases but conditions aloft could make this tough. An early look at cross sections suggests a period of sleet Friday evening and Friday night. The Tuesday evening run of the GFS though did show mostly snow however thus again offering its ray of hope in what has been a dark winter. The GFS has not performed well however and the weight of the overall pattern will make an all-snow event extremely difficult in my opinion. My guess right now is that after a burst of snow Friday evening, we will see an extended period of sleet and maybe some freezing rain. The best part of this storm is likely to be Saturday. As the system wraps up in the Canadian Martimes, it will allow a pool of instability to settle over the Green Mountains inviting both wrap-around and terrain induced snows to persist throughout the day. By Saturday temperatures will be a lot colder allowing any accumulation to be powder.

Saturday, February 18, 2012

A few inches here and a few inches there, it could be worse

A couple inches of snow certainly helped but it would have been nice to land that big one. We couldn't quite pull it off. Now La Nina is going to drive this train and do so in high gear. Temperatures will be on the mild side of average for the next 5 days or so but we should avoid an extended thaw. We should also see a series of weaker systems bring the chance for snow or mixed precipitation.

Both Sunday and Monday will feature dry weather and at least some sunshine, particularly Monday. Clouds should make a return later Tuesday in advance of the first of these aforementioned weather systems. It will not have a lot of moisture or cold air to work with but the push of mild weather also appears weaker than I had feared. Temperatures should sneak above freezing Tuesday afternoon and then hover around the freezing mark Tuesday night as light snow begins to fall. It will be another instance where wet snow falls over the low elevations while we get a more powdery accumulation near the summits. I don't expect much but we will take it where we can get it.

After a brief dry period later Wednesday, another system, with a little more moisture should bring what looks to be snow but possibly mixed precipitation to the region Thursday. These disturbances in the jet stream look like Alberta Clippers but they are getting propelled by the strong Gulf of Alaska ridge and intense jet in the eastern Pacific. The jet is also causing Pacific air to run much of the eastern part of the country over, thus the mild weather. Fortunately though we are not seeing a strong southeast U.S. ridge and thus we avoid the big thaw. With Thursday's system, temperatures will again be close to freezing. If we don't get precipitation to mix with sleet or freezing rain we could certainly see a few inches.

The last weekend in February into the following week looks extremely changeable. That is saying a lot since New England in February/March is typically very volatile. The good news involves the weekend. Ensembles are now all on board suggesting a major eastern U.S. trough amplification. It actually caught me a bit by surprise to see what appears to be a major and widespread shot of arctic cold interrupting a mediocre pattern. In addition, the third in a series of these weaker weather systems could again spread snow or mixed precipitation into the region either Friday or Friday night. This "third" system may actually get ignited somewhat by the amplifying upper air pattern and strengthen past the "weak" stage.

Cold weather should dominate for much of the weekend but it will be temporary in nature. An amplifying trough in the western half of the U.S. will result in a mild push of weather in the last few days of February that will be hard to fend off. This should also be temporary but it result in a bit of rain. We have managed to avoid that for much of the month believe it or not.

Wednesday, February 15, 2012

Let the rumor mill turn !!!

Here we go !! Big holiday weekend only days away and the high drama begins in VT. And yes, the snow event for Thursday night is still on the calendar. This is not an aesthetically appealing system on the weather map. It is the first in a series of events resulting from split flow in the jet stream. In the end however, it will never become a very organized storm and the light snow Thursday night into early Friday morning will total between 2 and 5 inches. Temperatures at the base of the mountain will also be close to freezing giving the snow a wetter consistency. Higher elevations should see some decent powder.

If Thursday night's storm is "beer in a shot glass" then the storm Sunday can be described as the "full keg". Its all about the split flow in the jet performing its normal tasks. Energy rotating through the southern branch of the jet early in the weekend will begin sucking moisture out of the Gulf Saturday. By early Sunday, a major winter storm will be moving northeast out of the southern states and toward the east coast. 3 Successive runs of the American GFS model complete the proverbial "bomb" with this storm, rapidly deepening the system as it tracks close to Long Island and over Cape Cod. Heavy snow, high winds, the whole gamut would be the result for later Sunday and Sunday night. Hypothetical snowfall totals ? well I think one can get the drift, no pun intended.

The reality, even without the repeated frustrations that have been so prevalent this winter, is this. The consensus of model guidance still takes this amazing looking weather system too far out to sea. The Canadian model is not so subtle by suggesting, "what storm?". The European shows a nice looking storm moving from the Gulf Coast to the Virginia Tidewater area, but the storm never takes a critical northward turn up the coast and rides innocently out into the Atlantic bringing rain and snow to areas much farther south. Even some of the American GFS ensemble members seem to suggest some internal strife in model-land. Interestingly, I have been told the GFS has recently had a "physics" upgrade which we all hope will improve the performance of a model that has performed quite bad this winter. It will have an early chance to prove its worth this weekend.

It is really just a timing question at this point. A clipper system is rotating through the Great Lakes just as this massive Gulf storm is strengthening. The American model is moving the southern energy along more efficiently allowing the upper air support from the clipper to inject its energy from behind, the we would prefer it. By moving the southern stream energy slower, the European shows the clipper system moving atop the Gulf storm, thus making it more difficult for the storm to make the northward turn. This is certainly a potentially big event and worth watching but the chances for big snow are still less than 50 percent right now. What was that line Jim Carrey unleashed in Dumb and Dumber ? "So your saying there's a chance".

Beyond Sunday La Nina will try and show its dark side again. One and perhaps two pushes of mild weather could impact the region between the middle of next week and the weekend of the 25th and 26th. It is still possible much of the mild air is confined to the Mid Atlantic and southeastern states so we will just wait and see.

So we found out today that there are organizations out making a concerted effort to poison the global warming debate with propaganda. The goal ? Plant the seeds of doubt and hope the garden grows. It worked, it seems half the country's political establishment feels the issue isn't even credible. The science is crap they say, look at what happened with climate-gate, the data was manipulated. Funny because if it doesn't come form a misguided politician, it comes from shadowy places and dark alleyways. Never does it actually come from a credible scientific group who are actually willing to go on the record with serious contradictory evidence. Well now, one of those dark alleyways got illuminated.

http://www.nytimes.com/2012/02/16/science/earth/in-heartland-institute-leak-a-plan-to-discredit-climate-teaching.html

There is nothing wrong with being a skeptic and be cynical of the aggressive assertions made by the climate science community. I know plenty of people in my own circle who wear that with pride. To brush the issue aside as non-credible is just plain silly. Certain political leaders should be wasting less time trying to undermine climate scientists and more time assessing the actual risks involved with climate change and devising policies to deal with it accordingly. It isn't just about whether or not you like Al Gore, the stakes are much higher.

Monday, February 13, 2012

3 precipitation producers in the next week should keep it interesting

It hardly looks like the ideal weather pattern but it will be an active one with plenty to blog about over the next week or so including three potential weather producers. Its still a few days from our first shot for snow and we have already seen most of the cold from the past weekend move out. Clouds should keep temperatures close to the freezing mark both Tuesday and Wednesday and flurries or a period of light snow could fall from those clouds later Tuesday into Tuesday night. Any sun on Thursday will also give way to clouds in advance of the first discussion-worthy system. This storm has very little cold air to work with but its attempt at making a run up the St Lawrence Valley will get thwarted when the Atlantic Coast, as it often does, magnetically pulls much of the system's energy to the coast. This process is one of the reasons why interior New England can be such an ideal location for snow from east coast storms. At least that is the case during most years.

Precipitation should begin as snow but with temperatures within a few degrees of freezing it could be on the gloppy side at lower elevations. Snow should continue into Friday morning with accumulations in the 4-8 inch range. Glop or powder, the snow will obviously be very welcome prior to what is a big holiday weekend. The "Ski the East" boys are looking to do the Unconventional Terrain Competition this Saturday so hopefully the Friday morning event is enough to make that a success.

A less aggressive east coast trough amplification this weekend will ensure seasonable temperatures through President's day. There is also a clipper system rotating through the Great Lakes which could provide at least a light accumulation of snow Saturday night into Sunday morning. This would be the soft bigotry of low expectations. It is worth mentioning "The Gulf", the buildup of moisture down there and what could ultimately result in a storm riding up the east coast. The storm would be advancing up the coast as the clipper is spreading its limited clouds and moisture in to the northeast. The general consensus is still to take this system too far away from the coast for a big interior New England hit. Its worth keeping an eye on though.

In the wake of this strengthening storm (offshore or not) we should see a reenforcing shot of cold for Sunday and Monday and some of the better skiing of the season. The AO however will be neutralized by early next week and with the emergence of a large "La Nina-like" Gulf of Alaska upper ridge, much of the best action will shift into the west. The first weather system that results from this pattern could therefore be a rough one for us with ice and rain included in the package. In past years however we have seen these patterns go both ways. Some have been a debacle consisting of rain and warm weather. Others have actually been quite good with some of the best snow falling over Vermont. We can guarantee that the skiing will quite bad further south as very warm weather could grip a large portion of the Mid-Atlantic and Southeast.

Saturday, February 11, 2012

Another weekend without much snow, time to focus on the next one late in the upcoming week

I have began the process of emotionally detaching myself from this 2012 winter. It is a necessary evil at this point and it is being done to preserve my mental health. We were hopeful that the current pattern which has most of the ingredients necessary to bring us away from these dark times has not come through. We got some bitterly cold weather which will persist through the weekend, we got a few inches of snow, but I had hoped for one of those 30-40 inch weeks. It never happened.

The polar vortex will gradually rotate out of southeastern Canada early in the upcoming week and temperatures will begin a slow moderation. For the first time this winter, we have legitimate split flow in the jet stream. This stems from energy in the jet stream undercutting the deteriorating ridge in western North America. We just can't get enough split flow and I want to say I am happy to see it, even for a little while, but remember I am not making the emotional investment. It's just not worth it. That being said, a significant weather producer will move from the Rockies into the Plains Wednesday. We will be running low on cold weather by then. Temperatures Tuesday and Wednesday might even sneak above freezing during the afternoon (although overnights should remain chilly). By Thursday clouds should arrive and precipitation should follow either later in the day or at night. What happens from there depends on a few different variables most important of which is the track of this storm. Right now the system appears as it it wants to make a run at the eastern Great Lakes but transition its energy to the coast. This would bring some decent snows to the region but lets just wait and set ourselves up for another big disappointment.

The storm's energy is significant energy enough to yank down some Canadian chill. Much of Canada will in fact be free of arctic air by next weekend meaning that temperatures will be seasonable but considerably warmer than the current weekend. This is the all important president's day holiday which should be free of any rain, free of any bitter cold, hopefully have at least some fresh snow from Thursday's system and perhaps some additional snow from any weak disturbance in the jet stream or some simple terrain enhancement.

The "classic" La Nina structure of the jet stream which is expected to take shape by next weekend will have the effect of re-positioning a lot of the action out west by the 20th of the month. I think next weekend into president's day is safe. Beyond that however all bets are off. Are we going to preserve enough of the high latitude blocking either across the North Atlantic or the Polar regions to thwart another big thaw ? Maybe. It's disconcerting but the only thing we can do at this point is to lower expectations and write off any rain event as a byproduct of a very bad winter.

Wednesday, February 8, 2012

Light snow Saturday, bigger storm still a long shot

Our attention is now focused on the weekend, a Polar Vortex and a clipper system. The European model has been the lone sailor showing that this system tries to blow up south of Long Island and potentially bring some significant snows to New England. Even the Euro has been a bit fickle with this system however and has yet to provide details with any consistency. Personally I am having doubts about this potential storm. The "PV" can be a very overwhelming feature consisting of very strong winds at jet stream level which often act to guide East Coast systems out to sea before they attain any real strength. Nevertheless, the clipper itself, even without the support of Atlantic moisture, can deliver the mountain a few inches of snow Friday night. It will be a very cold weekend, one of the coldest of the season with well below zero wind chills Saturday and a few nights of well below zero actual temperatures through Monday.

We are going to lose the support of the AO in roughly a week and the pattern will transition into a more traditional La Nina looking set-up. A large ridge across the Gulf of Alaska, a trough and unsettled weather over much of the west, warm weather in the southeast U.S. and a big question mark for New England. Actually the question mark relates to what should be a significant weather system that arrives between the 15th and 17th of the month. The breakdown of the "negative AO" opens up the possibility for a non-snow event but its still "to be decided".

Monday, February 6, 2012

You can't spell "Elite" without E-L-I but its time to focus on spelling out the word "Snow"

It was another terrific Pats vs Giants Super Bowl and a thrilling victory for the G-Men. A few bounces here, a less banged up tight end there and things could be different so I solute the Patriots for a great season and a great effort. For a while there, I thought they had the Giants "D" figured out. All that said, Eli needs to get the credit he deserves. Yeah he has some great receivers to throw to, but the whole "Awww Shucks" thing everyone gets on him for serves him well. He has the uncanny ability to shake off all the pressure and make big throw after big throw no matter the gravity of the situation.

So the Giants did their part, it is now mother nature's turn. Let me preface the following by stating that I am going to only remain cautiously optimistic since selling my soul to powdery forecast has done nothing for us. We are finally in the throws of a generally favorable high latitude blocking pattern but we continue to wait for the snow. We had alluded to a weaker disturbance that had the potential to freshen things up for Thursday but this will slide innocently to the south. Temperatures with the help of sunshine, will exceed the freezing mark for a few hours both Thursday and Friday afternoons

That brings us to the weekend and the big southward advance of the Polar Vortex. To a weathergeek like me, anything with the word "vortex" is going to be exciting, so I consider the "PV" to be a fun topic of conversation. In the two days since the last update I had hoped we could better sort the picture out this weekend. We have made a little progress but uncertainty remains. Generally speaking the Euro still shows a softer PV invasion and as a result, a clipper system is able to get some traction with moisture from the Atlantic Ocean and spread snow across interior New England Saturday. The American model shows the PV overwhelming the region resulting in a very cold but generally drier forecast. I am more inclined to side with the Euro on this although not wholeheartedly. This would mean our next chance for accumulating snow is Saturday.

A second impulse Sunday could bring another round of snow showers but it will be remembered more for triggering the southward advance of what is likely to be the coldest weather of the season. Bitterly cold temperatures is typically the end result of any intimate relationship that develops between New England and a Polar Vortex and this should be no exception. Temperatures of 15 or 20 below zero Sunday night or Monday is not out of the question.

The longer range outlook has improved slightly. We should see a significant temperature moderation by the middle of next week but the pattern looks significantly more active. This includes two potential precipitation producers in the period between the 14th and 18th of the month. Although the AO is expected to remain negative the ridge/trough axis across North America will shift west. It will resemble a fairly typical La Nina set up but I am hoping the support of the AO on the favorable side of what could be a succession of storms.

No "kiss of deathing" allowed in the comments section !!! Lets keep it clean ;)

Sunday, February 5, 2012

Snow remains a possbility late in the week

At the very least, I hope we are at the beginning of a long stretch void of any rain. We are expecting above-freezing temperatures Monday but we should keep this short streak alive as temperatures for the remainder of the week return to seasonable levels without rain. It has been an annoying habit on the blog to keep pushing back the next chance for snow. We won't do that this time which is a moral victory of sorts. What looks to be the most pathetic of disturbances will undercut the large western ridge and bring moisture into New England Thursday. This occurs just prior to when the Polar Vortex across Canada makes its southward descent into the United States. The weak weather system Thursday is nothing you can take to the bank but could provide the region with 1-4 inches. The arrival of the Polar Vortex also brings the chance for snow but this too is uncertain. If the PV progresses slow enough it can allow time for its associated clipper system to interact with the Atlantic, strengthen and spread more significant snows to both the Green and White Mountains in the Friday/Saturday time frame. If it makes a rapid descent, it will simply overwhelm the pattern and suppress any storm development. We would thus see only a period of snow showers before it turns bitterly cold for the weekend. Models have been provided a variety of answers to these questions but its nice to see two chances for at least some powder in the 2/9-2/11 time frame.

Beyond next weekend marked an even more uncertain time as indicated in the last update. The American GFS Ensemble indicating cold the European Ensemble back to warm. Both packages however showed the all important very negative AO. As of the current update both continue to show the negative NAO and have added a little more clarity in the form of a compromise. The bitterly cold temperatures that should dominate for the weekend will give way to yet another warm-up in the Monday the 13th to Wednesday the 15th time frame. The warmer temperatures could prove to be a another perilous stretch but it should be temporary as the support of both the AO and NAO should allow for the return of both colder temperatures and snow to return for the President's Day holiday.

That is all for now, enjoy the Super Bowl, it should be a good one.

Thursday, February 2, 2012

Cooler temperatures return but we are dry for another week

Across the entire continent of North America, there is only significant weather producer. Its a significnat one, a blizzard, poised to bury much of eastern Colorado with snow. Eastern Colorado and western Kansas are lonely places however, void of mountains and most vegetation. Resorts such as A-Basin, Keystone, Copper, Vail and Aspen are in the central and western sections of Colorado, west of the divide. Those areas will actually only get a few inches out of this storm proving that it has been a very painful year for almost everyone. The exception ? The Canadian Rockies which has reaped the benefits of the same very active Pacific Jet stream I have been groaning about all year.

The "loosening" of this active Pacific Jet will occur on schedule and the result will be the development of a large upper level Ridge across western North America. This feature will be the biggest in the Northern Hemiphsere for a period of a few days, so big in fact that it will take longer to funnel cold toward the eastern third of North America. Temperatures will be close to seasonable this weekend but the "blizzard" across the western Plains will not have a reinvigorating catalyst when it moves east and it will innocently move toward the Mid-Atlantic coast late Saturday then off the coast Sunday without threatening any part of New England with precipitation.

The beginning of next week is also expected to be benign with temperatures making another charge toward above-freezing levels Monday afternoon. Tuesday should see more clouds as the front marking the leading edge of colder temperatures marches southeast. This front will be riding the momentum of the aforementioned western ridge, it doesn't have much in the way of moisture to work with but flurries or a brief period of light snow is possible Tuesday and Tuesday night before another we enjoy another dry and seasonable day Wednesday.

The next chance of significant snow will come toward the end of next week in what appears to be an interesting time frame. As next week continues to progress, the ridge across the west will allow a polar vortex to move south from the polar regions to eastern Canada. Recent runs of many of the computer models have suggested that the impact of this "PV" will be confined to eastern Canada and the northeast U.S. next weekend. Certainly it could result in some of the coldest weather of the season but we are in dire need of a bit more than just bitter chill. We need some of this "PV" energy, even a small piece of it, to combine with undercutting Pacific energy to produce a storm. Its not an impossible task but requires "split flow" in the jet stream. The polar component of the flow looping around the western ridge deliving us the cold and upper air support and a southern branch of the jet delivering the moisture. We haven't heard much talk of "split flow" the last two years since La Nina makes it a tough sell. I would love to see it return however since it has certainly provided us with some epic times.

So we think a vague picture has emerged regarding next weekend including cold weather and hopefully at least a little new snow. Beyond that however begins an all out war between the two major ensemble packages. It is one of the biggest disagreements I have ever seen in the 10-15 day time frame. Interestingly, both ensembles keep a blocking pattern in place through the AO. The European however destroys the western ridge completely, showing another sharp tightening of the Pacific Jet and ultimately a return to zonal flow across the country. The American GFS weakens the western ridge but does not eliminate it. Instead, ridging that stretches from the North Atlantic, over Greenland and to the poles evolves gradually into a large "block" that allows for a continuation of both cold and frequent chances for snow. The European has been winning these arguments for much of the year but this battle has not been fought with the underlying teleconnection indices as favorable as they are now. I remain frustrated but have not abandoned hope.