Think Snow, Tweet Snow !!!

Saturday, December 15, 2018

Nice dose of snow coming late Monday but outlook takes a bad turn on storm late next week

Though we still have a dose of terrain enhanced snow to look forward to early in the upcoming week, the outlook has taken a bad turn today regarding what appears to be a sizable late week weather system. The Euro model showed signs of this subtropical phasing early Friday and other computer guidance has jumped on board. Often times "phasing" is a good thing but not this far south and this far west. More on that below.

In the meantime I would try and enjoy this upcoming dose of terrain enhanced snow. Precipitation Monday morning could remain a mix of rain and snow but the polar jet involvement will provide both the instability and cold air and shift everything to snow by afternoon which should occasionally be rather heavy. The snow would be rather fluffy thanks to the convective nature of the precipitation but the wind will be blowing rather fiercely which will compact some of what falls. Tuesday appears to be the best day to get out and enjoy it with snow showers continuing through at least part of the day and temperatures holding in the teens after falling into the 20's by Monday evening. Between late Monday and midday Tuesday, I am guessing the snow will total 4-8 inches but we could find ourselves in the lucky spot and score something even nicer. We deserve it because what's coming after isn't pretty.

Some clearing skies Tuesday night will bring temperatures back to the single numbers and Wednesday will feature a good bit of sunshine and afternoon temperatures of up around 30. Thursday will also be precipitation-free but will feature a bit more cloudiness and temperatures about 8 degrees warmer. We then get to our late week storm which appears to be an example of Nino delivering a large and very unwanted Christmas gift. Models hadn't really indicated too much activity in the southern branch of the jet but during El Nino winters, this activity is almost always underestimated and suddenly it's there and very ominous looking. The storm will begin to take shape along the gulf coast in the form of thunderstorms but the forming low pressure will phase with southeastward advancing clipper system and explode. Sometimes this is fantastic but we don't have the cold air and the phasing will simply occur way too early which allows the storm to suck very warm Atlantic Ocean air well inland, which it will do by late Friday all over New England from Cape Cod to Mt Washington. Rain will arrive early Friday and temperatures will continue to warm quite possibly making a run at 50 sometime Friday evening. We have to hope that the storm will simply occlude which will pinch off the northwestward advance of mild air and allow for a more modest thaw as opposed to a devastating one. If that happens, perhaps some of the most intense rain and mild air can confine itself to the coast and we can think of ourselves as lucky limit the rainfall to under a half an inch.

The high country will see a return to near freezing temperatures Saturday but the melt will continue across the low lying valleys. Snow showers will also return to areas above 2000 feet and we might see some accumulation as the storm proceeds into the Canadian Maritimes

The remaining issue for us is the continued presence of this positive EPO structure which is now indicated to persist through the Christmas holiday and probably through New Years as well. This does not appear to be a full fledged Evil Empire wrought with multiple rounds of Sir El Torchy, but we will need more help from our teleconnection friends to turn this weather pattern in the right direction and we could more high latitude blocking in the jet stream to send arctic air back in our direction. All of this said, since the EPO isn't overwhelmingly intense, both cold air and some snowfall will remain a possibility during the Xmas week though so does the possibility for another thaw. Lets give us some credit for surviving a pretty healthy chunk of this adverse MJO phase but we can't survive forever. When the MJO finally cycles through these phases, which it is doing slowly, we will slow the jet in the Pacific and get a pattern more conducive for cold and snowy conditions. I was hoping this might happen right around Christmas but unfortunately, we have to shift those expectations somewhat in light of what is being currently indicated.

Friday, December 14, 2018

Big improvements for the snow outlook next week with some substantial snow amounts possible for high country Mon/Tue

Thanks to the combination of northwest flow at jet stream level and the refrigerating effect of the existing deep December snowpack, cold air continues to dominate interior New England in unique fashion. Unique because the region is about the only place in the United States which is experiencing winter conditions as the cold has been largely scoured away from much of the rest of the nation. It's been a long time since I remember a weather pattern that has left us this distinguished. I certainly recall a few years in the early 90's where New England was the coldest relative to average for the winter season and one season in particular, 1991-92 which especially stands out because of how dramatic it was and because it was also a El Nino winter, much like this one and of a similar intensity.

I am delighted to report that the outlook going forward continues to improve. There are no particular indications of any big storms and the weather pattern continues to look non-arctic both for Vermont and for much of the lower half of North America. That said, the outlook on temperatures continues to move in the "not as mild" direction and what's better is the introduction of some accumulating snowfall to the outlook for at least early next week and quite possibly later in the week as well.

All of that talk about the tightened jet stream in the Pacific will finally bring some milder temperatures to Vermont, but we aren't expecting much if any rain. Temperatures will sneak above the freezing mark by evening on Friday and stay there for a good part of Saturday but will will remain below the 40-degree mark. In addition, much of the rain will stay to the south of Vermont and winds will remain calm. This basically means very little damage to the existing snow and clearing skies Saturday night will allow temperatures to chill back down to well-below freezing levels. Some early sun will send readings back toward the freezing mark Sunday before clouds encompass the region in advance of our next interesting little weather system.

It would be wrong to call it a Alberta Clipper since it won't enter the nation via that route. For now, lets just refer to it as the "Provincial Plunger" since the impulse originates from a vigorous Canadian storm system that will travel across central Canada over the weekend. This particular weather feature will grab the polar jet and yank it southward toward northern New England. Though the storm isn't flush with moisture, it has a little bit and will also bring the combination of instability and a very favorable wind direction for the north central Green's. Snowfall across the high country will begin early Monday and persist through much of the day into Monday night and even Tuesday. Accumulations will be elevations sensitive and the snow will be squally in nature but could be substantial. It would be very early to promise a foot-plus but that is within the range of possibilities. For now, I think 6 inches over that two day span (Monday-Tuesday) is a conservative guess and this is with modest temperatures mostly in the twenties. Though the rest of the week looks mild over the rest of the United States and not especially cold in New England, readings will generally remain below the freezing mark and the late week period brings the possibility for more snowfall or at worst some mixed precipitation (if everything goes wrong and that is not the trend). This second system is more of a traditional clipper-like storm which may or may not travel far enough south to deliver more snowfall but I have to admit, the outlook looks vastly improved.

Moving forward into the days immediately prior-to and during the X-Mas holiday, we are still contending with some adverse drivers in the weather pattern. The Arctic Oscillation is expected to be more negative now verses expectations from a few days ago and this will counter the negative influences from the MJO-EPO. But those influences will remain somewhat in play going into the holiday at a slightly weaker level. Can we again produce a little more late-2018 magic ? Quite possible again, but it would be disingenuous of me to suggest that we are obstacle-free in the Dec 21-26 range.

Monday, December 10, 2018

Though the pattern appears far from ideal in the 10 days leading up to Xmas, we may find a way through most of it

It has a mid-winter feel to it across Vermont thanks to the recent outbreak of colder temperatures, a little bit of new snow and plenty of existing snow from previous storms. We all know how totally erratic early December can be and to be perfectly frank, it usually sucks. December is now 4-6 degrees below average thanks to the weekend cold spell and the skiing remains incredibly good given the early date so we have no right to complain. Additionally we have some good news. Though the pattern leaves a few things to be desired  in the 10 days leading up to Christmas,  we may be able to find a way through most of it. Furthermore, gazing way out beyond the Christmas holiday, there are signs of some improvement and the possibility of infusing more cold into the mix as we approach the New Years holiday.

On twitter, I had teased about the possibility of some mid-week snow. This situation is real thanks to the fact that New England will be about the only location encompassed by cold this week and is at the clashing point between this existing cold and the advancing mild air building across the middle part of North America. A clipper system would be the catalyst for snow but this system appears very devoid of moisture. Still, we get a pretty good wind direction Tuesday night and early Wednesday so we might be able to squeeze out a 1-3 inch refresher. Most of this week however will simply remain chilly thanks to that northwest flow in the jet stream. This will mean low temperatures in the single numbers and teens and high temperatures in the 20's. We can also expect some intervals of sunshine through Thursday and more clouds by Friday.

Speaking of Friday, it continues to look like the beginning of a more adverse stretch of weather conditions. That said, it continues to trend in the "not that bad" direction. This is an example of some of the positive aspects of an El Nino. In this case, the southern branch of the jet stream appears powerful enough to potentially push this storm through to the Atlantic Coast rather than allowing the system to make a northward turn toward the Great Lakes and central Quebec. It also helps to have all that early season November cold effectively chill the Great Lakes aggregate down and this lessens some of that thermal gravity which can also pull storms in that aforementioned unfavorable direction. In spite of all this, temperatures are still expected to moderate toward the freezing mark by late Friday or early Saturday and it remains possible to see a bit of freezing rain or rain but it's also quite possible that we get through the entire weekend without much of any precipitation. Given the circumstances one would have to consider this a massive victory.

The above average temperatures which will commence in this Friday/Saturday time frame will continue through Sunday and into the upcoming week in the days approaching the Christmas holiday. Though it doesn't appear to be a blowtorch, temperatures will get above freezing multiple times and it's likely that we see some additional rainfall. The strength of the Pacific Jet and some of the adverse MJO phases that are contributing to this strength will peak in the current week and slowly subside as we move into next week. In the days just prior to Xmas the pattern appears neutral and it even appears possible, as mentioned, that we can introduce some arctic air back into the mix.

Thursday, December 6, 2018

Short term forecast remains cold but with limited snow, while challenges remain in the longer range

We have a relatively tranquil blog update which includes an ever so slightly colder outlook in the short term, still some challenges looming beyond December 13th and only limited chances for new snow. Beyond the clipper system Thursday night, a weak impulse and some warm advection is expected to spread some clouds and some light snow into the region for a time late Saturday and Saturday night. The story for the next few days is simply the cold weather however which appears now to be the coldest of the season so far. The arctic air mass will keep temperatures in the teens for much of the day Friday, provide for some blue skies late in the day and set the stage for sub-zero readings Friday night and early Saturday. Saturday will also see some sunshine but only enough to boost temperatures up to around 20 before clouds move in. Sunday's readings will approach 30 as the arctic air erodes somewhat and we get some limited sunshine on the heels of what should be a light accumulation of snow Saturday night if at all. 

Looking at the big picture, the story for the next week remains the tightening Pacific jet and the rapidly increasing EPO index. Though the models hedged and debated for a time on the intensity of the EPO change, it is expected to more or less max out around the 12th or 13th and then weaken somewhat beyond that. A shift of that magnitude is going to cause a substantial response from the standpoint of actual weather across North America and unsurprisingly, the biggest is the arctic air going into retreat-mode. Interestingly, in spite of milder temperatures across a large portion of the midwest and plains, northwest flow at jet stream level will keep it on the chilly side across New England for almost another week. The deep snowpack that remains doesn't hurt either. Barring a miracle, we won't taste any part of the big southern streamer Sunday into Monday and snowfall through the middle part of next week will be minimal, though we may be able to squeeze out an inch here and there. 

Once we move toward the 14th and 15th the thaw questions loom. The good news here is that it remains just a question. Though we know how limited the availability of arctic cold will be by this point in time, the southern branch of the jet is still a force to be reckoned and will likely keep the storm track to the regions south, likely stunting the intensity of the mild air. Yes, it's within the possibility spectrum to miraculously turn this potential thaw into some sort of winter weather event but it's asking a lot with eastern Canada almost entirely devoid of serious cold. 

The aforementioned conundrum is likely to continue beyond the 15th. The pattern doesn't appear overwhelmingly mild but glaringly non-arctic. Certainly a scenario very common during El Nino winters, and although this ENSO isn't nearly the magnitude of 2015-2016, it has strengthened in the last few weeks to about 1.2 C above normal. On the flip side, we just recorded a massive snow cover number in the Northern Hemisphere during the month of November. This colder feedback will help to counteract some of the warmer feedbacks caused by the state of the ENSO going forward or at least that is my hope. 

Tuesday, December 4, 2018

Forecast trends drier with chilly temperatures prevailing though Dec 12 and a possible thaw Dec 14-15

Colder temperatures have arrived and a few inches of snow came with it. Tuesday was the beginning of an extended stretch of sub-freezing temperatures, but the forecast has trended drier over the past 48 hours. We also are expecting some of the cold to retreat somewhat during the middle of the month, but this "retreat" doesn't appear especially severe right for now and temperatures appear just slightly above average in the period starting December 13th to about the solstice which is about as far out as we can reasonably prognosticate.

Wednesday will finally feature more than a glimpse of sunshine which will help boost temperatures into the 20's along with relatively calm winds. Clouds are expected to return Thursday and some light snow is expected from a clipper system Thursday night. Honestly, I had higher hopes for this system as it appears totally deprived of moisture and appears way too far north for any late coastal strengthening. Still, it will bring with it another charge of arctic cold, rivaling the Thanksgiving cold outbreak with temperatures below zero Saturday morning and rising toward 20 Saturday afternoon. Saturday will feature more sunshine however which is a welcome sight during what is the darkest days of the season.

Forecasters are watching the big southern streamer which is expected to slam the Gulf Coast with rain and thunderstorms this weekend. By Sunday evening, the storm will continue to be a sizable weather producer centered near the Carolina coast. Given the right configuration in the jet stream, this storm could make a northward turn and cripple the entire northeast with snowfall but the circumstances just aren't right this time. The polar jet is retreating and a large ridge in the jet stream is expected to build over south-central Canada just as the storm reaches the coastline. This simply does not provide a clear northward or northeastward avenue for this storm to travel and its speed is expected to slow, perhaps even stall and thus keeping the impact area smaller. Some snow could certainly fall across inland portions of Virginia and West Virginia but at this point I would be surprised to see this storm become a serious New England impact, even in southern sections though one can never say never, not with northeast weather.

As mentioned in previous posts, the jet in the Pacific will be tightening and strengthening and will force the polar jet and arctic air to go into retreat mode. This appears to be a slow process right now however for a couple reasons. First, given the time of the year and the low sun angle, it will take some time for the cold air to erode and will need some advection to do it. Secondly, the Pacific will go into full "evil empire" mode. No, we could certainly do a lot better but we've also seen a lot worse. Temperatures are thus expected to remain below freezing through at least the 12th or 13th of December. Barring a miracle from the aforementioned coastal storm, snowfall will also be minimal but there is a small disturbance capable of delivering a light accumulation this weekend.

We are likely to see a round of above freezing temperatures and rainfall sometime around the 14th-15th of the month which coincides fairly well with the peaking EPO (Pacific Jet strength). There doesn't appear to be any mechanism to provide for the return of arctic air after the 15th but the pattern doesn't appear to be terrible. If I had to guess, temperatures would likely remain above average but we might be able to reintroduce the possibility for snow with what looks to be the continuation of a stormy pattern overall.

Sunday, December 2, 2018

Cold returns in the short term but some critical questions remain unanswered for the middle of the month

We had to make a temporary retreat from our trip to fantasy island Sunday as temperatures warmed and snow changed to rain. After a balmy night, colder air will gradually regain control of the region's weather and another extended stretch of sub-freezing temperatures will commence beginning Monday afternoon. All of this has been well foretold but we have a nice addition to the incoming cold which comes in the form of a period of light snow during the day Monday. Nothing exceptional is expected but the northern Vermont high country (especially the very norther part) will see one to as much as 4 inches.

No complaints from me since I would trade snow for sun at any point during the ski season, but the sun is something we haven't seen much of going back nearly 10 days now. Our best chance for that comes Tuesday and Wednesday. I am not going to promise a lot, but we should see a few hours each day with better visibility and temperatures generally in the teens and 20's. On Thursday, an incoming clipper system should spread more clouds into the region and eventually bring some light snow. The clipper will also bring a re enforcing shot of stronger arctic cold. This means another day with some sunshine Friday,  but with temperatures hovering in the teens and then approaching the zero-degree mark Friday night.

The outlook for the upcoming weekend (December 8th and 9th) revolves around a potent southern streamer which seems poised to impact some part of the east coast. In truth, most of the weekend across northern New England looks just tranquil and cold. There are hints of a weak disturbance being the catalyst for some light snow Saturday with temperatures recovering into the low 20's after a near zero start. If we get any impact from the aforementioned storm, clouds from this arrive Sunday with precipitation arriving later in the day. Vermont is on the northern end of a range of the possible impact zones but a slightly different interaction of jet stream impulses could change the look of this storm quite dramatically so I would be hesitant to write this one off so early. The polar jet will also be in the process of weakening some around this time keeping the door ajar for east coast storms to make that northward turn under the right circumstances.

The weakening polar jet and retreating arctic air comes in response to a tightening of the jet in the Pacific. This topic has been center of debate activity as it relates to the weather pattern across the central and eastern parts of North America during the middle of December and beyond that into the Xmas holiday. The European model and its ensembles show a more resounding tightening in the jet which is illustrated well when one views how the model is simulating the changes in the MJO phase and EPO index (in both cases it predicts those will turn unfavorable). In this scenario, the pattern would turn more adverse for snow and cold in a very widespread fashion. Both the American GFS and Canadian Ensembles shows considerably less tightening in the Pacific however. The pattern does allow the cold to retreat some by December 11-12th but "El Torchy" would be very subdued and arctic cold would remain somewhat of a factor. No doubt this is a hugely critical question as we head further into December. In spite of the respect I have for the Euro model, I remain optimistic we can avoid much of that outcome for now.

Thursday, November 29, 2018

Some milder air/rain Sunday is the only blemish on a good looking first 10 days of December then pattern may turn milder for middle of month

With the amazing month of November coming to a close, I wanted to take just a moment to savor what was one of the most stunning stretches of weather I've seen in Vermont. Some have implied that I have been guilty of some wishcasting in the past, but I don't think I would be even capable of wishcasting a month like this, even with 110-percent effort. Most of the state saw temperatures between 4-6 degrees below average, easily the coldest November of this young century and actual temperatures on the mountain averaged between 25-30 degrees depending on elevation. Most locations also doubled their monthly precipitation amounts, which is a somewhat unique element of November 2018 when compared to other unusually cold months in the November-March period. Most importantly though was of course the snowfall which was simply historic. Almost 6-feet across much of the northern Vermont high country and much of it remains firmly in place going into December. Simply driving above 2000 feet gives one a clear sense of the amount of snow on the ground right now and it's also quite a contrast to some low lying areas which saw substantially less snow this month and especially during the very elevations-sensitive recent storm. 

The first half of December promises to bring a bit of everything to the region. There are certainly some signs of trouble during the middle of the month which I will try and detail as best as I can but instinct has been telling me that this will likely be one those years when many warm-ups will get thwarted and that a healthy percentage of the snow that has fallen will help anchor the base for the duration of this winter and into early spring. That's intuition talking and hopefully not too much wishcasting.

In the short term, we will get a small stretch of tranquil weather including some very limited sunshine Friday or at least some decent visibility. Temperatures on the mountain will continue to remain below the freezing mark through most of Saturday when clouds will thicken in advance of a push of milder air. Precipitation will accompany the warm front, arriving early Sunday, perhaps as a brief period of snow and then changing to freezing rain or rain with temperatures hovering right around the freezing mark and eventually rising by the evening. Much of Sunday night will feature readings near 40-degrees which means some limited melting.

Colder air and snow flurries will push back into the region on Monday and although the polar jet has yet to attain any serious strength (it typically doesn't in early December), it will nonetheless begin to have an impact on the regions weather. Snow is likely to fall from at least one clipper-like system sometime during the middle of the week. We are also operating under the assumption that the active southern branch of the jet will keep its activity further south, but this is likely to be a dangerous assumption without an overpowering polar jet so we will have to keep an eye out for that as well. The less-than over-powering polar jet will keep temperatures on the chilly side. Certainly below freezing beginning Monday night, and some single digit overnight temperatures in the middle to later part of the week. The cold is likely to get re-enforced in some fashion for the weekend of December 8th and 9th and we certainly could see some snow along temperatures readings between zero and 20.

Though the colder air is likely going to carry us through at least December 10th, there are now more declarative indications of some key changes in the jet stream in the Pacific. Specifically, that dreaded tightening which is expected to focus much of the unsettled weather on the west coast for a time and allow some of the arctic cold to retreat over the middle to eastern portions of North America. The cold will retreat from middle sections of the U.S. first and will likely linger across New England the longest but the impact stremming from these changes in the Pacific will be pretty widespread and will ultimately lead to a few milder days, even for us, sometime between December 13-20.