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Thursday, April 30, 2015

Winter 2014-2015 is one of a few ski seasons that will set a standard for greatness

Statistically speaking, one could call the winter of 2014-2015 almost “unremarkable”. Speaking from the standpoint of snowfall, most locations across the northern half of Vermont both down low in the valley and up high in the mountains only received slightly above normal snowfall. In reality however the winter was hardly “unremarkable” and most New England residents would quite safely categorize the recent the season as one of the most memorable in the span of a lifetime. From the standpoint of skiing, we had one of the earliest openings of the new century (December 12th), one of the latest closings (April 19), 44 straight days without above freezing temps (Jan 19 to March 5th), the coldest month of February since 1934, the coldest calendar month since January 1994 and one of the coldest 5 winters since the opening of MRG in 1949. All of this is quite remarkable, and the snowfall, though it fell generously over Vermont, fell in record quantities over southeast New England leaving many Massachusetts residents buried under a deep blanket of snow until April and inspiring all those selfee-taking Peter Pan wannabes to jump off 2nd and 3rd floor balconies.

Moving along as to not get distracted. Many of the winters that the SCWB has covered include one glaring global or at least hemispheric distinction. Some stand-out variable that can easily claim to be a root cause for a mild or cold or snowy or dry winter. In 2006-2007 it was a strong El Nino, the following year a strong La Nina. The 2009-2010 featured a record negative AO/NAO combination. In 2011-12 it was a positive EPO while in 2013-2014 massive early expansion of snow and ice. Some winters are totally devoid of any such personality. Those winters either turn out to be remarkable for an entirely unknown reason or turn out to be completely unremarkable like 2008-2009 or 2012-2013. The winter of 2014-2015 was no such winter. There were actually a few noticeable global distinctions going into the winter that pointed toward something extraordinary. As the winter progressed however it became more and more apparent that the PDO and specifically, the nature of the PDO was the driving force behind the weather pattern and a chunk of the weather that resulted from that weather pattern.

The Pacific Decadal Oscillation (PDO) has been discussed on several occasions as one of a few variables used to construct a seasonal outlook. It is measured as an index and describes the configuration of sea surface temperatures in the Pacific. I visualize the PDO geometrically as horseshoes. The blue horseshoe configuration is anomalously cold water in that shape from the Alaskan coast, down the west coast then circling back west just north of the equatorial region. This is considered a negative PDO phase. A positive PDO phase is the opposite with the red horseshoe configuration in the same region. This past winter featured the brightest of red horseshoes ever recorded. The index was over 2 for four consecutive months which has never been achieved in the observable history of the PDO. The December-January-February average was 2.42 which is way beyond anything ever recorded going back over 100 years. Add to this the pocket extreme anomalous sea surface temperature warmth in the Gulf of Alaska and you suddenly have an “elephant in the room”.

Sea surface temperatures, it is important to understand, can move upper air patterns. Variations and imperfections within a typical layout of sea surface temperatures have profound impact on how upper air patters behave. A large pocket of relative warmth in the ocean over the Gulf of Alaska down the U.S. west coast will effectively increase the frequency and duration of upper ridging events in that same region, PNA ridging events. The events which dictate weather patterns such as the one we saw through much of January, February and March of this winter. In New England, it is easy to think of all the snow and cold, but the impact of the PDO is more far reaching and is actually responsible for weather that has had fare more dire consequences than deep snow. In California, Governor Jerry Brown has issued water restrictions that include mandatory 25 to as much as 36 percent reductions in usage for the state. These are some of the most aggressive and strictest drought actions I’ve observed in the U.S. but appropriate for one of the worst drought’s the state has seen in a century. Lots of environmentalists and liberal activists have chimed in about the persistent drought in California and have not been shy about attributing the lack of precipitation to global warming. Even Bill Maher couldn’t resist the need to chime in as part of a well delivered punch line. Don’t get me wrong, global warming or global climate change is a very disconcerting phenomena that we only occasionally discuss in the SCWB. The issue has largely been poisoned needlessly in the political arena and although I blame a majority of this on the combination of ignorant right wing politicians and their lobbying benefactors, the left has been guilty of injecting its own dose of bad science into the argument and this is a perfect example. The drought in California will alleviate when this incredibly large positive PDO event dissipates. Until then however, it will be rough in the Golden State which also had to endure one of the worst ski seasons in quite some time.

Vermont will certainly enjoy plenty of green through the warm months that lay ahead and can reminisce about the great ski season that is now behind us. Though the cold and snow was expected by many including myself the winter got off to an inconsistent start. November was unusually cold and a post Thanksgiving Day storm of almost a foot provided some great early season skiing and nearly opened MRG. December was hit or miss to say the least. Ironically, the mountain was on the receiving end of one of the best  storms of the season Dec 9-11 and this indeed gave the mountain a terrific opening weekend. We hung on to just enough cold to keep that snow through the rest of December but a several day stretch of 40-50 degree temperatures Christmas week scrooged yet another holiday (amazing how many times that seems to happen in VT).

January was a largely different story. This was a month where we certainly begin witnessing the true effects of many of the feedbacks discussed in the pre-season outlook along with the enhancing PDO. Early in the month, the weather pattern hardly had the desired look, but arctic air found a way to win the day after a thaw on January 4th. Gradually, the snow began to pile up and although a good part of the month featured some fairly typical January conditions with lots of cold, shallow base and lots of firmness, we saw improvement as the weeks went by. If there was a turning point, it occurred January 18th as the mountain felt the full impact of a winter storm with very limited amounts of available cold air. This was a tenuous situation where the amounts of snow were highly dependent on elevation and although I made a firm guess on amounts, I can admit in hindsight how uncertain that storm looked. In the end the mountain got a mostly wet foot of snow that got a little drier with the cold air that settled into the region on January 19th. January 18th was the last day the mountain was above freezing until early March. It turned out be the best stretch of sub-freezing temperatures I have seen in Vermont since I first began following New England weather a quarter century ago.

January had a huge finish and although the first of a few SE Mass blizzards only sideswiped MRG, the powder continued to come in many different ways and so did the cold. The 40-day period beginning in late January and ending in early March included temperatures that failed to eclipse 10 on the mountain on nearly 20 of those days. Snow fell dramatically across a majority of New England, particularly in Massachusetts and southern New Hampshire in early February. MRG was not left out however, receiving nearly 4 feet of snow in the 2-week period beginning in late January and ending February 10th. More snow fell during the rest of the month but in somewhat smaller amounts. It is important to point out that although the ENSO was categorically in the El Nino sphere, we failed to see much enhancement in activity in the subtropical or southern branch of the jet. This kept much of the rest of the country on the drier side through much of both January and February. If the southern branch had played a larger role in the weather, snow totals could have been 100 inches hire in my humble opinion. The mountain did benefit however from a rather unexpected teleconnection. The NAO stayed mostly positive in late January and February. Though cold and snow is often attributed to a negative NAO, it would have, when combined with the forces of the positive PNA and PDO, suppressed much of the weather that so generously impacted ski country during this time. We discussed this on multiple occasions and made the decision to remove the “favorability index” from the blog a very prudent one since it would have simply created confusion for many readers and probably for myself as well.

March followed February and continued to be on the chilly side of average. Unfortunately the mountain missed much of the action during the first week of the month which featured snow in many of the big east coast cities but little in the high country of Vermont. Occasional snow fell through the rest of the month and occasionally the mountain did experience some brief thawing but the melting was fairly minimal until early April. Usually relative cold in March can almost guarantee you an epic month of skiing in New England but it simply remained dry. Precipitation in most locations, in all varieties was less than 50 percent of average.

Needless to say, the winter kept the blog very busy and I am certainly ready to put my SCWB responsibilities aside for awhile. It was a lot of fun this winter however and I enjoyed the interactions and the feedback as always. Give me a month and some intolerable 95-degree heat and humidity and I’ll be itching to fire it all back up again. Enjoy the summer everyone and be safe !!

Wednesday, April 22, 2015

MRG season ends but late April snows set to begin

The MRG season came to an appropriate finish this past week and weekend with a corn-fest. One might have intuitively expected that winter was finished given the several days of 60-degree weather we experienced but winter only just preparing for a late April encore performance. The show begins Wednesday night April 22 with rain at the very low elevations and snow above 2500 feet. The culprit for all this is an expanding upper level ridge encompassing most of central and western Canada. The remaining cold air at the poles will thus descend on the eastern two-thirds of the United States causing more than a week of unusual late April chill and in some locations, additional snows. Interestingly, the weak weather system responsible for the initial burst of rain and snow Wednesday night will strengthen, slow and ultimately get sucked west by a strengthening eastern U.S. upper trough. I think of these systems as “Maritime Stallers” since the storms travel to the Canadian Maritimes but then fail to make any additional eastward progress. The last several years have seen a scarcity of such events but they should be more common and are often very fruitful. They bring pockets of instability, moisture from Lake Champlain in addition to their own decaying areas of moisture to the Green Mountains and the slow moving nature of these weather systems can allow the results to “pile up” quite nicely.

Snow showers should impact even valley locations across Vermont later Thursday, Friday and into early Saturday. Some occasional dustings in the Valley should melt with sporadic sunshine. In the high country however, the snow will be more persistent fall occasionally quite hard. Between the snow Wednesday night and the additional snows late Thursday through early Saturday, accumulations in the highest locations could be well over a foot. The snow might be wet in nature late Wednesday but the airmass poised to invade Vermont is very chilly and the snowfall will be powdery above 2500 feet on Thursday and Friday.

Temperatures will moderate somewhat over the weekend as we watch a series of spring “cut-off” low pressure centers impact the eastern part of the nation. The first will entirely miss New England over the weekend and will bring a cold rainfall to the Mid-Atlantic. The 2nd next week might have a serious impact on the entire East Coast. There won’t be much cold air left by that point, but the storm could still bring some high elevations snows to the Green and White Mountains.

I am working on an end of season wrap-up that I wanted to keep separate from this update. Didn’t want readers to be looking at a late April update for the next 6 months.

Tuesday, April 14, 2015

Spring has arrived in Vermont though winter might give an encore late in the month

It took quite a while but as of mid-April, winter is rapidly receding and spring has arrived. Temperatures are likely to fall back under the freezing mark for a few short hours both Wednesday and Thursday mornings but plenty of sunshine will boost readings into the 50's during the afternoons. The El Nino might have failed in its effort to have much of an impact on the winter but it has strengthened over the last month and has helped to invigorate the southern branch of the jet stream this month. The consequences of this could prove interesting late in the month when a large upper level ridge is expected to reemerge over the Yukon and parts of Alaska. In the meantime, which covers the rest of the MRG season, weather conditions are expected to remain quiet.

Energy in the weakened polar branch of the jet stream will deliver some clouds Friday but aside from an isolated shower or occasional sprinkles, weather conditions should remain mainly dry. For Saturday and even into Sunday, the MRG grand finale, the weather remains uncertain. There is a large and moist weather system in the middle part of the nation that may or may not get kicked eastward. The European and Canadian models holds most of this wet weather off until April 20 and 21st while the American GFS model suggests we get wet over the weekend. I tend to think the GFS is moving things along too quickly in this time frame so I am inclined to believe the drier outlook. That being said, even the drier scenario allows for an unsettled day Saturday with scattered showers and perhaps some high elevation wet snow showers. Once the dust settled on this argument, I'll tweet out some final details.

If we get another round of wintry weather, an entirely feasible possibility given the evolving weather pattern, we probably don't see it until after April 23rd or so. By then the mountain is expected to be closed. I'll provide some details on any such excitement in a subsequent post which will also include our annual seasonal weather summary. Part of me wants to continue past the weekend  but a bigger part is blogged out this season and is ready to refuel for next season.

Friday, April 3, 2015

5-10 inches of glop Saturday morning could turn somewhat powdery as temperatures drop

If one is to forecast based simply on model derived "precip-type", the mountain will get thumped to the tune of up to a foot of snow between midnight Saturday and midday Saturday. The weather service isn't quite buying that however and I am a bit skeptical myself. It's a key question however, if the changeover occurs quickly due to the intensity of precipitation, MRG will do very well, scoring upwards of a foot of snow by late morning. I tend to think the changeover to snow will be a bit slower and thus accumulations will be in the 5-10 inch category. Snowfall will be wet and gloppy overnight but could turn powdery as temperatures above the mid-mountain fall to sub-25 by around 8 AM Saturday.

There are two additional changes for light snow from weaker disturbances or areas of moisture. One Sunday morning could result in an additional 1-4 inches. Another later Monday is more of the overrunning warm advection variety and could result in a few more inches.

Wednesday, April 1, 2015

Quick Saturday thump looking more likely

Though the weather has been generally sub-freezing through much of the month of March it will start becoming quite choppy in early April and some slow thawing is certainly on the horizon. In the short run, we finally have a moisture endowed weather system to talk about. A two-faced storm system with the first piece bringing a big mild push of air into the region. Some rain will arrive Thursday night and it will remain mostly cloudy and mild through Friday with temperatures in the 40's and 50's throughout the mountain. Models are currently confining a lot of the rain to the south of the mountain Friday which would turn out to be quite fortunate if your planning to do some spring skiing. I would not rule out a period of rain however during the day, at least not yet.

A strong cold front advances toward New England Friday night along with the 2nd piece of this storm. For a time it will remain a relatively weak low pressure center, but it will have a healthy amount of moisture and it will bring this moisture northeast out of the Plains as cold air descends southeast out of Canada. The storm will then strengthen very early Saturday and bomb off the New England coast later Saturday. Precipitation may remain rain for a few hours Friday night and then change to snow early Saturday around dawn. If the storm can deepen quickly Friday night, the snow could potentially be heavy for several hours and accumulate 6-10 inches by midday Saturday before tapering off during the afternoon. If the storm is slow to mature, we will be stuck with lighter snows.

Weaker disturbances are likely going to bring the mountain some additional snowfall Sunday or Monday or both. Needless to say it will be quite chilly in this period as well. Temperatures will fall back to sub-freezing levels by Saturday morning and will later turn blustery in the wake of whatever snow falls. Sunday morning will feature temperatures in the teens and limited sun will only bring afternoon readings to 30. By Tuesday, some thawing will recommence but the weather hardly appears delightful. A slow moving storm system in the middle of the country is likely to bring an expansive area of clouds to the central and eastern part of the country. Vermont will likely be on the north side of a nearly stationary temperature boundary and temperatures will remain mostly in the 30's as a result. Occasional rain and in places, some ice is also possible. If this entire conglomeration of weather can be further south, we might be talking about some snow but i would not count on it right now.