Think Snow, Tweet Snow !!!

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.

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