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Wednesday, March 19, 2008

Friday's our best shot for a powder day

The NAO did its best and our midweek storm is now indicated to track over southern Vermont as opposed to the St Lawrence Valley. Still, we have the glaring lack of fresh cold air on the front flank of this system and this will hurt us as far as Wednesday is concerned. As advertised, the storm will slow its eastward progress over Nova Scotia and this will allow for the extended period of enhanced TIS activity I was hoping for.

The specifics
After a few inches of wet snow early Wednesday, we get a period mixed sleet and rain which will persist into the evening. After that the precipitation becomes more showery (in the form of rain) until the passage of the storms associated front and the arrival of our long awaited supply of cold. The snow showers will intensify gradually and temperatures will become cold enough during the evening for an accumulation of powder. It is easy to land yourself way off course when trying to predict amounts in these situations but my best guess is anywhere from 4 to 10 inches between late Thursday and late Friday. Low level instability is actually indicated to linger through the weekend although the depth of the unstable layer is expected to gradually decrease. This essentially means the snow showers will become less frequent and will be less intense. Still, we could see flurries all the way through Sunday.

Still watching early next week for the possibility of a big system

The system for early next week appears to be a "snow or no" situation which is rarity in this winter season. Most of the model guidance has been indicating that the trough may be too overwhelming to allow the storm to track close enough to the coast. That being said, the last run of the European model was flashing big event and the American model had the storm much closer to the coast verses its own prior indication. This will be worth a close watch as we do tend to see longwave troughs with shorter wavelengths in March as opposed to December in January. The timing of all this would have the impact of the storm beginning late Monday and persisting through Tuesday. Plenty of questions remained unanswered however and our chances for a big dump are still somewhat less than 50 percent.

A worst case scenerio for early next week would still allow for some new snow from a clipper system. There remains strong indications for a temperature moderation later in the week as the strength of the negative NAO and associated blocking begins to subside.

2 comments:

Tim said...

You are an incredible resource and I look forward to reading your postings at every opportunity. Thanks so much for your insight and for making it exciting and suspenseful!

rucebay said...

Hey Josh, Two Years ago when the Valentines Day storm hit, according to the ENSO weather site at the time if I remember correctly, the Pacific SST's were normal or neutral. As the Pacific shifted from Elnino to La-Nina conditions,at the point that we were right at neutral sst's, thats when the storm hit. Since this storm came under neutral conditions as short as they were,(the charts show that they lasted less than two weeks) doesn't this suggest that big storms are more likely under normal conditions? There was no snow before that storm, and very little if any after. Just one big blast under normal conditions.What are your thougts? Thanks, Bruce Bump Johnstown NY