December 30, 2005
So where has winter gone all of a sudden? The pattern that had locked in roughly around the time of Thanksgiving through mid-December yielded 4 separate events which respectively produced some type of frozen precipitation throughout our region. However, that pattern was broken around mi-December as the Polar Vortex retreated back into Northern Canada and the progressive and powerful Pacific Jet Stream intensified causing little amplification in the jet across the US (which simply spells very little in the way of cold air outbreaks).
As we turn our attention toward the New Year, there are signals that the current and relatively "mild" weather regime across much of the United States will gradually begin to break down as the Arctic Air (ala early December pattern) reloads. What does this all mean? Well, hopefully everyone enjoyed the nice weather during the holiday break, because things are going to get downright nasty over the next week to ten days. How quickly the pattern can break down will determine just how much snow versus rain the region receives during the January 1 - 10 period.
First and foremost, the weather looks to turn ugly for parts of the Northeast on New Year's Eve and during part of New Year's Day. A clipper system will hitch a ride along the Northern Jet and take a path from the Northern Plains Eastward into the cornbelt and Ohio Valley as the day progresses on Friday. As the storm system nears the coast, it is forecast to redevelop near Assateague Island which lies on the Southern portion of the DelMarVa Peninsula. Precipitation should arrive here in Delco by noon on Saturday. Temperatures are going to be very close here in regard to what type of precipitation we will receive. At this time, it looks like we will see a mix of rain and snow during the day on Saturday. Location will be key, as some places near us, say just North of a Norristown (PA)-Trenton (NJ)-Sea Bright (NJ) line, may start AND remain all snow during the event. With that being said, accumulations of snow for our immediate Delco region should be on the light side (since we are barely South of that line), but the real trouble lies after nightfall. With light precip still forecast to be falling around midnight and temperatures dipping to below freezing for much of the area, road conditions will be slick at best. Couple this with late night partiers who are either tired or driving home drunk, and traffic conditions suddenly become quite hazardous. Keep this forecast in mind if you are headed out around the area on Saturday night: there is the chance for accumulating snows and icy conditions on area roadways during part of the day Saturday through to Sunday morning. Exercise caution while driving if you are going out and about to celebrate the New Year.
Longrange, there will be several more disturbances riding along the Southern Jet Stream over the next week to ten days. In any event, there are going to be some juicy storm rolling across the US during this period. If we can get a setup where the Northern Jet can buckle and the two streams phase over the TN Valley / Upper MS Valley via one of these disturbances, we could have quite an East Coast snow event. Bottom line: there is very good potential for a significant East Coast snowstorm in the next week to ten days. Usually a pattern collapse will yield a potent storm to usher in the change, so forecasters will be on guard for the foreseeable future. A measly couple hundred miles between jet streams can be the difference between a rainstorm, a fish storm (out-to-sea), or a significant winter storm. In my opinion, this period is going to be one where a decent storm sneaks up and surprises people.
So, some snow and rain on Saturday and early Sunday morning. Should start as rain then go to snow for a while. Changeover could be evident a few times on Saturday as energy transfers to the coast and the battle between the warmth to the East of the coastal front and cold air to the West takes place. This in mind, accumulations of snow should be minimal in Delco(coating - 2") but we are more concerned with driving conditions after dark. Roads will become icy and light snow may continue through morning making driving conditions quite hazardous. More updates later. For now, take care!
S.B.
