Old man winter intends to greet us during this first full week of work and remind us that his show is just beginning. Markedly colder air is sliding in as a deep upper level trough in the atmosphere swings down from Canada into the eastern US. As this trough digs to the south, there (as always) are pockets of energy which rotate around and through the trough, providing an opportunity for some type of weather mischief. Depending on the alignment of the trough and the positioning of the energy pockets therein, minor clippers can be created near the surface...fast moving low pressure system which can bring some snow with them. For us in the immediate DC area, another question has to be posed....at what angle does this clipper approach? If the clipper comes at us from the due west or west northwest, the bulk of any moisture the clipper has gets scraped away by the mountains to our west, resulting in cloudy, blustery conditions, with snow flurries and and occasional snow shower. The steeper the angle of approach, the less the mountains will affect a system, letting more moisture pass. For tomorrow, the trajectory painted by the models appears to be pretty flat....west northwest at best. Even so...the shorter range models, which should produce better forecasts based on their ability to see the terrain better, suggest an inch or two is possible tomorrow morning. The timing of this from a work perspective is not looking good, as we will likely make the morning commute a mess. The bulk of the moisture slides though western Maryland during the early morning hours, with the southern most extent far enough south to catch the northernmost counties in Virginia, yet miss most of the higher terrain to the west...so a perfect trajectory to allow this clipper to influence the weather. Snow moves into the western suburbs after 4am, northern and central DC areas by 6am, It will be cold enough to cold soak the roads so that the snow sticks, so hopefully our fearless road crews are preparing now with preemptive measures. A fast hitter, the show is over just after 10am with rapidly improving conditions, but colder air coming in. For the northern Virginia counties I expect up 0.75 - 1.5 inches to fall and a possibility of up to 1-2 inches in the immediate Maryland counties surrounding the DC area and to the north. Be sure to listen to Old Man Winters greeting as he passes by. Nothing posted yet by the NWS, but I would expect winter weather advisories to come out later today for the morning hours tomorrow. This is not a system where a big snowfall surprise could occur...but enough in a short period of time to snarl traffic. Will keep an eye on this. Stormy
Posted on: Mon, 05 Jan 2015 14:07:51 +0000
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