January 25, 2004
Complex weather event beginning to unfold across the central and eastern United States. A quick look at current radar and satellite will show you that this storm system does indeed mean business, not just based on the areal coverage of clouds and precipitation, but the strengthening anticyclone of high pressure across Eastern Canada. Two things that this cold high pressure will cause: 1) the storm system will be 'blocked' from heading North into the Great Lakes and will be forced to redevelop along the coastline, and 2) a nose of high pressure will keep cold air locked in leeside of the Appalachians. To give an idea of just how many people are being affected by this system, take a look at this Storm Warning Map of the United States. It is not everyday that a forecaster sees that many warnings spread out across the country. So, if you think that forecasting this gyre is / has been easy, you'd better guess again my friend.
In any event, we are still sticking with our original call from Thursday of 3-6" of snow for our area late tonight into Monday. Would likely bet that our total snowfall amounts through midday Monday will be closer to the lower end of those totals. One of the factors that will determine snowfall amounts will be the snowfall ratios. In general, the colder the temperature, the higher the 'fluff factor' or more powdery the snow is, hence, it piles up faster and accumulations increase. With temperatures during the onset of snow tonight expected to be in the teens, rations of snow:liquid will be around 20:1.
In terms of apparent weather, clouds will continue to thicken throughout the day today. It will be cold and breezy with the high temperature around 20F. Snow will overspread the region after midnight tonight. Snowfall should be light in nature with a few pockets of heavier snow thrown in closer to morning on Monday. Low temperature tonight around 14F. Periods of light snow continue Monday morning and may mix with or change to sleet and freezing drizzle in the afternoon. High temperature Monday of 32F. Total snowfall accumulations of 3-6".
Things get more complicated Monday night into Tuesday and Tuesday night as computer models are now showing stronger redevelopment of secondary low pressure off the North Carolina Coastline late Monday night. The trend by guidance over the past 18 hours has indeed been for a stronger second system on Tuesday with more moisture than previously thought. This may become a case of "the weaker the first storm, the stronger the second". For now, it looks like another round of moisture will reach our area sometime on Tuesday, starting as rain or a mix, then quickly turning to all snow. Accumulations are possible and several inches of snow could fall Tuesday afternoon and early Tuesday night. The spread among guidance is anywhere from little accumulation up to 8", with the trend being towards higher accumulation amounts. My feeling right now is that we will see another minor 'event' Tuesday with accumulations of less than an inch to 4".
So, as is always the case with the weather (though usually not quite as cut-throat as what we will see over the next 72 hours), much is dependent on what will happen with disturbance A in regards to disturbance B. Still seem comfortable with 3-6" through Monday, then we will have to wiat and see exactly what will unfold for Tuesday. Someone to our North will likely see a major snowstorm (12"+) out of the Tuesday system, but for now, it does not appear to be the PHL area (do you hear what I am saying folks in New England?!?). More later . . .
S.B.
