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A sunny Friday but more weekend madness

Sorry, but we’re in that kind of timing pattern in which the storms roll through here over the weekends. Today – Friday – Fredericksburg will actually thaw out a bit from yesterday’s January-ish high of 34 at the UMW weather station and this morning’s low of 15. The thermometer will actually climb back into the low 40s this afternoon under mostly sunny skies.

Clouds will roll back in this evening, however, as another complex system aims at us. This surface forecast graphic depicts the situation at 7: 00 a.m. tomorrow morning:

There are three main features to notice on this surface map, two of which are low pressure systems (red “L’s”). The one centered over the deep South will scoop up an abundance of Gulf of Mexico moisture and hurl it in our direction. The other one, centered over the Midwest, will drag cold air southward behind it. These two will combine their energies into one coastal system that will plague the Northeastern states with more storminess.

The third feature is the high pressure system (blue “H”) over eastern Canada. This time of year such a feature sets us up for a cold air damming event by forcing cold surface air down the coastal plain east of the mountains. This always complicates our forecast but this time the “wedge” will set up a bit further west. Instead of cold air draining down straight the coast and over the ‘Burg our winds will swap around to the southeast by early afternoon. Thus milder air from the southern Atlantic will warm things up and help switch the precipitation over to all rain tomorrow afternoon.

So what does Saturday’s weather entail? The official NWS Sterling forecast calls for snow to start during the early morning hours before changing to a mixture of snow, sleet, and rain around mid-morning. If the snow falls at a fast enough rate it could accumulate to perhaps an inch on grassy surfaces before the changeover occurs. Then after lunchtime the whole mess should turn to rain as the warmer air from off the Atlantic invades the I-95 corridor. (Oh, and Sunday looks be to dry with a high temperature in the low 40s.)

Could this forecast change? Possibly, since – yet again(!) – Fredericksburg sits right along the dividing line between warmer air to the east and colder air to the west. If the cold air damming wedge erodes slower than forecast the changeover to rain could happen later Saturday. If the storm track shifts 50-100 miles eastward the frozen stuff could stick around all day tomorrow. (It’s like trying to find that errant $0.02 difference between the checkbook balance and the bank’s statement.) But right now it appears that things will happen as advertised.

Enjoy the sunshine today and plan for a messy Saturday.

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