2008.01.31
Precipitation moving into area; how much does it cool?
The radar is starting to fill in with precipitation just to the west and southwest of our region. The first waves are falling into very dry air, so it may be a while before we see anything at the ground. I suspect we may see sleet -- possibly even a flake or two of snow -- as it begins, but then go to rain or freezing rain not long after, depending on exactly where that surface temperature rests. The dew points remain extremely low at the surface, all of 4 whopping degrees at 10 p.m. in Roanoke (with a temperature of 39). So as this precipitation, whatever form it's in, starts falling into that dry air, we'll see the temperatures drop. Following standard expectations with that temperature and dew point, the temperature could fall into the upper 20s with evaportional cooling. MIlder air moving in aloft and eventually sinking to the surface with the rain may make 30-32 more feasible.
My best stab at it says we do end up as low as 31 for about 3 or 4 hours in Roanoke, enough for some ice on the trees. It could get quite slick in higher elevation and outlying areas, and on bridges, and I would not be surprised to see a few power outages as ice starts building on trees in many areas. This does have the potential to be a signficant ice storm across much of the area if the full extent of the evaporational cooling is realized and the cold air hangs in a few hours before the warmth modifies it.
Once again, we're skating on the razor's edge.
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Very heavy sleet is falling in the Narrows area of Giles County. Temp has dropped to 28.
Comment by Ernest LOng — January 31, 2008 @ 10:36 pm