Wednesday, January 20, 2010

Winter Storm Watch in Effect


A winter storm watch is in effect for western parts of the state from Thursday afternoon through Friday afternoon. A mix of sleet, snow, and freezing rain will be likely in the watch area, with significant accumulations possible. Freezing rain and sleet will be the primary mode of precipitation for the southern half of the watch area, with sleet and snow more likely farther north.

Series Of Storms

A series of storms have been tracking eastward through the U.S. after slamming into the West Coast and dumping large amounts of rain and snow in a short period of time. Parts of California have received nearly 7" of rain through Wednesday morning, with more coming down today and tomorrow. Severe weather even accompanied yesterday's storm with several small tornadoes reported in Southern California. Snow totals in the mountains of California are greater than two feet and climbing. Each of these storms will bring Central Virginia an opportunity for precipitation later Wednesday through Friday, and again later Sunday into Monday.

A cold front moved through most of the state early Wednesday, bringing cooler temperatures to the Mid-Atlantic. Here is a look at the mid-day Wednesday surface map, where you can see the three low pressure systems in the Plains, the Rockies, and the West Coast:

Surface high pressure will slide southward over New England the next couple of days, keeping the cooler air funneling into Central Virginia. This can create a layer of sub-freezing air near the ground which allows rain falling into the layer to freeze as sleet. Northern and Western Virginia will have the highest chance for this wintry mix early Thursday and again on Friday while moisture from the approaching upper storm overspreads the region. Our rain chances later Wednesday through Friday will result from the first and second storms tracking eastward. Storm #3, which is currently slamming into California, will bring an opportunity for heavy rain in Virginia later Sunday into Monday. Strong southerly flow at all levels ahead of that storm should bring much milder temperatures surging back into the state, keeping the precipitation as just rain.