Wednesday, January 16, 2008

Winter 2.0, The Sequel

Clear commute; wintry mix likely tomorrow

Precisely one year ago today,'s PM Update noted that the pattern had shifted exactly halfway through meteorological winter from a mild regime to a more wintry one, and a similar shift is happening this year. With yesterday's return to within one degree of the daily average temperature, the stage is set for a wintry mix of precipitation as a developing low pressure area emerges from the Gulf of Mexico and moves northeastward up the Atlantic coast.

The key to the forecast is the fact that there is cold air in place and a good moisture supply, but the mechanism to hold the cold is not there, and as the wind moves to a southeasterly direction, much of the precipitation is likely to change to rain.

Tonight: After this afternoon's temperatures mainly in the low 40s, some high clouds will be accompanied by upper 30s to near 40 this evening. Clouds will increase overnight as lows reach 30-32 in the city and the mid to upper 20s in the 'burbosphere.

Tomorrow: Unless you sleep as late as we do here at CommuteCast Central, your morning commute should be cold, but dry. Precipitation in the form of snow or sleet will develop from southwest to northeast across the region from late morning into early afternoon. Temperatures in the low 30s will drop a couple of degrees to freezing or below when precipitation begins, but will gradually warm a little toward evening, and precipitation in the immediate metro area will change to freezing rain or plain rain. An inch or two of snow is possible before the change, especially north and west of the Beltway. As usual in this type of situation, the changeover will be most rapid east of I-95.

See Dan's post for the rest of the forecast, including a look ahead to the weekend.

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