Key points for today’s snow and rain event

*Winter Weather Advisory for N&W burbs (Montgomery, Loudoun, Howard, n. Fauquier) from 10 a.m.-noon to 8-10 p.m. (see map) *

* Unscheduled leave and telework options for Federal workers *

* CWG’s earlier coverage: Full Forecast | Steadiest snow may coincide with Wednesday PM commute *


Locations colored in purple are under a winter weather advisory. (National Weather Service)

* Start time ranges from late morning in far western suburbs to mid-afternoon east of town

* Precipitation may begin as rain in the District and points east and southeast; snow elsewhere. Precipitation should change to snow where it begins as rain within a couple hours of the onset.

* Temperatures from 35-40 when the snow starts mean little sticking through mid-afternoon. Current temperatures range from 36 (Hagerstown) - 40 (D.C.).

* The steadiest precipitation is most likely to fall between 3 and 6 p.m. today, coinciding with the afternoon commute.


Our accumulation map.

* Precipitation should end between 6 and 9 p.m. tonight from west to east.

* Accumulations: A heavy coating to 2” in winter weather advisory area (purple), less than 1” elsewhere. (See map after the jump)

* The National Weather Service is not impressed with the snow potential for this event. Its morning shift forecaster worried: “I’M A BIT CONCERNED SOME OF THE ADVISORY IS NOT GOING TO VERIFY.”

Assessment from Wes Junker, Capital Weather Gang’s winter weather expert:

The biggest issue with the upcoming event remains temperatures. The models have converged towards a solution that offers 0.10 to .20” of liquid equivalent (which would convert to at most an inch or two of snow if temperatures were freezing) but with most of the precipitation falling with the temperatures in the mid-to-upper 30s except out towards the higher terrain to the north and west.

The NAM has trended drier and warmer since yesterday and actually has the surface temperature around 40 when the precipitation begins, the GFS run from last night was a little cooler. The warm layer near the ground is relatively shallow suggesting that some of the precipitation will fall as snow. However, it may start as rain near and east of the city. The warm surface temperatures also suggest little if any accumulation around and east of the city and that any accumulations will probably end up north and west of the city, especially locations with higher elevations.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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