1:00 PM | **An update on tomorrow's first significant snow event of the season**

[High-resolution snowfall estimate forecast map from NAM model; courtesy NOAA]

Discussion

Overview All systems go for the first significant snow event of the season in much of the Mid-Atlantic region. Snowfall estimates (see below) in the region from DC-to-Philly-to-NYC have not changed with the latest model guidance; however, the timing of the event has speeded up by a couple of hours. As a result, the precipitation will likely begin in the pre-dawn hours in many areas along the I-95 region between DC and Philly and will end in all locations a bit sooner tomorrow evening.

Details Low pressure is developing today over the eastern Gulf of Mexico and it will intensify rapidly on Wednesday as it tracks quickly northeastward along the east coast. The low is expected to pass just east of Long Island on Wednesday evening before reaching Nova Scotia by Thursday morning. This storm will have a big impact on the interior Mid-Atlantic region on Wednesday with more snow to the north and west and less to the south and east. The map (above) shows snowfall estimates from the high-resolution version of the NAM computer forecast model and it clearly shows the higher amounts to the north and west and the lesser amounts to the south and east. The rain/snow line will be dropping from the northwest to the southeast tomorrow morning in the region near I-95. Precipitation will likely be in the form of all snow by early afternoon along I-95 and points to the north and west. Sleet can get involved as well on Wednesday during the transition period from rain to snow. Elevation will also play an important role with higher elevation locations to the north and west changing quicker to snow compared with nearby lower elevation locations.

Travel As far as travel is concerned, precipitation from this coastal storm will begin in the pre-dawn hours in many locations so “beating it” will be somewhat difficult given its quick movement. However, there will be a time period during the initial changeover to snow in which the snow will melt on the roadways given the warmth of recent days. In general, the worst driving conditions are likely to occur from the mid-day hours through the afternoon and then into the early evening before winding down. The snow will wind down from southwest-to-northeast later tomorrow (late afternoon in DC, early evening in Philly, late evening in NYC).

Summary of snowfall estimates

DC area: 1-3 inches in and around the District 3-6 inches in the N and W suburbs Coating-1 inch just S and E of the District

Philly area: 2-4 inches in and around Philly 4-8 inches in the N and W suburbs Coating-2 inches at the Jersey Shore

NYC area: 3-6 inches in and around the NYC metro region 6-10 inches in the N and W suburbs 2-4 inches across Long Island

[Water vapor image showing lots of moisture along the east coast; courtesy NOAA]