12:00 PM (Friday) | *Storm #1 is now underway in the Mid-Atlantic region…storm #2 impacts the region from Monday into Tuesday*
Paul Dorian
Mid-day radar shows an extensive area of precipitation from the Mid-Atlantic to the SE US and it is pushing in a general southwest-to-northeast direction; map courtesy University of Wisconsin, NOAA
Overview
There will be two storms to deal with in the Mid-Atlantic/NE US over the next few days with the first storm already impacting parts of the Mid-Atlantic region and another storm will impact the same area from Monday into Tuesday. The initial storm is going to be predominately a ‘plain’ rain event in the I-95 corridor and some of it will become heavy at times, but there are a few pockets of freezing rain at this hour in areas well to the north and west of Route I-95. Patchy fog may form as well in the overnight hours as the in flux of milder air moves over still cold grounds. The departure of this initial storm will result in an influx of another cold air mass at the end of the weekend and this could set the stage for some snow and/or ice on Monday at the onset of the next storm; especially, in areas north of the PA/MD border.
12Z GFS surface forecast map for early Saturday with rain (green, yellow) throughout the Mid-Atlantic/NE US during the storm #1 event; map courtesy NOAA, tropicaltidbits.com
Storm #1 (today, tonight, Saturday)
Precipitation has already broken out across parts of the Mid-Atlantic region from Pennsylvania on south. In some areas well to the west and north of Route I-95, it is still just cold enough for some icing, but temperatures are generally above freezing in the immediate I-95 corridor albeit by a small amount. The influx of somewhat milder air will ensure ‘plain’ rain tonight and on Saturday and some of it will come down heavy at times. In addition, fog will likely become quite dense in many areas of the Mid-Atlantic region later today, tonight and on Saturday as milder air moves over still quite cold grounds.
12Z NAM (3-km version) surface forecast maps for Saturday morning indicating a “line” of heavy showers and possible embedded thunderstorms associated with storm #1 may swing through the I-95 corridor from the southwest-to-the-northeast; maps courtesy NOAA, tropicaltidbits.com
There is even a chance for a rumble of thunder on Saturday as a boundary zone helps to generate a line of heavy showers and possible isolated thunderstorms as indicated by some high-resolution models (e.g. NAM 3-km). This ‘line’ will swing from southwest-to-northeast on Saturday morning and mid-day and it could cause briefs downpours and perhaps a rumble or two of thunder. The precipitation winds down later tomorrow and NW winds will intensify tomorrow night as another cold air mass pushes into the Mid-Atlantic/NE US on the back side of the departing low pressure system. The winds will continue to be quite noticeable on Sunday out of the northwest, but it should be a dry day featuring some sunshine in the DC, Philly and NYC metro regions. This influx of cold air during the latter stages of the weekend could set the stage for some snow and/or ice early next week; especially, to the north of the PA/MD border as the next storm system pushes into the eastern US.
12Z GFS surface forecast map for early afternoon on Monday with snow (blue) and ice (pink, purple) in parts of the Mid-Atlantic region as storm #2 arrives; map courtesy NOAA, tropicaltidbits.com
Storm #2 (Monday into Tuesday)
With cold air in place in the Mid-Atlantic/NE US on Monday, a narrow swath of precipitation is likely to break out in a west-to-east fashion from an intensifying low pressure system over the Tennessee Valley. As this narrow band of precipitation reaches the Mid-Atlantic region perhaps during the morning or mid-day hours on, it is likely to be cold enough for snow and/or ice; especially, in areas to the north of the PA/MD border. With the storm system likely pushing up to the west of the I-95 corridor later in the day on Monday, enough milder air will probably push in to result in a changeover to ‘plain’ rain for the DC-to-Philly-to-NYC corridor, but there can be some snow/ice accumulations before this takes place; especially, north of the PA/MD border, but perhaps even as far south as northern Maryland and northern Virginia. The ‘plain’ rain will likely continue Monday night and then end on Tuesday with the arrival of the next cold frontal system that will trail the center of the low pressure system. That frontal passage on Tuesday will usher in another cold air mass for the Mid-Atlantic/NE US for the middle and latter parts of next week. One final note of caution, there is still some time for changes to take place regarding storm #2 and the final evolution of storm #1 will actually have an impact on the overall environmental conditions for early next week…in other words, stay tuned.
Meteorologist Paul Dorian
Perspecta, Inc.
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