Area Forecast Discussion
Issued by NWS Sterling, VA

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345 FXUS61 KLWX 281858 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 258 PM EDT Tue Mar 28 2017 .SYNOPSIS... A cold front will cross the area tonight. High pressure builds over the region Wednesday into Thursday. Another disturbance will approach the area late Thursday into early Saturday. && .NEAR TERM /THROUGH TONIGHT/...
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Latest surface analysis depicts a stationary front draped near the Mason-Dixon Line on east, with low pressure over central Maryland. West of the low, the front continues west into the upper Ohio Valley, then turns southwest down the valley towards Missouri. Aloft, a sharp trough is located over the region, with ridges aloft to the immediate east and west. Through this evening, both the surface low and upper level trough will push eastward into the Atlantic. Dry air will slowly move into the region aloft, so despite relatively moist and warm low levels, the drying aloft will start to gradually limit storm development as CAPE dwindles. Shear is pretty low so think there should be very limited severe threat, but a few strong gusts are not impossible. With cold temps aloft, small hail will also be a concern. The surface front will then start dropping south across the region later this evening and overnight. Low levels will start to cool and dry out and the showers should completely end after midnight. Some patchy fog may try to develop in spots where the wind doesn`t pick up fast enough, but overall, think it should be minor since clouds will likely linger for a while. Lows will remain on the mild side, with 40s and 50s common.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
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High pressure builds in from the north on Wednesday with a breezy north wind. Temperatures will not be as warm and the humidity will be noticeably lower, but still on the nice side for late March with 60s common. Winds will relax Wednesday night as the pressure ridge pushes directly overhead, and with dry air in place, we may radiate down towards freezing or even a bit below in the colder spots. By Thursday, clouds will start to increase as warm advection begins ahead of the next approaching low pressure. The clouds should limit the insolation and temps will get stuck in the 50s. Some rain may move into western areas late in the day, but think for most areas, it will wait until after dark Thursday night. Low pressure will slide east toward us through the day Friday, with periods of rain looking likely. There is a good southerly fetch with this system overruning the cool wedge at the surface, so potential for some decent rain. Right now, it appears the wedge will mostly hold with this system, so highs Friday look to remain in the 50s.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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The chance for rain showers linger Saturday before drier and cooler air can filter into the region Saturday night when high pressure works its way into the mid-Atlantic. High pressure will settle into the region Sunday through early Monday. Dry and seasonable temperatures expected throughout the period. The next storm system will move into the region midday Monday through Tuesday, bringing the chance for rain showers to the region once again.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/...
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Scattered to numerous showers and isolated to scattered thunderstorms are expected through the rest of the day into this evening. Brief reductions in cig and vis, small hail and gusty winds to 35 knots are possible. Outside of storms, conditions should be mostly VFR, though some MVFR cigs and vis remain in spots. Overnight, some lower clouds look to linger until the cold front moves through, with cigs possibly dropping to IFR levels for a time. Early Wednesday, the front should sweep away the low clouds and it should turn VFR until Thursday night, when the next system will bring more rain and potential for IFR cigs and vis. Mvfr conditions Saturday. Winds northwest 10 knots Saturday. Vfr conditions evolving Saturday night. Winds northwest 5 knots Saturday night.
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&& .MARINE...
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Isolated thunderstorms possible into this evening. Winds in any storm could gust to 35 knots, though odds are low. An SCA has been issued for tonight and Wednesday behind a cold front. Northerly winds are expected to gust to 20 kt. Winds should diminish Wednesday night and remain sub SCA during the day Thursday with high pressure passing the area. Potential for Small Craft Advisory conditions increases Thursday night and Friday with increasing southeasterly winds ahead of an approaching system. Winds will then turn north/northwesterly on Saturday behind the system, with continued potential for SCA conditions.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 6 PM EDT Wednesday for ANZ531>534-537-539>541-543. Small Craft Advisory from 6 AM to 6 PM EDT Wednesday for ANZ530-535-536-538-542. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...KLW AVIATION...RCM/KLW MARINE...RCM/KLW

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