Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 300739 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 339 AM EDT Thu Mar 30 2017 .SYNOPSIS...
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High pressure will move offshore today through tonight. Low pressure will pass through the area Friday. High pressure will gradually return Saturday and Sunday before another low pressure possibly impacts the area Monday and Tuesday next week.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Ridge of surface high pressure has wedged itself down the eastern US seaboard and will remain in place for much of today. This has led to the development of low level easterly flow, and this in turn has promoted the formation of stratus clouds across central and western Virginia. These will slowly grow in coverage through the morning and advect northeastward as southwesterly flow develops a few thousand feet above the surface. At the same time, a low pressure system centered over Missouri this morning will move northeastward and into Illinois by this evening. Warm and moist air advection will increase aloft, leading to high clouds which will also stream aloft overhead through the day. Most of the shower activity should remain north/west of the region today towards the area of greater forcing, however, some showers may make their way into parts of eastern West Virginia and western Maryland during the day. Highs today will be in the 50s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
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Warm and moist air advection continues tonight and with that we`ll see increasing chances for rain, especially towards morning. Model guidance in good agreement that the low pressure system will track east-northeastward from over Illinois this evening to Ohio by Friday afternoon, before redeveloping near or over the area late Friday and Friday night. Most widespread and steady rain is expected Friday morning, and rain could be heavy at times. Lows tonight mainly in the 40s. With the low expected to track near the region, will continue to monitor trends as to how far north the warm sector can make it Friday afternoon following initial surge of rain. Best chances for thunder will be south of DC, and the Storm Prediction Center has placed portions of the region in a Marginal Risk for severe thunderstorms. High temperatures will be very dependent on initial rain and progress of warm sector, but will show low 50s north to mid 60s south. Showers will begin to taper off Friday night as low pulls away and northwest flow develops. Lows in the 40s. High pressure will begin to build in during the day Saturday. A lingering shower or two will be possible in northwest flow, but most places will likely remain dry. Highs should be near normal for the first day of April, from the upper 50s to mid 60s. High pressure then moves overhead Saturday night, with mostly clear skies and lows in the 40s.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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High pressure will build overhead for Sunday...bringing dry conditions along with sunshine and a seasonably mild afternoon. High pressure will move offshore Sunday night and low pressure will track into the Tennessee Valley Monday before passing through our area Tuesday. The exact track of the low is a bit uncertain at this time...but a soaking rain is likely Monday into Tuesday. Should the low track farther north...then a few thunderstorms would be possible. Confidence for thunderstorms is low at this point. High pressure will return during the middle portion of next week.
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&& .AVIATION /07Z THURSDAY THROUGH MONDAY/...
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VFR expected through today, although with multiple decks of increasing clouds. Light northeast winds this morning will turn southeast through today and increase up to about 10 knots. Ceilings will lower and rain will overspread the region later tonight and into Friday morning. Widespread IFR/sub-IFR conditions likely, especially during the 06z-18z time period. Some improvement possible after 18z Friday as steady rain ends, especially CHO. The northern TAF sites, MTN/BWI/MRB likely to remain locked into IFR/sub-IFR. IAD/DCA a bit more questionable. A few thunderstorms are also possible Friday afternoon, with highest chance at CHO. Improvement back to VFR will take place Friday night, with VFR area-wide expected Saturday and Saturday night. Winds will turn northwesterly Saturday as well. High pressure will build over the terminals Sunday. VFR conditions are expected. High pressure will move offshore Sunday night and low pressure will approach from the west on Monday. Clouds and chances for rain will increase during this time. SubVFR conditions are possible.
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&& .MARINE...
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Sub-SCA northeasterly winds this morning will turn southeasterly this afternoon and strengthen this evening. A SCA goes into effect at 6 PM for portions of the central Chesapeake and lower Tidal Potomac and continues through Friday where highest risk of 20 knot gusts lies. Winds will turn northwesterly behind the departing frontal system Friday night and on Saturday, and additional SCA winds are possible. Winds will decrease Saturday night as high pressure builds in. High pressure will build over the waters Sunday before moving offshore Sunday night through Monday. Low pressure may impact the waters Monday night into Tuesday.
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&& .TIDES/COASTAL FLOODING...
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An onshore flow will increase tonight into Friday as high pressure continues to move offshore. Low pressure will pass through the area Friday night. The onshore may increase ahead of this system. Elevated water levels are expected tonight through Friday night and minor tidal flooding is possible near times of high tide.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ530>534-537-539>541-543. Small Craft Advisory from 6 PM this evening to 6 PM EDT Friday for ANZ532>534-537-540>543.
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&& $$ SYNOPSIS...BJL NEAR TERM...MM SHORT TERM...MM LONG TERM...BJL AVIATION...BJL/MM MARINE...BJL/MM TIDES/COASTAL FLOODING...BJL

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