Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271819 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 219 PM EDT Thu Apr 27 2017 .SYNOPSIS...
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A weak cold front crosses the area from the west tonight. High pressure over the area Friday, then dropping off the southeast coast Saturday. A cold front will move over Pennsylvania Saturday night before lifting north. A cold front will move through the region from the west Monday night.
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&& .NEAR TERM /TONIGHT/...
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After watching low clouds/fog slowly dissipate both of the last two mornings this pattern should not repeat itself tonight. A weak cold front will move west of the Appalachians this evening...reaching the Bay around midnight. Showers can be seen on regional radar across WV. Given that low clouds have eroded temperatures are now climbing into the upper 70s/lower 80s. Neither CAPE nor helicity look particularly good but SPC has placed much of the western half of the forecast area in marginal risk, and WPC has placed the area just west of our forecast area in a marginal risk of excessive rainfall. Given the slow movement of the line the latter may be the greater concern for the evening shift team, but there is stronger convection over GA/SC which may rob the line further north of energy. Have chance PoPs/isolated thunderstorms forecast for the entire area this evening. Lows ranging from the upper 40s in the Highlands to the mid 60s in the cities. Much of the area will drop to 55-60.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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Weak front will move offshore Friday morning. Light fog is possible but not expected to be as dense/widespread as previous two nights. We will be in a warming trend heading into the weekend as high pressure strengthens off the SC coast. This will pump warm air into the Mid Atlantic, and by Saturday temperatures will have a decent shot at topping 90. The record temperatures for April 29 - we`ll be close to these values: Highs max High min DCA 91 68 BWI 91 67 IAD 87 62
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/...
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High pressure to the southeast will break down with a warm front sliding northward across the D.C. area Sunday into Sunday night. There is a chance for showers and a thunderstorm, mainly Sunday with the warm front nearby. An increasing southerly wind will usher in warmer and more humid air to help fuel showers and thunderstorms, mainly Monday afternoon and evening ahead of a strong cold front. A few thunderstorms could contain strong winds. Gusty westerly winds and drier and cooler air will filter into the region Tuesday and Tuesday night behind the cold front as high pressure builds in from the west. High pressure moves offshore Wednesday, while keeping conditions dry. A return flow will be an indication that a new warm front will try to push across the region late Wednesday into Thursday. The Thursday storm system that is expected to develop along the warm front could intensify over the Ohio Valley before sending energy eastward into the mid-Atlantic later in the day Thursday.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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VFR through the afternoon/early evening. Isolated showers and thunderstorms will be possible at TAF sites this evening. These are expected to weaken while progressing east of the mountains. Light fog possible Friday morning then VFR at all sites Friday into Saturday. Mvfr to ifr conditions expected Sunday and Sunday night with showers and a thunderstorm in the area near MRB, IAD, MTN and BWI terminals. Vfr conditions elsewhere. Ifr to lifr conditions Monday and Monday night with showers and thunderstorms. Winds east 5 to 10 knots Sunday, southerly 5 to 10 knots Sunday night, then southwest 10 to 15 knots Monday, and southwest 10 knots Monday night.
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&& .MARINE...
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SCA is in effect for all waters but is not currently occuring anywhere. Will leave up but let evening shift consider if this should remain. There is an approaching boundary but it is not very strong - showers/isolated thunderstorms will be possible around midnight. No marine hazards expected Sunday and Sunday night. Small craft advisories possible Monday and Monday night. Winds east 10 knots Sunday, southeast 10 knots Sunday night, increasing southwest 15 knots gusts 20 knots Monday, and southwest 10 to 15 knots Monday night.
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&& .TIDES/COASTAL FLOODING...
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The evening high tide cycle is the lower of the two so no coastal flood threat. Later shifts will have to contemplate the Friday morning 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 5 AM EDT Friday for ANZ531>534-537- 539>541-543. Small Craft Advisory until midnight EDT tonight for ANZ530-535- 536-538-542.
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&& $$ PRODUCTS...WOODY!/KLW

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