Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221858 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 258 PM EDT Wed Mar 22 2017 .SYNOPSIS...
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High pressure will build across the area tonight, and move offshore Thursday night. A warm front will cross the region Friday. Low pressure may affect the area Sunday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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High pressure over the Great lakes this afternoon will crest over the forecast area by Thursday morning. That will lead to decoupling of the wind field (the gradient has already started to relax) and radiational cooling. The best cooling will occur in the mountains, where lows will be in the teens. However, the entire area will be in the 20s by sunrise tomorrow. Ultimately, the extent of radiational cooling will depend upon when winds diminish. With dewpoints near 10 above, there is plenty of room for cooling, and the source of the uncertainty.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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Warm advection will commence by Thursday afternoon, and the axis of the high will move offshore by Thursday night. It is less certain whether the warming will be realized at ground level during the day. Therefore, forecast highs will be similar to today. The warming will begin to mix to the surface Thursday night. The ECMWF has been (and continues to be) much wetter than other guidance late Thursday night into early Friday morning near a warm front. Given warming aloft, that suggests a freezing rain threat. The ECMWF is alone in this solution; other guidance is all dry. Have reduced PoPs a pinch (have 20-30% in database). Am reluctant to remove PoPs outright, but at the same time am skeptical whether this will pose an impact. Forecast area will be on the warm side of the upper ridge on Friday. Highs near 60; lows 45-50.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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Warm southerly flow over our area as a high pressure sits offshore- will allow for well above normal temperatures on Saturday... reaching the 70s for most locations... 60s otherwise. Backdoor cold front pushes south Saturday night into Sunday and stalls near or above our CWA into Monday as low pressure approaches the southern Great Lakes. PoPs will be increasing as this low continues to move ENE through the front Sunday into Monday. There seems to be a drier period sometime Monday night into early Tuesday before a cold front pushes through the area Tuesday into Tuesday night as PoPs increases. Dry conditions return on Wednesday. High temperatures Sunday into Tuesday will be in the 50s and 60s, and in the 40s on Wednesday behind the front.
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&& .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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VFR flight conditions will prevail through the valid TAF period. Gusty northwest winds are diminishing, with gusts 20-30kt through sunset. Winds will continue to diminish, with winds less than 10 kt overnight. Few if any clouds through this period. Mostly clear/clear skies and light winds will continue through Thursday. South/southwesterly flow Thursday night into Friday. Clouds will overspread during this period. Do not anticipate flight restrictions during this period. Precipitation should remain north of the terminals. There is a slight chance that precip could move in before all cold air departs-- this would affect only MRB. Have low confidence that this would occur. Dry/VFR and warm conditions expected on Saturday. A front pushes south and stalls over our area Sunday and increases probability of precip over our region into Monday with possible sub-VFR periods.
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&& .MARINE...
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Winds continue to diminish. Will replace all Gale Warnings with Small Craft Advisories. The Small Craft will be able to be trimmed through the evening. WInds will be light Thursday and Thursday night. Southerly flow will increase again Friday. Dry and warm conditions expected on Saturday. A front pushes south and stalls over our area Sunday and increases probability of precip over our region into Monday with possible. Winds are expected to remain below the SCA threshold trough this period.
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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 8 PM EDT this evening for ANZ530- 531-538>540. Small Craft Advisory until 4 AM EDT Thursday for ANZ532>534- 537-541>543. Small Craft Advisory until 8 PM EDT this evening for ANZ535- 536.
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&& $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...IMR AVIATION...HTS/IMR MARINE...HTS/IMR

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