Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200952 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 552 AM EDT Tue Sep 20 2016 .SYNOPSIS... A weak front is positioned offshore. High pressure will build over the region through Thursday. A cold front will move through the area Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Dense fog advisory issued from central MD to Highland County until 9am. As of 3am, 1010mb surface low pressure over Cape Lookout, NC with a surface ridge around 1020mb stretching from southern New England to the Midwest. Cyclonic flow over the region with light Nly/NEly flow over LWX. Cloud shield is along the Mid-Atlantic seaboard stretching west to the Alleghenies. Breaks in these clouds west of I-95 has allowed fog/low clouds to develop across the Shenandoah Valley and portions of the Piedmont. Will continue to monitor for more than patchy dense fog which is currently covered by a Short Term Forecast. Temperature pattern dependent on cloud cover with mid to upper 70s maxima for cloudy southern MD where scattered light showers are expected and low to mid 80s for the rest of the area.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... Similar cloud pattern tonight though shunted south a little from high pressure to the north. Valley fog likely again with minima generally mid 60s inland (around 60F NW where it will be clearer) and very low PoPs for St. Marys county. Onshore NEly flow Wednesday and Thursday with above normal temperatures under mostly sunny skies. Cloud shield looks to be along southern periphery of the CWA. Low PoPs limited to far SWrn zones. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... The extended part of the forecast should be fairly quiet. The big story should be the cold frontal passage during the second half of Saturday. Friday should be an above-average-temperature day with highs in the mid to upper 80s. Given the trajectory of the front - from the north...the air ahead of it will not be moisture rich... hence chances and amounts of rain will be scant. Autumn begins on the 22nd...and the second half of the weekend will give us some taste of what is to come. Cooler air will push into the Mid Atlantic...taking the highs back into the 70s. What should really feel autumnal is Sunday night - expect to see lows east of the mountains drop into the 50s except for the warmer cities and along the Bay. Monday looks to be a pleasant day ahead of the next cold front. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... IFR conds expected develop through the mid-morning in onshore flow from low along NC coast. Low cigs likely east including DC metros with low vsbys west. Conds improve through the midday hours. Patchy fog tonight. VFR conds prevail Wednesday and Thursday high pressure persists. VFR conditions expected Friday and Saturday. && .MARINE... NEly flow 10-15kt through Thursday as low pressure lingers along the Carolina coast. Winds expected to remain below SCA values Friday. A cold front is expected to push through the waters Saturday afternoon. This could produce showers and gusty winds. && .TIDES/COASTAL FLOODING... No coastal flood headlines as of now. Northeast winds continue on the waters through Thursday as low pressure remains along the Carolina coast. However, anomalies will stay elevated and near action stages into Wednesday. Water levels will continue to be closely monitored with possible minor coastal flooding on the preferred high tide of Wednesday evening. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Dense Fog Advisory until 9 AM EDT this morning for MDZ003>005. VA...Dense Fog Advisory until 9 AM EDT this morning for VAZ025>031- 504. WV...Dense Fog Advisory until 9 AM EDT this morning for WVZ052-053- 055-502-506. MARINE...None.
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