Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 170024 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 824 PM EDT Thu Mar 16 2017 .SYNOPSIS... High pressure will gradually build east from the mid-Mississippi valley through early Friday. A warm front will move into the area Friday night into early Saturday before a cold front passes through Saturday afternoon. High pressure builds over the area for the second half of the weekend into early next week. && .NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
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High pressure will continue to build in from the west tonight, cresting near the region early Friday morning. This will lead to slackening winds, clear skies, and radiational cooling. Temperatures will once again be quite cold for mid March, with lows from the upper teens in the coldest locations to upper 20s in the urban centers.
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&& .SHORT TERM /7 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... High pressure will move offshore Friday and low pressure will track into the western Great Lakes during this time. The warm front associated with the low will approach the region Friday before moving overhead Friday night. Clouds will increase ahead of the warm front through midday. A period of rain and snow will likely develop later Friday afternoon and last into Friday night. The best chance for snow will be across northern Maryland...extreme northern Virgina...eastern West Virginia and for locations along and west of the Allegheny Front. However...a southerly flow ahead of this system will allow for surface temps to get above freezing during the day Friday. Therefore...any accumulation should be light and confined to grassy surfaces. The one exception will be for locations along and west of the Allegheny Front where 1-3" inches are most likely with surface temps near or even below freezing. Warmer air will work its way in aloft later Friday evening into overnight...causing most of the precipitation to fall as rain during this time. However...surface temps may be near freezing right along the Mason Dixon Line. A few pockets of freezing rain cannot be ruled out but confidence is low. Any freezing rain would most likely be on elevated surfaces with most paved surfaces being wet due to the warmer conditions preceding this on Friday. Upper-level low pressure will dive south toward our area Saturday while a cold front also moves through the area. A dry slot will allow for much of the day to be dry...but there should be enough instability for a few showers. Snow showers are possible in the mountains as colder air filters in Saturday afternoon behind the front. Saturday will turn out to be much milder compared to recent days for the valley locations as well as the Washington and Baltimore Metropolitan areas. The upper-level low will slowly pass through our area Saturday night. Blustery and chillier conditions will return along with a few rain and snow showers possible. The best chance for snow showers will be in the mountains and across northern Maryland. Accumulating snow is likely along/west of the Allegheny Front. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Cold and breezy conditions expected Sunday as upper level low moves away from the Mid-Atlantic coast. High temperatures in the 40s and 50s over our CWA, feeling around 10 to 15 degrees cooler. High pressure builds over our region Sunday night into Monday night, before a weak cold front moves across our area early on Tuesday. High pressure returns behind the front and into Thursday. High temperatures Monday and Tuesday will be in the 50s for most of our CWA, and then reaching the 40s and 50s for Wednesday and Thursday. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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VFR conditions are expected through midday Friday. Any lingering gusts out of the northwest this evening will dissipate overnight. A period of rain and snow is likely later Friday afternoon and Friday night. The best chance for snow will be across KMRB with rain more likely elsewhere. Sub-VFR conditions are possible during this time. A cold front will pass through Saturday and northwest winds will return later Saturday afternoon through Saturday night. A few rain and snow showers are possible during this time. Cold and breezy conditions Sunday, some showers possible as front moves through. VFR conditions Sunday night into Monday night before another front moves across early on Tuesday. High pressure returns later on Tuesday.
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&& .MARINE...
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Gusty northwest winds will gradually diminish tonight. A Small Craft Advisory remains in effect for portions of the waters tonight. High pressure will move off the coast Friday. A return flow will develop...and a Small Craft Advisory is in effect for portions of the waters again Friday night when the gradient strengthens. A cold front will pass through Saturday and high pressure will approach Saturday night. A Small Craft Advisory may be needed for portions of the waters during this time. Cold and breezy conditions Sunday, some showers possible as front moves through. Dry conditions Sunday night into Monday night before another front moves across early on Tuesday. Winds increase as high pressure builds over later on Tuesday. Small craft advisory possible Sunday.
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&& .CLIMATE... Record low maximum temperatures were set at IAD and BWI yesterday. See RERs for those two airports. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ530>534-537- 539>541-543. Small Craft Advisory from 8 PM Friday to 6 AM EDT Saturday for ANZ532>534-537-540-541-543.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL/MM SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/MM/IMR MARINE...BJL/MM/IMR CLIMATE...LFR

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