Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 211853 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 253 PM EDT Sun May 21 2017 .SYNOPSIS...
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A stationary front over the Carolinas will lift north into the area tonight. A cold front will move through the area Monday. High pressure will briefly return Monday night before low pressure develops over eastern Carolina Tuesday and moves northeast off the DelMarVa into Wednesday. Upper-level low pressure will linger over the area into Friday.
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&& .NEAR TERM /TONIGHT/...
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Visible satellite shows both the cloud cover from the stationary boundary over the Carolinas and the approaching boundary over WV, and composite radar shows rain from Lake Ontario to western NC. That rain is pushing slowly east and will affect the Mid Atlantic tonight from west to east. We have categorical PoPs at some time overnight everywhere in the forecast area. 1/4 to 1/2 inch will be possible. Little diurnal temperature variation - lows in the lower 60s east to mid 50s west.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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The rain probably will not have exited the coast by morning. Likely PoPS will persist east of the mountains. Some improvement in sky coverage is expected in the afternoon. High temperatures should reach the mid 70s, with the warmest temps being near Petersburg, WV where the sun will shine the longest. But in spite of that mention of sun the Mid Atlantic will be in a very wet string of weather. Upper trof is progged to move over the upper midwest while east coast moves into a feed of southerly moisture. There is some disagreement among the models regarding the timing of a short wave developing in the eastern trof - GFS is fastest with it passing through eastern VA Tuesday afternoon. Other models are slower. Have PoPs at likely levels east of the mountains Tuesday afternoon/night. These will need to be refined based on later model runs and probably need to be raised to categorical in the east. Total QPF could exceed one inch. Lows Monday night in the 50s (except warmer in the cities). Highs Tuesday primarily around 70, Rain chances will persist into Tuesday night given the upper level low moving into the Ohio Valley and moist southerly flow coming into the Mid Atlantic.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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There is a liklihood of rain showers Wednesday and Wednesday night as a broad storm system to the west sends energy into the mid- Atlantic region. The slow-moving low pressure system will allow for the chance for rain showers and a few thunderstorms to linger across the region Thursday into Thursday evening. The chance for rain showers shift to the Mason-Dixon line and adjacent areas Friday as the storm system finally departs northeast into New England. By Friday night and Saturday, weak high pressure will move into the region. Dry conditions and a gusty breeze should ensue. Rain showers get re-introduced to the region Saturday night and Sunday with a storm system moving east along the Ohio Valley.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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Ceilings presently in lower VFR condition. These will lower tonight as rain overspreads the area...to IFR after midnight. Some improvement expected during the afternoon. Ifr to lifr conditions Wednesday and Wednesday night. Winds south 5 to 10 knots Wednesday becoming light and variable Wednesday night. Mvfr conditions Thursday and Thursday night. Winds west around 5 knots Thursday and Thursday night.
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&& .MARINE...
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SCA in effect for much of the Bay for the remainder of the afternoon, and all of the waters overnight. Portions of the waters may require an SCA Tuesday. No marine hazards Wednesday through Thursday night.
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&& .TIDES/COASTAL FLOODING...
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Easterly onshore has allowed tidal anomalies to rise rather quickly. A Coastal Flood Advisory was issued for St. Marys County. Anamolies increase further...with minor tidal flooding likely at Straits (Coastal Flood Advisory extends through tonights cycle). Have issued a coastal flood advisory for Annapolis for the overnight high tide cycle. Evacuation from the estuary appears unlikely through at least Monday (and perhaps longer)...which will keep tidal levels elevated with continued minor flooding possible at the most sensitive sites near times of high tide.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory from 1 AM to 5 AM EDT Monday for MDZ014. Coastal Flood Advisory until 3 AM EDT Monday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 5 AM EDT Monday for ANZ530>533- 538>542. Small Craft Advisory from 8 PM this evening to 8 AM EDT Monday for ANZ534-537-543. Small Craft Advisory from 8 PM this evening to 5 AM EDT Monday for ANZ535-536.
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&& $$ PRODUCTS...WOODY!/KLW

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