Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221908 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 308 PM EDT Sat Apr 22 2017 .SYNOPSIS...
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A cold front will remain stalled to the south through Sunday. Low pressure will develop along the boundary...impacting our area through early next week. Low pressure will move out to sea Wednesday. A cold front may impact the area late in the week.
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&& .NEAR TERM /THROUGH SUNDAY/...
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Latest surface analysis depicts a cold front continuing to slide southward across southern Virginia, accompanied by a weak wave of low pressure. High pressure is centered over the Great Lakes and pushing east. Another low pressure is located to the south in Mississippi. Aloft, a trough of low pressure extends from Quebec southwestward to a closing-off low near St. Louis. Tonight, the front and weak low pressure wave will continue sliding southeastward away from our region, allowing cooler Canadian air associated with the high pressure to continue sliding southward into our region. Some instability aloft could bring a rumble of thunder to central Virginia and far southern Maryland over the next few hours, but otherwise it should be just some rain. As the shortwave aloft separates from the low closing off to the west and shifts east, precipitation should gradually wind down this evening from northwest to southeast, though with the front stalling in North Carolina and the closed low to the west starting to approach, rain may not completely end in far southern parts of the CWA. Temperatures will fall into the 40s. During the day Sunday, it now appears that drier Canadian air will press southward far enough to dry us out, though there may still not be much sun. The exception again will be the far south, central VA and southern MD, where some rain may linger through the day due to the proximity of the front and approaching closed low. Further north, there may be some breaks of sun, but otherwise it should be fairly cloudy and cool, with highs in the 50s to near 60.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
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Closed low aloft and associated surface system will continue sliding east across the southern US Sunday night, then turn northeast up the Atlantic Coast by Monday night. This will cause rain to overspread the region again, with temperatures remaining cool. An increasing northeast wind as the surface low strengthens will add to the rather uncomfortable weather, especially compared to recent warmth. Significant rain is possible, perhaps 1 to 3 inches. If heavy rainfall becomes concentrated, it is possible some flooding could occur, but right now, given it has generally been dry and there remains great model inconsistency about where any heavy rain may ultimately fall, do not have any plans for flood watches yet. This will no doubt be revisted by future shifts.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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Coastal low pressure will track north along the Carolina coastline Tuesday. Forecast guidance depicts a broad area of precipitation with this system as the upper level low is nearly stacked on the coastal low. Rain is expected across the region Tuesday into Tuesday night. Bands of heavier rain are possible during this time as easterly LLJ pumps moisture into the Mid- Atlantic. Stable conditions expected with temperatures in the 50s/60s. The coastal low will be off the Delmarva coastline Wednesday and rain will come to an end across the Mid-Atlantic region. Sunshine will help temperatures get closer to 70 on Wednesday. Winds become southerly Wed night ahead of the next cold front. A cold front will pass the region Thu-Fri and showers and thunderstorms are possible. Temperatures will become above normal Thu-Fri.
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&& .AVIATION /19Z SATURDAY THROUGH THURSDAY/...
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MVFR/IFR cigs and vis with rain across the region will slowly improve as drier Canadian air slides into the region this evening. Expect VFR by later tonight except CHO, where low clouds and rain may linger through Sunday. Winds will be northerly but generally less than 15 knots. Conditions likely to return to IFR all terminals Sunday night and linger at MVFR/IFR levels through Monday night with increasing northeast winds as a coastal low makes its way northeast up the Atlantic Coast. Low ceilings and vsbys possible Tuesday-Tuesday night as rain continues.
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&& .MARINE...
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Generally marginal SCA conditions across the bay and some adjacent waters through Sunday night as high pressure nudges in from the northwest while low pressure approaches from the southwest. SCA likely to continue Monday and Tuesday as the low moves northeast up the Atlantic Coast. An isolated thunderstorm may reach the central Chesapeake Bay and lower tidal Potomac over the next few hours, but otherwise not expecting thunder through Tuesday. Condtions may start to improve Wednesday.
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&& .TIDES/COASTAL FLOODING...
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A persistent onshore flow has already significantly elevated water levels in parts of the bay, with minor flooding having occurred at Straits Point this morning. This potential will continue through the next several days, with the greatest risk of minor flooding occurring later Sunday through Tuesday as a coastal low pressure moves northward into the region.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EDT Sunday for ANZ539. Small Craft Advisory from 6 PM this evening to 6 PM EDT Sunday for ANZ531-540. Small Craft Advisory until 6 AM EDT Sunday for ANZ542. Small Craft Advisory from 6 PM this evening to 6 AM EDT Monday for ANZ543. Small Craft Advisory until 6 AM EDT Monday for ANZ532>534-537- 541. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...HSK AVIATION...HSK/RCM MARINE...HSK/RCM TIDES/COASTAL FLOODING...BJL/RCM

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