Area Forecast Discussion
Issued by NWS Sterling, VA

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119 FXUS61 KLWX 271142 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 742 AM EDT Sat May 27 2017 .SYNOPSIS... High pressure overhead this morning will move offshore later today. A wave of low pressure will move across the area this afternoon or evening pushing a weak front south of the area late tonight. A stronger cold front will move through the area Monday. High pressure will return to the area mid next week. && .NEAR TERM /THROUGH TONIGHT/...
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Weakening t-storm complex over SW PA this morning is associated with a low pressure system over Ohio. Weakening showers will move across northern portions of the CWA through the rest of the morning. The low pres center will move east across the area this afternoon or this evening and will set up a warm front across the southern half of the fcst area. NSSL WRF- ARW and instability fcst fields from different models indicate the area from Augusta county south and east through Charlottesville will be the prime area for strong potentially severe convective development later this afternoon and early this evening. Damaging winds and large hail appear to be the main threat. 0-6km flow around 30kt should keep storms moving with flash flooding risk low despite saturated soils and potential training convection. The low pres system and associated front will push south of the area later tonight with showers ending.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Sunday will likely start out quiet, but with plenty of low clouds. Low pressure will be tracking from the mid-MS valley to southwest Ontario by late Sunday night. A sfc trof will establish across the area during the afternoon with PWATs increasing over 1.5 inches. Widespread convection appears likely Sun afternoon and evening with potential for flash flooding especially west of the Blue Ridge given saturated soils. Convection begins to weaken and shift east late Sun night due to loss heating and sfc trof shifting east. Convection could redevelop east of the Blue Ridge Mon afternoon with actual frontal passage.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/... Upper level low pressure will be slowly moving across Ontario and Quebec during the Tuesday through Thursday time frame. While overall flow will be from the SW to W aloft, there will still be opportunities for shortwave troughs to dive through the area. It does appear there will be two additional boundaries following Monday`s front that will drop southeast through the middle of the week. The second (likely late Wednesday or Thursday looks to be the stronger of the two in terms of airmass change. While this pattern is a little unsettled, rain chances should be scattered and instability for thunderstorms limited. Ensemble spread increases toward the end of the weak regarding the upper air pattern and evolution of the closed low. However, there should be a dry period at some point as surface high pressure builds into the area behind the cold front. Above normal temperatures on Tuesday will decrease through the remainder of the week behind the frontal passages. Highs will settle into the 70s with lows in the 50s, which is near normal. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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VFR conditions become MVFR in morning showers for DC metros and north. KCHO is most vulnerable to t-storms today with brief MVFR/IFR conditions possible. Widespread convection Sun evening with flying restrictions likely. Overall Tuesday and Wednesday should be VFR, but there could be some scattered showers and perhaps a thunderstorm as weak fronts move through the area.
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&& .MARINE...
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Light and variable flow this morning becoming south as weak low pressure approaches through the day. The weak low crosses the VA part of the Chesapeake Bay this evening with more variable flow becoming NEly overnight. Flow becomes southerly Sunday with a weak cold front moving through the waters Monday/Memorial Day. Winds are forecast to remain below SCA criteria Tuesday and Wednesday, although a cold front on Wednesday could lead to slightly higher winds.
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&& .TIDES/COASTAL FLOODING...
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Elevated water levels continue from recent onshore flow. The immediate DC area will see minor flooding with the preferred high tide mid-morning and an advisory is out through midday. Weak low pressure crosses the Chesapeake Bay this evening with light southerly flow this afternoon and again Sunday. Elevated water levels persist through the rest of the holiday weekend with Straits Point in St. Marys county being the most susceptible to minor flooding, particularly on the preferred high tide.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...None.
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&& $$ SYNOPSIS...BAJ/LFR NEAR TERM...BAJ/LFR SHORT TERM...LFR LONG TERM...ADS AVIATION...BAJ/ADS/LFR MARINE...BAJ/ADS/LFR TIDES/COASTAL FLOODING...BAJ

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