Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 261417 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1017 AM EDT Fri May 26 2017 .SYNOPSIS... Weak high pressure will return to the area tonight before moving off the coast Saturday afternoon. A warm front will stall out overhead Saturday night through Sunday. A stronger cold front will pass through the area late Sunday night. && .NEAR TERM /THROUGH SATURDAY/... Low pressure will move off the New England Coast tonight while high pressure approaches from the west. A tight pressure gradient between these two systems will cause breezy conditions today. Frequent gusts around 25 to 30 mph are expected from the west to northwest through this afternoon. 500mb heights will rise a bit this afternoon...but daytime heating should still be enough to cause limited instability underneath a strengthening subsidence inversion. This will cause a bkn cu deck across many locations along with isolated to widely scattered showers. The best chance for showers will be across the northern half of the CWA where the lower heights will hang on a bit longer. Even across these areas...much of the time will be dry. Max temps will range from the lower 60s in the mountains to lower 70s in northern Maryland...to the lower 80s in central Virginia. High pressure moves overhead tonight. Clearing is expected this evening but clouds return after midnight as the next system approaches from the Mid-West. Temps will drop into the mid to upper 50s tonight. Low pressure will move into the southern Great Lakes tonight while a warm front approaches the Ohio Valley/Appalachians Mtns. Showers are expected to move across the mtns into Saturday morning. The ECMWF-Hi Res is depicting a complex moving into the region Saturday morning that may bring widespread showers across the area. At this time conditions will likely be stable and due to the spread in QPF guidance confidence is low in the coverage. The warm front will move into the Mid-Atlantic region by Saturday afternoon. Showers and thunderstorms are expected in the warm sector mainly south of a line stretched from the Potomac Highlands to southern MD. 0-6 km bulk shear will increase to 40-50 kts across the warm sector. Dewpts will rise into the mid to upper 60s and 1-2 J/Kg of CAPE are expected. This will allow some thunderstorms to become strong to severe. There is a slight chance/15% of severe weather Saturday afternoon in the locations mentioned above. All threats, large hail, dmg winds and isolated tornadoes are possible. People planning to be outside Saturday should remain aware of changing weather conditions. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... Low pressure from the Great Lakes will move east and stretch down into the Mid-Atlantic region Sat night. This will push the warm sector to the south and east. A shortwave trough is expected to dive south across New England Sat night and showers will be possible through the night mainly across northern MD. An upper level ridge will move overhead by Sun morning and a brief period of dry conditions are expected. The active period continues later Sunday as another low pressure system approaches from the Great Lakes. Showers will move across the Appalachians Sunday afternoon. At this time...areas east of the Blue Ridge should be mostly dry Sun afternoon however this system may speed up resulting in showers across the region Sunday. Temps will reach the 70s Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Sunday evening could be a very active period according to latest 00Z ECMWF as it shows a sharp cdfnt moving through the area. Flash flooding appears the biggest concern given very wet antecedent conditions. A flash flood watch may be needed for the 18Z Sun- 06Z Mon time frame for parts of the area. By 06Z Mon, the cdfnt should be east of the area with wx conditions improving. Next week, conditions look relatively benign compared to this week as dry westerly flow establishes. Memorial Day looks nice under weak high pressure. A weak cdfnt will bring a chance of showers around the Tue-Tue night time frame with weak high pressure building again for the second half of next week. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... VFR conditions are expected through tonight. West to northwest winds will frequently gust around 20 to 25 knots through this afternoon. Isolated gusts around 30 knots are possible during this time. Winds will quickly diminish around sunset this evening. A few showers and thunderstorms are possible Saturday. Some storms may become strong to severe during the afternoon and evening hours. Sub-VFR conditions expected Sunday into Monday with rounds of showers and thunderstorms moving through our region with a boundaries stalled/moving through. Conditions will begin to improve late Sun night through the first half of next week as cdfnt pushes east and sw flow develops allowing for much needed drying. && .MARINE... A Small Craft Advisory is in effect for all of the waters today due to gusty west to northwest winds expected behind departing low pressure. Isolated to widely scattered showers are expected this afternoon. There is a concern that these showers may produce locally gusty winds. Winds will quickly diminish toward sunset and showers will dissipate as well. Weak high pressure will build overhead tonight before moving offshore Saturday. A warm front will stall out near the waters later Saturday through Saturday night. Additional showers and thunderstorms are possible during this time...especially Saturday afternoon and evening. Winds remain below SCA through Sunday afternoon. Gradient winds will remain below SCA all of next week, but winds and waves can be locally higher near thunderstorms especially Sunday night. && .TIDES/COASTAL FLOODING... Tidal anomalies will continue to decrease today due to a strengthening offshore flow. This morning`s high tide should be the last with coastal flooding issues for most locations except at Straits Point. Minor flooding is likely during the high tide cycle this afternoon...but water levels should be much lower compared to recent high tides. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 1 PM EDT this afternoon for DCZ001. MD...Coastal Flood Advisory until 1 PM EDT this afternoon for MDZ508. Coastal Flood Advisory until 11 AM EDT this morning for MDZ011. Coastal Flood Advisory until 5 PM EDT this afternoon for MDZ017. VA...Coastal Flood Advisory until 1 PM EDT this afternoon for VAZ054. WV...None. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ530>543. && $$ SYNOPSIS...LFR NEAR TERM...BJL/HSK SHORT TERM...HSK LONG TERM...LFR AVIATION...BJL/LFR MARINE...BJL/LFR TIDES/COASTAL FLOODING...BJL/LFR

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