Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 301400 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1000 AM EDT Thu Jun 30 2016 .SYNOPSIS... High pressure will move offshore today. A warm front across the Carolinas will lift north tonight into Friday. A cold front will move into the region Friday night. High pressure will return to the Great Lakes and northeast for the weekend. A frontal boundary is expected to hover over the Mid Atlantic Sunday night and Monday. && .NEAR TERM /THROUGH TONIGHT/... High pressure will move off to the east today and a southerly flow will develop...ushering more moisture into the area. Increased dewpoints will lead to more instability...and a pressure trough along with terrain circulation will act as lifting mechanisms to trigger scattered showers and thunderstorms this afternoon. The best chance for convection will be along the terrain into central Virginia where moisture will be highest. Having that been said...instability should remain somewhat limited with the deeper moisture remaining off to our south. This will minimize the threat for severe thunderstorms. Farther north and east across the Washington and Baltimore Metropolitan areas into northern Maryland...northern Virginia and the eastern West Virginia Panhandle most of the day will be dry. Any convection will be isolated and confined mainly to the late afternoon hours. Moisture advection will continue this evening. A few more showers and thunderstorms are possible during this time...but coverage should remain isolated to widely scattered. Will attempt to preserve a diurnal component as CAPE only a couple hundred joules; thus just have a few showers after midnight and a dry pre- dawn period. Clouds should be plentiful, but the increased humidity also makes fog a possibility by early Friday morning. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Friday`s forecast will be a little bit complicated. There will be the isentropic ridge in the eastern (metro) part of the forecast area. Meanwhile, a shortwave and surface cold front will be crossing the northeastern US. Both features would be capable of supporting convection given daytime heating. The former will be pushing east ahead of the front, primarily affecting the Eastern Shore/Delmarva; while the latter doesnt arrive until Friday night. Area may end up in between the two, but wish to broaden the range in forecast grids to account for uncertainty. Highest PoPs will be in the east. Will introduce chances in the west for the afternoon and early evening. While shear will be present, the other factors either aren`t aligning well or are poorly timed. Thus, will be forecasting scattered, non-severe convection. Will need to monitor the strength of the shortwave/surface convergence though-- the setup is quite similar to Tuesday. The cold front forecast to push through Friday night. (How often can one say that that for successive cold fronts in the Mid Atlantic in early July?) Given support of numerous model runs, am fairly confident that this will lead to a partly-mostly sunny Saturday...even though this solution is a departure from climatology. The only wrinkle may be the extent of high level clouds, as the jet stream will be overhead. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Zonal flow aloft is expected Sunday as a stationary front is located across the southern Mid-Atlantic region. The front will waver into Monday and showers will be possible in vicinity of the front... mainly across central VA and southern MD. The front is expected to retreat northward as a warm front into Tuesday. Showers may increase in coverage Monday night into Tuesday night. A shortwave trough may impact the region Wednesday and Thursday. Temps should stay below normal Sunday-Monday and near normal Tuesday-Wednesday. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... VFR flight conditions should generally prevail today. A warm front will approach the terminals late today and tonight. With it, thunderstorm chances increase. Scattered areal coverage preclude TAF mention at this time. However, the increase humidity may yield areas of fog. Will only be forecasting local predawn MVFR Friday morning, due in part to anticipated cloud cover. There is the potential for it to be worse. A cold front will approach the terminals on Friday, and cross Friday night. Scattered thunderstorms will be possible, especially during the afternoon and evening hours. Local IFR would be possible within any thunderstorms, but their coverage in doubt at this time. High pressure/VFR returns for Saturday. VFR conditions expected Sunday-Monday. && .MARINE... The flow will turn toward the south and southeast today into tonight...but wind speeds will remain below SCA criteria. The gradient will tighten on Friday as a cold front approaches. However, do not have much confidence in any strong winds outside of thunderstorms. There are a couple of possible period of storms... tonight as humidity returns, and Friday ahead of the cold front. The storms on Friday likely will be stronger, and may be capable of producing storms requiring Special Marine Warnings. The cold front will clear the waters Friday night, with high pressure returning Saturday. If mixing is strong enough, there may be a window of opportunity for Small Craft Advisory gusts behind the front Friday night-Saturday morning. Sub-SCA expected on the waters Sunday-Monday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...HTS NEAR TERM...BJL/HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...BJL/HTS MARINE...BJL/HTS is the U.S. government's official web portal to all federal, state and local government web resources and services.