Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271346 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 946 AM EDT Wed Jul 27 2016 .SYNOPSIS... A front will remain stationary across the area through Thursday then lift north Thursday night. Low pressure will track across the area Friday. High pressure builds for early next week && .NEAR TERM /THROUGH TONIGHT/...
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Stalled frontal boundary bisects northern third of the CWA as of 9 AM this morning. This front will drift south to near a line from Petersburg WV to Quantico VA to Solomons MD by mid-afternoon. North of this boundary, winds will become northerly causing dew points to drop. As such, more stable conditions are expected and have trimmed POPs back for this afternoon. Along and south of the boundary, instability will rise this afternoon. Diurnal showers and thunderstorms should develop again across the central Shenandoah Valley to around the Charlottesville area this afternoon. The right-entrance region of an upper-level jet streak may aid in a loosely organized band of thunderstorms passing through this area. Given CAPE values forecast to be 2000+ J/kg and effective bulk shear of 35-40 kts as well as PWATs approaching 2 inches, added a mention of gusty winds and heavy rain for these areas. More isolated showers and thunderstorms are expected further east into the Fredericksburg VA/southern MD area later this afternoon into early evening. With the loss of heating, any convection should wane shortly after sunset.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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500mb flow becomes W-SW Thursday in response of an approaching shortwave trough across the TN Valley. The frontal boundary will lift northward Thursday and Thursday night and the Mid-Atlantic will be in the warm sector. Scattered showers and thunderstorms are expected across the region Thursday afternoon as energy ahead of the shortwave trough moves into the region. Convection will likely persist into the evening hours and a few strong to severe storms are expected. Guidance has been depicting a sfc low moving near or across the region Thursday night into Friday. Uncertainty is low on timing and location but heavy rainfall is possible in an unstable moist airmass. The trough will pass overhead Friday and showers and thunderstorms will be possible. Subsidence behind the trough will likely lead to dry conditions Friday night.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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Multiple sfc waves and impulses aloft are fcst to move through the area during the weekend with the most significant of these Fri afternoon. Showers and t-storms will remain in the fcst through Mon as front remains nearly stationary across the area. By Mon night, most guidance show front pushing far enough south with sufficient dry air as weak high pressure builds in to suppress shower development everywhere with temperatures returning to more seasonable values in the mid to upper 80s.
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&& .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
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Prevailing VFR conditions expected today and tonight. TSRA expected at CHO this afternoon. SHRA/VCTS possible at MRB/IAD/DCA however confidence is low. Coverage will increase Thursday afternoon with SHRA/VCTS expected across the region. Convection will continue Thursday night into Friday and some SHRA/TSRA may produce heavy rainfall resulting in longer sub-vfr conditions overnight Thursday into Friday. Periods of rain during the weekend especially on Sun which may cause some restrictions. Improving weather Mon night on as weak high pressure builds in.
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&& .MARINE...
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Winds less than 15kts will continue on the waters. Showers and thunderstorms are possible on the waters late this afternoon and early evening, but coverage is expected to be isolated. Scattered showers and thunderstorms expected Thursday afternoon through Friday resulting in the potential for gusty winds through the period. SMW may be required in showers and thunderstorms. Winds generally 10 kt or less outside of thunderstorms, but winds and waves higher near thunderstorms.
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&& .CLIMATE...
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Record high minimums were either tied or broken at DCA and IAD airports. New record high minimum of 80F degs set at DCA yesterday breaking the old record of 79F set in 1987. Record high minimum of 76F degs set at IAD yesterday tying the previous record of set in 2005.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...HAS/DFH SHORT TERM...HAS LONG TERM...LFR AVIATION...HAS/LFR MARINE...HAS/LFR CLIMATE...HAS/LFR

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