Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 090751 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 351 AM EDT WED JUL 9 2014 .SYNOPSIS...
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A COLD FRONT OVER THE GREAT LAKES WILL APPROACH TODAY AND MOVE THROUGH THE AREA TONIGHT. THE FRONT WILL STALL OUT TO THE SOUTH THURSDAY THROUGH FRIDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTH.
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&& .NEAR TERM /THROUGH THURSDAY/...
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AN UPPER LEVEL TROUGH PERSISTS ACROSS THE NRN GREAT LAKES TODAY. A COLD FRONT IS DRAPED ACROSS THE SRN GREAT LAKES AND SOUTHERLY FLOW AHEAD OF IT HAS LED TO SCT SHOWERS AND THUNDERSTORMS ACROSS THE OHIO VALLEY EARLY THIS MORNING. A CLUSTER OF SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE ACROSS THE ALLEGHENY FRONT. LOWER DEWPTS AND LESS THAN 500 J/KG OF CAPE WILL LIKELY LEAD TO WEAKENING. ELSEWHERE...PARTIAL CLEARING WILL AIDE IN FOG DEVELOPMENT ESPECIALLY IN VALLEY LOCATIONS WITH HIGHER DEWPTS. DEWPTS RANGE FROM THE LOW 60S IN THE POTOMAC HIGHLANDS TO THE MID 70S IN SRN MD. A SFC TROUGH IS LOCATED ACROSS DELMARVA/SRN MD/CHO THIS MORNING AND WILL STAY NEARLY STATIONARY TODAY. DEWPTS NEAR 70 WILL RESULT IN MARGINAL INSTABILITY WITH CAPE VALUES AROUND 1-1.5 J/KG BY THIS AFTERNOON. A 90KT UPPER LEVEL JET WILL APPROACH THE MID ATLANTIC THIS AFTERNOON. SHEAR WILL INCREASE AND THUNDERSTORMS WILL FORM NEAR THE BOUNDARY THIS AFTERNOON. FURTHER NORTH...ISO SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE BUT MOST OF THE FORCING WILL BE FURTHER SOUTH NEAR THE SFC TROUGH...CHO-DCA-BWI AND SOUTH. ISOLATED SVR IS POSSIBLE IN THIS AREA LATE THIS AFTERNOON. FCST MAX TEMPS ARE IN THE MID TO UPPER 80S TODAY. THE SFC TROUGH WILL CONTINUE INTO TONIGHT AND SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE ACROSS SRN MD AND SURROUNDING WATERS THIS EVENING. A COLD FRONT WILL CROSS THE REGION OVERNIGHT AND NRLY WINDS WILL AIDE IN RELIEF BY BRINGING IN DRIER AIR. SWLY FLOW ALOFT WILL LEAD TO DISTURBANCES CROSSING THE REGION THURSDAY AFTERNOON. SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE MAINLY ALONG RIDGELINES WHERE TERRAIN CIRCULATIONS WILL BE POSSIBLE. FCST MAX TEMPS ARE IN THE LOW TO MID 80S THURSDAY.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
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COLD FRONT WILL RESIDE SOUTH OF THE CWA THURSDAY NIGHT INTO FRIDAY...WITH HIGH PRESSURE TO THE NORTH. THIS SHOULD LEAD TO A RELATIVE LULL IN CONVECTION DURING THE FORECAST PERIOD BUT STILL CAN/T RULE OUT A FEW THUNDERSTORMS DURING PEAK HEATING FRIDAY AFTERNOON MAINLY ACROSS THE SOUTHERN TIER OF THE CWA CLOSER TO THE BOUNDARY AND WHERE MOISTURE AND INSTABILITY MAY BE A LITTLE BETTER. STAYED CLOSE TO MOS WITH NEAR CLIMO TEMPS.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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WHATEVER IS LEFT OF THE BOUNDARY MENTIONED IN THE SHORT TERM WILL LIKELY LIFT BACK NORTH AS A WARM FRONT OVER THE WEEKEND...PROBABLY MORESO SUNDAY. THIS WILL ALLOW DEWPOINTS/PRECIPITABLE WATER VALUES TO CREEP UPWARD. FLAT RIDGING MAY HELP TO CURB A LOT OF THUNDERSTORM ACTIVITY ON SATURDAY BUT A FEW DIURNAL STORMS CAN/T BE RULED OUT. SLIGHTLY LOWER HEIGHTS AND A SURFACE TROUGH MAY HELP FOR A LARGER COVERAGE FOR SUNDAY. THIS TREND CONTINUES ON MONDAY AS A COLD FRONT ENTERS THE CWA...GRADUALLY PUSHING THROUGH DURING THE MIDDLE OF THE WEEK. UNTIL IT MOVES THROUGH THERE WILL BE A CHANCE OF CONVECTION.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
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MVFR VSBYS WILL BE POSSIBLE EARLY THIS MORNING MAINLY AT IAD DUE TO RECENT RAINFALL AND CLEAR SKIES. A SFC TROUGH WILL REMAIN TO THE SOUTH TODAY AND TSRA WILL BE POSSIBLE ACROSS CHO-DCA-BWI-MTN THIS AFTERNOON. VCTS EXPECTED ELSEWHERE. GUSTY WINDS WILL BE POSSIBLE WITHIN THUNDERSTORMS. A COLD FRONT WILL CROSS THE REGION TONIGHT AND WINDS WILL BECOME NWLY THURSDAY. ISO TSRA IS EXPECTED THURSDAY AFTERNOON. FRONTAL BOUNDARY REMAINS TO THE SOUTH FRIDAY INTO SATURDAY THEN LIFTS BACK NORTH SUNDAY. BEST CHANCE OF CONVECTION DURING THIS TIME LOOKS TO BE SUNDAY.
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&& .MARINE...
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SWLY WINDS WILL CONTINUE TO SUBSIDE ACROSS THE WATERS THIS MORNING. A SFC TROUGH WILL BRING SHOWERS AND THUNDERSTORMS TO THE WATERS THIS AFTERNOON AND EVENING. SOME MAY BRING GUSTY WINDS AND LOW VSBYS. A COLD FRONT WILL CROSS THE WATERS TONIGHT AND WINDS WILL BECOME NWLY AND BELOW SCA CRITERIA. RELATIVELY WEAK GRADIENT SHOULD PRECLUDE SCA CONDITIONS INTO THE FIRST PART OF THE WEEKEND. WILL HAVE TO WATCH SOUTHERLY FLOW BY SUNDAY AS MARGINAL SCA CONDITIONS MAY BE POSSIBLE UP THE BAY BY EVENING.
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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...HAS/BPP NEAR TERM...HAS SHORT TERM...BPP LONG TERM...BPP AVIATION...HAS/BPP MARINE...HAS/BPP

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