Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 280046 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 846 PM EDT SUN JUL 27 2014 .SYNOPSIS...
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LOW PRESSURE WILL TRACK ACROSS PENNSYLVANIA TONIGHT. AN ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION MONDAY. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING COOLER AND DRIER CONDITIONS DURING MIDWEEK.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR PORTIONS OF NORTHERN AND WESTERN MARYLAND...THE EASTERN WEST VIRGINIA PANHANDLE AND INTO THE NORTHERN SHENANDOAH VALLEY OF VIRGINIA UNTIL 2 AM. THUNDERSTORMS HAVE BEEN SLOWER TO MOVE INTO/DEVELOP ACROSS THE CWA THAN SOME GUIDANCE HAD EARLIER SUGGESTED. HAVE HAD ONE CELL IN WV /IN THE WATCH AREA/ THAT WE HAVE WARNED ON AND THAT HAS BEEN THE STRONGEST CELL WITHIN OUR CWA THUS FAR. 18Z KIAD RAOB REVEALED A CAP ACROSS THE CWA /AND SOME DRY AIR TOO/...BUT THAT CAP HAD DISAPPEARED BASED ON THE 00Z KIAD RAOB. DESPITE THE SETTING OF THE SUN...EXPECTATION IS FOR AN INCREASE IN CONVECTION DURING THE MID TO LATE EVENING AS LARGER SCALE LIFT AND SHEAR INCREASE. WITH THIS...THE SEVERE RISK WILL CONTINUE WITHIN THE WATCH AREA AND COULD ALSO EVENTUALLY SPREAD FURTHER DOWNSTREAM OF THE CURRENT WATCH EARLY TONIGHT. ACTUAL COLD FRONT LIKELY WON/T MAKE IT INTO THE POTOMAC HIGHLANDS UNTIL LATE TONIGHT.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
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THE TROUGH WILL BE OVER NY MONDAY AND WHILE THE COLD FRONT WILL MOVE OFF THE COAST. AS ENERGY ROUNDS THE BASE OF THE TROUGH MONDAY SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE MAINLY I-66 AND NORTH MONDAY AFTERNOON. NW WINDS WITH GUSTS UP TO 30 MPH WILL BE POSSIBLE IN THE AFTERNOON. FCST MIN TEMPS MONDAY NIGHT RANGE FROM THE MID 50S IN THE HIGHLANDS TO THE LOW 60S NEAR THE METROS AND WATERS. NRLY WINDS WIL CONTINUE TUESDAY AND TEMPS WILL ONLY RISE INTO THE UPPER 70S WHICH WILL FEEL LIKE A FALL DAY FOR THE MID-ATLATNIC.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... MEAN TROUGHING WILL PERSIST ALOFT OVER THE EASTERN CONUS THROUGH THE REMAINDER OF THE UPCOMING WEEK. DRY AIR AND NORTHWEST FLOW AROUND HIGH PRESSURE AT THE SURFACE WILL KEEP THE REGION DRY AND COOLER THAN NORMAL DURING THIS PERIOD. MODELS INDICATE THE TROUGH AXIS WILL SLOWLY RETROGRADE BACK WEST OF THE AREA LATE IN THE WEEK INTO NEXT WEEKEND AS SUBTROPICAL RIDGING RE-ESTABLISHES ITS HOLD OVER THE WESTERN ATLANTIC. AS THE TROUGH MOVES BACK/REDEVELOPS TO OUR WEST...WINDS WILL BECOME SOUTHERLY INCREASING THE HEAT AND HUMIDITY AS WELL AS THE CHANCES OF SHOWERS AND THUNDERSTORMS. THE LONGWAVE PATTERN BY THE END OF NEXT WEEKEND WOULD SUGGEST A POTENTIAL FOR HEAVY RAIN GIVEN THE LONG AND PERSISTENT TRAJECTORY OF WIND OUT OF THE GULF OF MEXICO RIDING ALONG A STALLED OR SLOW-MOVING FRONT. && .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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CHALLENGING THUNDERSTORM FORECAST THIS EVENING. HAD BACKED OFF ON TSRA A COUPLE OF HOURS IN 00Z TAFS. WHILE THERE STILL REMAINS SOME UNCERTAINTY IN COVERAGE AND TIMING...CONTINUED THE OVERALL TREND IN AN INCREASE IN COVERAGE DURING THE MID TO LATE EVENING...WITH POTENTIAL IMPACT AT HUBS MAINLY 02Z-06Z TIME FRAME. N-NW WINDS WILL MOVE IN AS A COLD FRONTAL PASSAGE OCCURS MONDAY. SHRA AND -TSRA IS POSSIBLE MONDAY AS ENERGY MOVES ACROSS THE AREA. NW WINDS AROUND 10-15KTS WITH GUSTS UP TO 25KTS EXPECTED AT THE TERMINALS. NW FLOW GENERALLY 10 KTS OR LESS W/ VFR TUE-THU.
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&& .MARINE...
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SOUTHERLY CHANNELLING WILL LIKELY SUPPORT OCCASIONAL SCA GUSTS UP THE BAY THROUGH THE OVERNIGHT. ANY LATE EVENING/OVERNIGHT THUNDERSTORMS MAY ALSO PRODUCE STRONG GUSTY WINDS. WINDS WILL BECOME NWLY MONDAY BEHIND A COLD FRONT. A SCA IS IN EFFECT FOR ALL THE WATERS MONDAY. RELATIVELY BENIGN SURFACE PRESSURE GRADIENT WITH HIGH PRESSURE NEARBY OR OVERHEAD TUE NIGHT-FRI IS EXPECTED TO RESULT IN SUB-SCA CONDITIONS ON THE WATERS. WINDS BECOME SOUTHERLY AND INCREASE NEXT WEEKEND...POSSIBLY TO SCA LEVELS BUT THAT IS UNCLEAR THIS FAR OUT.
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&& .TIDES/COASTAL FLOODING...
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ANOMALIES HAVE DECREASED TO AROUND 1/2 FT ON THE WESTERN SHORE OF THE CHESAPEAKE BAY. AT HIGH TIDE...WATER LEVELS WOULD REMAIN BELOW MINOR TIDAL FLOOD THRESHOLDS WITH THESE ANOMALIES.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ530-531- 535-536-538-539-542. SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT MONDAY FOR ANZ530- 531-535-536-538-539-542. SMALL CRAFT ADVISORY UNTIL 7 PM EDT MONDAY FOR ANZ532>534-537- 540-541-543. && $$ SYNOPSIS...HAS NEAR TERM...BPP/HAS SHORT TERM...HAS LONG TERM...DFH AVIATION...BPP/HAS/DFH MARINE...BPP/HAS/DFH TIDES/COASTAL FLOODING...BPP

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