Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 250122 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 922 PM EDT MON AUG 24 2015 .SYNOPSIS... A COLD FRONT APPROACHING FROM THE WEST WILL CROSS THE MID ATLANTIC STATES TONIGHT. HIGH PRESSURE WILL GRADUALLY BUILD INTO THE AREA DURING THE MIDDLE OF THE WEEK AND BECOME CENTERED OVER THE AREA FOR THE START OF THE WEEKEND. && .NEAR TERM /THROUGH TUESDAY/...
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WATCHING ONE CLUSTER OF THUNDERSTORMS WHICH STRENGTHENED OVER THE I-95 CORRIDOR NOW APPROACHING THE BAY. AIRMASS IS CHARACTERIZED BY SBCAPE OF 1000-1500 J/KG AND DEEP LAYER SHEAR AROUND 30 KT. THUS THERE HAS BEEN SOME ORGANIZATION...WHICH MAY HAVE BEEN ENHANCED BY A BOUNDARY SEEN LATE THIS AFTERNOON ON RADAR IN THIS AREA. CURRENTLY RADAR AND SATELLITE DO NOT INDICATE ANY FURTHER DEVELOPMENT BEHIND THE ONGOING CLUSTER. HOWEVER ACTUAL COLD FRONT IS STILL OVER THE MOUNTAINS (DEW POINTS STILL NEAR 70 IN PARTS OF THE NORTHERN SHENANDOAH VALLEY)...AND MESOANALYSIS INDICATES INSTBY STILL EXISTS AHEAD OF THE BOUNDARY. HRRR AND RAP HAVE BEEN CONSISTENT WITH DEVELOPING MORE ACTIVITY AHEAD OF THE FRONT. HOWEVER AM NOT TERRIBLY CONFIDENT IN THESE SOLUTIONS...BUT WILL CONTINUE TO MONITOR THE TRENDS. IF ADDITIONAL ACTIVITY WERE TO DEVELOP...IT MAY NOT EXIT FAR SOUTHERN MD UNTIL VERY LATE TONIGHT. WILL ALSO HAVE TO WATCH FOR PATCHY FOG DEPENDING ON TIMING OF CLEARING/DRIER DEW POINTS. COOLEST READINGS TONIGHT WILL LIKELY BE OUT WEST...WITH A MORE MUDDLED PICTURE OF 60S TO LOWER 70S IN THE EAST. HIGH PRESSURE SLOWLY BUILDS IN ON TUESDAY AS THE FRONT STALLS TO OUR SOUTHEAST. SOME PATCHY CLOUDS WILL BE AROUND BUT FOR THE MOST PART SUN WILL PREVAIL...AND DEW POINTS SHOULD REMAIN VERY LOW... IN THE LOW-MID 50S FOR THE MOST OF THE REGION. HIGH TEMPERATURES WILL ALSO BE COOLER WITH A TROUGH OF LOW PRESSURE CENTERED NEARBY ALOFT...WITH MOST READINGS 5-8 DEGREES BELOW THE HIGHS WE WILL REACH TODAY. OVERALL...A VERY NICE LATE AUGUST DAY.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... HIGH PRESSURE PERSISTS ACROSS THE UPPER MID-WEST INTO THE MID- ATLANTIC TUESDAYS NIGHT THROUGH WEDNESDAY NIGHT. LIGHT NRLY FLOW WILL PERSIST AT THE SURFACE RESULTING IN DRY CONDITIONS WITH TEMPS BARELY REACHING THE UPPER 70S AT HIGHER ELEVATIONS ALONG AND WEST OF THE BLUE RIDGE AND IN THE LOW 80S NEAR THE METROS ON WEDNESDAY. && .LONG TERM /THURSDAY THROUGH MONDAY/... SFC HIGH PRESSURE DOMINATES THE WEATHER PATTERN THROUGH THE LONG TERM...WITH LITTLE DAY-TO-DAY VARIABILITY IN SENSIBLE WEATHER AND LITTLE-TO-NO CHANCE OF MEANINGFUL PRECIPITATION. FULL LATE SUMMER INSOLATION WILL LEAD TO A SLOW INCREASE IN TEMPERATURES EACH DAY AS AIRMASS MODIFIES...WITH TEMPERATURES AOA NORMAL BY SATURDAY AND A FEW DEGREES WARMER...U80S/L90S...ACROSS THE ENTIRE CWA BY SUNDAY. DEWPOINTS REMAIN RELATIVELY LOW THROUGH THE END OF THE WEEK WITH L/M50S ACROSS THE CWA...WHICH WILL KEEP NIGHTTIME TEMPERATURES IN 50S/L60S...THOUGH THERE COULD BE A FEW ISOLATED SPOTS IN OUR FAR WEST WITH LOWS IN THE M/U40S FRIDAY MORNING. WEAK RETURN FLOW BEGINS OVER THE WEEKEND...BUT WITH QUALITY MOISTURE SHUNTED WELL SOUTH AND EAST OF OUR AREA...DEWPOINTS EXPECTED TO ONLY INCREASE INTO THE L60S...SO EVEN WITH TEMPERATURES IN L90S...HEAT INDICES WILL REMAIN AOB 85. ESSENTIALLY NO CHANCE OF PRECIP THURSDAY OR FRIDAY. SFC HIGH WEAKENS ITS GRIP SLIGHTLY OVER THE WEEKEND AND WITH WEAK MOISTURE RETURN...COULD BE A FEW SHOWERS/STORMS AROUND...THOUGH COVERAGE SHOULD BE ISOLATED AND MAINLY CONFINED TO HIGHER TERRAIN. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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AS OF 01Z...HEAVY STORMS ARE EXITING THE BALTIMORE AREA. AT THIS TIME...NO ADDITIONAL STORMS ARE ON THE RADAR. HOWEVER COLD FRONT IS STILL TO THE WEST...AND THEREFORE CANNOT TOTALLY RULE OUT ADDITIONAL STORMS LATE THIS EVENING. HOWEVER GIVEN STRENGTH OF CURRENT STORMS...AM NOT CONFIDENT IF THESE WOULD DEVELOP OVER THE METRO AREAS...ALTHOUGH SOME MODELS SUGGEST IT IS POSSIBLE. DO NOT HAVE ANY FOG IN THE TAFS AT THE MOMENT...BUT THERE COULD BE SOME IF CLEARING WORKS IN BEFORE DRIER LOW LEVEL AIR. WINDS WILL LIKELY BE SOMEWHAT VARIABLE UNTIL THE FRONT PASSES LATER TONIGHT...WHICH WILL ALLOW THEM TO BECOME MORE WESTERLY. OTHERWISE...VFR THROUGH THE REMAINDER OF THE PERIOD UNDER HIGH PRESSURE.
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&& .MARINE...
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ONE AREA OF STRONG STORMS CROSSING THE NORTHERN BAY NOW. THIS IS THE MAIN CONCERN AT THE MOMENT...ALTHOUGH SOME ADDITIONAL STORMS MAY DEVELOP AHEAD OF AN APPROACHING COLD FRONT LATER TONIGHT. A FEW SOUTHERLY GUSTS TO AROUND 20 KT HAVE OCCURRED OUTSIDE THE STORMS...AND IT STILL LOOKS LIKE THERE WILL BE A PRESSURE SURGE WITH THE COLD FRONT LATER TONIGHT. MADE SOME MINOR ADJUSTMENTS TO THE SCA BASED ON LATEST GUIDANCE. HOWEVER IT STILL LOOKS LIKE THE WINDS WILL BEGIN TO DIMINISH TOWARD DAWN. WINDS EXPECTED TO REMAIN SUB-SCA THROUGH THE REMAINDER OF THE FORECAST PERIOD UNDER HIGH PRESSURE.
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&& .TIDES/COASTAL FLOODING...
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STILL WATCHING TIDAL ANOMALIES CLOSELY WITH POTENTIAL FOR MINOR FLOODING WITH THE SOUTHERLY UP-BAY FLOW. HAVE ISSUED A COASTAL FLOOD ADVISORY FOR ANNAPOLIS TONIGHT AS A PERSISTENT ANOMALY WILL YIELD THE THRESHOLD. HOWEVER THIS COULD BE DISRUPTED BY THE ONGOING STORMS. STRAITS POINT WILL ALSO BE VERY CLOSE TO MINOR FLOOD STAGE WITH THE UPCOMING HIGH TIDE CYCLE. WESTERLY WINDS BEHIND A COLD FRONT LATE TONIGHT WILL HELP DECREASE THE ANOMALIES.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 4 AM EDT TUESDAY FOR MDZ014. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT TUESDAY FOR ANZ533-534-537- 541-543. SMALL CRAFT ADVISORY FROM 1 AM TO 6 AM EDT TUESDAY FOR ANZ542. SMALL CRAFT ADVISORY UNTIL 1 AM EDT TUESDAY FOR ANZ531-532.
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&& $$ SYNOPSIS...RCM NEAR TERM...ADS/RCM SHORT TERM...HAS/RCM LONG TERM...MSE AVIATION...ADS/HAS/MSE/RCM MARINE...ADS/HAS/MSE/RCM TIDES/COASTAL FLOODING...ADS

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