Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190759 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EDT TUE MAY 19 2015 .SYNOPSIS...
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A COLD FRONT WILL MOVE ACROSS THE AREA TODAY. A FEW MORE SHOWERS AND THUNDERSTORMS ARE POSSIBLE. BEHIND THE FRONT A COOLER AND DRIER AIR MASS WILL MOVE INTO THE REGION FOR THE MIDDLE OF THE WEEK. A WEAK SYSTEM MAY THEN BRING SOME RAIN BACK TO THE REGION THURSDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE LATEST SURFACE ANALYSIS DEPICTED A BACK DOOR COLD FRONT SLIDING SOUTHWEST ACROSS MARYLAND...AND A MORE TYPICAL COLD FRONT EXTENDING SOUTH AND WEST ACROSS THE EASTERN GREAT LAKES...OHIO VALLEY...MID MISSISSIPPI VALLEY...AND SOUTHERN PLAINS. THE BACK DOOR FRONT IS EXPECTED TO STALL OUT...WHILE THE FRONT TO THE WEST SHOULD CONTINUE MOVING EASTWARD TODAY. THIS FRONT WILL ARRIVE IN THE CWA EARLY THIS AFTERNOON AND CLEAR THE CWA LATE IN THE DAY. HOWEVER...IT APPEARS THE BEST UPPER LEVEL FORCING IS ACTUALLY CROSSING THE AREA EARLIER IN THE DAY...AS SUGGESTED BY THE ONGOING SHOWER ACTIVITY IN WESTERN AND NORTHERN PORTIONS OF THE CWA. THUS...IT WOULD APPEAR THAT THE ODDS OF SHOWERS AND THUNDERSTORMS ARE LOWER TODAY THAN THEY WERE YESTERDAY...BUT STILL EXPECT SOME SCATTERED SHOWER ACTIVITY THIS MORNING AND A FEW THUNDERSTORMS THIS AFTERNOON WITH THE ACTUAL FRONT. HIGHS WILL REMAIN VERY WARM PARTICULARLY SOUTH AND WEST OF THE BACKDOOR COLD FRONT...WITH SIMILAR IF PERHAPS SLIGHTLY COOLER READINGS TODAY AS COMPARED TO YESTERDAY. WITH LESS FORCING...FASTER STORM MOTION AND ONLY SLIGHTLY MORE SHEAR THAN YESTERDAY...DO NOT EXPECT A LOT OF ISSUES WITH ANY THUNDERSTORMS THOUGH AN ISOLATED SEVERE WIND GUST REPORT IS NOT COMPLETELY OUT OF THE QUESTION.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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HIGH PRESSURE FROM THE PLAINS WILL BUILD EAST BEHIND THE COLD FRONT TONIGHT AND WEDNESDAY...WITH NORTHWESTERLY FLOW AT THE SURFACE BRINGING IN A SURGE OF COOLER...AND IN PARTICULAR...LESS HUMID AIR TO OUR REGION. LOWS TUESDAY NIGHT ARE EXPECTED TO BE 10-15 DEGREES COOLER THAN MONDAY NIGHT`S WERE AND HIGHS WEDNESDAY SHOULD BE SIMILARLY LOWER AS COMPARED TO TODAY`S EXPECTED HIGHS. COMBINED WITH THE LACK OF HUMIDITY...IT WILL FEEL VERY COMFORTABLE. SUNSHINE WILL DOMINATE WEDNESDAY AS WELL...THOUGH HIGH COULDS AHEAD OF ANOTHER DISTURBANCE APPROACHING FROM THE WEST MAY START MOVING IN TOWARDS DAY`S END.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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FOR THE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...THERE IS STILL NOT SUPERB AGREEMENT ABOUT HOW A NORTHERN STREAM SHORTWAVE TROUGH WILL INTERACT WITH SFC LOW PRESSURE MOVING THROUGH THE CAROLINAS. WITH THE 00Z GUIDANCE SUITE...THE GFS IS MORE OF AN OUTLIER WITH A DRIER SOLUTION. INCREASED POPS ACROSS THE SOUTHERN CWA WHERE THERE IS GREATER AGREEMENT ON THE POTENTIAL FOR SHOWERS. START/END OF PRECIP IS MOST IN QUESTION...ALTHOUGH THE PROBABILITY OF THUNDER IS LOW. THURSDAY WILL BE COOL AND CLOUDY REGARDLESS OF THE SOLUTION...WITH HIGH TEMPS ONLY IN THE UPPER 60S TO AROUND 70. UPPER LEVEL TROUGHING WILL ENVELOP THE EASTERN CONUS FOR THE END OF THE WEEK AS HIGH PRESSURE BUILDS INTO THE MS AND OH VALLEYS. TEMPS WILL REBOUND TO NEAR-NORMAL VALUES. THE HIGH WILL BEGIN TO MOVE OFFSHORE ON SUNDAY AND A WARM FRONT WILL LIFT NORTH THROUGH THE OH VALLEY. LOW CHANCE OF SHOWERS MAINLY IN NORTHERN AREAS ON SUNDAY WITH THIS FEATURE. BY MONDAY...UPPER LEVEL RIDGING WILL BUILD. WARMER AND MORE HUMID CONDITIONS WILL LIKELY RETURN WITH A CHANCE OF SHOWERS AND THUNDERSTORMS.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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LOW CIGS ASSOCIATED WITH BACKDOOR COLD FRONT MOVING IN FROM THE NORTHEAST...AND LINGERING MOISTURE FROM STORMS YESTERDAY...ARE GOING TO BE THE MAIN ISSUE TO CONTEND WITH THIS MORNING. SOME AREAS WILL PROBABLY GO IFR FOR A TIME BUT PREDICTING EXACTLY WHERE IS PROBLEMATIC...THOUGH ODDS FAVOR OUR NORTHEASTERN TERMINALS (BWI AND MTN) DUE TO PROXIMITY TO THE BACKDOOR FRONT. ANY SHOWERS THIS MORNING SHOULD BE RELATIVELY INNOCUOUS...AND THUNDERSTORMS WHICH MAY DEVELOP THIS AFTERNOON SHOULD BE RATHER HIT-OR-MISS. SO...FOR NOW...HAVE NOT INCLUDED THUNDER IN TAFS...BUT WILL NEED TO RE- EVALUATE BASED ON LATEST GUIDANCE IN UPCOMING TAF PACKAGES. WINDS SHOULD REMAIN MOSTLY BELOW 15 KNOTS...SHIFTING TO THE WEST AND NORTHWEST FROM THE EAST AND SOUTH AS THE DAYS GOES ON AND A FRONT DOOR COLD FRONT MOVES IN FROM THE WEST. NO AVIATION CONCERNS ON WEDNESDAY THOUGH WINDS WILL BE A LITTLE GUSTY FROM THE NORTH. DEPENDING ON THE TRACK OF LOW PRESSURE TO OUR SOUTH...SUB-VFR CONDITIONS ARE POSSIBLE ON THURSDAY IN LOW CLOUDS AND SHOWERS. THE PROBABILITY IS SLIGHTLY HIGHER AT CHO. OTHERWISE NO WIDESPREAD AVIATION ISSUES ARE EXPECTED IN THE OUTLOOK PERIOD.
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&& .MARINE...
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THUNDERSTORM COVERAGE SHOULD BE CONSIDERABLY LOWER TODAY COMPARED TO COVERAGE ON MONDAY...BUT A FEW THUNDERSTORMS ARE STILL POSSIBLE SO MARINERS SHOULD REMAIN ALERT. BEHIND THE COLD FRONT WHICH WILL PASS LATER THIS AFTERNOON...WINDS MAY GUST UP TO 20 KNOTS TUESDAY NIGHT AND WEDNESDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED TONIGHT INTO WEDNESDAY. LOW PRESSURE WILL PASS THROUGH THE CAROLINAS AND OFFSHORE FROM WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. DEPENDING ON ITS TRACK...WINDS MAY APPROACH SCA LEVELS OVER MAINLY SOUTHERN PARTS OF THE MD BAY/LOWER POTOMAC. SHOWERS ARE ALSO POSSIBLE. NORTHERLY CHANNELING MAY OCCUR ON FRIDAY...BUT CONFIDENCE IS LOW ON ABILITY TO REACH SCA LEVELS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...ADS AVIATION...ADS/RCM MARINE...ADS/RCM

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