Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290757 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 357 AM EDT FRI AUG 29 2014 .SYNOPSIS...
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HIGH PRESSURE BUILDS OVER THE NORTHERN MID-ATLANTIC TODAY...THEN MOVES OFFSHORE FOR THE WEEKEND. A WARM FRONT WILL LIFT NORTH THROUGH THE AREA LATE SATURDAY. A COLD FRONT WILL APPROACH DURING THE FIRST PART OF NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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FRONT WAS LOCATED ACROSS SOUTHERN VIRGINIA AT 06Z...WHILE HIGH PRESSURE OVER THE GREAT LAKES WAS EXPANDING EASTWARD INTO THE NORTHEAST AND NORTHERN MID-ATLANTIC. SKIES WERE GENERALLY CLEAR ACROSS THE CWA WITH LIGHT NORTHERLY WINDS. FRONT WILL SINK A LITTLE FURTHER SOUTH INTO NORTH CAROLINA TODAY BEFORE COMING TO A HALT. HIGH PRESSURE WILL BE IN CONTROL TODAY WITH DRY AIR/LOW HUMIDITY IN PLACE. RESULT SHOULD BE A GOOD DEAL OF SUNSHINE. THUS DESPITE LIGHT ONSHORE FLOW THIS AFTERNOON FAVORED THE WARMER /BIAS CORRECTED/ ADJMAV GUIDANCE FOR MAXIMA TODAY.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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AS HIGH PRESSURE MOVES OFF THE COAST TONIGHT INTO SATURDAY....WINDS TURN TO THE SOUTHEAST. RETURN FLOW WILL BOLSTER AN INCREASE IN DEWPOINTS/MOISTURE DURING THIS TIME...RESULTING IN INCREASING CLOUDS OVERNIGHT AND PARTLY TO MOSTLY CLOUDY SKIES FOR SATURDAY. FOLLOWED SREFS FOR POPS...KEEPING CWA GENERALLY DRY TONIGHT THEN BRINGING CHANCE POPS INTO THE NORTHERN VIRGINIA PIEDMONT AND AREAS ALONG/WEST OF THE BLUE RIDGE. THIS IS IN DECENT AGREEMENT WITH 00Z GFS/ECMWF.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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THE CALENDAR WILL READ SEPTEMBER...BUT THE CONDITIONS WILL RESEMBLE WHAT WE WOULD TYPICALLY GET BACK IN JULY/AUG. CAUGHT UNDERNEATH A STRENGTHENING UPPER RIDGE...THE PLUME OF MOISTURE AND WARMER AIR FROM THE SOUTH WILL BE ON THE CONVEYOR BELT INTO EARLY NEXT WEEK. AFTER A COUPLE OF DAYS GRADUALLY BUILDING TO CLOSE OUT THE CURRENT WEEK...THE HEATING WILL REACH ITS CLIMAX OVER THE ERN SEABOARD ON SUN...AS THE TROUGH RESPONSIBLE FOR THIS BUILD-UP FINALLY PASSES BY THE AREA. THE RELATIVELY MINOR AND LOW AMPLITUDE TROUGH AXIS WILL ACTUALLY BE A SERIES OF OFFSET KINKS IN THE UPPER FLOW THAT CONNECT FROM HUDSON BAY TO THE GULF COAST. THE COMBINATION OF THESE FEATURES CENTERED A COUPLE OF STATES TO OUR WEST WILL FORCE THE ATLC COAST RIDGE TO AMPLIFY AND CREATE A MORE PRONOUNCED FETCH OF WARM/HUMID AIR FROM THE SRN ATLC STATES. THE SRN HALF OF THE UPPER RIDGE WILL BE STRONG ENOUGH TO DEFLECT THE INCOMING SHORTWAVE UP/OVER THE NRN SIDE - FROM ABOUT THE CAROLINAS AND NWD. A MUCH MORE POTENT TROUGH DIVING DOWN INTO THE NRN PLAINS WILL ALSO FORCE THE TROUGH QUICKLY OVER AND N OF OUR AREA SUN INTO MON. INSTABILITY LOOKS TO BE MARGINAL BUT HEATING SHOULD BE SUFFICIENT FOR SCT`D TSTMS DURING THE LATTER HALF OF THE DAY. SHEAR PROFILE NOT OVERLY FAVORABLE W/ A LARGELY WLY UNIDIRECTIONAL FLOW IN THE CRITICAL BOUNDARY LAYER...SO THE STRONGEST ACTIVITY WOULD LIKELY BE MORE LOCALIZED WHERE THE BEST PARAMETERS/FORCING COME TOGETHER - POSSIBLY OUTFLOW DRIVEN AS WELL. ELEVATED HEAT INDICES WILL ALSO BE A CONCERN HEADING INTO EARLY NEXT WEEK ESPECIALLY. DEWPOINTS WILL AGAIN BE HOVERING IN THE L70S - WHICH CAN ADD A HIGH LEVEL OF DISCOMFORT TO ANY AMBIENT TEMP. AND W/ TEMPS EXPECTED TO CRACK THE 90 DEG MARK...HEAT INDICES WILL EASILY REACH THE MID...IF NOT U90S - BOTH SUN AND MON AFTN. SKIES WILL WAVER BETWEEN PARTLY SUNNY AND MOSTLY CLOUDY WHICH MAY HELP A LITTLE IN TERMS OF MAX POTENTIAL HEATING BUT IT WILL STILL BE PLENTY HOT/HUMID FOR THIS TIME OF YEAR. THE UPPER RIDGE BEING DISPLACED ONLY SLIGHTLY TO THE SOUTH AS THE TROUGH SLIDES BY WILL REBOUND BACK OVER THE MID-ATLC THRU THE REST OF THE WEEK. LONG RANGE MODELS CONSISTENTLY SHOWING US ON THE NRN FRINGE OF THE HOTTER CONDITIONS THRU MUCH OF THE WEEK...W/ A COOLER/MORE ACTIVITY WX RESIDING JUST N OF THE MASON-DIXON LINE W/ ONE TROUGH AFTER ANOTHER SLIDING BY JUST TO OUR NORTH. BRIEF PERIODS OF CONVECTIVE ACTIVITY MAY DOT THE AREA BY MID WEEK AS A COLD FRONT STRADDLES THE REGION BUT NOT MUCH IN THE WAY OF AN ORGANIZED OR AIRMASS MODIFYING SYSTEM EXPECTED THRU THE CURRENT FORECAST PERIOD.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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HIGH PRESSURE WILL BE IN CONTROL TODAY WITH FEW-SCT CU/CI THIS AFTERNOON/EVENING. POTENTIAL EXISTS FOR LOW CLOUDS TO DEVELOP LATE TONIGHT OR SATURDAY MORNING AS FLOW BECOMES SOUTHEAST. CONFIDENCE IS LOW HOWEVER. PER SREFS...CHO MAY HAVE THE GREATEST CHANCE BUT EVEN THAT IS UNCERTAIN. MAY CONSIDER MVFR IN THE NEXT CYCLE FOR CHO...OTHERWISE VFR. AN UPPER RIDGE WILL CONTINUE TO BUILD-IN HEAT/HUMIDITY SUN INTO MON...W/ A POSSIBLE WAVE OF SCATTERED SHOWERS/TSTMS POSSIBLE SUN AFTN/EVE. ANOTHER LESSER POTENTIAL EXISTS ON MON AS WELL...AS THE HOT/HUMID AIRMASS STAYS IN PLACE FOR THE NEXT SEVERAL DAYS. ONLY BRIEF AND SHORT-LIVED PERIODS OF PRECIP POSSIBLE INTO MID NEXT WEEK...BUT MAINLY DRY AND MOSTLY SUNNY EACH DAY.
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&& .MARINE...
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WINDS HAVE TURNED A LITTLE MORE NE ON THE CHESAPEAKE BAY...COINCIDING WITH AN INCREASE IN SPEEDS WHOSE MAGNITUDES WERE NOT WELL HANDLED BY MOST GUIDANCE. EARLIER IN THE SHIFT RAISED A SCA FOR THE REST OF THE NIGHT FOR THE BAY FROM POOLES DOWN TO DRUM POINT FOR THIS SEVERAL HOUR NE SURGE. WINDS SHOULD RELAX BELOW SCA SHORTLY AFTER SUNRISE. HIGH PRESSURE MOVES OFF THE COAST TONIGHT AND SATURDAY...RESULTING IN WINDS VEERING TO THE SE. SPEEDS EXPECTED TO REMAIN BELOW SCA ATTM. S-SWLY WINDS WILL BE IN PLACE FOR THE FIRST HALF OF THE COMING WEEK...AS A HIGH SITS JUST OFF THE ATLC COAST AND STEERS WARM/HUMID AIR UP ACROSS THE ERN SEABOARD. ONLY MINOR PERIODS OF SLY CHANNELING AND/OR SCA CONDITIONS POSSIBLE INTO THE MIDDLE OF NEXT WEEK. A WEAK FRONT WILL LIKELY CROSS THE WATERS ON SUN...W/ ANOTHER PASSAGE POSSIBLE FROM A DIFFERENT SYSTEM TO OUR NORTH ON WED.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 AM EDT THIS MORNING FOR ANZ531>533-538>541.
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&& $$ SYNOPSIS...BPP/GMS NEAR TERM...BPP SHORT TERM...BPP LONG TERM...GMS AVIATION...BPP/GMS MARINE...BPP/GMS

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