Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 151519 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1019 AM EST MON DEC 15 2014 .SYNOPSIS... HIGH PRESSURE BUILDS ACROSS THE REGION THROUGH TONIGHT. A COLD FRONT MOVES THROUGH TUESDAY WITH HIGH PRESSURE BUILDING IN ITS WAKE FOR THE MIDDLE AND THE END OF THE WEEK. && .NEAR TERM /TODAY/...
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CLD CVRG OVR THE NRN 1/3 OF THE FCST AREA IS SLOWLY WANING FM RDG OVR THE E CST. RIDGE AXIS CROSSES THE AREA LATER TODAY...AND WITH PLENTY OF SUBSIDENCE ALOFT. SCT HIGH LVL CLOUDS ARE PSBL LATE AHEAD OF THE NEXT APPROACHING LOW PRESSURE SYSTEM. AS THE HIGH SHIFTS OFFSHORE...RETURN FLOW SETS UP...THOUGH MAINLY EXPECTING LIGHT WINDS TO PERSIST. WE HV WARMED THE DAYTIME TEMPS SVRL DEGS AS MANY SITES WERE CLOSE TO REACHING THE FCSTD HIGHS BY MID MRNG. XPCTG HIGHS TO REACH THE LM50S.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
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SFC HIGH NUDGES EAST TONIGHT AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. GENERAL CONSENSUS AMONGST THE 00Z MODEL SUITE KEEPS THINGS INITIALLY DRY TONIGHT...WITH PCPN MOVING INTO THE WESTERN AREAS AROUND 06Z...THEN SPREADING EASTWARD THROUGH THE REMAINDER OF THE NIGHT. A FAIRLY DRY AIRMASS NEEDS TO BE OVERCOME...AND IT MAY VERY WELL BE POPS WERE INTRODUCED TOO SOON TONIGHT...WITH THE BETTER CHC CLOSER TO 12Z...OR THAT ANY PCPN INITIALLY BE MORE IN THE FORM OF DRIZZLE. EASTERN AREAS SHOULD REMAIN DRY TILL AT LEAST DAYBREAK TUES. CLOUD COVER AND WAA KEEP TEMPS ABV FREEZING EVERYWHERE... THOUGH TEMPS MAY BE SLOWER TO WARM IN AREAS OF NORTHEASTERN MD AS THE HIGH EXITS. FOR TUESDAY...HIGH CONFIDENCE OF PCPN OCCURRING AS WARM FRONT LIFTS NORTH IN THE MORNING...THEN THE ASSOCIATED COLD FRONT PROGRESSES THROUGH TUES EVENING. A WEAK SHORTWAVE AHEAD OF THE MAIN UPPER LEVEL TROUGH PROVIDES ENOUGH FORCING TO GENERATE SHOWERS TUES MORNING. PCPN COVERAGE INCREASES TUES AFTN AS A DECENT SHORTWAVE SWINGS THROUGH...WITH A VORT MAX PLACED OVER EASTERN WV/SOUTHERN PA. THINKING THIS WILL BE THE BEST CHC FOR ANY HEAVIER SHOWERS SO HAVE THE HIGHEST POPS IN PLACE THERE FOR NOW...WITH THE THINKING OF SHOWERS TO THE EAST WILL BE LIGHTER IN NATURE. THE SHOWERS TAPER OFF SOUTHWEST TO NORTHEAST TUES EVENING. MAINTAINING CHC POPS OVER THE ALLEGHENY FRONT FOR MIX RAIN/SNOW SHOWERS AS WINDS TURNING WESTERLY IN THE WAKE OF THE COLD FRONT...RESULTING IN DECENT UPSLOPE DEVELOPMENT. CAA IS SLOW TO MOVE IN HOWEVER AS FLOW ALOFT TURNS ZONAL AS THE CLOSED LOW PERSISTS OVER THE GREAT LAKES.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... SFC HIPRES WL BLD ACRS THE CWFA WED INTO THU WHILE FAST ZNL FLOW RESIDES ALOFT. THE H5 PTTN NOT QUITE AS CLR-CUT ACRS THE GRTLKS AS SOME UNCERTAINTY RESIDES WRT THE POSITION OF THE UPR CLOSED LOW. IMPLICATIONS LCLLY WUD BE SKYCOVER...AS A TROF AXIS PIVOTS EITHER OVERHEAD OR N OF AREA. WL BE KEEPING MORE CLDS IN THE MTNS THAN THE CSTL PLAIN THRU THE PD. ASIDE FM WED EVNG...NO PLACE WL REALLY HV FULLY CLR SKIES DUE TO THE SITUATION ALOFT /JET AXIS AND POTL ULVL MSTR...EVEN W/ SUBSIDENCE BENEATH/. TRANQUIL CONDS CONT INTO FRI DUE TO SFC RDGG. A WARMER WED WL BE FLLWD BY BLO NRML TEMPS FOR THU-FRI. AFTER THAT...THE DILEMMA BEGINS. CLDS WL LKLY BE ADVCG EITHER FRI AFTN OR FRI NGT AS A SRN STREAM WV OF LOPRES DVLPS IN THE HEART OF DIXIE. ECMWF STILL RUNNING MUCH MORE AGGRESSIVE WITH THIS SYSTEM THAN THE GFS. BY 12Z SAT...THE DETERMINISTIC MDL CHOICES ARE EITHER 999 MB LOPRES OVR AL /ECMWF/ OR 1011 MB LOPRES IN WRN TN/KY /GFS/. THE FORMER SEEMS OVERDONE...AND THE LATTER SEEMS A BIT SLOW GIVEN THE WIND FIELD ALOFT. LETS START BY WHAT SEEMS APPARENT-- THERE SHUD BE PCPN SOMEWHERE ALONG THE EAST COAST SAT. HENCE...LKLY POPS. THE TYPE AND TIMING REMAINS QUITE UNCERTAIN. NEED TO INCL MENTION OF SNW GIVEN POTL FOR MARGINALLY COLD AIR...HWVR JUST ABT ANY WX TYPE STILL SHUD BE CONSIDERED IN PLAY...DEPENDING UPON HOW THIS ALL PANS OUT. BY SUNDAY THE SFC LOW SHUD BE PULLING AWAY...AND HV MUCH IMPRVD CONDS IN THE DATABASE. A CAUTION THO...A SLOWER SOLN CUD SKEW THIS TIMING. && .AVIATION /15Z MONDAY THROUGH FRIDAY/...
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VFR EXPECTED THROUGH TONIGHT. SUB-VFR CONDITIONS PSBL TUES-TUES NIGHT WITH RAIN SHOWERS. WINDS LIGHT AND VRB TODAY...THEN INCREASE FROM THE S ON TUES...BUT REMAINING GENERALLY 10 KTS OR LESS. WIND SHIFT TUES NIGHT BEHIND THE FRONT...BCMG W. WED-FRI...VFR.
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&& .MARINE...
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SUB-SCA CONDITIONS IN PLACE TODAY THROUGH TUE. GUSTS MAY APPROACH 18 KTS TUES AFTN RIGHT AHEAD OF AN APPROACHING COLD FRONT...BUT CONFIDENCE IS TOO LOW AT THIS TIME TO ISSUE A SCA. SCA CONDS LKLY WED. LIGHTER WNDS XPCTD THU-FRI.
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&& .TIDES/COASTAL FLOODING... WATER LEVELS RUNNING ABOUT A HALF TO 3/4 FT ABV ASTRO NORMALS. WHILE ELEVATED...NO ISSUES EXPECTED TODAY OR TONIGHT. THE SAME CANT BE SAID WITH CERTAINTY FOR TUE-TUE NIGHT AS WINDS TURN SOUTHERLY. THE RISK IS NOT SIGNIFICANT...BUT LEVELS MAY REACH THE MINOR THRESHOLD AT SENSITIVE LOCATIONS. WE MAY LUCK OUT AS THE HIGHER ASTRO TIDES COMES DURING THE DAY...BEFORE ANOMALIES HAVE TIME TO INCREASE. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ UPDATE...WOODY! PRVS...AS/HTS

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