Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 150847 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 347 AM EST MON DEC 15 2014 .SYNOPSIS...
-- Changed Discussion --
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.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
DRY CONDITIONS EXPECTED TODAY WITH DEEP LAYER RIDGING BUILDING IN ALOFT AND SFC HIGH PRESSURE EXTENDING DOWN THE EAST COAST. INITIALLY LOOKING AT A BKN STRATUS DECK THIS MORNING...PERSISTING UNDER A LOW LVL INVERSION. PATCHY DZ STILL PSBL AREAS WEST OF ALLEGHENY FRONT...BUT OVERALL CONFIDENCE IS LOW OF OCCURRING. FORTUNATELY...A COMBINATION OF WAA...WIND...AND PERSISTENT CLOUD COVER ARE KEEPING TEMPS ABV FREEZING AND THUS NOT EXPECTING ANY FZDZ THREAT THRU THIS MORNING. RIDGE AXIS CROSSES THE AREA LATER TODAY...AND WITH PLENTY OF SUBSIDENCE ALOFT...EXPECTING TO SEE THIS EARLY MORNING STRATUS SCT OUT. 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. DECENT SPREAD IN GUIDANCE CONCERNING TEMPS WITH THE MAV WELL WARMER THAN THE MET. CHOSE A BLEND OF THE TWO...SIDING MORE TO THE COOLER NAM IN THE NORTHERN AREAS TO ACCOUNT FOR THE EXPECTED CLOUD COVER...AND THE WARMER GFS IN THE SOUTH WHERE ALREADY CLEAR SKIES ARE EXPECTED TO CONTINUE.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
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.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
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.
-- End Changed Discussion --
&& .AVIATION /09Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
MVFR CIGS OVER ALL TAF SITES BUT KCHO THIS MORNING. CIGS SHOULD IMPROVE TO VFR BY MID MORNING...THOUGH THE IMPROVEMENT COULD BE OFF 1-2 HOURS. VFR THEN 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.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
MAINLY SUB-SCA CONDITIONS IN PLACE TODAY THROUGH TUES NIGHT. 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.
-- End Changed Discussion --
&& .TIDES/COASTAL FLOODING...
-- Changed Discussion --
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.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE.
-- End Changed Discussion --
&& $$ SYNOPSIS...SEARS/HTS NEAR TERM...SEARS SHORT TERM...SEARS LONG TERM...HTS AVIATION...SEARS/HTS MARINE...SEARS/HTS TIDES/COASTAL FLOODING...HTS

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.