Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 232220 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 520 PM EST MON FEB 23 2015 .SYNOPSIS... HIGH PRESSURE OVER IOWA WILL MOVE ONTO THE EAST COAST TUESDAY. A COLD FRONT IS EXPECTED TO PASS THROUGH THE MID ATLANTIC STATES TUESDAY NIGHT INTO WEDNESDAY. LOW PRESSURE WILL TRACK ACROSS GEORGIA WEDNESDAY NIGHT. HIGH PRESSURE WILL RETURN FOR THE LATTER PORTION OF THE WEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... WE WILL BE DOWN TODAY FOR A MAJOR UPGRADE. NWS CTP WL BE HANDLING OUR PRODUCTS. HIGH PRESSURE CENTERED OVER THE NORTHERN PLAINS WILL BUILD TO THE SOUTH AND EAST TODAY...KEEPING THE REGION ON THE EASTERN PERIPHERY. WHILE MOST OF THE AREA SHOULD REMAIN DRY AS THE RESULTANT OF THE COLD...DRY AIRMASS BEING USHERED IN WITH THE HIGH...TWO AREAS COULD POTENTIALLY SEE SNOWFLAKES THIS MORNING. 08Z OBS OVER SW PA CURRENTLY SHOWING LIGHT SNOW...SO THINKING THAT PATCH COULD MOVE INTO THE NW CORNER OF THE CWA THRU 12Z. A WEAK SHORTWAVE RIDING THE SOUTHERN BIT OF THE UPPER LVL TROUGH COMBINING WITH NW FLOW COULD GENERATE LIGHT SNOW SHOWERS ON THE WESTERN SLOPES OF THE ALLEGHENY THEN THRU THE MORNING...THOUGH LESS THAN A TENTH OF AN INCH EXPECTED. SECONDLY...MODELS TRYING TO PRODUCE LIGHT PCPN ASSOCIATED WITH WEAK LOW RIDING THE FRONT TO THE SOUTH. THINKING THE PCPN MIGHT BE OVERDONE ACROSS MOST OF THE CWA WITH LACK OF MOISTURE EXPECTED AFTER 12Z. ALONG WITH THE DRIER AIR...COLD TEMPS BEING USHERED IN...AS MANY AREAS WILL STRUGGLE TO REACH THE UPPER 20S...AND EVEN THE 20S IN THE WESTERN/NORTHERN EXTENDS OF THE AREA. THE COLDER TEMPS HAVE HOWEVER BEEN SLOW TO MOVE IN THIS MORNING. AS SUCH...HAVE ADJUSTED THE WIND CHILL ADVISORY FOR WESTERN ALLEGHENY...GRANT AND MINERAL TO START IT LATE THIS AFTN AND CONTINUING IT THROUGH TONIGHT TO ACCOUNT FOR THE BETTER CHC OF WHEN CRITERIA WILL BE MET. AS THE SURGE OF CAA ARRIVES...WINDS WILL INCREASE...WITH GUSTS INTO THE 20S EXPECTED THROUGH THE DAY. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... MAIN CONCERN TONIGHT WILL BE THE WELL BELOW NORMAL TEMPERATURES AS THE HIGH SETTLES OVER THE MID ATLANTIC. WIND CHILL CONTINUES THROUGH THE NIGHT. COULD SEE TEMPS DROPPING DOWN 5 TO 10 BELOW ZERO OVER OTHER PORTIONS OF THE WESTERN SLOPES...MAINLY IN PENDLETON AND HIGHLAND COUNTIES. AM NOT ISSUING WIND CHILL ADVISORY THOUGH DUE TO A LACK OF WIND. COULD ALSO SEE ISOLATED AREAS ALONG THE MASON-DIXON LINE DROP TO 5 BELOW ZERO...BUT DUE TO COVERAGE AND LACK OF WIND...WILL NOT ISSUE ANY PRODUCTS THERE AS WELL. ELSEWHERE...APPARENT TEMPS WILL BE IN THE SINGLE DIGITS ABV ZERO. COLD PERIOD CONTINUES INTO TUESDAY...THOUGH SHOULD SEE WARMER TEMPS THAN TODAY AS SOUTHERLY FLOW SETS UP WAA AHEAD OF THE NEXT APPROACHING COLD FRONT. NOT ANTICIPATING THE EXTENSION OF THE WIND CHILL ADVISORY TO BE NEEDED. GENERAL CONSENSUS OF THE 00Z MODELS KEEP PCPN TO THE WEST THROUGH 00Z WED...AND AS SUCH WILL RUN WITH A DRY FORECAST. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... LOPRES RAMBLES ACRS SERN CNDA TUE NGT-WED...DROPPING A REINFORCING CDFNT ACRS THE CWFA. BELIEVE THAT FROPA WL OCCUR TUE NGT...MOST LKLY AFTR MIDNGT. CLDS WL INCR WELL AHD OF THE FNT...MAINLY IN THE EVNG HRS. AREA NOT WELL SITUATED WRT JETMAX STRUCTURE OR VORTICIY PTTN TO RECEIVE ADDED LIFT. THEREFORE BELIEVE FNT WL PASS THRU DRY FOR ALL BUT THE MTNS...WHERE UPSLP ENHANCEMENT MAY BE ABLE TO SQUEEZE OUT CHC POPS. DUE TO THIS UNCERTAINTY OF LOW PROBABILITY...HV ACCUM GRIDS BLANK. CAA WL TAKE RESIDENCE ON WED. DOWNSLOPING WL PROVIDE A PD OF PRTL SUNSHINE E OF THE APLCNS...WHILE THE FLOW PTTN WL YIELD CONTD UPSLP SHSN TO THE WRN SLOPES. H8 TEMPS CHG OVER 24 HRS TUE NGT TO WED DAY ON THE ORDER OF 2-3 DEGC. ITS NOT A HUGE CHG...AND SUBSEQUENTLY HV KEPT WINDS ON THE LIGHTER SIDE. WED NGT A BIT TRICKIER AS AN AREA OF LOPRES SHOOTS EWD TO THE S OF THE AREA...PER GFS/NAM. THE CATCH IS THAT THE EURO SEND THE LOW A BIT FURTHER N...CLIPPING SRN CWFA W/ A SWATH OF PCPN. THERMALLY... THIS WOULD BE COLD ENUF FOR SNOW. IF ITS WERE TO HPPN...CHO-EZF ONT HE EDGE...SO ACCUMS WUD BE SMALL. HV ATTEMPTED TO MAINTAIN A PINCH OF CONTINUITY...AND CONFINED A 20 POP ACRS THE FAR S. THIS WL NEED TO BE WATCHED IN CASE LATER GFS/NAM RUNS CARRY LOW MORE LIKE CURRENT ECMWF. OVERALL...TEMP CHGS IN GRIDS NOT THAT SGFNT. STAYED SLGTLY WARMER MIN-T TUE NGT DUE TO INSUALTING BLANKET OF SLY WNDS/CLDS. WHILE CAA NOT INCREDIBLY STRONG WED...DID SHADE ABT A DEGF COOLER TO ACCNT FOR EFFECTS OF CDFNT/CAA. BLENDED GDNC FOR WED NGT MIN-T. END RESULT WL BE CONTINGENT UPON BOTH THE LOW AS WELL AS HOW FAR S ARCTIC AIR CAN PLUNGE ONCE AGN. THURSDAY THROUGH SUNDAY/... ARCTIC HIGH PRESSURE BUILDS INTO THE AREA OVERNIGHT WEDNESDAY..WITH COLD AND DRY WEATHER OVER THE CWA. 00Z ECMWF/GEFS HAVE SIMILAR TRACK FOR NEXT LOW PRESSURE SYSTEM DEVELOPING IN THE GULF ON THURSDAY...WILL NOT INCLUDE ANY POPS AT THIS TIME AS IMPACTS APPEAR TO STAY TO OUR SOUTH THRU THURSDAY. MODELS BEGIN TO DIVERGE SIGNIFICANTLY BEYOND THURSDAY...WITH SOME MODELS MOVING PIECES OF ENERGY TO OUR SOUTH FRIDAY AND AGAIN ON SATURDAY...BRINGING PRECIPITATION TO PARTS OF THE CWA. OTHERS KEEP OUR ENTIRE AREA COMPLETELY DRY. FOR NOW WILL KEEP PREVIOUS FORECAST OF SLIGHT CHANCE POPS GOING LATE FRIDAY NIGHT THROUGH SUNDAY. REGARDLESS...AIR TEMPERATURES WILL BE WELL BELOW NORMAL THROUGH AT LEAST SATURDAY EVENING. && .AVIATION /22Z MONDAY THROUGH SATURDAY/...
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HIGH PRESSURE AND ASSOC DRY AIR MASS WILL SETTLE SOUTH OVER THE REGION TONIGHT...RESULTING IN A NEAR CERTAINTY OF VFR CONDS AND A DIMINISHING WIND. THERE IS A SLIGHT CHC OF MINOR FLIGHT RESTRICTIONS TUE PM FROM A BIT OF LGT SNOW...MAINLY AT KCHO. THE REGION WILL BE ON THE NORTHERLY PERIPHERY OF A STORM SYSTEM OVR THE SE STATES. OUTLOOK TUE NGT...MVFR CIGS PSBL INVOF CDFNT. WED...MAINLY VFR. WED NGT...WL DEPEND UPON TRACK OF LOPRES PASSING S OF TERMINALS. IF IT STAYS FAR ENUF S...THEN VFR. OTRW...MAY BE MVFR-IFR IN SNW. THU-SAT...LOW CONFIDENCE IN FLGT RESTRICTIONS.
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&& .MARINE... SCA REMAINS IN EFFECT FOR ALL THE WATERS THIS MORNING THROUGH THE FIRST HALF OF THE COMING NIGHT WITH GUSTS 20-30 KTS EXPECTED. 00Z GUIDANCE KEEPS WINDS BELOW GALE CONDITIONS. THE SCA COULD END AS EARLY AS 00Z FOR THE TIDAL POTOMAC. SUB-SCA CONDITIONS THEN EXPECTED THE REMAINDER OF THE NIGHT THROUGH TUES WITH SOUTHERLY FLOW SETTING UP TUESDAY AHEAD OF THE NEXT COLD FRONT. CDFNT WL CROSS MARINE AREA LT TUE NGT. IN THE CAA THA ENSUES WED... ENUF MIXING FOR LOW END SCA PSBL. HV SOME GUSTS FCST THAT WUD BARELY TRIGGER SCA/S. CONFIDENCE THEREAFTER WANES. LOPRES WL PASS S OF WATERS WED NGT-THU MRNG...PERHAPS CLOSE ENUF TO IMPACT WATERS. THRU THE END OF THE WEEK THE QSTN WL BE HOW STRONG/QUICKLY ARCTIC HIPRES WL BUILD...AND WHAT TYPE OF P-GRAD WL RESIDE BTWN IT AND THE STORM TRACK TO THE S. THAT IS WHAT WL DICTATE WHEN/WHERE SCA WL BE REQD. WONT CHG CURRENT THINKING THAT WED NGT-THU A PD OF OPPORTUNITY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...WIND CHILL ADVISORY UNTIL 9 AM EST TUESDAY FOR MDZ501. VA...NONE. WV...WIND CHILL ADVISORY UNTIL 9 AM EST TUESDAY FOR WVZ501>503. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ530>543. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM... AVIATION...99 MARINE...

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