Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271859 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 259 PM EDT FRI MAR 27 2015 .SYNOPSIS... AN UPPER-LEVEL TROUGH WILL SLOWLY MOVE ACROSS THE EASTERN UNITED STATES TONIGHT AND SATURDAY. HIGH PRESSURE WILL BUILD OVERHEAD SUNDAY. SEVERAL WEAK FRONTS WILL CROSS THE AREA NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... LINGERING RA SE OF NAK-EZF TAFTN. AS PROGGED ERLR...ITS DEPARTURE PAINFULLY SLOW DUE TO STEEPENING TROF AXIS ACRS THE GRTLKS/MIDWEST. WL KEEP POPS GOING PAST SUNSET FOR THESE AREAS. SUNSHINE ALSO A RARE COMMODITY...AS CU DVLPG AS QUICKLY AS LLVL MSTR THINS. THINK THAT MOCLDY AT BEST WL DESCRIBE SKYCOVER INTO THE EVNG. H5 TROF AXIS WL DROP INTO CWFA AFTR MIDNGT AND CROSS THRU ELY/MID AFTN. THIS TIMING A PINCH QUICKER THAN PRVS PROGS. CAA WL BE ONGOING FM TAFTN THRU TMRW AFTN...W/ H8 TEMPS BTTMG OUT ARND -10 TO -14C. HWVR...BEST INSTBY AND PVA MIGHT NOT BE COINCIDENT...WHICH MAKES ORGANIZED PCPN LESS LKLY. AM LEANING MORE TWD DYNAMIC FORCING MECHANISMS FOR PCPN PRODUCTION...WHICH SUGGEST THAT POP CHCS PREFERRED OVNGT INTO ELY MRNG CENTRAL VA INTO THE PTMC HIGHLANDS... AND MRNG/MIDDAY HRS I-95 CORRIDOR/CATOCTINS-NRN BLURDG/HGR-MRB AREA. MD MAY BE A BIT MORE SUSCEPTIBLE INTO ELY AFTN AS LTMD INSTBY BUILDS IN DAYTIME HEATING. THAT SAID...MSTR WL BE LIMITED AND HIT-OR-MISS IN NATURE-- NOT WORTHY OF MORE THEN CHC POPS. DUE TO COLD AIR ALOFT /AND TO A CERTAIN EXTENT AT THE GRDN FOR THOSE SITES THAT SEE ANYTHING DURING THE AM/...PCPN THAT MAKES IT TO THE GRND STANDS A GOOD CHC TO REACH AS SNOW PRIOR TO MELTING BUT THERE WUD BE TOO LTL TO BE CONCERNED ABT ACCUMS. HIPRES BUILDS DURING THE MID-LT AFTN...WHICH WL ALLOW FOR SKIES TO BEGIN CLRG. THUS DONT HV ANY POPS FOR THE LATTER HALF OF THE AFTN. WINDS WL BE GUSTY ALL DAY...AND THAT WL CONT TO NIGHTFALL. TOP OF MIXED LYR CONTAINS 25 KT...WHICH GIVES A REASONABLE IDEA OF THE GUST POTL. TEMP GDNC FAIRLY WELL CLUSTERED AND CONSISTENT W/ GOING FCST. AS SUCH...HV TAKEN A BLEND TO IRON OUT ANY CONSISTENCIES THAT MAY RESIDE. THAT MEANS MIN-T MID TEENS-20S MTNS AND 30-35F CSTL PLAIN. MAXT MID 30S-MID 40S. SHADED TEMPS ACRS THE NORTH AND WEST DOWN BY A DEGF OR TWO TO ACCT FOR IMPACT OF CAA. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... AFTER A DAY IN WHICH IT MAY FEEL LIKE WINTER IS STILL HERE - ON SAT...SUNDAY WILL BE A SLIGHT REBOUND BACK TOWARD MORE AVERAGE CONDITIONS. ULTIMATELY WE`LL MISS THE MARK IN TEMPS OF AVG HIGHS ON SUN BY A SOLID 10F DEG OF SO...BUT LIGHT WINDS AND MOSTLY CLEAR SKIES WILL AT LEAST SUPPLEMENT THE COOLER TEMPS. A WEAK UPPER RIDGE WILL BE RESPONSIBLE FOR OUR QUIET WX CONDITIONS ON SUN...BUT WITH A STILL VERY ACTIVE JET STREAM - MULTIPLE UPPER DISTURBANCES REMAIN IN THE QUEUE FOR PASSAGE OVER THE COMING WEEK. FAST ON THE HEELS OF THE UPPER RIDGE WILL BE RELATIVELY LARGE BUT FAIRLY MOISTURE-STARVED UPPER WAVE FROM THE GREAT LAKES REGION. OVERNIGHT LOWS WILL AGAIN DROP DOWN INTO THE M-U30S BUT W/ A LIGHT SLY WIND OUT AHEAD OF THE APPROACHING DISTURBANCE...THESE CONDITIONS WILL BE MODERATED AND PREVENT MOST AREAS FROM REACHING THE FREEZING MARK. A WEAK COLD FRONT WILL ARRIVE EARLY MON MRNG...QUICKLY PASSING ACROSS THE REGION AND MAINLY JUST SWITCHING THE SFC WIND DIRECTION FROM SLY TO WLY...ALSO EFFICIENTLY MIXING DOWN SOME GUSTY WINDS FOR THE DAYTIME HRS. WEST WINDS OF 20-30MPH EXPECTED W/ LOCALLY HIGHER GUSTS...CREATING SOME DOWNSLOPING AND A SUPPLEMENTAL TEMP INCREASE IN THE LEE OF THE APLCNS/BLUE RIDGE. HIGHS OVER THE WRN HALF OF THE AREA WILL LIKELY JUMP INTO THE M-U50S...THOUGH NOVA THE PIEDMONT MAY SEE SOME M-U60S BY LATE AFTN W/ CLEARING SKIES AFTER THE EARLY MRNG FRONTAL PASSAGE. && .LONG TERM /MONDAY THROUGH FRIDAY/... THERE MAY BE ENOUGH MOISTURE AVAILABLE OUT OF LOW PRESSURE SYSTEM OVER GREAT LAKES FOR WEAK PVA TO TRIGGERS A LIGHT RAIN SHOWER OR TWO TUESDAY. GREAT LAKES LOW WILL PASS TO OUR NORTH. TEMPERATURE PROFILE SUPPORTS MIXED PRECIPITATION IF ANY OCCURS LATE TUESDAY AND EARLY WEDNESDAY. WEAK PVA IN ZONAL FLOW WILL SUPPORT RAIN AHEAD OF A WEAK FRONTAL BOUNDARY DURING THE LATTER HALF OF THE WEEK. THIGHTNING GRADIENT BETWEEN APPROACH FRONT AND OFFSHORE RIDGE WILL PRODUCE S-SW WINDS 10-15 KTS THURSDAY. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... MVFR CIGS STILL LINGERING CHO/MTN...OTRW VFR PREVAILS. CHO CIGS CONTAINS MORE VARIABILITY AS ITS ON THE EDGE OF THE MSTR SHIELD. CONDS SHUD IMPROVE TO VFR AREAWIDE BY DARK...AND SHUD REMAIN THAT WAY THRU SAT. S/WV ENERGY WL CROSS THE TERMINALS TOMORROW...MAINLY BUT NOT EXCLUSIVELY IN THE AM. MSTR SCANT...BUT TEMPS ALOFT COLD ENUF TO SUPPORT SNOW. DUE TO COVERAGE/CONFIDENCE CONCERNS...AM NOT INCLUDING IN TAFS ATTM. TIMING SHUD BE LIMITED AT ANY ONE SITE...AND DIFFICULT TO PINPOINT. WINDS SHUD BE GUSTY BHD TROF...FROM THE NW ARND 20-25 KT. SUSTAINED WINDS LKLY IN THE TEENS...NOT PROVIDING ENUF SEPARATION TO EXPLICITLY INCL GUSTS IN TAF. NO HAZARDOUS WX CONDS EXPECTED FROM LATE SAT INTO MON...OUTSIDE OF SOME BREEZY CONDS ON MON AFTN BEHIND A COLD FRONT. BOUNDARY LAYER WINDS IN THE 30-40KT RANGE W/ SOME 20-25KT GUSTS AT THE SFC DURING THE DAYTIME HRS. && .MARINE... MIXING HAS BEEN LIMITED THUS FAR DUE TO A SOLID CLD DECK. THE LT AFTN HRS SHUD BE A LULL...WITH WINDS PICKING UP THEREAFTER DUE TO CAA. THAT WILL HAPPEN TONIGHT...ALTHO BETTER MIXING MAY NOT REACH THE NARROWER WATERS TIL SUNRISE TMRW. HV MADE APPROPRIATE ADJUSTMENTS TO THE DATABASE. ONCE IT BEGINS...TOP OF MIXED LYR CONTAINS 25 KT...WHICH GIVES A REASONABLE IDEA OF THE GUST POTL. SCA FOR ALL WATERS SAT. BREEZY NW WINDS WILL CONTINUE OVER MUCH OF THE WATERS SAT NIGHT...ESPEC THE MAIN STEM OF THE MD CHES BAY. A SLOW STEADY WIND DROP OFF ON SUN AS HIGH PRESSURE MAKES A BRIEF APPEARANCE BEFORE ANOTHER COLD FRONT ON MON MRNG. BEHIND THE FRONT...WEST WINDS WILL AGAIN PICK UP INTO SOLID SCA RANGES FOR THE DAYTIME HRS MON. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM EDT SATURDAY FOR ANZ535- 536. && $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...GMS LONG TERM...CEM AVIATION...GMS/HTS MARINE...GMS/HTS

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