Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 161607 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1107 AM EST TUE DEC 16 2014 .SYNOPSIS... A COLD FRONT IS MOVING INTO THE MID ATLANTIC. HIGH PRESSURE BUILDS IN THE WAKE OF THE FRONT THROUGH THE END OF THE WEEK. LOW PRESSURE WILL APPROACH FROM THE SOUTHWEST SATURDAY. && .NEAR TERM /TODAY/... RW ONGOING E OF THE MTNS AHD OF THE CD FNT. HV UPGRADED TO CAT POPS THRU MID AFTN. QPF GNRLY UNDER 1/10 OF AN INCH. NOT XPCTG MUCH MVMNT ON TEMPS...45-50 MOST LOCALES. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... COLD FRONT QUICKLY EXITS TO THE EAST TONIGHT...TAKING ASSOCIATED PCPN TO THE EAST WITH IT. HAVE CHC POPS OVER AREAS SURROUNDING CHESAPEAKE BAY FOR THE EVENING...THEN DRYING OUT FOR THE REMAINDER OF THE NIGHT. TO THE WEST...MAINTAINING CHC POPS FOR THE ALLEGHENY FRONT AS A SFC TROUGH SWINGS THROUGH ON THE BACKSIDE OF THE LOW PRESSURE SYSTEM. PCPN LOOKS TO REMAIN IN LIQUID FORM AS THE CAA IS SLOW TO MOVE IN WITH A ZONAL FLOW TAKING HOLD ALOFT. THE ZONAL FLOW PERSISTS THROUGH WED...FINALLY WEAKENING ENOUGH WED NIGHT TO ALLOW THE CLOSED LOW POSITIONED JUST TO THE NORTH TO PUSH SOUTHWARD...FINALLY ADVECTING IN THE COLDER TEMPS. FOR WEDNESDAY...BROAD HIGH PRESSURE BUILDS IN AND WITH SUBSIDENCE INCREASING ALOFT...SHOULD SEE DRY WX AND CLEARING SKIES. PCPN CHC JUST REMAINS WED WEST OF THE ALLEGHENY FRONT. TAPERED POPS OFF IN THIS AREA FOR THE SECOND HALF OF WED NIGHT TO ACCOUNT FOR LOSS OF MOISTURE DESPITE THE CONTINUING UPSLOPE FLOW. DID INCLUDE A MENTION FOR PATCHY DRIZZLE/FREEZING DRIZZLE FOR THE ALLEGHENY FRONT RESULTING FROM ANY LINGERING PCPN STUCK IN THE LOWER LVLS UNDER THE INVERSION. FOR TEMPS THROUGH THIS PERIOD...LOWS TONIGHT AND HIGHS TOMORROW STILL ABV NORMAL. WITH THE CAA WED NIGHT...FINALLY TEMPS DROP TO AROUND NORMAL. && .LONG TERM /THURSDAY THROUGH MONDAY/... HIPRES RDG XTNDG SEWD ACRS AREA WL BE KEY SYNOP FEATURE FOR THU-FRI. MEANWHILE...FLOW ALOFT WL BE ZONAL AND QUITE FAST...SO DO NOT XPCT TTLLY SUNNY SKIES. CLDS WL BE MORE NMRS IN THE MTNS...AS A DOWNSLOPE COMPONENT TO SFC FLOW WL PROVIDE SOME SUBSIDENCE. WIND FIELD BETTER THU. TEMPS WL BE SEASONABLE. WHILE ECMWF AND GFS STILL MILES APART WRT DVLPG STORM SAT...AM STARTING TO SEE A FEW SIGNS OF A CNVGNC OF FCST SOLN. LTST ECMWF A BIT MORE SURPRESSED...WHICH WUD BE LOGICAL FOR THE TIGHT FLAT HGT PTTN ALOFT. MEANWHILE...GFS FINALLY RECOGNIZING THAT THERE IS A DVLPG SRN STREAM WAVE. IMPLICATIONS LOCALLY INCL A DELAY OF THE PCPN START TIME TIL SAT AND A LWRG OF POPS ON SAT AS CORRIDOR OF LKLY PCPN WUD BE SHUNTED S. WHILE EXTENT OF COLD AIR MARGINAL...LTST TRACK WUD ALLOW FOR SOME POTL SNOW /OR SOMETHING OTHER THAN RAIN/... SPCLY SAT NGT. THIS CYCLE HAS A LOT MORE POTL OF JUST LGT RAIN IN LWR ELEVS THO...SPCLY DC SWD. STILL HV A CLSD LOW EMERGING OFF HAT...BUT NOW NOT TIL SUN...SO NEEDED TO ADD POPS INTO THAT DAYTIME PD. WINDS AND UPSLP SHSN FOLLOW. ECMWF STILL MUCH STRONGER IN CSTL DVPMNT...WHICH WUD LEAD TO A MUCH WINDIER SUN IF CORRECT. MID-RANGE POPS COMMON THRU THE WKND...AND WL BE TIL A WINNING SOLN CAN BE DETERMINED. HIPRES/CAA BLDS IN THE WAKE OF THIS SYSTEM...FOR A CHILLY BUT DRY MON. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... IFR CONDS IN ASSO W/ THE RW ATTM. SLOW IMPRVMNT XPCTD THIS AFTN AS THE MAIN BAND OF PCPN MVS ONTO THE ERN SHORE. CD FNT WL BE MOVG INTO THE AREA TNGT. SUB-VFR CONDITIONS PERSIST UNTIL THIS EVENING AND POSSIBLY THRU THE FIRST HALF OF THE NIGHT. MAINLY VFR CONDITIONS THEN EXPECTED THROUGH THE END OF THE WEEK. S WINDS TODAY GENERALLY LESS THAN 10 KTS. WIND SHIFT OCCURS LATE AFTN/EVENING TO A W FLOW. GUSTS MIX IN AFTR 12Z WED...WITH GUSTS UP TO 20 KTS PSBL DURING THE DAY WED. LIGHT WNW FLOW CONTINUES THROUGH FRIDAY. SAT...FLGT RESTRICTIONS /MVFR-IFR/ XPCTD AS LOPRES PASSES S OF TERMINALS. HOW FAR S...HOW STRONG THE STORM WL BE...AND THE EXTENT OF COLD AIR ALL STILL TBD. && .MARINE... S FLOW TODAY WITH WINDS MAINLY 10 KTS OR LESS AND GUSTS 15 KTS OR LESS AS LOW LVL INVERSION KEEPS STRONGER WINDS ALOFT FROM MIXING TO THE SFC. WIND SHIFT OCCURS TONIGHT WITH INCREASING W FLOW BEHIND THE COLD FRONT. SCA IN EFFECT FOR THE CHESAPEAKE BAY FOR LATE WED MORNING LASTING UNTIL WED EVENING FOR GUSTS UP TO 20 KTS. THE SCA MAY NEED TO BE EXTENDED THROUGH WED NIGHT. HIPRES SETTLES OVER THE WATERS THU-FRI. THERE WL STILL BE A GRADIENT THO. SCA LKLY W/ DIURNAL MIXING IN NW FLOW THU. WNDS WL BE LIGHTER FRI. STILL QUESTIONS SAT AS LOPRES PASSES S OF WATERS. STRENGTH/TRACK ISSUES REMAIN...WHICH ULTIMATELY WL AFFECT WIND FIELD. && .TIDES/COASTAL FLOODING... WATER LEVELS TO RUN ABT ONE FOOT ABV ASTRO NORMS. THIS IS BLO ADVSRY LVLS. WINDS TURN WEST TNGT. DO NOT EXPECT A DRAMATIC DROP. RATHER...THERE SHOULD BE A SLIGHT EASING TO ANOMALIES. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EST WEDNESDAY FOR ANZ530>534-538>543. && $$ PRODUCTS...WOODY! PRVS...AS/HTS

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