Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 311237 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 837 AM EDT FRI OCT 31 2014 .SYNOPSIS... HIGH PRESSURE LOCATED OVER THE AREA WILL MOVE OFFSHORE TODAY. DEEP LOW PRESSURE WILL DESCEND FROM THE GREAT LAKES...CROSSING THE CAROLINAS SATURDAY BEFORE STRENGTHENING ALONG THE NEW ENGLAND COAST SUNDAY. HIGH PRESSURE WILL THEN RETURN INTO MONDAY FOLLOWED BY ANOTHER COLD FRONT DURING MIDWEEK. && .NEAR TERM /THROUGH SATURDAY/...
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W.V. STLT IMGRY SHOWS SHORT WV HAS PUSHED INTO WI. THIS WILL DIVE TO SC AS UPPER LEVEL PATTERN UNDERGOES SUBSTANTIAL AMPLIFICATION AND NORTHERN AND SOUTHERN STREAMS PHASE OFFSHORE. SURFACE LOW IS WEAK AT THIS TIME AND WILL LOSE DEFINITION AS ENERGY EVENTUALLY TRANSFERS A COASTAL LOW OFF THE CAROLINA COAST ON SATURDAY. WITH SUCH A SOUTHWARD TRAJECTORY...FORCING WILL BE FOCUSED OVER THE MOUNTAINS FOR THE FIRST STAGE OF THIS SYSTEM. SOME RAIN SHOWERS ARE POSSIBLE THIS AFTERNOON THERE BUT MUCH OF CENTRAL MD AND VA WILL BE IN A SQUEEZE PLAY UNTIL TONIGHT OR SATURDAY WHEN THE SYSTEM WINDS UP AND BROAD SCALE LIFT WILL PRODUCE SHOWERS AREA-WIDE. HOWEVER...ANY HEAVIER PRECIPITATION FROM THE COASTAL LOW WILL LIKELY REMAIN TO THE EAST OF THE AREA. IN TERMS OF ANY SNOWFALL...AT LEAST THROUGH SATURDAY COLD ADVECTION WILL BE VERY MINIMAL WITH THIS OCCLUDED SYSTEM. AN ANALYSIS OF SOUNDINGS AND LOW LEVEL THICKNESS SUGGEST THAT ANY SNOW WILL BE LIMITED TO THE VERY HIGHEST ELEVATIONS OF WV...AND MOSTLY AS A RAIN/SNOW MIX AT THAT. THE SNOW WILL BE FAVORED DURING DIURNAL MINIMUMS IN TEMPERATURE AND ANY SLUSHY ACCUMULATIONS WILL BE MINOR. HIGH TEMPERATURES TODAY WILL RANGE FROM THE UPPER 40S AT HIGHER ELEVATIONS TO NEAR 60 IN THE LOWLANDS. LOWS TONIGHT TEMPERED BY CLOUD COVER IN RANGING FROM THE MID 30S HIGHLANDS TO MID 40S EAST. PRECIPITATION SATURDAY WILL BE MOST WIDESPREAD WEST OF THE BLUE RIDGE ON SATURDAY AND WILL LIMIT HIGHS A BIT MORE THERE...WELL INTO THE 40S. STILL NEAR 50 TO THE EAST. NORTHERLY WINDS WILL ALSO INCREASE ON SATURDAY AS THE LOW STRENGTHENS OFF THE COAST.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... BY SAT NGT...S/WV ENERGY WUD HV SHIFTED OFF THE ATLC CST...INDUCING CYCLOGENESIS SOMEWHERE OFF CAPE HATTERAS. IN TERMS OF PCPN E OF THE APLCHNS...THAT PRETTY MUCH WL MARK THE END...AS DRIER AIR WL WORK IN ON THE NW SIDE OF THE CYCLONE. HV OPTED TO HOLD ONTO MORE CLDS THAN GFS INDICATING...PARTLY DUE TO TIMING/UNCERTAINTY DIFFS AND THE OTHER PART DUE TO LOW H5 HGTS/PVA STILL PIVOTING ACRS CWFA. WINDS MAY BE THE BIGGEST IMPACT...BUT THE NOCTURNAL TIMING MAY PREVENT THE FULL 30-40 KT AVBL H9-8 FM MIXING DOWN. WL BE KEEPING GUSTS 25-30 MPH. ACRS THE MTNS...THE AMS WL BE COOLING SUFFICIENTLY FOR SOME SNOW. HWVR...THE BEST DYNAMIC COOLING WL PASS S OF AREA. THIS LEAVES ONLY A MARGINALLY FVRBL AMS W/ WARM GRND. HV TRIMMED SNW TTLS BACK A LTL. WL KEEP HWO MENTION...AS ITS NOT OUT OF THE QSTN THAT ACCUMS POTENTIALLY CUD YIELD AN ADVY. DECISIONS WL BE MADE AS EVENT NEARS. H8-5 RDGG BLDS QUITE QUICKLY SUNDAY...SHUTTING OFF UPSLP SHSN. DOWNSLOPE FLOW WL ERODE MOST OF THE CLDS DURING THE MRNG. THE INCRSG SUBSIDENCE WL TAKE CARE OF THE MTNS BY MIDDAY. WL HV A TIGHT P-GRAD OVER AREA FOR MUCH OF THE DAY...AND BETTER MIXING. GFS QUITE ENTHUSIASTIC ON 35-40 KT WNDS. THAT REMAINS TO BE SEEN...BUT DO HV 30-35 MPH GUSTS IN GRIDS. AM PRESERVING A GOOD AMT OF FCST CONTINUITY FOR TEMP FCSTS THRU THIS PD. BIGGEST CHG COMES SAT NGT...AS THE STRONG GRADIENT SUGGESTS THAT ANY TEMP LOSS WL PRIMARILY BE ADVECTIVE. THAT MEANS MIN-T IN THE 30S AREAWIDE SAT NGT/SUN MRNG...AND TEMPS STRUGGLING TO REACH 50F SUN AFTN. RDGG BLDS OVER AREA SUN NGT...W/ ALL THE ASSOCD FEATURES-- CLR SKIES/DCPLG WNDS/DEWPTS IN THE 20S. ITS LOOKING LIKE A HARD FREEZE FOR MOST OF THE CWFA XCPT FOR THE URBAN DOWNTOWNS AND COMMUNITIES NEAR THE BAY. THAT LIKELY WL MARK THE END OF THE GROWING SEASON. && .LONG TERM /MONDAY THROUGH THURSDAY/... THE HIGH SLIDES SOUTHEAST ACROSS THE CAROLINAS AND NEAR THE SOUTHEAST COAST MONDAY AND MONDAY NIGHT. TEMPERATURES WILL MODIFY SOME DURING THE DAY BUT REMAIN A LITTLE ON THE CHILLY SIDE MONDAY NIGHT. HIGH PRESSURE SLIDES OFFSHORE TUESDAY THROUGH WEDNESDAY NIGHT TO ALLOW A COLD FRONT TO GRADUALLY SLIDE INTO THE REGION AND BRING A CHANCE FOR RAIN SHOWERS. PRECIP TIMING HAS BEEN PUSHED BACK TO WED-WED NIGHT. HIGH PRESSURE WILL BUILD ON THURSDAY. && .AVIATION /13Z FRIDAY THROUGH TUESDAY/...
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A LOW PRESSURE SYSTEM WILL APPROACH FROM THE WEST TODAY AND TONIGHT BUT ANY PRECIPITATION SHOULD STAY WEST OF THE TAF SITES THROUGH MOST OF THIS PERIOD. A VFR CEILING MAY BE PREVALENT WITH VERY FEW BREAKS WITH THE APPRAOCHING SYSTEM. AS LOW PRESSURE STRENGTHENS OFF THE COAST ON SATURDAY...NORTHERLY WINDS WILL GUST UP TO 20-25 KT AND MVFR CEILINGS WILL BE POSSIBLE WITH SHOWERS. WINDS WL PROVIDE PRIMARY OP IMPACT SAT NGT-SUN...AS AN ELEVATED CORE OF 40+ KT WNDS CROSS TERMINALS. THE LLJ WL RESIDE ABT 2K FT ABV SFC. SHUD HV 25-30KT GUSTS IN NW FLOW AT GRND LVL...MAYBE A LTL HIER THAN THAT SUN MRNG-MIDDAY. ANY CIGS WUD BE MVFR-VFR SAT NGT AND SHUD CLR BY/SOON AFTR SUNRISE SUN MRNG. VFR SUN AFTN INTO TUE.
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&& .MARINE... EAST TO NORTHEAST WINDS UNDER SMALL CRAFT CONDITIONS WILL PREVAIL TODAY AND TONIGHT AS A LOW PRESSURE SYSTEM PASSES WEST AND SOUTH OF THE AREA. WITH THE STRENGTHENING LOW MOVING OFF THE COAST ON SATURDAY...SMALL CRAFT CONDITIONS WILL BE MET WITH NORTHERLY WINDS GUSTING TO AROUND 30 KT. GRADIENT INCREASES SAT NGT. AM NOT CERTAIN IF GLW WL ENCOMPASS ENTIRE MARINE AREA...BUT IT SHUD HIT A MAJORITY OF IT. SINCE THE GLW WUD MEANS A HEADLINE RAMP-UP IN THE 4TH PD...HV OPTED TO NOT ISSUE ATTM PER POLICY. NONETHELESS...THE OPEN WATERS OF THE MID BAY SHUD EXPERIENCE 35-40 KT GUSTS. CONDS WUD CONT INTO SUN BEFORE THE GRADIENT RELAXES AND WNDS SUBSIDE. SCA CONDS PROGGED TO HOLD ON THRU SUN NGT PER CURRENT FCST. AS HIPRES BLDS ELY NEXT WEEK...NO HAZARDS EXPECTED AT THAT TIME. && .TIDES/COASTAL FLOODING...
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A DEEP AREA OF LOW PRESSURE WILL CROSS THE CAROLINAS SATURDAY MORNING AND THEN TRACK NORTHEAST ALONG THE MID-ATLANTIC COAST SATURDAY NIGHT. POSITIVE DEPARTURES UP TO A HALF FOOT ON THE WATERS ATTM...AND THESE MAY INCREASE A LITTLE BIT MORE THROUGH TONIGHT. TIDAL FLOODING ISSUES WOULD ONLY OCCUR IF DEPARTURES EXCEEDED A FOOT. AT THIS POINT...SUSPECT THAT WONT HAPPEN. BLOWOUT CONDITIONS ARE EXPECTED SAT AFTERNOON THROUGH SUNDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 8 AM TO 8 PM EDT SATURDAY FOR ANZ530>543.
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&& $$ UPDATE...WOODY! PRVS...HTS/ADS

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