Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210527 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 127 AM EDT MON APR 21 2014 .SYNOPSIS... HIGH PRESSURE OVER EASTERN NEW ENGLAND WILL BUILD INTO THE AREA THROUGH MONDAY. A COLD FRONT WILL MOVE THROUGH THE AREA TUESDAY AND TUESDAY EVENING. HIGH PRESSURE BUILDS BACK IN FOR THE SECOND HALF OF THE WORK WEEK. && .NEAR TERM /THROUGH TODAY/...
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UPDATE...SCA EXPIRED. SEE MARINE SECTION. AXIS OF SURFACE HIGH HAS MOVED LTL SINCE TAFTN. IT REMAINS ALONG THE SRN SHORE OF LONG ISLAND EWD ACRS ACK. ITS ALREADY EXPANDING WWD INTO THE MID ATLC...AND IT/LL CONT TO DO SO OVNGT. ALOFT...A RDG AXIS IS ALSO SETTING UP...WHICH WL AIDE IN COOLER/DRIER AIR DRAINING SWWD. WHILE DEWPTS STILL IN THE LWR-MID 30S LCLLY... WIDESPREAD MID-UPR 20S DEWPTS PRESENT ACRS NJ/ERN PA. THUS...PTTN IN PLACE FOR WINDS TO DECOUPLE OVERNIGHT RESULTING IN GOOD RADIATIONAL COOLING. HV MADE A FEW MORE TWEAKS TO TEMPS/DEWPTS BASED ON LTST DATA. THE PART OF THE CWFA WHICH SHUD SEE THE BEST RADL COOLING /BALT-WASH CRRDR/ ALSO HAS THE HIEST DEWPTS AND BEST WIND GRADIENT CURRENTLY. AM STILL A LTL WORRIED ABT LOUDOUN-MONTCO-HOWARD CNTYS...BUT TEMPS HV FAR TO DROP AND DEWPTS NEED TO EDGE DOWN A LTL AS WELL. SUSPECT INVOF HEF WL SEE SOME FROST...BUT DOUBT IT/LL BE A MAJORITY OF PW CNTY. THEREFORE...DONT HV ENUF CONFIDENCE TO ADD ANYONE TO A FROST ADVY ATTM. IF LWR DEWPTS DO INDEED DRAIN SWD AND TEMPS START PLUMMETING...THEN THE ADVY MAY NEED TO BE XPNDD. OTRW...FCST LOOKS REASONABLE. BY MONDAY AFTERNOON AND NIGHT SURFACE LOW PRESSURE MOVES INTO THE GREAT LAKE STATES AND A COLD FRONT BEGINS TO APPROACH THE AREA. MODELS KEEP SUNSHINE IN PLACE FOR MOST OF TOMORROW BEFORE HI CLOUDS INCREASE LATE IN THE DAY AND NIGHT. LIGHT SOUTHERLY WINDS DEVELOP BUT DRY AIR REMAINS IN PLACE FOR MUCH OF THE DAY. WOULD EXPECT TEMPERATURES TO BE A BIT WARMER WITH HIGHS IN THE UPPER 50/S TO UPPER 60/S...AND IT WILL FEEL MILDER WITH LESS WIND. MIN TEMPS MON NGT IN THE MID 40S TO LOWER 50S.
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&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... SUB-1000 MB SFC LOW TRACKS EWD ACROSS UPSTATE NY AND NRN NEW ENGLAND ON TUE. ATTENDANT COLD FRONT OVER THE OH VLY IS EXPECTED TO CROSS THE APPALACHIANS BY ABOUT 18Z TUE BEFORE MOVING EWD THRU THE CWA BETWEEN APPROX 18Z TUE AND 00Z WED. THE BEST FORCING LOOKS TO STAY NORTH OF CWA AND CLOSER TO TO SFC LOW AND UPPER SHORTWAVE TROUGH. PREVIOUS FCST HAD LIKELY POPS WITH FROPA. DID NOT WANT TO INCREASE POPS FURTHER DUE TO THE LIMITED FORCING AND PROGRESSIVE NATURE WITH THIS SYSTEM. THUNDER A POSSIBILITY WITH TIMING OF FROPA COINCIDENT WITH PEAK HEATING. WEAK MID-LVL LAPSE RATES AND INCREASING CLOUD COVER AHEAD OF THE FRONT DURING THE MRNG SHOULD LIMIT DEGREE OF DESTABILIZATION. FCST MEAN MLCAPE VALUES FROM THE 09Z SREF ARE UNDER 500 J/KG FOR THE ENTIRE CWA AND MLCAPE PROBABILITIES AOA 500 J/KG ARE LOW...JUST TWO INDICATIONS OF A VERY LIMITED TSTM POTENTIAL. EVEN WITH CLOUD COVER...MAX TEMPS IN THE 70S AHEAD OF THE FRONT. THE COLD FRONT MOVES OFF THE DELMARVA COAST TUE NGT WHILE HIPRES BUILDS IN FROM CENTRAL CANADA. A STRONG PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS WILL PRODUCE BREEZY NW WINDS TUE NGT AND CONTINUING INTO WED. 12Z NAM/GFS BUFKIT PROFILES SHOW A POTENTIAL FOR WIND GUSTS OF 30-35 MPH TO MIX DOWN THE SFC ON WED. MAX TEMPS A FEW DEGREES BELOW NORMAL ON WED OWING TO THE CAA IN WAKE OF FROPA. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... SURFACE HIGH BUILDING ACROSS AREA WEDNESDAY NIGHT. TEMPERATURES MAY DROP 5 DEGREES BELOW NORMAL BEFORE REBOUNDING THROUGH THURSDAY NIGHT. HIGH PRESSURE MOVING OFFSHORE FRIDAY EVENING AND NIGHT AS COLD FRONT FROM CENTRAL PLAINS TRACK EAST ACROSS GREAT LAKES/OHIO VALLEY. MARGINALLY SUPPORT FOR PRECIPITATION WITH THE FRONT AS MAIN AREA PVA IS NORTH OF AREA. INCREASED CHANCES OF PRECIPITATION SATURDAY MORNING WHEN A SECOND FRONT SUPPORTED BY STRONG PVA ENTERS THE AREA FROM THE NORTH. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... VFR SKC-SCT250 THRU MONDAY AFTERNOON AT THE TERMINALS. E/SE WNDS AOB 10 KT WL CONT TO DIMINISH OVNGT...AND WL REMAIN LGT MON AS HIPRES OHD. IF THERE/S ANY WIND TMRW...ITLL HV AN ELY COMPONENT... GRDLY BCMG SLY BY THE PM PUSH. A COLD FRONT IS ANTICIPATED TO MOVE THRU THE TERMINALS FROM WEST TO EAST BETWEEN 18Z TUE AND 00Z WED. SHRA LIKELY AND ISO TSRA DURING THE AFTN WITH FROPA. BRIEF/LOCAL RESTRICTIONS POSSIBLE WITH HEAVIER SHRA OR TSRA. SLY WINDS AROUND 10 KT AHEAD OF THE FRONT WILL BECOME NWLY 10-15 KT FOLLOWING FROPA. WIND GUSTS UP TO 30 KT POSSIBLE ON WED AS HIPRES BUILDS IN FROM THE NW. VFR WITH HIPRES OVERHEAD WED NGT THRU FRI. && .MARINE...
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WATERS SANDWICHED BTWN HIPRES OVER FAR ERN NEW ENGLAND AND LOPRES OFF THE CAROLINAS. STILL HV A FAIR AMT OF GRADIENT WND ACRS THE MARINE AREA...BUT GNLY IN THE 10-15 KT RANGE. THE GRADIENT WL BE TIGHTEST FOR THE LWR PTMC AND SRNMOST TWO BAY ZONES. HV THRESHOLD SCA CONDS THERE ATTM...AND THE P-GRAD SHUD BE THERE MOST OF TNGT. WINDS WILL BE LIGHT/VRBL MON-MON NGT IN RESPONSE TO RDG AXIS. SLY FLOW AHEAD OF A COLD FRONT GENERALLY 10 KT ON TUE. THERE IS A LIMITED POTENTIAL HOWEVER FOR WINDS TO REACH SCA CRITERIA IN THE MAIN STEM OF THE CHSPK BAY DUE TO SLY CHANNELING. CAPPED WINDS AT 15 KT IN THESE ZONES FOR NOW WITH SUCH A MARGINAL WIND FIELD. SHRA AND POSSIBLY AN ISO TSTMS WITH THE FROPA LATE TUE AFTN AND EVE. NW WINDS BEHIND THE FRONT WILL BECOME GUSTY AS HIPRES BUILDS IN FROM THE NW. SCA LIKELY TUE NGT AND WED. WINDS BELOW SCA LVLS BY WED NGT AS HIPRES BUILDS OVERHEAD.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MDZ004>007. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ UPDATE...GMS PREV DISCUSSION...JRK/CEM/HTS

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