Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 202122 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 522 PM EDT SUN APR 20 2014 .SYNOPSIS...
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HIGH PRESSURE OVER EASTERN NEW ENGLAND WILL BUILD INTO THE AREA TONIGHT AND 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.
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&& .NEAR TERM /THROUGH MONDAY NIGHT/...
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AXIS OF SURFACE HIGH HAS MOVED SOUTH OF LONG ISLAND AND ACRS CAPE COD. IT WILL WEAKEN AND PUSH INTO THE MID ATLANTIC OVERNIGHT. ALOFT...A RDG AXIS IS ALSO SETTING UP...WITH WL AIDE IN COOLER/DRIER AIR DRAINING SWWD. WHILE DEWPTS IN THE LWR-MID 30S LCLLY /UPR 20S FOR SOME SITES IN THE APLCNS AND SHEN VLY/... WIDESPREAD MID-UPR 20S DEWPTS PRESENT ACRS NJ/ERN PA. THUS...PTTN IN PLACE FOR WINDS TO DECOUPLE OVERNIGHT RESULTING IN GOOD RADIATIONAL COOLING. BASED ON THIS...MIN-T ADJUSTED A LTL. MOST SUSCEPTIBLE WAS NERN MD...WHICH IS NEARER THE RDG AND THUS POSITIONED TO RECEIVE SOME OF THE BETTER RADL COOLING. THAT MAKES PATCHY FROST A CONSIDERATION. HV OPTED TO RAISE A FROST ADVY FOR NERN MD FROM FDK-HARFORD AT THIS TIME. WL ALSO NEED TO MONITOR LOUDOUN-MONTCO-HOWARD TO SEE HOW THEY RESPOND. IF LWR DEWPTS DO INDEED DRAIN SWD AND TEMPS START PLUMMETING...THEN THE ADVY MAY NEED TO BE XPNDD SWD. 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 /TUESDAY 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 /21Z SUNDAY THROUGH FRIDAY/... VFR SKC-SCT/BKN250 THRU MONDAY AFTERNOON AT THE TERMINALS. EAST SURFACE WINDS 10-15KT WILL SUBSIDE AT SUNSET THIS EVENING THEN SHIFT TO THE SOUTH BUT LESS THAN 10KT MONDAY. INCREASING HI CLOUDS LATE MONDAY. 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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FOR THE MOST PART...WNDS SUBSIDING BLO SCA THRESHOLDS ATTM. THE EXCEPTION TO THIS REMAINS THE MAIN CHANNEL OF THE BAY BELOW BALT HARBOR...AND MORE PERSISTENTLY THE BAY FROM DRUM PT-SMITH PT INCL THE MOUTH OF THE PTMC/TANGIER SOUND. IN THESE AREAS...WNDS STILL FUNNELED IN A SLIGHTLY TIGHTER P-GRAD BTWN HIPRES OVER FAR ERN NEW ENGLAND AND LOPRES OFF THE CAROLINAS. THE GRADIENT WL BE THERE MOST OF TNGT. FURTHER...MDL GDNC SUGGESTING THAT THE MIXED LYR MAY TAP INTO THESE WNDS THRU AT LEAST THE EVNG. HV XTNDD SCA PAST MIDNGT FOR THESE 3 SRNMOST MARINE ZNS. 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 FROM 2 AM TO 8 AM EDT MONDAY FOR MDZ004>007. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ531>533-536-541-542. SMALL CRAFT ADVISORY UNTIL 1 AM EDT MONDAY FOR ANZ534-537-543.
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&& $$ SYNOPSIS...HTS/JRK NEAR TERM...HTS/SDG SHORT TERM...JRK LONG TERM...CEM AVIATION...SDG/JRK/CEM MARINE...HTS/JRK/CEM

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