Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 140757 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 357 AM EDT TUE APR 14 2015 .SYNOPSIS...
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A COLD FRONT WILL CROSS THE REGION THIS MORNING. A WAVE OF LOW PRESSURE WILL PASS BY TO OUR SOUTH ALONG THE BOUNDARY THIS AFTERNOON AND EVENING. HIGH PRESSURE WILL BUILD IN BEHIND THIS SYSTEM FOR WEDNESDAY INTO THURSDAY BEFORE MOVING OFF THE COAST LATE IN THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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CDFNT SLIPPING INTO THE NWRN CWFA ATTM. WATER VAPOR IMAGERY DEPICTS A ROBUST LOW IN THE TN VLY...WHILE THE NRN STREAM DISTURBANCE HAS BEEN QUITE PROGRESSIVE THX TO ITS POSN WRT UPR JETSTREAM. AS A RESULT...THE FNT HAS BECOME A LITTLE STRETCHED LATITUDINALLY...AND WL SLIP THRU IN A SOMEWHAT BACKDOOR FASHION TDA. IN TERMS OF SYNOPTIC FEATURES...THERE/S DECENT AGREEMENT IN THIS SOLUTION. HOWEVER...WHEN IT COMES TO FINER SCALE DETAILS...THERE IS SOME SPREAD IN SOLUTIONS. NAM HAS INITIALIZED MUCH BETTER...AND ITS QPF DEPICTION HAS COME MUCH CLOSER TO REALITY DURING THE OVNGT HRS. THEREFORE...FCST WL BE BASED ON ITS SOLN. XPCT PCPN TO OVERSPREAD CWFA BY/SOON AFTER SUNRISE. AMS ALONG FRNTL BNDRY ALSO W/IN THTE RDG AXIS AND COINCIDENT W/ PWAT UP TO 1.5 IN. THEREFORE MDT RAFL PSBL. SINCE THE FNT WL BE ORIENTED WEST-EAST...IT WL PROVIDE A CORRIDOR FOR THE TN LOW TO TRACK ALONG. THAT WL TAKE PLACE TAFTN INTO TNGT. AS A RESULT...THINK THAT IMPRVMNT WL BE PAINFULLY SLOW...AND HV SLOWED DOWN ENDING OF PCPN. EVEN ONCE PCPN DOES END...THERE WL BE ENUF MEAN LYR RH AND OVERRUNNING TO KEEP CLDS IN THE PICTURE WELL INTO TNGT. WHILE INGREDIENTS FOR MDT-LCLLY HVY RA PRESENT...INDIV ELEMENTS SHUD BE PROGRESSIVE. THAT WL BE LESS APPLICABLE TO CENTRAL VA AS PCPN WL BE OF LONGER DURATION...AND AMT TO AN INCH OR MORE. THE SWRN CORNER OF THE CWFA MAY BE IN THE BULLSEYE OF HVY QPF...W/ A CONSENSUS FCST OF 2 INCHES PSBL. HIGHLAND CNTY ALSO HAS LWR FFG THAN AUGUSTA/ELSW. THEREFORE WL RAISE A FLOOD WATCH JUST FOR HIGHLAND...IN COLLAB W/ NEIGHBORING OFFICES. XPCT A DECENT SWATH OF CAA POST-FROPA. THEREFORE THERE WL BE TWO SOURCES OF COOLING TDA...THE OTHER BEING EVAP. TEMPS LKLY WONT BE COMPLETELY DIURNAL. MAXT WL BE CLOSE TO TEMPS AT SUNRISE...WHICH IS HOW DATABASE WAS POPULATED. STAYED CLOSER TO PREFERRED NAM FOR MIN-T TNGT.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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MADE A FEW CHGS TO THE WED FCST BASED ON EVOLUTION IN INITIAL 24 HRS OF THE FCST. SINCE FNT LKLY WONT SINK TOO FAR S OF CWFA...XPCT A MOIST ELY FLOW TO LINGER ACRS SRN SXN OF CWFA. THAT MSTR TRANSPORT AND OVERRUNNING WL SUPPORT CONTD CLDCVR INTO WED...SPCLY FOR SWRN CWFA WHERE LIFT UP UPSLP WL ALSO BE AVBL. MAY BE PDS OF LGT RA/DZ THRUT THE DAY THERE. ELSW HIGH PRESSURE WL BUILD SWD FM THE ERN GRTLKS...THE SUBSIDENCE FROM WHICH WL ASSIST IN SCATTERING OUT LLVL MSTR/CLDS. TEMPS LKLY WL BE HIER IN BALT-DC THAN IN SWRN ZONES DUE TO THE ADDED INSOLATION. A STAGNANT PTTN WL CONT INTO WED NGT...W/ LTL CHG IN SYNOP FEATURES.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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HIGH PRESSURE WILL PIVOT OFF THE NEW ENGLAND COAST THURSDAY WHILE LOW PRESSURE DEVELOPS OFF THE CAROLINA COAST. HIGH PRESSURE IS EXPECTED TO STAY WEDGED ACROSS THE MID-ATLANTIC DURING THIS TIME AND EASTERLY ONSHORE FLOW WILL CONTINUE INTO THURSDAY NIGHT. MOISTURE WILL INCREASE ACROSS THE REGION THURSDAY NIGHT INTO FRIDAY AS LOW PRESSURE INTENSIFIES TO THE SOUTH. MULTIPLE SHORTWAVE TROUGHS MAY CROSS THE REGION DURING THIS TIME AND RAIN MAY MOVE ACROSS THE REGION FROM WEST TO EAST. STABLE CONDITIONS WILL LEAD TO LIGHT RAINFALL AMOUNTS THROUGH FRIDAY. LOW PRESSURE WILL SLOWLY MOVE OFF CAPE HATTERAS BY FRIDAY NIGHT. THE WEDGE OF HIGH PRESSURE WILL TAKE TIME TO BREAK DOWN FRIDAY BUT SOUTHERLY FLOW WILL ALLOW TEMPS TO GET NEAR 70 DURING THE DAY. AN ACTIVE PERIOD MAY BE ON STORE FOR MUCH OF CONUS THIS WEEKEND. MODELS DIVERGE WITH THE NEXT CLOSED UPPER LEVEL LOW ACROSS THE CENTRAL PLAINS. ADDED CHANCE OF RAIN FOR SATURDAY AND SUNDAY AS THE SOUTHERN STREAM MAY REACH THE GULF COAST STATES AND AIDE IN RAIN AND PRESSURE DROPPING.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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VFR CONDS ATTM WL HEAD DOWNHILL RAPIDLY DURING MRNG PUSH AS CDFNT CROSSES TERMINALS...PROMPTING SHRA TO OVERSPREAD AREA. AM KEEPING FLGT CONDS ON EDGE BTWN MVFR AND IFR THRU DAY. DO NOT HV MUCH CONFIDENCE ON WHICH SIDE OF THE THRESHOLD IT WL END UP. MDL SOLUTIONS ARE MORE PESSIMISTIC THAN FCST. WHEREVER IT DOES BTTM OUT...XPCT IT TO STAY THERE THRU THE DAY...W/ SLOW IMPRVMNT DURING THE EVNG. XPCT CIGS TO REMAIN INTO WED...BUT AT LEAST W/ VFR BASES. CLEARING WL COME FM NE TO SW...REACHING MRB AND BWI/MTN IN THE MRNG AND DCA/IAD BY MIDDAY. LOW CIGS RESULTING IN POSSIBLE FLIGHT RESTRICTIONS THURSDAY NIGHT AND FRIDAY.
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&& .MARINE...
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STILL HV STUBBORN SCA WIND GUSTS IN THE MAIN CHANNEL OF THE BAY AS WELL AS MID BAY INLETS...SO HV XTNDD SCA TIL 10Z. FLOW SHUD SLACKEN AS SHRA ASSOCD W/ CDFNT ARRIVES DURING THE FIRST PART OF THE DAYLIGHT HRS...SO AM COMMITTED ON ENDING WIND HAZARDS BY SUNRISE. HWVR...THESE WL BE REPLACED W/ MDT-LCLLY HVY RAIN WHICH WL LAST THRU DAY. SCA IN EFFECT FOR MID BAY-LWR PTMC TAFTN-TNGT. WHILE THERE IS SOME EVIDENCE OF INCRSD WINDS BENEATH SHALLOW INVSN...DO NOT HV HIGH CONFIDENCE IN THIS SOLN. WUD THINK THAT MIXING WUD BE QUITE POOR IN ANTICIPATED LOW CLDS AND FOG. SINCE HAZARD UP...WL KEEP IT GOING... BUT WL NOT EXTEND IT INTO WED AS SIMLR CONDS WL CONT THRU THE PD. SFC LOW TO THE SOUTH MAY RESULT IN SCA CONDITIONS FROM NRLY FLOW ON THURSDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...FLOOD WATCH THROUGH THIS AFTERNOON FOR VAZ503-504. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR ANZ531>534-537-539>541-543. SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 AM EDT WEDNESDAY FOR ANZ532>534-537-540>543.
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&& $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...HTS/HAS MARINE...HTS/HAS

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