Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 300758 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 358 AM EDT TUE SEP 30 2014 .SYNOPSIS... LOW PRESSURE OVER LAKE ERIE WILL TRACK ACROSS THE NORTHEASTERN U.S. THIS AFTERNOON AND THIS EVENING BRINGING RAIN CHANCES TO THE MID ATLANTIC REGION. HIGH PRESSURE WILL RETURN TO THE EAST COAST WEDNESDAY AND REMAIN IN PLACE UNTIL A COLD FRONT APPROACHES THE AREA FRIDAY. && .NEAR TERM /TODAY/... HV GONE OUTSIDE MULTIPLE TIMES TO TAKE OBS NEAR IAD TNGT - THERE IS DFNTLY FOG OUTSIDE BUT IT SEEMS MORE LK A LOW CLD DECK DESCENDING TOWARD THE GRND THAN THE MORE TRADITIONAL DROPPING VSBYS FM A RAD COOLING ENVIRONMENT. A FEW OBS ARE COMING IN W/ LOW VSBYS AS WELL - CHO REPORTING 1/4 SM. BUT LOOKING AT TRAFFIC CAMS DOWN I-81/RT 29/I-64 VSBYS AREN`T BAD. IR STLT SHOWS CLDS MOVG OFFSHORE BUT W/ SUCH A LGT WINDS FIELD I DON`T KNOW THAT MEANS LO LVL MOISTURE WL BE EXITING VERY QUICKLY. WE`LL CONT TO KEEP OUR EYES ON THIS AND ISSUE A DENSE FOG ADVSRY IF NEEDED. BY MID MRNG XPCTG SOME BRKS IN THE CLDS TO DVLP. TEMPS SHOULD RISE INTO THE MU70S. AREA OF LOW PRES HAS MOVED E OF MI. UPR LOW ASSO W/ THIS IS XPCTD TO TRACK ACROSS PA LATE TDA/TNGT. THIS WL BRING A CHC OF RW/TRW TO THE NWRN PART OF THE CWA THIS AFTN. BUFKIT PROFILES ARE NOT IMPRESSIVE - PERHAPS CAPES OF 500 W/ AN ALMOST NOT EXISTANT WIND FIELD THRU 10K FT. SVR THREAT LOOKS MINIMAL. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... THIS EVE THE SHORT MAY BE IMPACTING THE NERN PART OF THE FCST AREA...AND HV TAKEN CHC POPS ALL THE WAY TO THE NRN PART OF THE BAY. SOME BRKS IN CLDS XPCTD OVRNGT...AND HENCE FOG CHCS WL RETURN AFTR MDNGT. LOWS IN THE L60S E OF I-95...MU50S W. WEAK HIGH PRES BDLG INTO THE AREA FM THE N WED. HIGHS IN THE M70S. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... BEHIND THE EXITING UPPER LOW WED NIGHT...LOW-LEVEL MOISTURE WILL BE TRAPPED OVER THE MID-ATLC REGION TO CLOSE OUT THE WORK WEEK. THU WILL BE MAINLY DRY...BUT WAVERING BETWEEN CLOUDY AND MOSTLY CLOUDY. THESE SKY CONDITIONS WILL MODERATE TEMPS...AS THEY DID ON MON. EVEN W/ A HIGH PRESSURE RIDGE SLIDING OVERHEAD...THE BOUNDARY LAYER WILL REMAIN MOIST. A HANDFUL OF LIGHT SHOWERS MAY DEVELOP ACROSS THE MTNS BUT BARELY ENOUGH TO WARRENT POPS ACROSS THESE AREAS. THE SKY COVER WILL BE A FAIRLY SHALLOW LOW STRATUS DECK THAT WILL BEGIN TO MIX OUT DURING THE LATE AFTN HRS - W/ SOME POKES OF SUN BEFORE EVE. A MODERATED OVERNIGHT TEMP PROFILE THU NIGHT. EVEN THOUGH A STRONG COLD FRONT WILL BE FAST-APPROACHING FROM THE UPPER MIDWEST/TENN VLY...OUR AREA WILL BE WELL E OF THIS FEATURE OVERNIGHT AND HAVE ANOTHER RELATIVELY WARM NIGHT SET-UP FOR THE REGION/. SMALLER UPPER WAVES OF MID-LEVEL ENERGY WILL MAKE THEIR WAY ACROSS THE CNTRL APLCNS AND BEGIN TO COMBINE OR AT LEAST INTERACT AS THEY REACH THE MS VLY REGION. WHAT STARTED AS A MORE COMPACT LOW PRESSURE SYSTEM OVER THE PLAINS ON THU WILL BE A MORE POTENT AND ENTENSIVE SYSTEM STRETCHING FROM THE GULF COAST TO NORTH OF THE GREAT LAKES EARLY FRI. THE MAIN RESULTANT VORT MAX WILL START TO DISSIPATE AS IT CROSSES THE SRN APLCNS AND MOVES TOWARD THE VA TIDEWATER REGION. SLIGHTLY LAGGING BEHIND BUT NOT LACKING ANY PUNCH WILL BE YET ANOTHER UPPER WAVE - THIS ONE PACKING THE CANADIAN AIR - WILL SWING IN FROM THE BEHIND LATER IN THE DAY. A WAVE OF PRE-FRONTAL RAINS WILL SLIDE ACROSS THE EAST COAST...INCLUDING OUR REGION...BUT IT DEPENDS ON THIS SECONDARY INCOMING CANADIAN AIRMASS. THE STRENGTH AND TIMING OF THIS FEATURE COMING IN ON THE BACKSIDE OF THE EAST COAST SYSTEM WILL DETERMINE IF MUCH OF PRECIP DISSIPATES AND PULLS UP NORTH OF US LATE FRI NIGHT. THE GFS IS LESS-SHARP W/ THE INCOMING TROUGH AXIS THAN THE RUN AT THIS TIME LAST NIGHT. A COMPLEX COUPLE OF UPPER VORT LOBES WILL BE SWINGING AROUND THE BOTTOM OF THE UPPER TROUGH AS IT NEARS THE AREA. EACH ONE COULD INDIVIDUALLY HAVE AN INFLUENCE...LIKE DIGGING THE SYSTEM FURTHER SOUTH OR FORCING A BRIEF AREA OF STRONG LIFT ACROSS THE WARM SECTOR. HOWEVER...THE DYNAMICS OF THE SYSTEM SHOULD LARGELY EXIT OFF TO THE NORTH INTO EARLY SAT...LIMITING NOT ONLY THE CONVECTIVE POTENTIAL BUT RAIN POTENTIAL ACROSS THE REGION. NOT MUCH QPF BEING PRINTED-OUT BY LONG TERM GUIDANCE AS MODELS LARGELY BYPASS OUR AREA FOR RAINFALL. SEEMS REASONABLE W/ WHERE THE DYNAMICS OF THE SYSTEM WILL BE AND THE RELATIVE MOVEMENT AWAY FROM THE AREA. HIGHS ON FRI WILL LIKELY REACH THE M-U70S AND THE COLD FRONT WILL MOVE THRU OVERNIGHT...LOWS WILL STILL ONLY DROP INTO THE 50S FOR MUCH OF THE AREA. THE MTNS WILL START TO SEE 40S OVERNIGHT W/ THE COLDER LOW LEVEL AIR COMING IN...BUT THE FRONT WON`T ARRIVE QUICK ENOUGH TO REALLY COOL OFF THE AREA - THAT WILL BE THE NEXT NIGHT. THE TROUGH AXIS WILL BE APPROACHING ON SAT...SO CONDITIONS WILL BE PLEASANT W/ HIGHS IN THE L70S AND A DRIER AIRMASS...BUT W/ THE TROUGH AXIS SLIDING OVER THE AREA LATE IN THE DAY - SWEEPING IN THE COLDER AND MUCH DRIER AIRMASS...OVERNIGHT LOWS SAT NIGHT WILL DROP BACK INTO THE U40S AND L50S. ANOTHER ONE-DAY REPRIEVE BEFORE ANOTHER CLIPPER SHORTWAVE LACKING PRECIP WILL SWING DOWN FROM THE GREAT LAKES...REINFORCING THE COOLER/DRIER AIRMASS. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... MRNG LO CLD/FOG DFNTLY A PROB. ATTM CONDS IN THE IFR/LIFR RNG. GIVEN THE WIND FIELD IS SO LGT IT MAY BE SVRL HRS AFTR SUNSET B4 CONDS IMPRV SIGNIFICANTLY. VFR CONDS XPCTD AFTR MID MRNG...LASTING THRU THE EVE. FOG MAY DVLP AGN OVRNGT W OF I-95. TRAPPED LOW LEVEL MOISTURE ACROSS THE REGION OVER THE NEXT FEW DAYS WILL KEEP THE CLOUDS IN PLACE. PERIODIC LIFTING OF THE STRATUS DECK HEIGHT POSSIBLE...ESPC DURING THE AFTN HRS EACH DAY UNTIL FRI. SHOULD REMAIN DRY AND CLOUDY/MOSTLY CLOUDY UNTIL A FRONTAL PASSAGE LATE FRI NIGHT. HIGH PRESSURE INTO THE WEEKEND...BUT COOLER AND DRIER CANADIAN AIRMASS. && .MARINE... WINDS BLO SCA VALUES TDA THRU WED. AN UPPER LOW MOVING OFF THE NY/NEW ENGLAND COAST WILL KEEP AN ARM OF LOW LEVEL MOISTURE STRETCHED ACROSS THE REGION ON THU. ALTHOUGH WE`LL BE DRY THAT DAY...SLY WINDS WILL PICK UP AHEAD OF A COLD FRONT APPROACHING FROM THE WEST. THE FRONT WILL ARRIVE LATE FRI...BRINGING NW WINDS BEHIND IT THAT WILL LAST INTO THE WEEKEND. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ PRODUCTS...WOODY!/GMS

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