Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290758 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 358 AM EDT MON SEP 29 2014 .SYNOPSIS...
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HIGH PRESSURE OVER THE REGION WILL WEAKEN TODAY AS LOW PRESSURE FORMS OVER THE GULF COAST STATES. THE LOW WILL MOVE OFF THE EAST COAST TUESDAY...AS A TROUGH APPROACHES THE MID-ATLANTIC WEDNESDAY. HIGH PRESSURE IS EXPECTED TO RETURN LATE IN THE WEEK. A COLD FRONT MAY PUSH THROUGH THE AREA LATE FRIDAY INTO SATURDAY.
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&& .NEAR TERM /TODAY/...
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THE PAST SVRL NGTS I`VE BEEN ON THE LONG TERM SIDE...LOOKING AT THE WX FOR THE 1ST PART OF THE NEW WK. THE WORD I USED TO DESCRIBE THE SYNOPTIC PATTERN WAS "NEBULOUS" - THERE WERE NO MAJOR SIGNATURES TO LOCK ONTO. AND NOW HERE WE ARE...AT DAY 1...AND THE PATTERN STILL LOOKS FAIRLY INDETERMINATE. ONE CLR THING IS THAT TDA WON`T XPRNC THE ABUNDANT SUNSHINE OF THE PAST 3. MOISTURE XNTDS FM THE GULF STATES TO NEW ENGLAND. A LONG PD W.V IMGRY LOOP SHOWS UPR LVL LOW PRES AREAS ALONG THE GULF CST W/ A 2ND MOVG INTO OH. THIS COMBINATION IS ALLOWING UPR LVL MOISTURE TO STREAM E OF THE APLCNHS. HENCE SKIES ARE M CLDY... WHICH IN TURN HAS CAUSED TNGT`S LOW TEMPS TO BE WARMER THAN THE PRVS FEW NGTS...AND CUT DOWN ON THE AMT OF FOG. TEMPS TDA SHOULD BE A FEW DEGS COOLER THAN IN PRVS DAYS DUE TO THE INCRSD CLD CVR. PCPN-WISE MDLS HV QUITE A DISPARITTY OF POPS. FOR NHK MET GIVES A 70 POP WHILE MAV GIVES A 20. LATEST LAV GIVES SAME SPOT A 5 POP! ALSO LOOKING AT INCOMING EURO. THIS KEEPS THE BULK OF THE MOISTURE SHUNTED OVR THE CAROLINAS/PSBLY INTO SERN VA. THIS IS ACTUALLY THE SCENARIO I WROTE LAST NGT...AND STILL SEEMS THE WAY TO GO - ALTHO M CLDY TDA SHOULD BE GNRLY DRY - PERHAPS A FEW LGT AREAS OF RA IN THE CENTRAL SHEN VLLY/LWR SRN MD. HIGH TEMPS IN THE MU70S...XCPT A80 IN THE CITIES AND A70 IN THE HIGHLANDS.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY/...
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AS THE DISORGANIZED UPR LVL SHORT WV MOVES INTO THE CAROLINAS IT APPEARS THAT ANOTHER SHORT WV CURRENTLY OVR NRN MN WL BE TRACKING INTO THE ERN GRT LKS TNGT. IN REPONSE THIS WL HELP TO PUSH THE CAROLINA LOW OFFSHORE. IF THERE IS A CHC OF RA TNGT THE BEST SHOT WOULD BE IN LWR SRN MD. LOWS IN THE 50S...XCPT L60S IN THE CITIES. THE FOREMENTIONED GRT LKS SHORT WV IS XPCTD TO TRACK ACROSS PA DURG THE DAY TUE. THIS MAY SPAWN RW/ISOLD TRW IN ERN W.V./WRN MD DURG THE AFTN. POPS WL HELD TO 30 IN THE NWRN SXN OF THE CWA. HIGHS GNRLY IN THE U70S.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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A CLOSED UPPER LOW WILL BE DRIFTING JUST NORTH OF THE AREA TUE NIGHT INTO WED. THIS FEATURE SHOULD STAY LARGELY NORTH OF THE MASON-DIXON LINE AS IT GETS COERCED EASTWARD AND DISSIPATES. THE PRECIP BANDS ASSOCIATED W/ THE WEAK LOW-LEVEL BOUNDARIES SHOULD SPREAD SOME SCATTERED SHOWERS ACROSS THE MTNS AND SOME ISOLATED SHOWERS ELSEWHERE. KEPT A LOW CHANCE POP FOR NRN PARTS OF THE AREA AND MORE OF AN OUTSIDE CHANCE ACROSS THE PIEDMONT FOR WED. DEPENDING ON HOW QUICKLY THE UPPER LOW EXITS...THERE COULD BE MORE CLOUD COVER/LOWER TEMPS AND MORE OF A DRIZZLY DAY FOR SECTIONS OF THE AREA...ESP IF SOME WEAK CAD SETS UP. THURSDAY SHOULD BE THE ONE-DAY PASSAGE OF A WEAK RIDGE...IN BETWEEN THE EXITING UPPER LOW AND THE NEXT COLD FRONT. SOME TRAPPED LOW LEVEL MOISTURE MAY BRING A FEW ISOLATED SHOWERS TO THE WRN HALF OF THE AREA...MAINLY THE HIGHER TERRAIN AREAS. TEMPS WILL BE RIGHT ON TARGET FOR AVERAGE VALUES W/ PARTLY SUNNY SKIES. FAST ON THE HEELS OF THIS BRIEF REPRIEVE WILL BE A POTENT AND QUICK-DEVELOPING LOW PRESSURE SYSTEM. A COUPLE OF SMALLER UPPER WAVES WILL COMBINE OVER THE ENTIRE LENGTH OF THE MS RVR VLY LATE THU...SPREADING ACROSS THE DEEP SOUTH - TENN VLY AND UPPER MIDWEST INTO THE EARLY MRNG HRS 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 00Z EURO DOES JUST THAT...W/ A DEEP 537DM CLOSED UPPER LOW OVER THE WRN GREAT LAKES - WHICH TAKES THE DYNAMICS OF SYSTEM OFF TO THE NORTH...ESSENTIALLY SCRAPING THE NRN PART OF THE CWA. ALTHOUGH OUR 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.
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&& .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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ALTHO SKIES SHOULD BE M CLDY TDA CIGS SHOULD RMN VFR. THESE CLDS SHOULD HELP TO SUPRESS FOG TNGT. ISOLD TRW ARE PSBL TUE AFTN IN VNCTY MRB. AN ACTIVE NEXT SEVERAL DAYS...W/ A SYSTEM OR FRONTAL PASSAGE ABOUT EVERY OTHER DAY. AN UPPER LOW WILL PASS BY ON WED...BRINGING A FEW ISOLATED SHOWERS AND LOW STRATUS. CONDITIONS CLEARING OUT A BIT ON THU...WHILE A STRONG COLD FRONT APPROACHES FROM THE WEST. THE FRONT WILL SLIDE THRU THE REGION LATE FRI. HIGH PRESSURE INTO THE WEEKEND...BUT COOLER AND DRIER CANADIAN AIRMASS.
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&& .MARINE...
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WINDS XPCTD TO RMN BLO SCA VALUES TDA THRU TUE. WEAK LOW PRES ON WED AND A QUIET THU. SLY WINDS WILL PICK UP AHEAD OF A COLD FRONT ON FRI. THE FRONT WILL BRING NW WINDS BEHIND IT THAT WILL LAST INTO THE WEEKEND.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ PRODUCTS...WOODY!/GMS

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