Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 200324 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1024 PM EST WED NOV 19 2014 .SYNOPSIS... HIGH PRESSURE BUILDS ACROSS THE SOUTHEAST THROUGH TONIGHT. A WEAK...DRY FRONTAL SYSTEM WILL CROSS THE REGION THURSDAY...WITH HIGH PRESSURE REBUILDING OVER THE AREA LATER THURSDAY AND FRIDAY. HIGH PRESSURE MOVES OFFSHORE SATURDAY AHEAD OF ANOTHER COLD FRONT WHICH APPROACHES FROM THE WEST LATE IN THE WEEKEND. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... CLIPPER FRONT WILL APPROACH FROM THE NW OVERNIGHT AS AN AREA OF MID/HIGH CLOUDS MOVES THROUGH. TEMPS TONIGHT WILL BE MILDER THAN LAST NIGHT. LOWS IN THE UPR 20S TO LOW 30S. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... UPPER LOW AND SHORTWAVE ENERGY EMBEDDED IN BROAD/DEEP CYCLONIC FLOW OVER THE ERN CONUS WILL CROSS THE GREAT LAKES ON THURS. ASSOCIATED SFC LOW WILL LIFT INTO QUEBEC THURS AS THE WEAK...DRY CLIPPER FRONT CROSSES THE REGION THURS. THIS FRONT WILL BRING A REINFORCING SHOT OF COLD/DRY AIR THURS NIGHT. IN ADVANCE OF THE FRONT...SWLY FLOW INCREASES WITH GUSTS 20-25 MPH. WAA/INCREASING LOW-LEVEL THICKNESSES AND MIXING WILL RESULT IN WARMER DAYTIME TEMPS...WITH HIGHS FORECAST IN THE UPPER 40S NW TO MID 50S SE (STILL AROUND 10 DEGS BELOW NORMAL). H85 TEMPS ALSO RECOVER TO AROUND 0C. GUIDANCE COMING IN DRIER THURS COMPARED TO PREVIOUS RUNS...WITH DEWPOINTS MIXING INTO THE MID TEENS DURING THE AFTERNOON. THIS WILL DROP MIN RH VALUES BELOW 30 PCT. FRONT PUSHES OFFSHORE THURS NIGHT AS WINDS BECOME NWLY. UPPER TROUGH ALSO BEGINS TO EJECT NEWD OVER NEW ENGLAND THURS NIGHT AS SFC HIGH PRESSURE BUILDS OVER THE OH VALLEY. GUIDANCE COMING IN STRONGER WITH CAA THURS NIGHT-FRI COMPARED TO PREVIOUS RUNS. THIS AS A ~1035MB SFC HIGH BUILDS OVER THE OH VALLEY THURS NIGHT INTO FRI. HAVE LOWERED TEMPS THURS NIGHT AND FRI ACCORDINGLY. H85 TEMPS DROP TO AROUND -6 TO -8C (-1 TO -2 STD DEV) FRI AS LOW LEVEL THICKNESSES DROP AROUND 30M...YIELDING TEMPS IN THE LOW TO MID 40S. SFC HIGH BUILDS OVERHEAD FRI NIGHT...RESULTING IN OVERNIGHT LOWS IN THE LOW TO MID 20S. PIEDMONT MAY AGAIN BE BACK INTO THE UPPER TEENS. HIGH PRESSURE IS SLOWER THAN PREVIOUS FORECAST TO EXIT THE COAST SAT...RESULTING IN WEAK MIXING SAT AFTERNOON. H85 TEMPS AND LOW LEVEL THICKNESSES MODERATE SAT...BUT TEMPS STILL EXPECTED ONLY IN THE MID 40S NW TO LOW 50S SE. MID-UPPER CLOUDS INCREASE LATE SAT AS A SRN STREAM SYSTEM APPROACHES FROM THE SW. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... COMPLEX SYSTEM TO AFFECT RGN EARLY NEXT WEEK. MODELS IN BETTER AGREEMENT WITH DEPICTION OF LOW PRES PUSHING ACROSS THE RED RIVER VLY/NRN TX SAT NIGHT AND EARLY SUNDAY...TAKING ON A NEG TILT AS IT EJECTS NE INTO THE MID MS VLY ON SUN & TOWARDS THE GREAT LAKES BY EARLY MONDAY. MODELS ALSO AGREE THAT ABUNDANT GULF MOISTURE GETS TRANSPORTED NORTH (AIDED BY A SRN STREAM S/W) AHEAD OF THE COLD FRONT WHICH ALLOWS FOR A WIDESPREAD OVERRUNNING RAIN EVENT INVOF THE ADVANCING WARM FRONT. ORIENTATION OF FRONTAL BNDRY WILL LIKELY BE THE DETERMINING FACTOR TEMP WISE...AND A GOOD DEAL OF UNCERTAINTY REMAINS WITH TEMPS. MODELS CONTINUE TO HINT AT PSBL IN-SITU DAMMING OVR THE PIEDMONT SUN NIGHT/ERLY MON...WHILE TEMPS IN THE U60S-L70S OVER THE COASTAL PLAIN. UPSHOT...EXPECT A WET AND WRMR PERIOD AHEAD OF THE CDFRNT. PER LATEST MODELS...SLOWED THE ONSET OF PCPN A BIT SUN MORN AS THE MODELS DO NOT BRING IN THE BEST LIFT / OMEGA UNTIL AFTR 18Z. CONFIDENCE HIGH ENUF TO INCREASE POPS TO CATEGORICAL SUN AFTRN AND EVENING. BEST SUPPORT / LIFT SHIFTS NORTH OF THE FA AFTR MIDNIGHT AS WRM FRNT ADANCES TO THE NORTH SO EXPCT CHC POPS TO CONTINUE LATE (MAYBE MORE OF A LIGHT RAIN / DRIZZLE REGIME). LOWS 50-60. INCRG PRS GRDNT BEHIND WRM FRNT AND AHEAD OF CDFRNT SHUD RESULT IN A BREEZY TO (WINDY ALONG THE COAST) PERIOD LATE SUNDAY NIGHT THRU MONDAY. PCPN TYPE BECOMES MORE CONVECTIVE IN NATURE AS FA GETS INTO WRM SCTR. LATEST DATA SUGGESTS A WARM DAY MONDAY WITH ONLY SCT SHWRS AS DEEP MSTR WILL BE LACKING. HIGHS U60S-L70S. MODELS DIFFER A BIT ON TIMING OF CDFRNTL PASSAGE WITH THE ECMWF MORE PROGRESSIVE TAKING THE BNDRY AND ASSCTD PCPN OFFSHORE LATE MON NIGHT WHILE THE GFS STALLS THE BNDRY ALONG THE COAST AS YET ANTHR S/W RIDES NE ALONG IT PROLONGING THE PCPN INTO TUE. GIVEN THE MODEL DIFFERENCES...WENT AHEAD AND KEPT LOW CHC SHWRS INTO TUE. HIGHS U50S-M60S. DRIER AND A BIT COOLER WED. HIGHS 50-55. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... AS OF 01Z...A COLD FRONT OVER THE GREAT LAKES AND OHIO VALLEY WILL CROSS THE APPALACHIANS EARLY THURSDAY AND REACH THE MID ATLANTIC COAST LATE THURSDAY. LITTLE CHANGE IN SENSIBLE WEATHER IS INDICATED. A STEADY SW WIND OVERNIGHT WILL BECOME A BIT GUSTY DURING THE DAY THURSDAY. SCATTERED HIGH CLOUDS ARE FORECAST OVERNIGHT AND MODEL SOUNDINGS INDICATE THAT SCT CU MAY DEVELOP THURSDAY AFTN. OUTLOOK...THURSDAY NIGHT THROUGH MONDAY...THE COLD FRONT CLEARS THE AREA THURSDAY EVENING WITH WINDS TURNING TO THE NW. HIGH PRESSURE SETTLES OVER THE MID ATLANTIC REGION FRI AND SAT...MOVING WELL OFFSHORE ON SUNDAY. A COMPLEX WEATHER SYSTEM IS EXPECTED TO BRING PERIODS OF RAIN SUNDAY THROUGH MONDAY WITH IFR CONDITIONS POSSIBLE. && .MARINE... PRS GRDNT AHEAD OF APPRCHG CDFRNT WILL QUICKLY INCREASE THIS EVENING RESULTING IN SCA`S FOR ALL AREAS TONIGHT AND THU. GUSTS TO 30 KT PSBL ACROSS NRN WTRS AND MIDDLE CHES BAY BUT DON`T XPCT ANY GALES ATTM. DATA SUGGESTS WNDS MAY DECREASE FOR A FEW HRS LATE THU AFTRN AS FRNT CROSSES THE AREA THEN INCRS THU NIGHT DUE TO CAA BEHIND IT. THUS...HAVE HELD ONTO THE SCA`S THRU THURSDAY NIGHT INSTEAD OF SPLITTING INTO TWO SEPERATE EVENTS. SEAS WILL BE MARGINAL AS MOST 5 FOOTERS WILL REMAIN OUT NEAR 20 NM. HIGH PRESSURE SETTLES OVER THE MID ATLANTIC REGION FRI AND SAT... MOVING WELL OFFSHORE ON SUNDAY. NEXT CHC FOR SCA`S WILL COMR LATE SUNDAY INTO MONDAY AS SRLY WINDS INCRS AHEAD OF NEXT SYSTM APPRCHG FROM THE WEST. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM EST THURSDAY FOR ANZ635>638. SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR ANZ630>634-650- 652-654-656-658. && $$ SYNOPSIS...MAM/SAM NEAR TERM...JDM/SAM SHORT TERM...SAM LONG TERM...MPR AVIATION...LSA MARINE...MPR

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