Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 201833 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 133 PM EST THU NOV 20 2014 .SYNOPSIS... A WEAK BUT DRY FRONTAL SYSTEM WILL CROSS THE REGION TODAY. HIGH PRESSURE REBUILDS INTO THE AREA LATE TONIGHT THROUGH FRIDAY NIGHT. HIGH PRESSURE SLIDES OFFSHORE SATURDAY AHEAD OF ANOTHER COLD FRONT...WHICH APPROACHES FROM THE WEST LATE IN THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... TEMPS THIS MORNING HAVE WARMED QUICKLY INTO THE UPPER 40S TO LOW 50S THANKS TO SW SFC WINDS 10-15 MPH WITH GUSTS OF 20-25 MPH. 20/12Z KWAL SOUNDING DEPICTS A MUCH WARMER COLUMN BELOW 700MB WITH THE 950-900MB LAYER WARMING NEARLY +15C FROM 24 HOURS AGO. A DRY...CLIPPER FRONT/SFC TROUGH HAS LOCATED ALONG THE SPINE OF THE APPALACHIANS THIS MORNING AS SFC HIGH PRESSURE GETS SUPPRESSED TO THE SOUTH. ALOFT...POTENT SHORTWAVE EMBEDDED IN UPPER LONG WAVE TROUGH HAS LOCATED OVER THE GREAT LAKES REGION PER LATEST WATER VAPOR IMAGERY AS A SHEAR AXIS/VORT LOBE LIFTS INTO THE REGION FROM THE SOUTH. STRONG 135+ KT UPPER JET STREAK ORIENTED W-E ACROSS THE LOCAL AREA. CROSS SECTIONS DEPICT MODEST INCREASING MID-LEVEL MOISTURE IN TANDEM WITH UVM FROM VORT LOBE/INCREASING WINDS ALOFT...RESULTING IN A FEW AFTERNOON CLOUDS AS THE FRONT CROSSES THE REGION. SKIES AVG MOSTLY SUNNY TO PARTLY SUNNY. STRONG WLY WINDS ALOFT WILL RESULT IN GUSTS OF 20-25 MPH THIS AFTERNOON. DEWPOINTS WILL MIX INTO THE LOW 20S/UPPER TEENS RESULTING IN RELATIVE HUMIDITY VALUES AOB 30 PCT. HOWEVER...BASED ON RECENT RAINFALL AND COOL TEMPS NO FIRE WEATHER CONCERNS ARE EXPECTED. CLIPPER FRONT PUSHES OFFSHORE LATE TODAY BRINGING A REINFORCING SHOT OF COLD AIR THIS EVENING. STRONGEST CAA ARRIVES TONIGHT. WHILE H85 TEMPS AND HEIGHTS DECREASE THIS AFTERNOON...WLY DOWNSLOPE DRY FLOW WILL RESULT IN INCREASING LOW-LEVEL THICKNESSES. WITH TEMPS ALREADY WARMING INTO THE LOW 50S...HAVE OPTED TO BUMP TEMPS UP ACROSS THE BOARD INTO THE LOW-MID 50S. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/... A DEEP LONGWAVE TROUGH PASSES ACROSS THE NE CONUS TONIGHT INTO FRIDAY AS SFC HIGH PRESSURE BUILDS OVER THE OHIO VALLEY TONIGHT AND INTO THE MID ATLANTIC REGION ON FRIDAY/FRIDAY NIGHT. THE UPPER TROUGH WILL ALLOW COOLER AIR TO CONTINUE SPILLING INTO THE REGION TONIGHT...WITH GRADUAL WARMING FRIDAY/FRIDAY NIGHT. MOSTLY CLEAR AND DRY CONDITIONS WILL PROMOTE EXCELLENT RADIATIONAL COOLING CONDITIONS THU/FRI NIGHTS AND KEEP HIGH TEMPS ON THE COOL SIDE AGAIN ON FRIDAY. LOWS IN THE LOWER 20S NW TO LOWER 30S FAR SE TONIGHT...THEN IN THE LOW-MID 20S FRIDAY NIGHT (NEAR 30 IMMEDIATE COAST). HIGHS IN THE LOW-MID 40S AGAIN ON FRIDAY (UPPER 30S FAR NORTH DUE TO THE CLOSE VICINITY OF THE LONGWAVE TROUGH). HIGH PRESSURE SLIDES OFF THE COAST ON SATURDAY...RESULTING IN A SHIFT TO SLY WINDS AND ANOTHER GRADUAL WARM-UP AS THE RIDGE AXIS MOVES EAST OF THE MID ATLANTIC COASTLINE. EXPECT HIGHS IN MID-UPPER 40S NW TO LOWER 50S SE. MID- HIGH LEVEL CLOUDS INCREASE FROM THE WEST AND SOUTHWEST SATURDAY NIGHT AS GULF MOISTURE GETS PULLED INTO THE REGION BEHIND THE DEPARTING HIGH PRESSURE AND AHEAD OF AN UPPER LEVEL DISTURBANCE DIGGING ACROSS TEXAS INTO THE ARKLATEX REGION. MEANWHILE...THE ASSOCIATED SFC LOW MOVES INTO THE LOWER MISSISSIPPI VALLEY. THIS WILL BE THE NEXT SYSTEM TO WATCH SINCE IT IS EXPECTED TO BRING WIDESPREAD RAINFALL TO THE AREA SUNDAY INTO MONDAY. SEE LONG TERM DISCUSSION BELOW FOR ADDITIONAL DETAILS. && .LONG TERM /SUNDAY 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 AFTN AND EVENING. BEST SUPPORT / LIFT SHIFTS NORTH OF THE FA AFTR MIDNIGHT AS WRM FRNT ADVANCES 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 /19Z THURSDAY THROUGH TUESDAY/... A COLDFRONT WILL APPROACH FROM THE W THIS AFTN...CROSSING THE REGION TONGHT. SW WINDS THIS AFTN WILL GUST 20 TO 25 KT WITH THE APPROACH OF THE SURFACE TROUGH. THE COLDFRONT CLEARS THE COAST THIS EVENING...WITH WINDS TURNING NW AND REMAINING GUSTY. 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... STEADY SW WNDS (MNLY TO 20 TO 25 KT) OVR MUCH OF THE WTRS ATTM...CONTG INTO THE MRNG HRS. MDLS CONT TO SUGGEST A DCRS IN SPEEDS BY MID/LT AFTN JUST AHEAD OF CDFNT ENTERING THE WTRS. WNDS BECOME W...THEN NW POST CDFNT TNGT...WHILE INCRSG IN SPEEDS BACK TO SOLID SCA AS LO CAA OCCURS. SCAS WILL BE HELD IN PLACE DESPITE BREAK IN SPEEDS XPCD TDA. MAY HAVE TO CONSIDER RAISING SCAS FOR RIVERS IF NEC (DURG LO CAA PD TNGT). SEAS WILL BE MARGINAL AS MOST 5-6 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 COME LATE SUN INTO MON AS SRLY WINDS INCRS AHEAD OF NEXT SYS APPROACHING FROM THE SW. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR ANZ630>634-638- 652-654-656-658. SMALL CRAFT ADVISORY UNTIL 10 AM EST FRIDAY FOR ANZ650. && $$ SYNOPSIS...BMD NEAR TERM...SAM SHORT TERM...BMD LONG TERM...MPR AVIATION...DAP MARINE...ALB

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