Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 202100 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 400 PM EST SAT DEC 20 2014 .SYNOPSIS...
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WEAK LOW PRESSURE WILL PUSH OFF THE SOUTHEAST COAST TONIGHT...AS HIGH PRESSURE REMAINS OVER THE LOCAL AREA THROUGH SUNDAY EVENING. ANOTHER LOW PRESSURE AREA MOVES NORTHEAST OUT OF THE GULF OF MEXICO AND UP ALONG THE CAROLINA COAST LATE MONDAY INTO TUESDAY...AS HIGH PRESSURE DRIFTS OFF THE NEW ENGLAND COAST INTO THE CANADIAN MARITIMES. A COLD FRONT WILL CROSS THE WEDNESDAY NIGHT WITH HIGH PRESSURE RETURNING BY CHRISTMAS DAY.
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&& .NEAR TERM /THROUGH SUNDAY/...
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LATEST ANALYSIS SHOWS ~1030 MB SFC HIGH PRESSURE CENTERED OVER EASTERN CANADA...RIDGING DOWN INTO THE MID ATLC. SFC LOW PRESSURE SLIDING INTO THE ATLC OFF THE COAST OF NORTHERN FL. DRIER AIR BEGINNING TO ERODE SOME OF THE CLOUD COVER OVER THE REGION ALTHOUGH SKIES ARE STILL MOSTLY CLOUDY OVERALL THIS AFTN...WITH TEMPERATURES MAINLY IN THE UPPER 30S TO LOWER 40S. SPOTTY LIGHT PRECIP NOW BECOMING CONFINED TO NE NC AND SHOULD MOVE OFFSHORE OVER THE NEXT FEW HRS. WILL MAINTAIN 20% POPS IN THE FAR SE ZONES...OTHERWISE WILL HAVE A DRY FORECAST THIS EVENING/OVERNIGHT. MODEL BUFKIT SOUNDINGS SHOW A FAIR AMOUNT OF LINGERING LOW LEVEL MOISTURE OVERNIGHT SO NOT CONFIDENT THAT SKIES COMPLETELY CLEAR OUT OVERNIGHT (WILL GO PARTLY CLOUDY). LOWS WILL RANGE FROM THE MID 20S OVER MUCH OF THE NORTHERN 1/2 OF THE CWA AWAY FROM THE COAST...TO THE LOWER 30S OVER SE COASTAL SECTIONS. IF SKIES COMPLETELY CLEAR OUT MAY SEE TEMPS A FEW DEGREES COLDER THAN THIS. HIGH PRESSURE REMAINS ENTRENCHED OVER THE MID-ATLANTIC SUNDAY WITH A MIX OF SUN AND CLOUDS. LIGHT WINDS OVERALL WITH A LIGHT ONSHORE NE FLOW OVER THE SE COASTAL ZONES...SEASONABLE HIGHS IN THE LOWER- MID 40S NE TO AROUND 50 F IN SOUTH CENTRAL VA.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
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MODELS SHOW NEXT SHORTWAVE TROUGH AMPLIFYING ACRS THE NORTHERN PLAINS SUN NIGHT/MON...AS STRONG UPPER LEVEL RIDGING HOLDS STRONG FROM FLORIDA TO THE CARRIBEAN. MID/UPPER LEVEL FLOW PROGGED TO TURN MORE SW AND THIS WILL HELP STEER LOW PRESSURE NE FROM THE GULF COAST STATES INTO THE SE AND MID ATLC COASTAL WATERS MON/MON NIGHT. POSITION OF SFC HIGH TO OUR N...SHIFTING EAST TO THE NEW ENGLAND COAST BY 12Z/MON IS NOT FAVORABLE FOR LOCKING COLD AIR OVER THE AKQ CWA. STILL SHOULE SEE ENOUGH COLD AIR INITIALLY OVER THE REGION SUN NIGHT/MON MORNING DUE TO CLEAR SKIES THROUGH PART OF THE NIGHT. THIS WILL LEAD TO THE CHC OF A FEW HRS WORTH OF OVERRUNNING FROZEN PRECIP OVER CLIMO FAVORED PIEDMONT ZONES NW OF RICHMOND (WITH LITTLE CHC FOR ANYTHING BUT ALL RAIN OVER THE REST OF THE CWA). LOW LEVEL THICKNESSES (1000-850MB) ARE MARGINAL BUT BUFKIT SOUNDINGS SHOW A NARROW LAYER OF BELOW FREEZING TEMPS AT THE SFC FROM ABOUT 09-15Z/MON AT KCHO (AND LIKELY AT KLKU). STILL SOME QUESTION AS TO HOW FAST PRECIP ARRIVES BUT OVERALL LOOKS LIKE CHANCES RAMP UP SIGNIFICANTLY DURING THE 09-12Z TIMEFRAME. WILL GO WITH A CHC FOR SLEET OVER THE PIEDMONT BETWEEN 09-12Z...TRANSITIONING TO SLEET/FREEZING RAIN FROM ABOUT 12-15Z/MON (ALTHOUGH BECOMING CONFINED TO THE FAR NW BY THIS POINT). IN ANY EVENT...THIS LOOKS LIGHT AS BULK OF DEEPER MOISTURE LIKELY ARRIVES AFTER A CHANGEOVER TO ALL RAIN. ALSO...NOT ANTICIPATING TEMPS IN MID 20S...GENLY CLOSER TO 30-32 F...SO IMPACTS ARE EXPECTED TO BE MINIMAL FOR THE MOST PART. HIGHS MON ONLY IN THE UPPER 30S/AROUND 40 NW TO THE MID 50S FAR SE IN CAD SETUP. MAINTAINING LIKELY TO CATEGORICAL POPS THROUGH MON AFTN...ALTHOUGH QPF AMOUNTS ONLY AVG 0.25-0.50". LOW PRESSURE LIFTS TO THE NE MONDAY NIGHT WITH POPS SLOWLY DIMINISHING FROM SW-NE OVERNIGHT. MID-LEVEL RIDGING BRIEFLY BUILDS INTO THE REGION TUESDAY. HOWEVER...MOIST SOUTHERLY FLOW ORIGINATING FROM THE GULF STREAM WILL PREVAIL SO LOW CHC (30%) POPS WILL BE MAINTAINED. HIGHS IN THE LOW 60S FAR SE TO THE UPPER 40S NW.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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A VERY DYNAMIC SYSTEM LIFTS NNE WEST OF THE APPALACHIANS TUESDAY NIGHT WITH THE ATTENDANT COLD FRONT CROSSING THE MID-ATLANTIC WEDNESDAY. THE FIRST POTENTIAL OF RAIN ARRIVES TUESDAY NIGHT ASSOCIATED WITH MOIST WAA. THE SECOND POTENTIAL WILL BE WEDNESDAY AHEAD OF THE COLD FRONT. THERE IS A POTENTIAL FOR THUNDER WEDNESDAY AS SURFACE DEWPOINTS POTENTIALLY EXCEED 60F (ESPECIALLY OVER THE COASTAL PLAIN). THE PATTERN DOES SUPPORT THE POSSIBILITY OF A DYNAMICALLY FORCED LINE OF CONVECTION CONTAINING STRONG WIND GUSTS AS CURRENT FORECAST GUIDANCE SUGGESTS A 925-700MB WIND FIELD AVERAGING 40-50KT. THIS WOULD BE A CLIMATOLOGICALLY RARITY THIS TIME OF YEAR...SO CONFIDENCE IS ON THE LOW-SIDE GIVEN THAT THIS IS 5-6 DAYS OUT. TEMPERATURES WILL BE VERY MILD AHEAD OF THE FRONT TUESDAY AND WEDNESDAY...WITH HIGHS AVERAGING FROM THE MID 50S NW...TO MID/UPPER 60S SE. DRY AND BREEZY CONDITIONS WILL LIKELY PREVAIL BY CHRISTMAS DAY...WITH HIGH TEMPERATURES OF 50-55. THE FLOW BECOMES MORE SW BY FRIDAY WITH CURRENT FORECAST HIGHS OF 55-60...BUT 60-65 IS POSSIBLE BASED ON LOW-LEVEL THICKNESS FIELDS.
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&& .AVIATION /21Z SATURDAY THROUGH THURSDAY/... MOSTLY VFR CONDITIONS EXPECTED ACROSS THE AREA WITH SOME -RA OR SPRINKLES DEPICTED ON RADAR ACROSS NE NC. HIGH PRESSURE MOVES WEST OVERNIGHT AS THE WEAK WAVE OFF THE SE US COAST CONTINUES TO PUSH OUT TO SEA. LIGHT WINDS AND VFR CONDITIONS EXPECTED THROUGH SUN EVENING BEFORE THE APPROACH OF THE NEXT WAVE MOVING NE FROM THE GULF OF MEXICO AND UP THE EAST COAST. OUTLOOK...A SERIES OF LOW PRESSURE SYSTEMS AND COMPLEX FRONTAL BOUNDARIES WILL BRING CHANCES FOR RAIN AND PERIODS OF LOW CEILINGS AND VISIBILITIES MONDAY THROUGH WEDNESDAY. && .MARINE... LATEST OBS HIGH PRESSURE SPREADS EAST ACROSS NEW ENGLAND THROUGH TONIGHT, RIDGING SOUTH INTO THE AREA TODAY. MEANWHILE, WEAK SFC LOW PRESSURE WILL PASS SOUTH OF THE REGION LATER TODAY AND TONIGHT. THIS WILL MAINTAIN LIGHT NORTHERLY FLOW ~10 KT OVER THE MARINE AREA TODAY. HIGH PRESSURE MOVES FARTHER E SUNDAY AND SUNDAY NIGHT, AS LOW PRESSURE DEVELOPS OFF THE SOUTHEAST COAST SUNDAY NIGHT BEFORE TRACKING NE OFF THE LOWER MID ATLANTIC COAST LATER MONDAY AND MONDAY NIGHT. THE RESULTANT TIGHTENING SURFACE PRESSURE GRADIENT WILL ALLOW ONSHORE (EAST) FLOW TO GRADUALLY INCREASE MONDAY AFTN, GRADUALLY BUILDING SEAS MONDAY NIGHT AND EARLY TUESDAY. 15-20KT EASTERLY FLOW OVER THE OCEAN AND LOWER BAY COULD PRODUCE A PERIOD OF SCA CONDITIONS ESPECIALLY OVER THE SRN OCEAN ZONES (MAINLY FOR SEAS) AND LOWER BAY/MOUTH OF JAMES. THERE IS NO CAA IN THE WAKE OF THIS LOW...SO SUB-SCA CONDITIONS SHOULD PREVAIL BEHIND THE SYSTEM LATER MONDAY NIGHT INTO TUESDAY. A STRONG LOW PRESSURE SYSTEM LOOKS TO DEVELOP ACROSS THE OHIO VALLEY, TRACKING WEST OF THE MOUNTAINS TUESDAY NIGHT. HOWEVER, THIS SYSTEM WILL PUSH A STRONG COLD FRONT ACROSS THE MID ATLANTIC COAST LATER WEDNESDAY. SCA CONDITIONS ARE LIKELY WEDNESDAY NIGHT INTO CHRISTMAS DAY AS HIGH PRESSURE BUILDS IN FROM THE WNW. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...NONE. && $$ SYNOPSIS...LKB NEAR TERM...LKB SHORT TERM...JDM/LKB LONG TERM...BMD AVIATION...MAM/DAP MARINE...BMD/MAM

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