Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 200558 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1258 AM EST SAT DEC 20 2014 .SYNOPSIS... WEAK LOW PRESSURE WILL TRACK FROM THE GULF OF MEXICO EASTWARD AND OFF THE SOUTHEAST COAST LATE TONIGHT THROUGH SATURDAY NIGHT. HIGH PRESSURE WILL BE OVER THE AREA AGAIN DURING SUNDAY. ANOTHER LOW PRESSURE AREA MOVES NORTHEAST OUT OF THE GULF OF MEXICO AND UP ALONG THE COAST LATE SUNDAY NIGHT THROUGH MONDAY NIGHT. && .NEAR TERM /THROUGH TODAY/... QUIET ACROSS THE FORECAST AREA THIS EVENING AS UPPER/SFC HIGH PRESSURE BUILDS INTO THE REGION. LIGHT NLY WINDS...THIN HIGH CLOUDS AND DEWPOINTS IN THE LOW-MID 20S HAVE ALLOWED TEMPS TO QUICKLY DROP INTO THE LOW-MID 30S INLAND AND UPPER 30S NEAR THE COAST THIS EVENING. UPSTREAM SHORTWAVE ENERGY AND INCREASING MOISTURE WILL THICKEN AND LOWER THE CLOUD DECK. INCREASING CLOUDS AND MODELS SUGGEST TEMPS WILL LEVEL OFF THRU THE OVERNIGHT...FALLING INTO THE MID-UPPER 20S. 295K SFC DEPICTS INCREASING ISENTROPIC LIFT OVER THE REGION BY LATE TONIGHT AS SMALL AMPLITUDE SHORTWAVE ENERGY LIFTS INTO THE REGION. WINDS ALOFT ALSO INCREASE. HOWEVER...COND PRES DEFICIT AND BUFR SOUNDINGS DEPICT TOO MUCH DRY AIR FOR ANY FORCING TO OVERCOME. THE RESULT WILL BE A DRY FORECAST THRU THE OVERNIGHT. SAT...SYSTEM FROM THE GULF CONTINUES TO REMAIN SHUNTED OFF TO OUR SOUTH AS MID LEVEL FLOW REMAINS FAIRLY ZONAL. NAM/GFS STILL SHOW SOME FORCING ALOFT MAKING WAY INTO PIEDMONT BETWEEN 12-18Z/SAT AND BUFKIT SOUNDINGS SHOW SOME MODEST LIFT THROUGH THE DENDRITIC GROWTH LAYER. PTYPE ACRS THE PIEDMONT WOULD TEND TO BE SNOW/SLEET SAT AM ALTHOUGH SFC TEMPS SHOULD BE ABOVE 32 F (SFC WET BULBS IN THE UPPER 20S INITIALLY). LOW LEVELS REMAIN QUITE DRY HOWEVER...SO ANY PRECIP WILL BE VERY LIGHT (GENLY A FEW HUNDREDTHS IF THAT...WITH A TRACE MORE LIKELY). THUS...WILL ONLY GO WITH 30% POPS AT MOST. BY LATE MORNING/EARLY AFTN...AREA OF FORCING OVER THE PIEDMONT/CENTRAL VA WEAKENS AS THE SFC LOW PUSHES OFF THE SE COAST. WILL CARRY LOW CHC POPS IN FAR SE ZONES (ALL RAIN) THROUGH THE AFTN (ALTHOUGH MOST OF THE PRECIP SHOULD STAY S OF THE CWA). CLOUDY TO MSTLY CLOUDY W/ HIGHS GENLY 40-45 F SAT. && .SHORT TERM /TONIGHT THROUGH MONDAY/... SFC HIGH PRESSURE NOSES SOUTH INTO THE REGION SAT NIGHT/SUN...WITH DRY CONDS THEN FOR SAT NGT AND SUN. LOWS IN THE 20S N TO THE 30S SE SAT NIGHT...WITH HIGHS MAINLY FROM 45-50 F ON SUN. NEXT SYSTEM...THIS ONE MORE AMPLIFIED WILL AFFECT THE AREA ON MON...WITH LIKELY POPS ALL ZONES BY LATE MON AM/MON AFTN. LOOKS LIKE ALL RAIN ASIDE FROM A BRIEF MIX POSSIBLE AT ONSET IN FAR NW COUNTIES. HIGHS MON ONLY AROUND 40 F NW TO THE MID 50S FAR SE IN CAD SETUP. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... LOW PRESSURE LIFTS TO THE NE MONDAY NIGHT WITH POPS 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. 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. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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VFR CONDS IN PLACE ACROSS THE REGION THIS MORNING, WITH PREDOMINATELY VFR CONDS TO PERSIST THROUGH THE TAF PERIOD. HIGH PRESSURE WILL CONTINUE TO RIDGE SOUTH ACROSS THE REGION FROM THE EASTERN GREAT LAKES/NORTHEAST THROUGH THE TAF PERIOD, AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE SOUTHEAST TOWARD THE CAROLINAS TODAY, WHILE ASSOCIATED WEAK SFC LOW MOVES ACROSS THE SOUTHEAST TODAY AND TONIGHT. EAST FLOW WILL ALLOW FOR LOWERING CIGS THROUGH THE MORNING, WITH OVC AT 5-8 KFT AGL EXPECTED THROUGH AFTN. FORCING WILL BE ENOUGH FOR SOME SPOTTY LIGHT RAIN SHRAS, MAINLY IN FAR SRN PORTIONS OF THE AREA. PERIODIC MVFR CIGS WILL BE POSSIBLE ACROSS PHF/ORF/ECG AFTER 18Z. HOWEVER, RAIN SHOULD BE LIGHT ENOUGH TO PRECLUDE ANY VSBY RESTRICTIONS. OUTLOOK...ANY PRECIP COMES TO AN END EARLY SATURDAY EVENING AND CONDITIONS WILL GRADUALLY IMPROVE FROM WEST TO EAST THROUGH THE REST OF SAT NIGHT. HIGH PRESSURE BUILDS TO THE NORTH OF THE AREA SUNDAY. A SERIES OF LOW PRESSURE SYSTEMS AND COMPLEX FRONTAL BOUNDARIES WILL BRING CHANCES FOR RAIN AND PERIODS OF LOW CEILINGS AND VISIBILITIES BEGINNING MONDAY.
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&& .MARINE... HIGH PRESSURE REMAINS NW OF THE REGION TONIGHT...WITH LINGERING LIGHT CAA ALONG THE COAST. THIS WILL MAINTAIN A 10-15KT NNW WIND OVERNIGHT...WITH 2-3FT SEAS IN THE OCEAN AND 1-2FT WAVES IN THE BAY. HIGH PRESSURE SPREADS ACROSS NEW ENGLAND SATURDAY AND SATURDAY NIGHT...WITH THE SURFACE RIDGE AXIS REMAINING INLAND OVER THE PIEDMONT. THIS WILL MAINTAIN LIGHT (5-10KT) NORTHERLY FLOW OVER THE MARINE AREA. HIGH PRESSURE MOVES FARTHER E SUNDAY AND SUNDAY NIGHT...AS LOW PRESSURE DEVELOPS OFF THE SOUTHEAST COAST SUNDAY NIGHT...AND THEN TRACKS NE OFF THE MID ATLANTIC COAST MONDAY AND MONDAY NIGHT. THE SURFACE PRESSURE GRADIENT TIGHTENS AHEAD OF THE LOW MONDAY...WHICH HAS THE POTENTIAL TO PRODUCE 15-20KT EASTERLY FLOW OVER THE OCEAN AND LOWER BAY. THIS ONSHORE FLOW 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 LATER MONDAY NIGHT INTO TUESDAY. A STRONG LOW PRESSURE SYSTEM TRACKS W OF THE MOUNTAINS TUESDAY NIGHT...WITH A STRONG COLD FRONT CROSSING 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/SAM SHORT TERM...LKB/MAS LONG TERM...AJZ/MAS AVIATION...MAM/LSA MARINE...AJZ

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