Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 241714 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 1214 PM EST WED DEC 24 2014 .SYNOPSIS... LOW PRESSURE STRENGTHENS WEST OF THE MOUNTAINS TODAY...AND . AN ASSOCIATED COLD FRONT WILL CROSS THE AREA TONIGHT. HIGH PRESSURE BUILDS BACK IN FROM THE SOUTHWEST CHRISTMAS DAY THROUGH FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... LATEST WX ANALYSIS CONTINUES TO FEATURE A DYNAMIC SYSTEM TAKING SHAPE OVER THE DEEP SOUTH INTO THE TENNESSEE VALLEY AT MIDDAY. LOCALLY...A RESIDUAL COOL-WEDGE AIRMASS IS HANGING TOUGH ACROSS THE PIEDMONT, KEEPING TEMPS IN THE MID/UPPER 40S TO LOW 50S ALONG AND W OF THE RIC METRO AREA. MEANWHILE, SFC WARM/COASTAL FRONT IS MOVING ONSHORE WITH TEMPERATURES NOW WELL INTO THE 60S OVER SE VA & NE NC. WV SAT IMAGERY SHOWING BROAD SWATH OF WARM CONVEYOR BELT MOISTURE LIFTING NORTH FROM THE EAST CENTRAL GULF COAST ACROSS THE LOCAL AREA. SFC LOW OVER THE SE CONUS WILL DEEPEN AND TRACK NNE INTO THE OHIO VALLEY THROUGH THIS EVENING. BROAD SWATH OF MOISTURE WILL LIFT ENE ACROSS THE REGION THROUGH THE BALANCE OF THE DAY, WITH PERIODIC SHOWERS CONTINUING OVER THE PIEDMONT. THE NEW NAM/ARW IS A BIT CLOSER IN HRRR DEPICTION OF BRIEF LULL IN PCPN BY LATE AFTN ON INTO THE EARLY EVENING AS MID-LEVEL DRY SLOT, CURRENTLY LIFTING ACROSS THE MID SOUTH INTO THE WESTERN CAROLINAS, SWINGS ACROSS THE REGION. HOWEVER, PLENTY OF LLVL MOISTURE TO KEEP OVC WORDING THROUGHOUT. REGARDING CONVECTIVE POTENTIAL, HAVE CONFINED THUNDER WORDING TO THE SE COASTAL PLAIN AFTER 20Z AS TEMPERATURES AND DEWPOINTS CONTINUE TO RISE. SPC HAS ADDED THE SE IN A SLIGHT SEVERE RISK FOR TONIGHT IN THE PRESENCE OF A WARM AND MOISTURE RICH AIRMASS AND A STRONG 925-700MB WIND FIELD. DESPITE MEAGER SFC BASED INSTABILITY WITH LACK OF CLOUD COVER, MID LVL SHEAR/HELICITY PARAMETERS WOULD ARGUE FOR A CONTINUED THUNDER MENTION OVER THE COASTAL AREAS. THUS, WL RETAIN SLIGHT CHC T OVER THE COASTAL PLAIN, MAINLY FOR THE LATE AFTN AND EVENING HOURS. THE COLD FRONT ARRIVES FROM THE W LATE THIS EVENING AND MOVES W-E ACROSS THE AREA BETWEEN 03-06Z TONIGHT. DROPPED POPS OFF DURING AFOREMENTIONED LULL PERIOD EARLY THIS EVENING, WITH MORE SCATTERED RAIN SHRAS TO PERSIST LATER IN THE EVENING AND AFTER MIDNIGHT...RAPIDLY DIMINISHING BEHIND THE FRONT AFTER 06Z TOWARDS DAWN CHRISTMAS MORNING. BY LATE AFTERNOON, EXPECT TEMPS TO RANGE FROM THE LOW TO MID 50S WELL INLAND...MID/UPPER 60S FOR CENTRAL PORTIONS TO AROUND 70 SE. THESE HIGHS WILL BE NEAR DAILY RECORDS...SEE THE CLIMATE SECTION BELOW FOR DETAILS. GIVEN ONLY WEAK CAA, EXPECT TEMPS TO BE SLOW TO DROP OFF OVERNIGHT, LIKELY LINGERING IN THE 50S AND 60S FOR MUCH OF THE NIGHT. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... DRIER AIR ARRIVES CHRISTMAS MORNING AS HIGH PRESSURE BUILDS IN FROM THE W. A SLOWER FRONTAL PASSAGE WILL RESULT IN A MILD CHRISTMAS MORNING WITH LOWS RANGING FROM THE MID 40S FAR W...TO THE MID/UPPER 50S SE. THE SKY SHOULD BECOME MAINLY SUNNY WITH SCT AFTERNOON CU ALONG WITH BREEZY WESTERLY FLOW BY MID/LATE MORNING CHRISTMAS DAY. HIGHS SHOULD RANGE FROM THE MID 50S TO LOWER 60S CHRISTMAS DAY AS CAA IS WEAK AND WILL BE OFFSET BY DOWNSLOPE WARMING (AND DUE TO A WARM BEGINNING). CLEAR/SEASONABLE THURSDAY NIGHT WITH LOWS IN THE UPPER 20S TO MID 30S. SURFACE HIGH PRESSURE SETTLES IMMEDIATELY OFF THE COAST FRIDAY RESULTING IN LIMITED MIXING/LIGHT WINDS AND SUNNY CONDITIONS. HIGHS SHOULD GENERALLY BE IN THE 50S. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... THE MODELS ARE IN GOOD AGREEMENT TO BEGIN THE PERIOD FRIDAY NIGHT WITH THE STRONG RIDGING OVER THE SOUTHEASTERN US AND HIGH PRESSURE OVER THE SOUTHEAST...CENTERED OVER EASTERN VA/NC. BUT THE MODELS STRUGGLE WITH THE BREAKING DOWN OF THE RIDGE WITH THE GFS BREAKING IT DOWN MUCH MORE QUICKLY THAN THE ECMWF. THE GFS ALLOW THE NEXT COLD FRONT TO DROP INTO THE ARE SAT NIGHT AND MOVES IT SOUTH OF THE REGION BY SUNDAY MORNING...SETTING UP AN OVERRUNNING PATTERN SUNDAY AFTERNOON INTO MONDAY MORNING. THE ECMWF...AND THE 12Z IS FURTHER NORTH WITH FEATURES THAN 00Z RUN...KEEPS THE RIDGE MUCH STRONGER OVER THE SE AND DOES NOT ALLOW THE COLD FRONT TO MOVE THROUGH THE AREA SAT NIGHT. IT STALLS THE FRONT OVER THE AREA ON SUNDAY AND AS A WAVE OF LOW PRESSURE FORMS ALONG THE BOUNDARY AND LIFTS NE INTO THE CENTRAL APPALACHIANS...IT PUSHES GULF MOISTURE INTO THE AREA. THE 00Z ECMWF PUSHED THE WAVE OFF THE COAST BY MONDAY...BUT THE 12Z RUN LIFTS THE LOW TO THE NORTH AND DRAGS A COLD FRONT ACROSS THE REGION ON TUESDAY. SO FOR NOW WITH THE GREAT SPREAD IN THE MODELS...HAVE TRENDED TOWARD HPC/WPC GUIDANCE...WHICH IS SIMILAR TO THE 00Z ECMWF AND BROUGHT THE WAVE INTO THE REGION ON SUNDAY AFTERNOON AND EVENING WITH IT EXITING BY MONDAY AFTERNOON. HAVE INCREASED POPS TO 50% FOR THAT PERIOD...KEEPING SATURDAY DRY. HAVE ALSO GONE DRY ON MONDAY NIGHT INTO TUESDAY. THE BIG DIFFERENCE COMES TO TEMPERATURES AS THE GFS WOULD ALLOW MUCH COLD AIR INTO THE REGION BEGINNING ON SUNDAY THROUGH TUESDAY. THIS COULD ALSO POTENTIALLY LEAD TO SOME WINTRY PCPN WITH WAVE ON SUNDAY NIGHT. FOR NOW HAVE KEPT TEMPERATURES ABOVE FREEZING AND ALL RAIN WITH THE COLD AIR BEING KEPT MORE TO THE NORTH. FOR TEMPERATURES HAVE ALLOW FOR A GRADUAL COOL DOWN THROUGH THE PERIOD WITH THE COLDEST AIR ARRIVING ON TUESDAY WITH HIGHS IN THE 40S. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 12Z...ANOTHER BAND OF RAIN WAS PROGRESSING INTO THE CWA FROM THE SW. CIGS AND VSBYS WILL CONTINUE TO BE VARIABLE BUT ARE EXPECTED TO BE PREDOMINANTLY IFR OR LOWER THIS MORNING. A BIT OF IMPROVEMENT IS EXPECTED THIS AFTERNOON AS THE AREA BECOMES WARM SECTORED BUT THE TAF SITES SHOULD BE MAINLY IFR IS STILL EXCEPT AT ORF AND ECG. CONFIDENCE IN THE DEGREE OF IMPROVEMENT IS MARGINAL. A COLD FRONT APPROACHES FROM THE WEST TONIGHT WITH SHOWERS AND A SLGT CHC OF THUNDER (THIS PCPN NOT INCLUDED IN THE TAF). CONDITIONS IMPROVE FROM THE WEST IN THE MORNING AS WINDS TURN TO WESTERLY. OUTLOOK...HIGH PRESSURE DOMINATES THURSDAY AFTERNOON THROUGH SATURDAY WITH DRY WEATHER. A CHC FOR RAIN RETURNS SUNDAY AS LOW PRESSURE APPROACHES FROM THE WEST. && .MARINE... DENSE FOG ADVISORY IS IN EFFECT FOR THE MARINE AREA THROUGH LATE THIS AFTERNOON AS WARM MOIST AIR MOVES OVER THE RELATIVELY COOL WATERS. AS OF 11Z...WINDS WERE BEGINNING TO INCREASE FROM THE SE. SCA STARTED AT 15Z FOR THE MOUTH OF THE BAY AS WAVES WILL SOON REACH 4 FT IN THE CHANNEL. PREVIOUS DISCUSSION... AS OF 08Z...WINDS REMAIN LIGHT OVER THE MARINE AREA BUT ARE FORECAST TO INCREASE FROM THE SE AND THEN S THIS MORNING AS A WARM FRONT MOVES N THROUGH THE WATERS AND LOW PRESSURE DEEPENS OVER THE OHIO VALLEY. SCA IS IN EFFECT FOR ALL THE WATERS EXCEPT THE RIVERS SAVE THE LOWER JAMES. SCA CONDITIONS OVER INLAND WATERS MAY BE MINIMAL AT FIRST DUE TO LIMITED MIXING BUT WILL BECOME MORE FAVORABLE THURSDAY MORNING. HAVE ADDED THE LOWER JAMES WITH TIMES STAGGERED SLIGHTLY FROM THE BAY (STARTING AT 21Z TODAY AND ENDING 3 HOURS EARLIER THURSDAY). LATER SHIFTS MAY NEED TO CONSIDER SCA BEHIND THE COLD FRONT FOR OTHER RIVER ZONES ON THURSDAY MORNING. SCA IS ALREADY IN EFFECT N OF PARRAMORE ISLAND. SEAS ARE EXPECTED TO BUILD TO 5 FT OR HIGHER BY 18Z S OF THERE AND DECIDED TO BEGIN SCA S OF PARRAMORE ISLAND AT 15Z TO ALLOW SUFFICIENT CUSHION. HIGH PRESSURE THEN BUILDS INTO THE REGION ON THURSDAY NIGHT AND LINGERS THROUGH SATURDAY AS A STRONG UPPER LEVEL RIDGE BUILDS INTO THE SOUTHEASTERN US AND KEEPS STRONG HIGH PRESSURE AT THE SURFACE OVER THE REGION THROUGH SATURDAY. LOW PRESSURE APPROACHES FROM THE SW SUNDAY AND MOVES ACROSS THE REGION MONDAY. PRELIMINARY INDICATIONS DO NOT INDICATE THAT A SCA WILL BE NEEDED WITH THIS SYSTEM. && .TIDES/COASTAL FLOODING... WATER LEVELS AT BISHOPS HEAD AND CAMBRIDGE ARE EXPECTED TO APPROACH MINOR FLOODING LATE TODAY AND EARLY THIS EVENING. && .CLIMATE... RECORD HIGHS FOR CHRISTMAS EVE/WED 12/24: RICHMOND.......71 F (1988) NORFOLK........75 F (1891) SALISBURY......67 F (1990) ELIZ CITY NC...75 F (1990) && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...COASTAL FLOOD ADVISORY UNTIL 8 PM EST THIS EVENING FOR MDZ021>023. NC...NONE. VA...NONE. MARINE...DENSE FOG ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ630>638- 650-652-654-656-658. SMALL CRAFT ADVISORY UNTIL 4 PM EST THURSDAY FOR ANZ633-634- 650-652-654-656-658. SMALL CRAFT ADVISORY UNTIL 4 PM EST THURSDAY FOR ANZ630>632. SMALL CRAFT ADVISORY UNTIL 1 PM EST THURSDAY FOR ANZ638. && $$ SYNOPSIS...AJZ/ALB NEAR TERM...AJZ/MAM SHORT TERM...AJZ/LKB LONG TERM...ESS AVIATION...LSA MARINE...LSA TIDES/COASTAL FLOODING... CLIMATE...

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