Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 230838 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 338 AM EST TUE DEC 23 2014 .SYNOPSIS...A COLD AIR DAMMING RIDGE WILL REMAIN LOCKED IN PLACE EAST OF THE APPALACHIANS THROUGH THIS EVENING. A WARM FRONT WILL LIFT NORTHWARD THROUGH THE AREA WEDNESDAY MORNING AS A LOW PRESSURE SYSTEM STRENGTHENS WEST OF THE MOUNTAINS. AN ASSOCIATED COLD FRONT WILL SURGE EASTWARD ACROSS THE CAROLINAS WEDNESDAY NIGHT. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 300 AM TUESDAY... OVERVIEW: POTENT SHORTWAVE ENERGY IN VICINITY OF THE FOUR-CORNERS REGION WILL DIG SOUTHEAST INTO THE LOWER MIDWEST ALONG THE SOUTHWESTERN PERIPHERY OF A CUT-OFF LOW ANCHORED OVER THE CENTRAL PLAINS THIS AFTERNOON...AMPLIFYING THE LONGWAVE TROUGH IN PLACE OVER THE CENTRAL CONUS. IN RESPONSE...CYCLOGENESIS WILL OCCUR IN VICINITY OF THE TX/LA GULF COAST THIS AFTERNOON AS THE AFOREMENTIONED SHORTWAVE ROUNDS THE BASE OF THE AMPLIFYING LONGWAVE TROUGH. THE SFC LOW WILL TRACK NORTHWARD ACROSS THE DEEP SOUTH AND INTO THE TN VALLEY TONIGHT. FURTHER DOWNSTREAM...SMALL AMPLITUDE WAVES EMBEDDED WITHIN STRENGTHENING SOUTHWEST FLOW WILL TRACK NORTHEAST INTO THE CAROLINAS THIS AFTERNOON INTO TONIGHT. PRECIPITATION: PATCHY LIGHT RAIN WILL REMAIN POSSIBLE THROUGH THE MORNING...PRIMARILY IN THE WESTERN PIEDMONT VIA LOW-LEVEL WARM ADVECTION /925 MB FRONTOGENESIS/ ATOP THE PRONOUNCED COLD AIR DAMMING WEDGE LOCKED IN PLACE ACROSS THE STATE. ELSEWHERE AND OTHERWISE...FOG AND OCCASIONAL DRIZZLE WILL PERSIST INTO THE AFTERNOON. EXPECT WIDESPREAD RAIN TO DEVELOP UPSTREAM OVER GA/SC TODAY AS LOW-LEVEL FLOW /WARM ADVECTION/ STRENGTHENS IN RESPONSE TO THE ARRIVAL OF MORE POTENT SHORTWAVE ENERGY /DPVA/ IN SW FLOW ALOFT...PROGRESSING NORTHWARD INTO CENTRAL NC DURING THE LATE AFTERNOON AND EVENING HOURS. EXPECT WIDESPREAD RAIN TO PERSIST OVERNIGHT IN ASSOC/W STRENGTHENING WARM ADVECTION ATOP THE PRONOUNCED (ALBEIT INCREASINGLY SHALLOW/ERODING) COLD AIR DAMMING WEDGE. TEMPERATURES: NEAR STEADY TEMPS TODAY WILL GRADUALLY RISE FROM SOUTHEAST TO NORTHWEST LATE THIS EVENING INTO TONIGHT AS A WARM FRONT ADVANCES NORTHWARD INTO THE AREA AND THE COLD AIR DAMMING WEDGE ERODES. THOUGH TEMPS WILL REMAIN IN THE 40S WHERE THE WEDGE REMAINS IN PLACE (TRIAD) THROUGH 12Z WED...TEMPS IN THE WARM SECTOR (COASTAL PLAIN...SANDHILLS AND PORTIONS OF THE TRIANGLE) WILL HAVE RISEN TO THE LOWER 60S. -VINCENT && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... AS OF 240 AM TUESDAY... ...WARMER...BREEZY...WITH HEAVY RAIN THREAT WEDNESDAY INTO WEDNESDAY EVENING... OVERALL... MODELS ARE IN GOOD AGREEMENT WITH THE STORM TRACK TO THE WEST OF THE APPALACHIANS. WEDNESDAY WILL BEGIN WITH LINGERING CAD IN THE PIEDMONT DAMMING REGION... BUT A WARM FRONT WILL BE SURGING NORTHWARD WITH WIDESPREAD RAIN... LOCALLY HEAVY EARLY IN THE DAY. THE WARM FRONT WILL SURGE INTO VA IN THE AFTERNOON... THEN A LINE OF CONVECTION CAN BE EXPECTED WITH THE MAIN COLD FRONT LATER IN THE DAY INTO THE EVENING. THE AFOREMENTIONED WARM FRONT IS EXPECTED TO BE LIFTING NORTHWARD THROUGH THE PIEDMONT WEDNESDAY MORNING WITH CATEGORICAL POP. THE NW QUADRANT OF THE PIEDMONT WILL BE THE LAST REGION TO HANG ON TO THE RESIDUAL CAD WITH LOW CEILINGS AND VISIBILITIES/COOL STABLE SURFACE TEMPERATURES BEFORE EVEN THAT REGION BREAKS INTO THE WARM SECTOR WEDNESDAY AFTERNOON. THERE IS STILL A QUESTION OF TIMING OF THE WARM FRONT WHICH WILL AFFECT HIGH TEMPERATURES IN THE PIEDMONT WEDNESDAY. IN ADDITION... SOME ENSEMBLE MEMBERS OF BOTH THE GFS AND EC INDICATE SHOWERY CONDITIONS AND LOW CEILINGS EVEN AFTER THE WARM FRONT MOVES INTO VA. HOWEVER... A LULL IN SIGNIFICANT RAINS IS EXPECTED AFTER THE WARM FRONT IN THE EAST AND SOUTH. HIGHS SHOULD REACH WELL INTO THE 60S AND EVEN SOME 70S DOWN EAST. SOUTHWEST WINDS WILL INCREASE TO 10-20 MPH. A PRE-FRONTAL CONVECTION LINE AND/OR A LINE OF CONVECTION WITH THE ACTUAL COLD FRONT WILL FOLLOW LATER WEDNESDAY INTO WEDNESDAY EVENING (PROGRESSING FROM WEST TO EAST ACROSS THE STATE). SOME LOCALLY VERY HEAVY RAIN CAN BE EXPECTED. A FLASH FLOOD WATCH HAS BEEN CONSIDERED. HOWEVER... GIVEN THE RELATIVELY DRY ANTECEDENT CONDITIONS... ESPECIALLY IN THE WEST DURING THE PAST MONTH - FLASH FLOOD GUIDANCE REMAINED HIGH. THE QPF FOR STORM TOTAL OF 2-3 INCHES WOULD GET MOST AREAS NEAR THE THRESHOLD. HOWEVER... GIVEN THAT THE HEAVIEST RAIN SHOULD COME IN 2-3 ROUNDS... THE GROUND SHOULD BE ABLE TO RECOVER SOMEWHAT IN BETWEEN THE HEAVIEST RAINS. THEREFORE... LOCAL RUNOFF PROBLEMS WILL LIKELY BE THE END RESULT WHICH SHOULD AFFECT MOSTLY URBAN AREAS. WE WILL ADD THIS TO THE HAZARDOUS WEATHER OUTLOOK. THE FINAL LINE OF CONVECTION MAY DROP LOCAL 1 TO 1.5 INCHES IN AN HOUR... SO SOME URBAN FLASH FLOODING MAY OCCUR IF THIS HAPPENS. THIS WOULD MOST LIKELY OCCUR LATE WEDNESDAY IN THE WEST... AND LATE AFTERNOON INTO THE EVENING IN THE EAST. SEVERE STORMS ARE NOT EXPECTED AT THIS TIME. HOWEVER... GUSTY WINDS TO 40-45 MPH ARE LIKELY TO OCCUR WITH THE FINAL LINE OF CONVECTION WEDNESDAY AFTERNOON AND EVENING. MLCAPES IN ADVANCE OF THE FRONT SHOULD BE HELD DOWN BY THE EXTENSIVE MOISTURE AND CLOUDS/SHOWERS KEEPING THE SEVERE THREAT LIMITED. SENSIBLE WEATHER WILL BE FOR RAIN INTO WEDNESDAY MORNING... TAPERING TO SCATTERED SHOWERS DURING THE DAY. BECOMING BREEZY FROM THE SOUTHWEST AND TEMPS RISING INTO THE 60S TO LOWER 70S. ANOTHER LINE OF TWO OF SHOWERS/ISO THUNDERSTORMS SOME WITH GUSTY WINDS WED AFTERNOON INTO THE EVENING. PARTIAL CLEARING WEDNESDAY NIGHT WITH LOWS IN THE 40S TO LOWER 50S. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 235 AM TUESDAY... MILD AND DRIER THURSDAY INTO SATURDAY... BREEZY WEST WINDS CHRISTMAS DAY WITH SKIES BECOMING PARTLY TO MOSTLY SUNNY. MILD HIGHS IN THE 50S TO LOWER 60S EXPECTED. WINDS SHOULD DIMINISH DURING THE MID TO LATE AFTERNOON AS THE PRESSURE GRADIENT WEAKENS AS THE SURFACE HIGH BUILDS IN FROM THE GULF COAST STATES. MILD TEMPERATURES AND MOSTLY CLEAR SKIES ARE EXPECTED FRIDAY INTO SATURDAY AS HIGH PRESSURE BUILDS OVER THE SOUTHEAST STATES. EXPECT LOWS IN THE 30S AND HIGHS IN THE 50S. MODEL SPREAD STILL INCREASES THROUGH THE WEEKEND...WITH THE EC CONTINUING MUCH DEEPER WITH THE NEXT MID/UPPER LEVEL TROUGH...RESULTING IN A STRONGER SURFACE WAVE THAT WOULD BRING YET ANOTHER WET AND UNSETTLED PERIOD SUNDAY INTO MONDAY. WHEN THE ENSEMBLES ARE CONSIDERED... A MUCH WEAKER WAVE RESULTS. THEREFORE... WE WILL SIMPLY INDICATE AN INCREASE IN CLOUDINESS THEN WITH COOLER TEMPERATURES. THERE MAY BE AN IMPORTANT STORM IF THE EC DOES INDEED VERIFY LATER SUNDAY INTO EARLY NEXT WEEK. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... AS OF 200 AM TUESDAY... 24-HR TAF PERIOD: STATUS QUO. ADVERSE CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD IN ASSOCIATION WITH A PRONOUNCED COLD AIR DAMMING WEDGE IN PLACE OVER THE REGION. LIFR/VLIFR CEILINGS (100-300 FT AGL) THIS MORNING SHOULD IMPROVE TO LIFR/IFR (400-700 FT AGL) THIS AFTERNOON...THOUGH INCREASING CHANCES FOR RAIN MAY ULTIMATELY NEGATE THE POSITIVE (ALBEIT MEAGER) INFLUENCE OF DIURNAL HEATING... ESPECIALLY AT THE INT/GSO TERMINALS. CEILINGS ARE EXPECTED TO RETURN TO LIFR/VLIFR (100-300 FT AGL) THIS EVENING AND PERSIST OVERNIGHT. LOOKING AHEAD: CEILINGS WILL GRADUALLY IMPROVE DURING THE DAY WEDNESDAY AS A WARM FRONT LIFTS NORTHWARD THROUGH THE REGION... HOWEVER...GIVEN WIDESPREAD/PERSISTENT RAINFALL WILL LIKELY LIMIT IMPROVEMENT TO IFR/MVFR (700-1400 FT AGL) AT BEST. VFR CONDITIONS WILL RETURN IN THE WAKE OF A STRONG COLD FRONTAL PASSAGE WED EVE/NIGHT WINDS WILL BECOME SOUTHERLY AT ~15 KT WITH GUSTS TO 25 KT IN THE WAKE OF THE WARM FRONT WED...VEERING TO THE SOUTHWEST AND EVENTUALLY WEST AT 15-20 KT WITH GUSTS UP TO 30 KT WED EVENING/NIGHT IN THE WAKE OF A STRONG COLD FRONTAL PASSAGE. VFR CONDITIONS WILL PREVAIL THEREAFTER AS HIGH PRESSURE BUILDS INTO THE REGION IN THE WAKE OF THE FRONT. -VINCENT && .HYDROLOGY... AS OF 245 AM TUESDAY... THIS IS THE OUTLOOK FOR AREA RIVERS THROUGH THE UPCOMING STORM. RAINFALL OVER THE PAST 24 HOURS RANGED FROM AROUND 0.10 IN THE WESTERN PIEDMONT TO OVER 1 INCH IN THE NORTHEAST PIEDMONT AND COASTAL PLAIN. THIS WILL PRODUCE ONLY MINOR RISES ON THE TAR/ROANOKE/NEUSE AND CAPE FEAR RIVERS. THIS IS THE THIRD SIGNIFICANT RAINFALL EVENT (>0.5 INCHES) OVER THE AREA SINCE 12/10. RELATIVE SOIL MOISTURE PERCENTAGES IN THE 0-200 CM COLUMN HAVE BEEN INCREASING...WITH HIGHER WATER PERCENTILES NEARER THE SURFACE. THEREFORE MORE RUNOFF IS EXPECTED FROM OUR UPCOMING RAIN EVENT. CURRENT QUANTITATIVE PRECIPITATION FORECASTS FROM THE MODELS INCLUDING THE GEFS AND NAEFS ENSEMBLES ARE IN AGREEMENT WITH 1 TO 1.5 INCHES TONIGHT THROUGH EARLY WEDNESDAY... THEN ANOTHER ROUND OF LOCALLY 1+ INCH TOTALS LATER WEDNESDAY AND WEDNESDAY NIGHT WITH THE COLD FRONT. STORM TOTAL RAINFALL OF 2 TO LOCALLY 3 INCHES FOR THE ENTIRE EVENT ENDING WEDNESDAY NIGHT WILL POTENTIALLY CAUSE MINOR FLOODING ON THE NEUSE RIVER AND TAR RIVER LATE ON CHRISTMAS DAY. HOWEVER... IT WOULD BE LOW IMPACT WITH THOSE RIVERS LIKELY ONLY REACHING MINOR FLOOD STAGE. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT HYDROLOGY...MLM/BADGETT

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