Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280217 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1010 PM EDT WED AUG 27 2014 .SYNOPSIS...WEAK HIGH PRESSURE WILL REMAIN CENTERED OVER THE SOUTHERN APPALACHIANS AHEAD OF A COLD FRONT THAT WILL SETTLE SOUTH INTO CENTRAL NC LATE THU AND THU NIGHT. && .NEAR TERM /THROUGH THURSDAY NIGHT/... AS OF 1010 PM WEDNESDAY... HIGH PRESSURE OVER THE REGION CONTINUES TO WEAKEN AND GIVE WAY TO A COLD FRONT APPROACHING FROM THE NORTH AND WEST. STARTING TO SEE SOME LOW-LEVEL MOISTURE ADVECTION AHEAD OF THE FRONT ACROSS VIRGINIA...BUT THE FEW AREAS OF SHOWERS ALONG THE FRONT...WHICH STRETCHES ACROSS KY/WV/PA...ARE EXPECTED TO DIMINISH AS THEY CROSS THE MOUNTAINS OVERNIGHT. NOT A LOT OF HIGH CLOUDS AHEAD OUT AHEAD OF THE FRONTAL ZONE...SO IT LOOKS LIKE MOST AREAS SHOULD REMAIN MOSTLY CLEAR WITH LIGHT WEST-NORTHWESTERLY AS HURRICANE CRISTOBAL PASSES WELL OFFSHORE. MAY SEE SOME RURAL AREAS IN THE UPPER 50S...BUT WITH DEWPOINTS BEGINNING TO CREEP UP FROM THE NORTH...SHOULD SEE MORE LOWER 60S THAN NIGHTS PAST. THE COLD FRONT WILL SLIP INTO THE NORTHERN PORTIONS OF THE AREA THURSDAY AFTERNOON. MODELS DO INDICATE SOME MOISTURE POOLING ALONG THE FRONT...HOWEVER OVERALL MOISTURE CONTENT IS EXPECTED TO REMAIN RATHER LOW AS THE LOW LEVEL FLOW TAKES ON A WESTERLY COMPONENT. THIS NEVERTHELESS...GIVEN THE SLIGHTLY INCREASED MOISTURE AND CONVERGENCE ALONG THE FRONT...THERE COULD BE SOME ISOLATED CONVECTION THAT DEVELOPS DURING THE AFTERNOON HOURS...MAINLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA. THE SEVERE THREAT IS RATHER MINIMAL GIVEN THAT DEEP LAYER SHEAR VALUES ARE PROGGED TO STAY AROUND OR BELOW 20 KNOTS. HOWEVER... THE NAM CONTINUES TO SHOW MORE IN THE WAY OF INSTABILITY (ALTHOUGH IT STILL SEEMS OVERDONE GIVEN THE LOWER DEWPOINTS WITHIN THE WESTERLY FLOW). NEVERTHELESS...THE GFS DOES SHOW SOME INSTABILITY AND IF A STORM IS ABLE TO GROW DEEP ENOUGH... IT COULD PRODUCE A STRONG WIND GUST GIVEN THE DRY SUB-CLOUD LAYER. LOW LEVEL THICKNESS VALUES ARE PROGGED TO INCREASE ANOTHER 10-15M ON THURSDAY...WHICH SHOULD TRANSLATE INTO HIGHS SURGING INTO THE LOW TO MID 90S (ESPECIALLY WITH THE DRY DOWNSLOPE WESTERLY FLOW). THE FRONT IS EXPECTED TO STALL ACROSS THE NORTHERN PORTIONS OF THE FORECAST THURSDAY NIGHT. THERE COULD BE AN ISOLATED SHOWER OR TWO OVERNIGHT...BUT CHANCES ARE RATHER LOW. MORE IN THE WAY OF CLOUDS AND MOISTURE SHOULD RESULT IN MILDER OVERNIGHT LOW (RELATIVE TO PREVIOUS NIGHTS)...WITH MOSTLY UPPER 60S TO NEAR 70 DEGREES EXPECTED. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 250 PM WEDNESDAY... SUBTROPICAL RIDGE WILL STRENGTHEN OVER THE REGION ON FRIDAY. DIABATIC HEATING FROM STRONG INSOLATION WILL EVENTUALLY WASH OUT THE STALLED FRONTAL ZONE INVOF THE NC/VA BORDER...BUT NOT BEFORE SERVING AS A FOCUS FOR ISOLATED/SLIGHT CHANCE CONVECTION FRIDAY AFTERNOON. LOW-LEVEL THICKNESSES AND H8 (1430M AND 18-19C RESPECTIVELY)ARE PROGGED TO BE ON PAR TO THURSDAY. HIGHS IN THE LOWER 90S. LOWS IN THE UPPER 60S TO LOWER 70S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 250 PM WEDNESDAY... SUBTROPICAL RIDGE/BERMUDA HIGH PRESSURE OVER THE SOUTHEAST US WILL REMAIN A FORMIDABLE PLAYER INTO THE WEEKEND WITH WARM AIR ALOFT ACTING TO LARGELY SUPPRESS CONVECTION ON SATURDAY WITH A CONTINUATION OF ABOVE NORMAL TEMPERATURES INTO THE LOWER TO MID 90S SATURDAY AFTERNOON. BY SUNDAY...AS THE SUBTROPICAL RIDGE AXIS BEGINS TO SLIDE EASTWARD AND OUT OVER THE WESTERN ATLANTIC...RAIN CHANCES WILL BEGIN TO INCREASE ACROSS WESTERN PORTIONS OF THE STATE VIA RING OF FIRE CONVECTION PATTERN. RAIN CHANCES RETURN CWA WIDE MONDAY AND TUESDAY...UNDER WEAKENING HEIGHTS AND COOLING TEMPS ALOFT WITH SCATTERED DIURNAL CONVECTION FIRING ALONG A THERMAL TROUGH IN PLACE EAST OF THE MOUNTAINS. THE GFS REMAINS ON THE FAST SIDE OF MODEL GUIDANCE WITH BRINGING A COLD FRONT THROUGH THE AREA TUESDAY NIGHT/EARLY WEDNESDAY...WHILE THE EC IS NEARLY A FULL DAY BEHIND. FOR NOW WILL GO WITH THE SLOWER TIMING...KEEPING CHANCE POPS THROUGH WEDNESDAY. HIGHS EARLY NEXT WEEK IN THE UPPER 80S TO LOWER 90S. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 845 PM WEDNESDAY... VFR. UNDER THE INFLUENCE OF WEAKENING SFC HIGH PRESSURE CENTERED OVER THE SOUTHERN APPALACHIANS...CLEAR AND GENERALLY CALM CONDITIONS TONIGHT WILL YIELD TO SCT TO BRIEFLY BKN 4-7 THOUSAND FT CLOUD BASES AND A LIGHT WEST TO SOUTHWEST SFC WIND AHEAD OF A COLD FRONT APPROACHING FROM THE NORTH...ON THU. AN ISOLATED TO WIDELY SCATTERED SHOWER OR STORM MAY ACCOMPANY THE FRONT AT NORTHERN TERMINALS BETWEEN 22Z THU AND 04Z FRI. OUTLOOK: SFC WINDS WILL BECOME N TO NE BEHIND THE FRONT THU NIGHT; AND THERE IS A MEDIUM CHANCE OF THE DEVELOPMENT OF MVFR CEILINGS IN NNE POST-FRONTAL FLOW FRI MORNING...MAINLY AT NORTHERN SITES. SCT TO BKN HIGH MVFR-RANGE TO LOW-VFR RANGE CLOUD BASES WILL REMAIN POSSIBLE THROUGH FRIDAY NIGHT...OWING TO THE STALL OF THE FRONT IN THE VICINITY OF CENTRAL NC THROUGH EARLY SAT. THE PROBABILITY OF PATCHY FOG WILL ALSO INCREASE BY THE WEEKEND...AS THE LOW LEVEL FLOW ASSUMES A MORE SOUTHERLY (MOIST) COMPONENT WITH THE DISSIPATION/ NORTHWARD RETREAT OF THE FRONT. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...KRD/BLS SHORT TERM...CBL LONG TERM...CBL AVIATION...MWS

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