Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 040013 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 810 PM EDT THU SEP 3 2015 .SYNOPSIS...A WEAK DISTURBANCE WILL PASS OVER NORTHERN NORTH CAROLINA TONIGHT. A BACKDOOR COLD FRONT WILL APPROACH FROM THE NORTH LATE FRIDAY... THEN PUSH SOUTHWARD THROUGH THE AREA FRIDAY NIGHT... BEFORE SETTLING TO OUR SOUTH ON SATURDAY. HIGH PRESSURE WILL NOSE IN FROM THE NORTH OVER THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 235 PM THURSDAY... CONVECTION CHANCES STILL LOOK PRETTY SLIM FOR THE REST OF THE DAYLIGHT HOURS IN CENTRAL NC. THE LATEST MESOANALYSES INDICATE PW VALUES NEAR OR BELOW NORMAL OVER THE NRN TWO THIRDS OF THE CWA... WITH SMALL MLCAPE OF 500 J/KG OR LOWER WITH CINH PERSISTING IN THE NORTHEAST CWA... AND VERY WEAK DEEP LAYER SHEAR. THE ONLY CONVECTION THUS FAR OUTSIDE OF THE VA MOUNTAINS HAS BEEN ACROSS EXTREME SE NC ALONG THE OLD OUTFLOW BOUNDARY AND BENEATH THE WEAK MID LEVEL SHEAR AXIS. BASED ON THE BOUNDARY LOCATION AND ATTENDANT LOW LEVEL MASS CONVERGENCE AS WELL AS MOISTURE AVAILABILITY... CONTINUE TO THINK THAT THE FAR SRN AND SE FRINGE OF THE CWA MAY STILL SEE ISOLATED SHOWERS AND STORMS OVER THE NEXT SEVERAL HOURS... GIVEN THAT LOW AND MID LEVEL LAPSE RATES ARE BEST ACROSS THIS SRN TIER. LOWER PW AND LOWER POTENTIAL FOR INSTABILITY ELSEWHERE WITH A LACK OF TRIGGER SHOULD PRECLUDE SHOWER/STORM DEVELOPMENT OVER THE REST OF THE CWA THROUGH EARLY EVENING. THEN AFTER NIGHTFALL... IT`S A TOUGH CALL ON WHETHER OR NOT WE`LL SEE ISOLATED SHOWERS OVERNIGHT. SOME SREF MEMBERS AS WELL AS THE NAM AND GFS SPIT OUT A LITTLE LIGHT PRECIP MAINLY N AND NE OF RDU... LIKELY A RESULT OF WEAK DPVA DRIFTING SOUTHWARD FROM VA AND/OR WEAK UPPER DIVERGENCE ALONG A SUBTLE UPPER SHEAR AXIS THAT WILL EXTEND FROM WV ACROSS NE NC LATE TONIGHT. IN EITHER CASE... COVERAGE AND AMOUNTS DO NOT APPEAR TO BE VERY HIGH... GIVEN THE WEAKNESS OF ANY POSSIBLE FORCING FEATURES AND THE ABSENCE OF ANY PRECIP LATE TONIGHT ON OTHER MODELS SUCH AS THE NSSL WRF. HOWEVER... WILL LEAVE IN A SLIGHT CHANCE OF SHOWERS ACROSS THE FAR N AND NE GIVEN THE GOOD AGREEMENT ON THE UPPER DIVERGENCE BAND. LOWS 67-72. -GIH && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 325 PM THURSDAY... OUR BEST SHOT AT SCATTERED TO NUMEROUS SHOWERS AND STORMS WILL BE LATE FRI INTO FRI NIGHT... WITH SEVERAL FAVORABLE FACTORS IN PLAY. FIRST... MODELS DEPICT A POCKET OF ABOVE-NORMAL PW SLIDING SOUTHWARD FROM VA INTO/THROUGH CENTRAL NC TOMORROW... IN CONJUNCTION WITH WEAK DPVA SPREADING IN FROM THE NW AND NE AND IMPROVING UPPER DIVERGENCE FROM THE NORTH... ALL AHEAD OF THE INCOMING BACKDOOR COLD FRONT. THE LARGE-SCALE MODELS INCLUDING THE NAM/GFS/ECMWF/SREF ARE IN AGREEMENT ON CONVECTION DEVELOPING DURING THE EARLY TO MID AFTERNOON OVER CENTRAL NC... FOCUSING THE BEST COVERAGE AND HIGHEST AMOUNTS OVER THE FAR NW PIEDMONT. GIVEN THE EXPECTED MID-UPPER LEVEL DYNAMIC CONTRIBUTIONS TO ASCENT... DESTABILIZATION WITH GOOD HEATING DURING THE DAY... AND RISING MOISTURE THROUGH THE COLUMN... CONVECTIVE COVERAGE LOOKS SUFFICIENT TO RAISE POPS A BIT... TO LIKELY IN THE NW CWA WITH GOOD CHANCES ELSEWHERE FOR NOW (ALTHOUGH THESE MAY GO UP TO LIKELY HERE AS WELL IN LATER FORECASTS IF TRENDS HOLD). THE WEAK DEEP LAYER SHEAR SHOULD LIMIT STORM STRENGTH... ALTHOUGH THE PROFILE AND DCAPE NOTED ON NAM FORECAST SOUNDINGS WOULD SUGGEST A MARGINAL WIND THREAT. THE ANTICIPATED SLOW MOVEMENT WITH HIGH WATER CONTENT WILL BRING A RISK OF SLOW-MOVING STORMS GENERATING URBAN FLOODING. EXPECT HIGHS OF 90-95 WITH DECENT PREFRONTAL HEATING AND CONTINUED ABOVE NORMAL THICKNESSES. POPS SHOULD TREND DOWNWARD AFTER NIGHTFALL WITH LOSS OF INSOLATION... HOWEVER WITH LOW LEVEL CONFLUENT FLOW NEAR THE BACKDOOR FRONT AND INCREASED ATLANTIC-SOURCE FEED WITH PERSISTENT UPPER DIVERGENCE OVERNIGHT... WILL KEEP A MENTION OF SCATTERED SHOWERS AND STORMS THROUGH THE NIGHT... WITH THE BEST CHANCES WEST. LOWS 67-71. -GIH && .LONG TERM /SATURDAY THROUGH THURSDAY/... AS OF 150 PM THURSDAY... COOLER TEMPERATURES EXPECTED FOR MUCH OF THE LONG TERM AS THE COLD FRONT THAT IS PROGGED TO COME THROUGH FRIDAY NIGHT WILL BRING A CHANGE IN AIRMASS FROM THE NORTHEAST. WITH THIS WILL COME A GREATER FETCH OF MOISTURE FROM OFFSHORE...DRIVEN BY SEVERAL SHORTWAVE IMPULSES THAT ARE EXPECTED TO MOVE INTO THE STATE DURING THE WEEKEND AND INTO EARLY NEXT WEEK. FOR THE WEEKEND...THE GREATEST THREAT FOR RAIN WILL BE IN THE WEST ON SATURDAY AS THE FRONT MOVES THROUGH AND A CAD-LIKE SCENARIO SETS UP. AS THE WEEKEND PROGRESSES HOWEVER...AN INVERTED TROUGH ALONG THE EAST COAST WILL SHARPEN AND THUS BRING A MORE NORTHERLY COMPONENT TO THE WIND AND SHUT OFFSHORE MOISTURE FEED INTO THE NW PIEDMONT AND INSTEAD BEGIN TO FOCUS THE BEST CHANCE FOR CONVECTION OVER THE EASTERN PART OF THE STATE. THUS RAIN CHANCES FOR SUNDAY WILL BE BETTER IN THE EAST THAN IN THE WEST. THIS PATTERN WILL CONTINUE INTO LABOR DAY WITH SOUTHEASTERN COUNTIES HAVING THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS. HIGHS IN THE LOW TO MID 80S FOR THIS PERIOD WITH THE POTENTIAL FOR SOME UPPER 70S IN THE NW IF CLOUD COVER LOCKS IN. THE BERMUDA HIGH BEGINS TO TAKE BACK OVER FOR MIDWEEK AND THE SURFACE HIGH OVER OUR AREA AND THE INVERTED TROUGH WILL BEGIN TO BREAK DOWN. THIS WILL SEE A RETURN TO WARMER TEMPERATURES...ALTHOUGH GRADUALLY...WITH DIURNAL CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS THROUGH THURSDAY. AT THIS TIME...ANY THUNDERSTORMS THAT DO OCCUR EITHER THIS WEEKEND OR NEXT WEEK ARE NOT EXPECTED TO BE SEVERE...BUT A FEW STRONG STORMS CANNOT BE RULED OUT. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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AS OF 810 PM THURSDAY... THE 24 HR TAF PERIOD...VFR CONDITIONS WILL PERSIST THROUGH THE EVENING HOURS AND IN MOST LOCATIONS OVERNIGHT. AREAS OF FOG WILL DEVELOP LATE TONIGHT TOWARD FRIDAY MORNING WITH MAINLY VFR-MVFR VSBYS WITH THE POTENTIAL FOR IFR/LIFR VSBY/CIG RESTRICTIONS FOR A SHORT PERIOD TOWARD DAYBREAK AT KRWI AND PERHAPS KFAY. RESTRICTIONS WILL GRADUALLY IMPROVE AFTER SUNRISE WITH MULTIPLE CLOUD LAYERS EXPECTED DURING THE DAY FRIDAY. MOST LOCATIONS WILL HAVE BKN MID LEVEL CLOUDS THROUGHOUT THE DAY WITH A LOWER SCT CLOUD DECK AT 4- 6KFT BECOMING BKN TOWARD MIDDAY AND THE EARLY AFTERNOON. SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP DURING THE MID TO LATE AFTERNOON HOURS...FOCUSED ACROSS THE NORTHEAST PIEDMONT AND NORTHERN COASTAL PLAIN AND THEN SHIFTING TOWARD THE WEST AND SOUTHWEST WITH LOCALLY REDUCTIONS IN VSBYS AND CEILINGS. MAINLY CALM WINDS ARE EXPECTED OVERNIGHT WITH A LIGHT NORTH TO NORTHEAST WIND AT LESS THAN 7KTS EXPECTED ON FRIDAY...EXCEPT HIGHER IN THUNDERSTORMS. LOOKING BEYOND 00Z SATURDAY...SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO THE EVENING HOURS ON FRIDAY. MORE WIDELY SCATTERED CONVECTION IS POSSIBLE DURING THE AFTERNOON AND EVENING ON SATURDAY AND SUNDAY WITH A DECREASE IN COVERAGE AND A FOCUS TOWARD THE COASTAL PLAIN ON MONDAY AND TUESDAY. LATE NIGHT AND MORNING FOG AND STRATUS WITH POTENTIALLY SIGNIFICANT RESTRICTIONS APPEAR PROBABLE ON SATURDAY AND SUNDAY MORNINGS. -BLAES
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...ELLIS AVIATION...HARTFIELD

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