Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291925 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 325 PM EDT FRI MAY 29 2015 .SYNOPSIS...HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC WILL EXTEND INTO THE REGION THROUGH SATURDAY. A COLD FRONT WILL DROP INTO THE MID ATLANTIC AND SOUTHERN APPALACHIANS ON SUNDAY AND MOVE INTO THE CAROLINAS ON MONDAY AND TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 315 PM FRIDAY... NEAR TERM: THROUGH TONIGHT: SURFACE HIGH PRESSURE REALLY DOMINATING THE PATTERN THE PAST FEW DAYS AND TODAY IS REALLY NO DIFFERENT. WITH VIRTUALLY NO FORCING ALOFT (AS EVIDENCED BY FORECAST SOUNDINGS WHICH ARE SHOWING LESS THAN 10 KTS ALL THE WAY UP THROUGH 30 KFT) ALL OF THE ACTION WILL BE SURFACE BASED WITH MUCH OF IT OCCURRING NW OF THE FORECAST AREA. THE TRIAD WILL CONTINUE TO HAVE SHOWERS AND POSSIBLY A WEAK THUNDERSTORM IN THE AREA FOR THE REMAINDER OF THE AFTERNOON AND POSSIBLY INTO THIS EVENING. RAP AND NAM FORECAST SOUNDINGS SHOW THE BEST INSTABILITY OCCURRING RIGHT NOW AND ACTUALLY DIMINISHING THROUGH THE AFTERNOON SO WHAT IS OUT THERE NOW COULD BE THE PEAK OF IT BUT WILL REQUIRE WATCHING THROUGH THE AFTERNOON. ANYTHING THAT FORMS HAS BEEN SLOWLY DRIFTING NORTHWARD AND OUT OF THE AREA. HIGHS THIS AFTERNOON SHOULD TOP OUT IN THE MID TO UPPER 80S WITH THE SANDHILLS RECEIVING THE HIGHEST TEMPERATURES. HIGH RESOLUTION MODELS ALSO HINTED AT SOME SHOWERS FORMING ON THE SEA BREEZE BUT SO FAR THESE HAVE BEEN VERY MINIMAL AND CONFINED TO THE COAST. OVERNIGHT TONIGHT EXPECT A CHANCE FOR SOME LOW STRATUS...ESPECIALLY IN THE TRIAD WHERE CEILINGS AS LOW AS IFR COULD SHOW UP FOR A FEW HOURS AROUND 12Z. ELSEWHERE MVFR CEILINGS ARE MORE LIKELY. RETURN TO VFR IS EXPECTED AFTER 15Z ON SATURDAY MORNING. LOWS OVERNIGHT IN THE MID 60S. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 315 PM FRIDAY... SATURDAY AND SATURDAY NIGHT: SURFACE HIGH PRESSURE BUILDS BACK IN A LITTLE FURTHER THAN RECENT DAYS AND THE UPSHOT IS POSSIBLY A DRIER DAY IN THE TRIAD THAN PREVIOUS AFTERNOONS. WILL STILL CARRY A SLIGHT CHANCE OF SHOWERS IN THE WEST TOMORROW BUT CONTINUED MINIMAL SHEAR AND EVEN LESS INSTABILITY THAN TODAY DONT BODE WELL FORE CONVECTION PROSPECTS. THIS IS BACKED UP BY CAMS WHICH SHOW MINIMAL ACTIVITY TOMORROW AFTERNOON. INSTEAD EXPECT ANOTHER DAY OF WARM RETURN FLOW WITH HIGHS AGAIN MOSTLY IN THE UPPER 80S. LOWS SATURDAY NIGHT IN THE MIDDLE 60S ONCE AGAIN. && .LONG TERM /SUNDAY THROUGH THURSDAY/...
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AS OF 325 PM FRIDAY... A LARGE SCALE PATTERN CHANGE IS AFOOT... WHEREIN THE WRN ATLANTIC RIDGE WILL FINALLY GIVE WAY TO A SOUTHWARD DIP IN THE WESTERLIES OVER THE CONUS. THIS WILL BRING IMPROVING CHANCES FOR MUCH-NEEDED RAINFALL BEGINNING EARLY IN THE WORK WEEK. THE VAST MAJORITY OF CENTRAL NC HAS SEEN VERY LITTLE RAIN IN THE LAST COUPLE OF WEEKS... BETWEEN 1 AND 2 INCHES BELOW NORMAL IN THE LAST 14 DAYS ACCORDING TO WATER.WEATHER.GOV/PRECIP/. SUNDAY SHOULD BE OUR LAST STEAMY BUT MOSTLY DRY DAY. THE APPROACHING COLD FRONT IS EXPECTED TO STRETCH ACROSS THE MASON DIXON LINE DOWN THROUGH ERN KY LATE SUN... WITH ITS ASSOCIATED MID LEVEL TROUGH EXTENDING FROM THE GREAT LAKES TO THE LOWER MISS VALLEY AS THE WRN ATLANTIC RIDGE HOLDS ON FOR ONE MORE DAY. LATEST MODEL OUTPUT SHOWS SCATTERED TO NUMEROUS SHOWERS/STORMS POPPING UP BY AFTERNOON OVER THE HIGHER TERRAIN TRACKING TO THE NE WITHIN THE WEAK MEAN STEERING FLOW AROUND THE RIDGE. THIS CONVECTION IS EXPECTED TO WEAKEN DURING THE EVENING BUT EASE EASTWARD INTO THE NORTHWEST CWA SUN NIGHT... FOLLOWING THE PROGRESSION OF THE NRN PORTION OF THE MID LEVEL TROUGH INTO THE NORTHEAST STATES THROUGH MON. THE REST OF THE CWA SHOULD REMAIN MOSTLY DRY (ALTHOUGH AN ISOLATED SLOW-MOVING CELL OR TWO IS CERTAINLY POSSIBLE) GIVEN THE SOMEWHAT DRY LOW LEVELS (LIMITING CAPE) AND DRY AIR THROUGH THE COLUMN (BELOW NORMAL PW OVER ERN HALF OF CWA). HIGHS SUN 85-90. LOWS SUN NIGHT MAINLY IN THE UPPER 60S WITH CONVECTIVE DEBRIS CLOUDS AND A SMALL CHANCE OF SHOWERS OVER THE NRN/WRN CWA OVERNIGHT. WHILE WE SHOULD SEE A PIEDMONT TROUGH FORMING (OR BECOMING BETTER DEFINED) OVER THE CWA MON... MODELS ARE KEEPING A THERMAL RIDGE ACROSS OUR AREA WITH THE FRONTAL ZONE HOLDING TO OUR NW THROUGH THE DAY... A FUNCTION OF THE SLOW SPEED AND LOW AMPLITUDE OF THE MID LEVEL TROUGH TO OUR WEST. WE`LL NEED TO WAIT FOR ADDITIONAL ENERGY TO DROP FROM SW ONTARIO DOWN THROUGH THE GREAT LAKES STARTING MON IN ORDER FOR THE TROUGH TO MAKE ANY MEANINGFUL EASTWARD PROGRESS. ALL OF THIS WILL SERVE TO DELAY COOLING INTO NC UNTIL THE SURFACE FRONT DROPS INTO NC TUE NIGHT OR EARLY WED. BOTH MOISTURE AND FORCING FOR ASCENT WILL DEEPEN AND INCREASE AHEAD OF THE FRONT... AND BY LATE MON AFTERNOON WE SHOULD SEE GOOD COVERAGE OF SHOWERS AND STORMS PARTICULARLY OVER THE WRN AND SW CWA WHERE LOW LEVEL MOISTURE POOLING SHOULD BE GREATEST. COVERAGE AND INTENSITY WILL WANE MON NIGHT WITH LOSS OF HEATING... BUT NOT GO AWAY ENTIRELY GIVEN THE PERSISTENCE OF ELEVATED INSTABILITY OVERNIGHT AND ABOVE-NORMAL PW. MODERATE INSTABILITY AND HIGH MOISTURE SHOULD PERSIST AREAWIDE TUE... SUPPORTING ABOVE NORMAL CHANCES FOR SHOWERS AND STORMS (50- 60%). EXPECT HIGH COVERAGE AGAIN WED ACROSS ALL BUT THE NW AS THE FRONT SETTLES INTO THE NRN/WRN CWA. THE GFS/ECMWF SOLUTIONS DIVERGE WITH THE LATTER SHOWING A DEEPER TROUGH JUST TO OUR IMMEDIATE WEST TUE AND SHIFTING OVER THE ERN STATES WED... WHILE THE GFS KEEPS THE STREAMS UNPHASED WITH A CUTOFF MID LEVEL LOW OVER THE LOWER MISS VALLEY. PREFER THE WEAKER-FLOW GFS WITH THE FRONT LOITERING ACROSS ERN AND SRN NC THROUGH THU/FRI... AS THE ONCE-COOL SURFACE HIGH CENTERED OVER THE ERN GREAT LAKES EARLY WED MODIFIES AND STARTS TO DRIFT OFF THE NORTHEAST COAST BY FRI. THE FRONT SHOULD BE MOSTLY WASHED OUT AND BE OVERTAKEN BY COASTAL INVERTED TROUGHING OVER THE SOUTHEAST COAST. WILL TREND POPS TOWARD MORE CLIMATOLOGICALLY NORMAL VALUES THU/FRI -- 25-35% CHANCES MAINLY IN THE EAST AND SOUTH -- GIVEN THE DECREASING DEEP LAYER SHEAR AND WEAKENING FORCING FEATURES. DESPITE WHAT SHOULD BE A PERIOD OF MOSTLY CLOUDY SKIES FROM CONVECTIVE DEBRIS AND LIFTING MORNING STRATUS ON MON... WE SHOULD SEE ENOUGH HEATING WITHIN THE WARM SECTOR TO PUSH TEMPS UP TO HIGHS FROM THE MID 80S TO AROUND 90 (COOLEST NW AND FAR NORTH). HIGH TEMPS SHOULD SLIP BACK CLOSER TO NORMAL TUE GIVEN THE EXPECTED CONSIDERABLE CLOUDINESS... WITH THESE CLOUDS EQUATING TO MILD/HUMID OVERNIGHT LOWS THROUGH TUE NIGHT. SLIGHTLY BELOW NORMAL TEMPS WED... THEN TRENDING BACK TOWARD NEAR OR SLIGHTLY ABOVE NORMAL THU/FRI AS THE FRONT WASHES OUT AND THE RESIDENT AIR MASS MODIFIES. -GIH
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... AS OF 145 PM FRIDAY... 24 HOUR TAF PERIOD: EXPECTING MOSTLY VFR CONDITIONS THROUGH THE TAF PERIOD WITH A POSSIBLE COUPLE EXCEPTIONS. THE FIRST IS WITH AFTERNOON CONVECTION. THE TRIAD SITES WILL BE MOST VULNERABLE TO THIS AS SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ALONG A BOUNDARY RUNNING FROM CHARLOTTE TO RICHMOND WHICH CLIPS THE TRIAD BUT STORMS FORMING HERE WILL MOVE NORTH AND AWAY FROM THE AREA. TO THE SOUTH THERE IS A SLIGHT CHANCE OF SOME SEA BREEZE SHOWER ACTIVITY THAT WOULD BE BRIEF AND OCCUR LATER THIS AFTERNOON/EARLY EVENING. OTHERWISE LIGHT SOUTHEASTERLY WINDS WITH BROKEN CEILINGS IN THE 4-6 KFT RANGE EXPECTED. THERE WILL BE A CHANCE FOR SOME LOW STRATUS ON EARLY SATURDAY MORNING WITH TRIAD SITES POSSIBLY RECEIVING A COUPLE OF HOURS OF IFR CEILINGS WITH MOSTLY MVFR POSSIBLE AT OTHER SITES. AFTER 15Z CONDITIONS ARE EXPECTED TO RETURN TO VFR FOR THE REMAINDER OF THE TAF PERIOD. LONG TERM: PATTERN REMAINS THE SAME FOR MUCH OF THE LONG TERM WITH A SLIGHTLY EASTWARD SHIFT EARLY NEXT WEEK. MAINLY LOOK FOR DIURNAL CONVECTION WITH CHANCES FOR FOG/LOW STRATUS DURING THE EARLY MORNING HOURS EACH DAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BLAES NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...ELLIS

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