Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 071815 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 215 PM EDT MON JUL 7 2014 .SYNOPSIS...
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HIGH PRESSURE SLOWLY WEAKENS OVER THE REGION...WITH A WEAK SURFACE TROUGH EXTENDING FROM THE MID-ATLANTIC SOUTH ACROSS THE CAROLINAS OVERNIGHT AND TUESDAY. A COLD FRONT MOVES SOUTH FROM THE GREAT LAKES INTO THE MID-ATLANTIC BY WEDNESDAY. THIS FRONT THEN SLOWLY MOVES SOUTH THROUGH THE MID-ATLANTIC AND INTO NORTH CAROLINA BY THE END OF THE WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 950 AM MONDAY... THE LATEST SURFACE ANALYSIS SHOWED BROAD HIGH PRESSURE OVER CENTRAL NORTH CAROLINA...AND TEMPERATURES IN MOST LOCATIONS HAD WARMED QUICKLY WITH READINGS ALREADY NEAR 80. UPPER-AIR ANALYSES AND THE LATEST WATER VAPOR IMAGERY SHOWED A SHEAR AXIS OVER THE WESTERN PART OF THE STATE...BUT THE AIR MASS WAS PREDOMINANTLY DRY WITH THE KGSO PRECIPITABLE WATER VALUE AT AN INCH ON THE 12Z SOUNDING AND BELOW 1.2 INCHES THROUGHOUT CENTRAL NORTH CAROLINA ON THE SPC MESOANALYSIS. THESE VALUES REMAIN BELOW THE NORMAL 1.5 INCHES FOR JULY. RAP MODEL SOUNDINGS SHOW THE AIR MASS OVER THE VAST MAJORITY OF CENTRAL NORTH CAROLINA IS CAPPED TO DEEP CONVECTION. THE RAP DOES FORECAST A NARROW RIBBON OF LIFT AND RELATIVELY HIGH 850MB THETA-E VALUES LATE TODAY SOUTH OF A LINE FROM ABOUT KGSB TO KCTZ...AND WHILE THE RAP HAS NO QPF IN CENTRAL NORTH CAROLINA TODAY THROUGH TONIGHT...THE LATEST HRRR WRF DOES FORECAST THE POTENTIAL FOR AN ISOLATED SHOWER OR STORM TOWARD KCTZ AND HARRELLS LATE IN THE DAY... COINCIDENT WITH A MODEST INCREASE ON THE RAP FORECAST 300MB WIND TOWARD THE COAST THIS AFTERNOON. FOR THE MORNING UPDATE RETAINED THE DRY FORECAST FOR ALL OF CENTRAL NORTH CAROLINA EXCEPT THE FAR SOUTHEAST...AND DUE TO THE FAST WARMING THIS WARMING NUDGED HIGHS UPWARD ROUGHLY A DEGREE MAINLY TOWARD THE TRIAD. RAP SOUNDINGS SHOW THE POTENTIAL FOR A FEW GUSTS IN THE LOWER TO MID TEENS KNOTS WITH MIXING BUT IN GENERAL A SUSTAINED SOUTHWEST WINDS OF 5 TO JUST OVER 10 MPH SHOULD PREVAIL. TONIGHT...CLEAR TO PARTLY CLOUDY SKIES WILL DOMINATE AS AIR MASS REMAINS RELATIVELY DRY...ESPECIALLY IN THE MID- UPPER LEVELS. MIN TEMPS SHOULD BE SEVERAL DEGREES WARMER COMPARED TO CURRENT NIGHTS DUE TO AIR MASS MODIFICATION...UPPER 60S TO LOWER 70S. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 253 AM MONDAY... LEESIDE TROUGH SHARPENS IN RESPONSE TO A S/W ALOFT MOVING E-SE ACROSS THE OH VALLEY/LOWER GREAT LAKES. THIS STRENGTHENING OF THE SURFACE TROUGH WILL RESULT IN AN UPTICK IN SW SURFACE WINDS WITH SUSTAINED SPEEDS 9-12KTS EXPECTED WITH GUSTS AROUND 20 KTS. THIS STOUT SW FLOW IN CONJUNCTION WITH PARTLY-MOSTLY SUNNY SKIES WILL AID TO BOOST AFTERNOON TEMPS INTO THE LOW-MID 90S. A WEAK DISTURBANCE ALOFT MAY INTERACT WITH AVAILABLE (BUT STILL RATHER LIMITED) MOISTURE TO SUPPORT AN ISOLATED THUNDERSTORM DURING THE MID-LATE AFTERNOON HOURS ACROSS THE NW PIEDMONT. LOW LEVEL MOISTURE WILL CONTINUE TO GRADUALLY INCREASE LEADING TO A LITTLE MORE HUMID CONDITIONS...ESPECIALLY BY TUESDAY NIGHT. MIN TEMPS TUESDAY NIGHT 69- 74. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 310 AM MONDAY... WEDNESDAY THROUGH FRIDAY NIGHT: MID TO UPPER LEVEL MOISTURE WILL BEGIN TO INCREASE ACROSS THE AREA ON WEDNESDAY AS THE THE NEXT MID LEVEL TROUGH IS FORECAST TO DEEPEN AND SHIFT EASTWARD. THIS WILL HELP TO SHARPEN THE LEE SIDE TROUGH ACROSS THE AREA AND LEAD TO A BETTER CHANCE OF LATE DAY/EVENING SHOWERS AND STORMS ACROSS MAINLY THE NORTHWESTERN PIEDMONT. THE LATEST GFS BUFR SOUNDINGS ARE SHOWING A FAIRLY DEEP DRY SUB-CLOUD LAYER WITH THE EXPECTED LOW LEVEL WESTERLY FLOW. THUS... IF ANY STRONG CONVECTION IS ABLE TO MOVE INTO THE AREA EXPECT WE WOULD HAVE A THREAT FOR SOME STRONG TO SEVERE DAMAGING WIND GUSTS. GUIDANCE IS A BIT MIXED ON HOW MUCH CONVECTION WILL MAKE IT OUR AREA THOUGH. THUS... WILL ONLY RAISE POPS INTO THE CHANCE CATEGORY ACROSS THE NORTH/NORTHWESTERN PIEDMONT LATE WEDNESDAY/WEDNESDAY EVENING... WITH MOST OF THE LINGERING CONVECTION DYING OFF BY 06Z OR SO AT THE LATEST. AFTERNOON LOW LEVEL THICKNESS VALUES ARE EXPECTED TO CLIMB INTO THE 1420S TO 1430S. THUS... EXPECT WE SHOULD SEE TEMPS CLIMB INTO THE 90S... WITH POSSIBLY SOME UPPER 90S IN THE SOUTH/SOUTHEAST... WHERE CONVECTIVE CHANCES AND CLOUDS WILL BE THE LEAST. LOWS THURSDAY MORNING... WITH THE APPROACHING COLD FRONT TO THE NORTH AND WEST OF THE AREA... ARE EXPECTED TO BE IN THE UPPER 60S/AROUND 70 NW TO THE LOWER 70S ELSEWHERE... WITH EVEN SOME MID 70S POSSIBLE ACROSS THE SOUTH. THURSDAY AND FRIDAY LOOK TO BE THE MOST ACTIVE DAYS OF THE FORECAST PERIOD.... WITH THE AFOREMENTIONED TROUGH ALOFT SLOWLY CROSSING THE REGION ALONG WITH AN ACCOMPANYING WEAKENING SURFACE FRONT. THIS COMBINED WITH A MOIST AIR MASS CHARACTERIZED BY PW`S CLIMBING TO AROUND 2 INCHES WILL LEAD TO A GOOD CHANCE FOR SHOWERS AND STORMS... WITH CHANCES EACH DAY PEAKING IN THE AFTERNOON INTO THE EVENING HOURS. THE BEST DEEP LAYER SHEAR WILL REMAIN TO THE NORTH OF THE AREA. HOWEVER... WE COULD SEE DEEP SHEAR INCREASE INTO THE 20-25 KT RANGE. THUS... THIS COMBINED WITH POSSIBLY MODERATE AFTERNOON/EVENING INSTABILITY (MLCAPE VALUES DURING THE AFTERNOON APPROACHING 1500 J/KG... POSSIBLY 2000 J/KG)... THINK WE WILL HAVE AT LEAST A SMALL SEVERE THREAT... AS WE SHOULD SEE AT LEAST SOME MULTICELLULAR ACTIVITY EACH DAY. GIVEN THE MOIST AND WARM ATMO... EXPECT THE MAIN SEVERE THREAT WILL BE FROM DAMAGING WINDS. IN ADDITION.... GIVEN THE HIGH MOISTURE CONTENT AIR MASS LOCALIZED FLASH FLOODING THREAT WILL ALSO BE POSSIBLE EACH DAY. HIGHS WILL BE A BIT COOLER WITH THE ADDED CLOUD COVER AND STORMS. THUS... WILL GO WITH HIGHS GENERALLY IN THE UPPER 80S TO AROUND 90/LOWER 90S. LOWS IN THE UPPER 60S TO LOWER 70S. SATURDAY AND SUNDAY: THE MAIN MID LEVEL TROUGH AXIS IS EXPECTED TO MOVE TO THE EAST OF CENTRAL NC BY SATURDAY MORNING RESULTING IN DRYING ALOFT AND RESULTANT MUCH LESS COVERAGE OF AFTERNOON SHOWERS AND STORMS. STILL THINK WE WILL SEE SOME ISOLATED TO MAYBE WIDELY SCATTERED ACTIVITY WITH A SURFACE TROUGH REMAINING ACROSS THE REGION. WITH MORE SUN EXPECTED OVER THE WEEKEND EXPECT HIGH TEMPS WILL BE SEVERAL DEGREES WARMER AS LOW LEVEL THICKNESS VALUES ARE GENERALLY EXPECTED TO REBOUND TO AT LEAST THE 1420S. THIS WILL GENERALLY RESULT IN HIGH TEMPS BACK IN THE LOWER 90S... WITH POSSIBLY SOME MID 90S ACROSS THE SOUTH BY SUNDAY. LOWS IN THE UPPER 60S TO LOWER 70S. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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AS OF 215 PM MONDAY... VFR CONDITIONS ARE EXPECTED OVER CENTRAL NORTH CAROLINA FOR MUCH OF THE 18Z VALID TAF PERIOD. SOUTHWEST SURFACE WINDS WITH A FEW GUSTS IN THE TEENS KNOTS WILL DIMINISH THIS EVENING...WHILE STAYING NEAR 20 TO 25KT AROUND 2000FT OVERNIGHT...THEN THE SURFACE WINDS SHOULD INCREASE AGAIN TUESDAY MORNING WITH SOUTHWEST GUSTS AROUND 20KT. THE GUIDANCE DOES NOT SUGGEST ANY LOW CLOUDS OR FOG IN CENTRAL NORTH CAROLINA. WHILE THERE SHOULD BE ENOUGH MIXING TO PRECLUDE ANY MORE THAN LIGHT FOG...EXTRAPOLATION OF THE HRRR WRF MODEL GUIDANCE WOULD SUGGEST THE POTENTIAL FOR A PERIOD OF LOW CLOUDS LATE TONIGHT TOWARD KFAY...AND THE TAF FOR KFAY HAS A PERIOD OF MVFR CEILINGS THERE BETWEEN 10Z AND 14Z. BEYOND THE 18Z VALID TAF PERIOD...THERE IS A SMALL CHANCE OF SHOWERS OR THUNDERSTORMS MAINLY FROM THE TRIANGLE NORTH AND WEST LATE TUESDAY AND TUESDAY NIGHT. THE CHANCES FOR SHOWERS AND THUNDERSTORMS INCREASE WEDNESDAY INTO FRIDAY ALONG WITH THEIR ACCOMPANYING SUB-VFR CONDITIONS. LATE NIGHT AND EARLY MORNING LOW CLOUDS ARE ALSO POSSIBLE AS THE WEEK PROGRESSES AS MOISTURE AND...AGAIN...THE CHANCES FOR RAIN INCREASE. SOMEWHAT DRIER AIR AND A DECREASED CHANCE FOR ADVERSE AVIATION CONDITIONS ARE CURRENTLY EXPECTED FOR SATURDAY.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...WSS/DJF SHORT TERM...WSS LONG TERM...BSD AVIATION...DJF

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