Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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454 FXUS62 KRAH 190636 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 236 AM EDT TUE MAY 19 2015 .SYNOPSIS...
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A SURFACE TROUGH WILL STRENGTHEN OVER VA AND THE CAROLINAS TODAY...AHEAD OF A COLD FRONT THAT WILL CROSS OUR REGION TONIGHT. THE FRONT WILL STALL OVER SC ON WED...THEN RETREAT NORTH IN ADVANCE OF AN AREA OF LOW PRESSURE THAT WILL CROSS THE CAROLINAS ON THU.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 1020 PM MONDAY... THE MID LEVEL RIDGE AXIS HAS SHIFTED SLOWLY EASTWARD TODAY... NOW POSITIONED ACROSS EASTERN NC. THIS WITH THE HELP OF A SHARPENING TROUGH AXIS HAS ALLOWED FOR ISOLATED TO SCATTERED (TO LOCALLY NUMEROUS) SHOWERS AND STORMS TODAY ACROSS CENTRAL NC. PW VALUES CONTINUE TO RUN WELL ABOVE NORMAL FOR THIS TIME OF YEAR... RANGING FROM 1.7 INCHES NW TO NEAR 1.9 INCHES ACROSS THE EAST. THUS... ANY DECENT CONVECTION WILL HAVE THE POTENTIAL TO PRODUCE SOME HEAVY RAIN. A COUPLE OF CLUSTERS OF SHOWERS AND STORMS REMAIN ACROSS SOUTHERN PORTIONS OF CENTRAL NC THIS EVENING. HOWEVER... WITH THE SPC MESO PAGE SHOWING CIN DEVELOPING WITH ONLY VERY WEAK INSTABILITY (GENERALLY 250 TO 500 J/KG OF MLCAPE) EXPECT THIS ACTIVITY WILL BEGIN TO WEAKEN OVER THE NEXT SEVERAL HOURS WITH CONTINUED NOCTURNAL STABILIZATION. WILL KEEP A SLIGHT CHANCE POP IN THE FORECAST OVERNIGHT GIVEN THE MOIST AIRMASS AND POTENTIAL FOR WEAK DISTURBANCES IN THE WEST-SOUTHWESTERLY MID LEVEL FLOW. CANT RULE OUT SOME PATCHY FOG OVERNIGHT FOR LOCATIONS THAT RECEIVED SOME DECENT RAINFALL TOTALS TODAY. OTHERWISE... EXPECT SKIES WILL BE PARTLY TO MOSTLY CLOUDY OVERNIGHT WITH A GOOD BIT OF MID AND HIGH CLOUD COVER. THIS SHOULD HELP TO KEEP OVERNIGHT LOWS WELL ABOVE NORMAL... GENERALLY IN THE UPPER 60S TO NEAR 70. THESE LOWS ARE VERY NEAR RECORD HIGH MIN VALUES (RDU 69... GSO 67... FAY 71). && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 312 PM MONDAY... A SERIES OF S/W ROTATING THROUGH THE GREAT LAKES AND INTO NEW ENGLAND WILL WEAKEN THE UPPER LEVEL RIDGE OVER CENTRAL NC. THE LEAD S/W IN THIS SERIES WILL ALSO USHER A SFC COLD FRONT INTO OUR REGION TUESDAY...DRIFTING SLOWLY SEWD AND EXITING OUR REGION LATE TUESDAY NIGHT. SUFFICIENT MOISTURE AND DESTABILIZATION WILL TRIGGER SCATTERED CONVECTION BY AFTERNOON...ESPECIALLY FOR LOCATIONS ALONG AND EAST OF HIGHWAY 1. OVER THE WEST-NW SECTIONS OF THE PIEDMONT...CONVECTION EXPECTED TO BE NO WORSE THAN 25-30 PERCENT COVERAGE...DECREASING APPRECIABLY IN COVERAGE BY LATE AFTERNOON. SIMILAR TO TODAY...WHILE CONVECTIVE PARAMETERS SUPPORTIVE OF CONVECTION...MARGINAL/WEAK INSTABILITY AND WEAK SHEAR WILL LIMIT CHANCE FOR THE DEVELOPMENT OF SEVERE STORMS. HIGH TEMPS TRICKY FOR TUESDAY AS POTENTIAL FOR STRONG HEATING PRIOR TO THE INITIATION OF CONVECTION. WILL FAVOR THE WARMER MAV GUIDANCE WITH MAX TEMPS UPPER 80S TO AROUND 90. IF CLOUDS/CONVECTION DEVELOP SOONER THAN EXPECTED...MAX TEMPS MAY END UP 3-5 DEGREES COOLER THAN FORECAST. WITH SLOW FRONTAL MOVEMENT ANTICIPATED TUESDAY NIGHT...A THREAT FOR SHOWERS AND ISOLATED STORMS WARRANTED WELL INTO THE NIGHT ACROSS SECTIONS OF THE COASTAL PLAIN AND SANDHILLS. DUE TO SLUGGISH MOVEMENT AND DELAYED ARRIVAL OF COOLER/STABLE AIR...HAVE ADJUSTED MIN TEMPS CLOSER TO THE WARMER MET GUIDANCE. MAY ALSO SEE AREAS OF FOG DEVELOP...ESPECIALLY AREAS THAT EXPERIENCE HEAVIER SHOWERS EARLIER IN THE DAY. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 312 PM MONDAY... THE COLD FRONT WILL LIKELY BE LOCATED ALONG THE CAROLINA COAST AT 12Z WEDNESDAY WITH A 1028MB HIGH PRESSURE SYSTEM CENTERED NEAR THE DAKOTAS EXTENDING SOUTHEAST INTO THE OHIO VALLEY AND MID ATLANTIC. THE FLOW ALOFT ACROSS THE EASTERN CONUS IS GENERALLY WESTERLY SUGGESTING LITTLE ADDITIONAL SOUTHWARD PROGRESS FOR THE FRONT. THE AIR MASS BEHIND THE FRONT IS NOTABLY COOLER AND DRIER...ALTHOUGH IT IS UNCLEAR HOW MUCH TRUE AIR MASS CHANGE WILL BE REALIZED IN CENTRAL NC BEHIND THE FRONT. REGARDLESS...WEDNESDAY SHOULD FEATURE A QUIET WEATHER DAY WITH LOTS OF SUNSHINE. HAVE KEPT HIGHS SLIGHTLY ABOVE GUIDANCE AS THICKNESSES ARE STILL RATHER WARM AND THE TRUE AIRMASS CHANGE MAY BE SLOW TO ARRIVE CENTRAL NC. HIGHS WILL RANGE FROM 82 NORTHEAST TO 89 NEAR THE SC BORDER. HEIGHTS BEGIN TO FALL SLIGHTLY WEDNESDAY NIGHT AS MEAN TROUGHINESS AND A CYCLONIC FLOW ALOFT STRENGTHENS IN THE EASTERN US. A SHEARING SHORT WAVE TROUGH DROPS ACROSS THE GREAT LAKES INTO THE OH VALLEY ON THURSDAY AND A WEAK SURFACE WAVE DEVELOPS IN RESPONSE ACROSS THE CAROLINA PIEDMONT. DETERMINISTIC MODEL RUNS SHOW LITTLE CONSISTENCY IN THE PLACEMENT OF THE SURFACE WAVE ON THURS MORNING WITH THE EC`S LOW NEAR KFAY...THE NAM LOW NEAR KCAE AND THE GFS NEAR KSAV. STILL ALL OF THE GUIDANCE NOTE A NORTHWARD ADJUSTMENT TO THE LINGERING COLD FRONT AND SUFFICIENT CONVERGENCE AND FORCING FOR AN INCREASE IN CONVECTION ON THURSDAY AND ESPECIALLY AFTERNOON AND EVENING THAT WILL LINGER INTO THE COASTAL PLAIN ON FRIDAY MORNING. THE SURFACE LOW POSITION AND THE DEGREE OF CLOUD COVER AND PRECIPITATION WILL HAVE A BIG IMPACT ON TEMPERATURES. THE 00Z EC ENSEMBLE GUIDANCE HAD A HIGH TEMP RANGE FOR THURSDAY OF 88 TO 75 AT KRDU AND 92 TO 80 AT KFAY. HAVE INCREASED POPS UPWARD FOR THIS PERIOD. WITH VERY LIMITED INSTABILITY...THE AMOUNT AND INTENSITY OF CONVECTION ON THURSDAY SHOULD BE RATHER MODEST. HOWEVER...ITS WORTH NOTING THAT THE JUXTAPOSITION OF 35-50 KTS OF DEEP LAYER SHEAR NEAR THE VICINITY OF THE SURFACE WAVE ATTRACTS SOME INTEREST. EXPERIMENTAL SHERBS3 PARAMETERS ARE NOT TOO EXCITED EITHER. SEVERE CONVECTION APPEARS TO BE A VERY LOW PROBABILITY POSSIBILITY AT THIS POINT. HIGHS ON THURSDAY WILL RANGE IN THE UPPER 70S NEAR THE VA BORDER TO MID 80S NEAR SC. LOWS WILL RANGE IN THE LOWER TO MID 60S. ANY LINGERING SHOWERS OR STORMS SHOULD SHIFT EAST OF CENTRAL NC ON FRIDAY AFTERNOON AND EVENING AS A 1028MB AREA OF HIGH PRESSURE BUILDS INTO THE REGION. HIGHS FRIDAY SHOULD RANGE IN THE UPPER 70S TO LOWER 80S. THE AREA OF HIGH PRESSURE WILL STRENGTHEN AND BUILD INTO THE REGION ON SATURDAY...YIELDING A VERY NICE DAY WITH A MIX OF SUNSHINE AND A FEW CLOUDS. THE AIR MASS WILL BE MORE PLEASANT WITH DEWPOINTS FALLING WELL INTO THE 50S AND HIGHS RANGING FROM 79 NORTHEAST TO 84 SOUTHWEST. THE HIGH WILL SHIFT OFFSHORE ON SUNDAY AND MONDAY WITH A GRADUAL INCREASE IN SOUTHERLY FLOW. THIS WILL RESULT IN A FEW MORE CLOUDS AND AN INCREASE IN TEMPERATURES AND HUMIDITY. SUNDAY WILL BE A DRY DAY AND MONDAY SHOULD BE DRY ACROSS MOST OF THE AREA EXCEPT IN THE WEST WERE A FEW THUNDERSTORMS MAY DEVELOP IN THE MOUNTAINS AND FOOTHILLS AND PUSH INTO THE WESTERN PIEDMONT LATE IN THE DAY. HIGHS ON SUNDAY WILL RANGE IN THE LOWER TO MID 80S WITH HIGHS IN THE MID TO UPPER 80S ON MONDAY. MORNING LOWS WILL RANGE IN THE LOWER TO MID 60S. -BLAES && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 235 AM TUESDAY... EARLIER SHOWERS AND STORMS HAVE DISSIPATED AND/OR MOVED EAST...SO ASIDE FROM PATCHY FOG WHERE RAIN EARLIER OCCURRED -INCLUDING AT GSO AND FAY- VFR CONDITIONS ARE ANTICIPATED UNTIL SHOWERS AND STORMS RE- DEVELOP THIS AFTERNOON. THE RELATIVE GREATEST CHANCE OF STORMS WILL BE AT RWI AND FAY...IN THE VICINITY OF A SURFACE TROUGH AND ASSOCIATED LOW LEVEL CONVERGENCE. AREAS OF FOG WILL THEN BE POSSIBLE TONIGHT WHERE PRECEDING RAIN OCCURS DURING THE AFTERNOON AND EVENING...UNTIL A COLD FRONT AND ASSOCIATED DRIER AIR ARRIVE FROM THE NW LATE. OUTLOOK: AN AREA OF LOW PRESSURE WILL TRACK ACROSS THE CAROLINAS AND RESULT IN A CHANCE OF SUB-VFR CEILINGS AND RAIN LATE WED NIGHT AND EARLY THU...FOLLOWED BY SHOWERS AND STORMS THU AFTERNOON.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RAH26 NEAR TERM...77 SHORT TERM...WSS LONG TERM...BLAES AVIATION...RAH26

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