Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 301210 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 810 AM EDT SAT APR 30 2016 .SYNOPSIS... A QUASI-STATIONARY FRONT --WITH COOL AND CLOUDY CONDITIONS TO THE NORTH...AND MUCH WARMER ONES TO THE SOUTH-- WILL REMAIN OVER SOUTHERN AND SOUTHWESTERN NC TODAY. THE FRONT AND ASSOCIATED FOLLOWING WARMER TEMPERATURES WILL RETREAT NORTH ACROSS THE MIDDLE ATLANTIC STATES LATE TONIGHT AND ESPECIALLY SUNDAY. WARM SOUTHWESTERLY FLOW WILL THEN RESULT THROUGH MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 410 AM SATURDAY... LOW OVERCAST IN NORTHEASTERLY LOW LEVEL FLOW WILL CONTINUE TO DEVELOP SOUTHWESTWARD ACROSS CENTRAL NC THIS MORNING...ON THE COOL SIDE OF A SURFACE FRONT NOW DRAPED ACROSS SOUTHERN AND SOUTHWESTERN NC. A RESULTANT WEDGE OF COOL/CLOUDY/STABLE AIR WILL EXTEND DOWN THE MIDDLE ATLANTIC COAST AND INTO CENTRAL NC TODAY...BENEATH SHORTWAVE RIDGING ALOFT EXTENDING FROM THE EASTERN GOM TO THE UPPER MIDWEST. THE LOW CLOUDS MAY ERODE FROM THE EDGES...PARTICULARLY ON THE SOUTHERN AND SOUTHWESTERN FLANK (IE. INVOF THE SURFACE FRONTAL ZONE); AND THIS MAY ALLOW THE BOUNDARY TO RETREAT INTO THE SOUTHERN PIEDMONT AND SANDHILLS THIS AFTERNOON. TEMPERATURES WILL CONSEQUENTLY DISPLAY A LARGE RANGE OVER CENTRAL NC TODAY...RANGING FROM THE LOWER 60S IN THE HEART OF THE WEDGE/LOW OVERCAST OVER THE NE PIEDMONT...TO 70S-NEAR 80 DEGREES OVER THE FAR SOUTHERN PIEDMONT. DESPITE THE AFOREMENTIONED RIDGING ALOFT/SUBSIDENCE...MASS CONVERGENCE AND THE FRONTOGENETIC CIRCULATION ABOUT THE FRONTAL ZONE SHOULD SUPPORT THE DEVELOPMENT OF SCATTERED STORMS INVOF THE FRONT - MOSTLY JUST WEST OF/UPSTREAM OF CENTRAL NC. A WSW MEAN WIND WOULD THEN ADVECT THE ASSOCIATED CONVECTION INTO THE WESTERN AND SOUTHERN PIEDMONT OF NC...THOUGH IN A WEAKENED STATE AS THEY BECOME INCREASINGLY ELEVATED...AND REMOVED FROM THE WARM SECTOR INSTABILITY AXIS...WITH NE EXTENT INTO THE STABLE WEDGE OVER CENTRAL NC. THE ONE EXCEPTION MAY BE OVER THE FAR SOUTHERN PIEDMONT FROM ALBEMARLE AND WADESBORO TO LAURINBURG...WHERE STORMS WOULD PROPAGATE IN A MORE ESE DIRECTION INVOF THE FRONT. A CONDITIONAL SEVERE WEATHER THREAT WILL EXIST THERE OWING TO ENHANCED EFFECTIVE LOW LEVEL SHEAR ALONG THE BOUNDARY...AMIDST MODEST 25-35 KTS OF MID LEVEL FLOW - SUPPORTIVE OF MULTI-CELL AND/OR TRANSIENT SUPERCELL STORM MODES. TONIGHT: NOCTURNAL COOLING OF THE ALREADY STABLE SURFACE LAYER WILL CAUSE LOW CLOUD BASES TO FURTHER LOWER/RE-DEVELOP WHERE ANY BREAKS MAY OCCUR ALONG THE EDGES THIS AFTERNOON. THE REMAINS OF UPSTREAM CONVECTION...AND AN ASSOCIATED MID-LEVEL DISTURBANCE...WILL MOVE INTO THE WESTERN HALF OF THE RAN FORECAST AREA LATE THIS EVENING- EARLY TONIGHT...BUT CONTINUED DOWNSTREAM RIDGING AND STATIC STABILITY OVER THE EASTERN PART OF THE STATE WILL LIMIT THE EASTWARD PROGRESS. AS SUCH...SHOWERS WILL BE LIKELY OVER THE WESTERN PIEDMONT...SOME POSSIBLY ACCOMPANIED BY A FEW RUMBLES OF THUNDER LATE OWING TO MIXING/BOUNDARY LAYER DESTABILIZATION...WITH JUST A SLIGHT CHANCE OF SHOWERS IN THE I-95 CORRIDOR AND POINTS EAST. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 350 AM SATURDAY... A PORTION OF THE COMPLEX UPPER LOW OVER THE WESTERN US WILL EJECT EASTWARD AND RACE ACROSS LOWER GREAT LAKES ON SUNDAY...SHUNTING THE SHORTWAVE RIDGE OVER THE SOUTHEAST US OFFSHORE. MEANWHILE...THE FRONTAL ZONE LINGERING OVER CENTRAL NC TODAY WILL RETREAT NORTHWARD IN TO THE MID-ATLANTIC REGION. ONGOING OVER SHOWERS OVER WESTERN NC...OWING TO SOUTHEASTERLY LOW-LEVEL FLOW AND WEAK HEIGHT FALLS ALOFT...WILL LIKELY BLEED INTO THE WESTERN PIEDMONT SUNDAY MORNING...THOUGH WITHOUT BETTER SUPPORT ALOFT THE COVERAGE OF SHOWERS AND STORMS IS A LITTLE UNCERTAIN WITH EASTWARD EXTENT SUNDAY AFTERNOON. NAM/GFS FORECAST SOUNDINGS SHOW MODEST STEEPENING OF MID- LEVEL LAPSE RATES AND MLCAPE POSSIBLY REACHING 1000-1500 J/KG CAPE AMIDST PW OF 1.25-1.50". CAPE GENERALLY APPEARS TO BE HIGHER IN THE WEST..THOUGH THE DEGREE OF SURFACE HEATING IS UNCERTAIN GIVEN THE AFOREMENTIONED MORNING PRECIP/CLOUD COVER. DEEP LAYER SHEAR IS MODEST...30-35KT ACROSS THE NORTH IN CLOSER TO PROXIMITY TO THE SHORTWAVE CROSSING THE GREAT LAKES AND STRONGER MID-LEVEL FLOW. THE MAIN LIMITATION FOR SEVERE WEATHER APPEARS TO BE A LACK OF A FOCUS...OUTSIDE IF A RIPPLE IN THE FLOW ALOFT. THUS..ITS HEARD TO HAVE MORE THAN CHANCE POPS AT THIS POINT...WITH LOW CONFIDENCE IN ANY SEVERE STORMS. HIGHS IN THE MID 70S NW TO AROUND 80 SE. THE NAM AND GFS INDICATE AT LEAST A CHANCE OF LINGERING SHOWERS INT HE COASTAL PLAIN SUNDAY NIGHT AS THE DEEP LAYER FLOW VEERS TO MORE WESTERLY AND DEEP MOISTURE SHIFTS EASTWARD. LOWS 61-68 WEST TO EAST. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 350 AM SATURDAY... DEEP LAYER FLOW WILL BECOME MORE WEST-SOUTHWESTERLY ON MONDAY AS DISTURBANCES CONTINUE TO TRACK FROM THE CENTRAL PLAINS TO THROUGH THE OH VALLEY. MID-LEVEL DRYING AND STRONGER BL MIXING WILL LIMIT INSTABILITY ACROSS THE NORTHERN/WESTERN PIEDMONT...FOCUSING SCATTERED SHOWERS AND STORMS TO SOUTHERN PIEDMONT AN COASTAL PLAIN. MONDAY AFTERNOON. HOWEVER...A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE MONDAY...OFFERING A BETTER FOCUS FOR CONVECTION MONDAY NIGHT AND INTO TUESDAY...DEPENDING ON HOW FAR SOUTH THE FRONT SETTLES. FORECAST CONFIDENCE THEN FALLS FOR THE MID TO LATE WEEK PERIOD AS RIDGE BUILDS OVER THE WESTERN US AND SHORTWAVES DROPPING SOUTH OUT OF CANADA RESULT INTO A DEEP TROUGH OVER THE EASTERN US. THE EVENTUAL AMPLITUDE OF THE TROUGH IS UNCERTAIN...BUT THE EC ENSEMBLE SUGGESTS 2-3 STD BELOW NORMAL OVER THE DEEP SOUTH AND THE OPERATIONAL GFS SETTLES AN UPPER LOW OVER THE CAROLINAS BY THE END OF THE WEEK. THIS PATTERN SUGGESTS PERIODS OF SHOWERS WILL CONTINUE TO BE POSSIBLE...WITH A SURFACE LOW LIKELY TO DEVELOP OFF THE SOUTHEAST COAST BY THURSDAY...AND DAILY HIGHS AT LEAST A COUPLE CATEGORIES BELOW NORMAL...IF NOT MORE. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... AS OF 800 AM SATURDAY... MOSTLY IFR RANGE STRATUS --IN NORTHEASTERLY LOW LEVEL FLOW ON THE COOL SIDE OF A SURFACE FRONT OVER WEST-CENTRAL NC-- HAVE ENVELOPED CENTRAL NC THIS MORNING. THIS FRONTAL ZONE WILL SEPARATE LOW OVERCAST TO THE NORTH FROM WARM AND VFR CONDITIONS...AND A CHANCE OF THUNDERSTORMS ALONG AND SOUTH OF THE FRONT. ALL CENTRAL NC TAF SITES ARE EXPECTED TO REMAIN ON THE COOL/CLOUDY SIDE OF THE BOUNDARY TODAY...WITH MERELY A GRADUAL RISE OF SUB-VFR CEILINGS INTO THE 1500- 2500 FT RANGE THIS AFTERNOON. HOWEVER...SOME EROSION OF THE LOW CLOUDS FROM THE EDGES MAY LEAD TO A BRIEF LIFTING AND SCATTERING TO VFR --MOST LIKELY AT FAY AND RWI-- FOR A FEW HOUR PERIOD THIS AFTERNOON AND EVENING. A FEW SHOWERS MAY ALSO AFFECT TRIAD TAF SITES THIS AFTERNOON AND EVENING. CEILINGS WILL OTHERWISE LOWER ONCE AGAIN (OR RE-DEVELOP WHERE/IF SCATTERING OCCURS) OVERNIGHT...ALONG WITH THE ARRIVAL OF SHOWERS AND PERHAPS A FEW THUNDERSTORMS AT PIEDMONT TAF SITES THROUGH EARLY SUNDAY. OUTLOOK: A SERIES OF WAVES OF LOW PRESSURE WILL TRACK ALONG A STALLED FRONTAL ZONE ALONG THE SOUTHEAST UNITED STATES COAST...WITH ASSOCIATED PERIODS OF RAIN AND SUB-VFR CONDITIONS OVER CENTRAL NC...MON NIGHT THROUGH WED. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...26 SHORT TERM...22 LONG TERM...22 AVIATION...26

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.