Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 140659 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 257 AM EDT SUN SEP 14 2014 .SYNOPSIS...A BACK DOOR COLD FRONT WILL STALL SOUTH OF THE AREA THROUGH MONDAY AS HIGH PRESSURE EXTENDS SOUTHWARD FROM THE MID ATLANTIC INTO THE CAROLINAS. && .NEAR TERM /THROUGH TONIGHT/... AS OF 250 AM SUNDAY... OVERVIEW: THE BACKDOOR COLD FRONT HAS MOVED THROUGH CENTRAL NC AND WILL CONTINUE SOUTHWARD THROUGH SOUTH CAROLINA INTO GEORGIA BY 12Z SUN AS HIGH PRESSURE BUILDS FROM THE OH VALLEY INTO THE MID- ATLANTIC. THIS FRONT IS THEN EXPECTED TO REMAIN NEARLY STATIONARY TO OUR SOUTH THROUGH THE NEAR TERM PERIOD. CENTRAL NC WILL REMAIN ON THE NORTHEAST PERIPHERY OF AN UPPER LEVEL RIDGE SITUATED OVER THE NORTHERN GOMEX AND DEEP SOUTH GULF COAST...WITH UPPER LEVEL FORCING CONFINED TO WEAK DIFFLUENCE ALOFT AND PERHAPS GLANCING BOUTS OF DPVA AS SMALL AMPLITUDE DISTURBANCES IN THE WESTERLIES TRACK EAST ACROSS THE MID-ATLANTIC. PRECIP CHANCES: ALMOST ALL OF THE CONVECTION HAS SHIFTED SOUTH OF CENTRAL NC ALONG WITH THE BACKDOOR COLD FRONT. HOWEVER...EXPECT ELEVATED CONVECTION TO DEVELOP BETWEEN 12-18Z SUN ACROSS SOUTHERN PORTIONS OF CENTRAL NC (I.E. SANDHILLS/SE COASTAL PLAIN/SC BORDER) WHERE THE LATEST GUIDANCE INDICATES DESTABILIZATION ASSOC/W H85 WARM ADVECTION OCCURRING IN VICINITY OF THE STALLED/WEST-EAST ORIENTED/925 MB FRONT...ALL OF WHICH WILL BE ATOP A STRENGTHENING COLD AIR DAMMING WEDGE NEAR THE SURFACE. FURTHER NORTH...FORCING WILL BE EVEN LESS AND A SLIGHTLY DRIER AIR MASS WILL BE IN PLACE. WITH THE ABOVE IN MIND...WILL HAVE THE BEST PRECIP CHANCES NEAR THE SC BORDER...WITH ONLY SLIGHT CHANCE (IF ANY AT ALL) TOWARDS THE VA BORDER. TEMPS: CHALLENGING TEMPERATURE FORECAST GIVEN THE COLD AIR DAMMING WEDGE IN PLACE AND THE POTENTIAL FOR PRECIP DEVELOPMENT...ESPECIALLY ACROSS THE SOUTH. REGARDLESS...TEMPS WILL BE BELOW NORMAL AND MAY BE COOLEST IN THE SOUTH (IF THE PRECIP DOES INDEED DEVELOP). IN FACT... FORECAST SOUNDINGS SHOW NEAR STEADY TEMPS DURING THE MORNING... REMAINING STEADY AND PERHAPS FALLING DURING THE DAY AS PRECIP ASSOC/W ELEVATED CONVECTION FALLS INTO THE DRY NEAR-SFC AIRMASS CURRENTLY ADVECTING INTO THE REGION FROM THE NORTH. WILL ALL OF THIS IN MIND...WILL HAVE HIGH TEMPS RANGING FROM NEAR 70 DEGREES NEAR THE SC BORDER TO THE LOWER 70S CLOSER TO THE VA BORDER... PERHAPS MID 70S IN THE NE COASTAL PLAIN (BUT TEMPS COULD BE WARMER IF THE PRECIP DOES NOT DEVELOP AND/OR THE WEDGE ERODES SOME). ANY PRECIP SHOULD COME TO ANY END SUNDAY EVENING...BUT WITH A CONTINUED OVERRUNNING ATOP A MOIST AIR MASS...CONSIDERABLE LOW CLOUDINESS EXPECTED. THERE MAY NOT BE AS MUCH STRAUS ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA (GIVEN SLIGHTLY DRIER AIR)... BUT THE CLEARER SKIES COULD THEN RESULT IN SOME FOG FORMATION. OVERNIGHT LOW WILL GENERALLY BE IN THE MID/UPPER 50S TO MID 60S... COOLEST ACROSS THE NORTHERN PIEDMONT. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... AS OF 300 PM SATURDAY... MON: LOW LEVEL STABILITY WILL CAUSE LOW CLOUDS TO BE SLOW TO LIFT AND ERODE MON...PARTICULARLY OVER THE SANDHILLS AND COASTAL PLAIN...WHERE NWP GUIDANCE INDICATES A RELATIVE MAXIMUM IN MOISTURE DEPTH AND ASSOCIATED CONTINUED CLOUDY (OR MOSTLY SO) CONDITIONS THROUGHOUT THE DAY. WITH THE EXPECTATION OF LINGERING CLOUDINESS...HIGH TEMPERATURES ARE APT HOLD WITHIN A FEW DEGREES EITHER SIDE OF 80...IN AN ATYPICAL DISTRIBUTION OF WARMEST NW AND COOLEST SE. DEEP MOISTURE WILL ALSO REMAIN RELATIVELY MAXIMIZED OVER THE SOUTHERN AND SOUTHEASTERN HALF OF THE CWFA...WHERE PROJECTED K- INDICES AND MLCAPE IN THE LOWER-MIDDLE 30S C AND 500 J/KG... RESPECTIVELY...WILL SUPPORT A CHANCE OF SHOWERS DURING THE AFTERNOON. MON NIGHT: A STRONG S/W TROUGH WILL CROSS THE OH VALLEY AND NORTHERN MIDDLE ATLANTIC STATES MON NIGHT...AND CONSEQUENTLY SWEEP AN AREA OF 20-30 METER MID LEVEL HEIGHT FALLS; A MID LEVEL MOIST AXIS; AND SFC COLD FRONT ACROSS CENTRAL NC OVERNIGHT. THE PASSAGE OF THESE FEATURES WILL SUPPORT A CHANCE OF SHOWERS...PARTICULARLY OVER THE NORTHERN PIEDMONT AND NORTHERN COASTAL PLAIN - IN AN AREA LEAST LIKELY TO HAVE BEEN EARLIER CONVECTIVELY OVERTURNED...AND IN CLOSEST PROXIMITY TO THE PASSING MID LEVEL TROUGH. LOWS MOSTLY IN THE MIDDLE TO UPPER 60S...GIVEN A RELATIVELY LATE PASSAGE OF THE COLD FRONT... AND TRAILING CAA. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 257 AM SUNDAY... IN THE WAKE OF THE PASSAGE OF THE MID LEVEL TROUGH AND ASSOC SFC BOUNDARY EARLY TUESDAY...HIGH PRESSURE WILL BUILD INTO OUR AREA FROM THE NW ON TUESDAY AND THEN REMAIN EXTENDED SOUTHWARD ACROSS THE CAROLINAS FROM THE PARENT HIGH CENTERED OVER THE NE STATES AND SE CANADA...THROUGH THE REST OF THE WORK/SCHOOL WEEK. MEANWHILE DURING THIS TIME...A NEARLY STATIONARY SFC BOUNDARY WILL BE FOUND JUST OFF THE SE COAST...BUT FAR ENOUGH TO OUR SOUTH AND EAST TO PRECLUDE THE RISK FOR PRECIP ACROSS OUR AREA. OVERALL...TUESDAY THROUGH THE REST OF THE LONG TERM PERIOD SHOULD BE MAINLY DRY ACROSS CENTRAL NC. THE WARMEST DAY DURING THIS PERIOD WILL BE TUESDAY THANKS TO DRYING AND RESULTING SUNSHINE IN THE WAKE OF THE FRONT...BUT THEN TEMPS WILL FALL AND REMAIN A COUPLE DEGREES BELOW NORMAL DURING THE MIDDLE TO LATTER HALF OF THE WEEK WITH THE RIDGE EXTENDING ACROSS OUR AREA FROM THE NORTH AND RESULTING NE LOW LEVEL FLOW. HIGHS WILL BE IN THE UPPER 70S TO AROUND 80...AND LOWS IN THE UPPER 50S TO AROUND 60...DURING THIS TIME. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 200 AM SUNDAY... A FAIRLY LOW CONFIDENCE FORECAST WILL CONTINUE FOR THE CURRENT TAF PERIOD AS A COLD AIR DAMMING WEDGE DEVELOPS BEHIND THE FRONT THAT MOVED THROUGH THE REGION THIS PAST AFTERNOON/EVENING. AFTER A BRIEF PERIOD OF VFR CONDITIONS DEVELOPED IMMEDIATELY BEHIND THE FRONT...CIGS WILL CONTINUE TO FALL INTO THE MVFR RANGE TONIGHT. CIGS ARE EXPECTED TO REMAIN BELOW VFR THROUGH MUCH OF THE TAF PERIOD AS WINDS JUST ABOVE THE SURFACE SHIFT TO THE SOUTH AND OVERRUNNING COMMENCES. HOWEVER...JUST HOW LOW THE CIGS WILL FALL IS IN QUESTION. FOR NOW...WILL KEEP ALL TAF SITES IN THE MVFR RANGE WITH THE EXCEPTION OF KFAY. FURTHER SOUTH...THE RESIDUAL LOW LEVEL MOISTURE WILL BE HIGHER AND THE OVERRUNNING STRONGER...THEREFORE THERE WILL BE A HIGHER CHANCE OF PRECIP AND IFR/LIFR CIGS ACROSS THE SOUTHERN PORTIONS OF THE FORECAST AREA (KFAY) LATER TODAY. OUTLOOK...ADVERSE AVIATION CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE BEGINNING OF NEXT WEEK GIVEN THE LINGERING MOISTURE ALONG THE AFOREMENTIONED FRONT...ESPECIALLY ACROSS THE SOUTHERN HALF OF THE AREA (ALTHOUGH THERE COULD BE SOME BRIEF BREAKS). OUR NEXT FRONT IS EXPECTED TO CROSS THE AREA MONDAY NIGHT INTO TUESDAY...AND ENOUGH DRYING MAY OCCUR WITH THIS FRONTAL PASSAGE TO ALLOW A RETURN TO MOSTLY VFR CONDITIONS (OUTSIDE OF TYPICAL EARLY MORNING LOW STRATUS/FOG) FOR THE MIDDLE/END OF NEXT WEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...KRD/VINCENT SHORT TERM...MWS LONG TERM...NP AVIATION...KRD

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