Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Graphics & Text | 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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 140615 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 214 AM EDT SUN SEP 14 2014 .SYNOPSIS... A BACK DOOR COLD FRONT SURGING SOUTHWARD THROUGH THE REGION OVERNIGHT WILL STALL OUT NEAR THE GULF COAST THROUGH MONDAY AS HIGH PRESSURE EXTENDS SOUTHWARD FROM THE MID ATLANTIC INTO THE CAROLINAS. && .NEAR TERM /THROUGH SUNDAY/... AS OF 1145 PM SATURDAY... OVERVIEW: THE LEADING EDGE OF A BACKDOOR COLD FRONT PROGRESSING SOUTHWARD THROUGH CENTRAL NC THIS EVENING WAS LOCATED VERY NEAR THE NC/SC BORDER AT 03Z. THIS FEATURE IS EXPECTED TO CONTINUE SOUTHWARD THROUGH SOUTH CAROLINA INTO GEORGIA BY 12Z SUN AS HIGH PRESSURE BUILDS FROM THE OH VALLEY INTO THE MID-ATLANTIC... EVENTUALLY STALLING OUT NEAR THE DEEP SOUTH GULF COAST BY 18Z SUN TO 00Z MON. 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: CONVECTION WILL REMAIN POSSIBLE NEAR THE SC BORDER OVERNIGHT AS THE BACKDOOR COLD FRONT SURGES SOUTHWARD INTO SC...WITH CHANCES DIMINISHING ON THE NC SIDE OF THE BORDER BY 06-09Z. 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. WITH THE ABOVE IN MIND...WILL INDICATE PRECIP CHANCES RANGING FROM 50-60% NEAR THE SC BORDER TO SLIGHT CHANCE (20%) ALONG AND JUST SOUTH OF HWY 64 DURING THE DAY SUNDAY. TEMPS: CHALLENGING TEMPERATURE FORECAST WITH A GOOD 5F+ BUST POTENTIAL FOR HIGHS ON SUNDAY...ESP IN THE SOUTH. FCST SOUNDINGS SHOW TEMPS FALLING INTO THE UPPER 50S TO LOWER 60S NORTH TO MID/UPPER 60S SOUTH BY 12Z SUNDAY IN ASSOC/W COLD ADVECTION IN THE WAKE OF THE BACKDOOR FRONTAL PASSAGE. GIVEN EXPECTED PRECIP IN THE SOUTH (AS MENTIONED ABOVE)...EXPECT 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. WITH THIS IN MIND...WILL REDUCE HIGH TEMPS BY SEVERAL CATEGORIES FROM PRIOR FORECASTS...ESP IN THE SOUTH WHERE CALENDAR DAY HIGHS MAY OCCUR AT MIDNIGHT OR PRIOR TO NOON (AS LONG AS PRECIP DEVELOPS AS EXPECTED)...WITH AFTERNOON TEMPS RANGING FROM THE MID/UPPER 60S NEAR THE SC BORDER TO THE LOWER 70S NEAR THE VA BORDER... PERHAPS MID 70S IN THE NE COASTAL PLAIN. -VINCENT && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... AS OF 300 PM SATURDAY... SUN NIGHT: WHILE THE LOW LEVEL FRONTAL ZONE AND ASSOCIATED TEMPERATURE GRADIENT WILL BECOME MORE DIFFUSE SUN NIGHT...THE MOIST AXIS ALONG THE FRONT WILL DRIFT NORTH WITH THE DEVELOPMENT OF VEERING AND ISENTROPIC UPGLIDE-INDUCING SE 925 MB FLOW. THESE PROCESSES IN CONJUNCTION WITH NOCTURNAL COOLING...WILL RESULT IN A NORTHWARD EXPANSION AND LOWERING OF STRATUS OVERNIGHT...WITH EXCEPTION OF OVER THE FAR NORTHERN PIEDMONT WHERE DRIER AIR WILL RESIDE IN THE LOW LEVELS AND ARRIVE ALOFT TOWARD DAYBREAK. AREAS OF FOG WILL CONSEQUENTLY BE POSSIBLE IN THESE POCKETS OF RELATIVE CLEARING EARLY MON MORNING. LOWS 57 TO 65...COOLEST OVER THE NORTHERN PIEDMONT. 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. TUE: AFTER A LINGERING CHANCE OF A SHOWER OVER THE FAR SOUTHEAST CWFA EARLY TUE...CLEARING SKIES WILL SUPPORT TEMPERATURES WARMING INTO THE LOWER TO MIDDLE 80S. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... AS OF 325 PM SATURDAY... THE MEDIUM RANGE WILL BE CHARACTERIZED BY A SLOWLY PROGRESSIVE LONGWAVE PATTERN ACROSS THE CONUS...WHICH WILL INCLUDE A DEVELOPING/ DEEPENING TROUGH OVER THE EASTERN US. MEANWHILE AT THE SFC...A PAIR OF SFC HIGHS WILL BUILD SOUTH FROM CANADA AND RIDGE DOWN THE EAST COAST. THE RESULT WILL BE A RELATIVELY PROLONGED PERIOD OF EAST TO NORTHEAST LOW LEVEL FLOW AND ASSOCIATED BELOW NORMAL TEMPERATURES. THE DAYTIME TEMPERATURES WILL LIKELY BE FURTHER MUTED BY PERIODS OF BKN MULTI-LAYERED CLOUD COVER WHEN A COUPLE OF WAVES OF LOW PRESSURE MAY RIPPLE ALONG AN OFFSHORE FRONTAL ZONE AND SPREAD MOISTURE/CLOUDS INLAND...WITH RAIN CHANCES HOLDING ALONG COASTAL AREAS...THU-FRI. && .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...VINCENT SHORT TERM...MWS LONG TERM...MWS AVIATION...KRD

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