Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 280052
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
852 PM EDT WED AUG 27 2014

.SYNOPSIS...WEAK HIGH PRESSURE WILL REMAIN CENTERED OVER THE
SOUTHERN APPALACHIANS AHEAD OF A COLD FRONT THAT WILL SETTLE
SOUTH INTO CENTRAL NC LATE THU AND THU NIGHT.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
AS OF 250 PM WEDNESDAY...

SURFACE HIGH PRESSURE OVER THE AREA WILL BEGIN TO GET SHUNTED TO
SOUTH AND WEST TONIGHT AS A BACKDOOR COLD FRONT APPROACHES THE AREA.
NEVERTHELESS...ANOTHER PLEASANT NIGHT (AT LEAST FOR LATE AUGUST) IS
EXPECTED AS TEMPS FALL INTO LOW TO MID 60S (MAYBE SOME UPPER 50S)
UNDER MOSTLY CLEAR SKIES...LIGHT WINDS AND RELATIVELY DRY AIR.

THE COLD FRONT WILL SLIP INTO THE NORTHERN PORTIONS OF THE AREA
THURSDAY AFTERNOON. MODELS DO INDICATE SOME MOISTURE POOLING ALONG
THE FRONT...HOWEVER OVERALL MOISTURE CONTENT IS EXPECTED TO REMAIN
RATHER LOW AS THE LOW LEVEL FLOW TAKES ON A WESTERLY COMPONENT. THIS
NEVERTHELESS...GIVEN THE SLIGHTLY INCREASED MOISTURE AND CONVERGENCE
ALONG THE FRONT...THERE COULD BE SOME ISOLATED CONVECTION THAT
DEVELOPS DURING THE AFTERNOON HOURS...MAINLY ACROSS THE NORTHERN
HALF OF THE FORECAST AREA. THE SEVERE THREAT IS RATHER MINIMAL GIVEN
THAT DEEP LAYER SHEAR VALUES ARE PROGGED TO STAY AROUND OR BELOW 20
KNOTS. HOWEVER... THE NAM CONTINUES TO SHOW MORE IN THE WAY OF
INSTABILITY (ALTHOUGH IT STILL SEEMS OVERDONE GIVEN THE LOWER
DEWPOINTS WITHIN THE WESTERLY FLOW). NEVERTHELESS...THE GFS DOES
SHOW SOME INSTABILITY AND IF A STORM IS ABLE TO GROW DEEP ENOUGH...
IT COULD PRODUCE A STRONG WIND GUST GIVEN THE DRY SUB-CLOUD LAYER.
LOW LEVEL THICKNESS VALUES ARE PROGGED TO INCREASE ANOTHER 10-15M ON
THURSDAY...WHICH SHOULD TRANSLATE INTO HIGHS SURGING INTO THE LOW TO
MID 90S (ESPECIALLY WITH THE DRY DOWNSLOPE WESTERLY FLOW). THE FRONT
IS EXPECTED TO STALL ACROSS THE NORTHERN PORTIONS OF THE FORECAST
THURSDAY NIGHT. THERE COULD BE AN ISOLATED SHOWER OR TWO
OVERNIGHT...BUT CHANCES ARE RATHER LOW. MORE IN THE WAY OF CLOUDS
AND MOISTURE SHOULD RESULT IN MILDER OVERNIGHT LOW (RELATIVE TO
PREVIOUS NIGHTS)...WITH MOSTLY UPPER 60S TO NEAR 70 DEGREES
EXPECTED.

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
AS OF 250 PM WEDNESDAY...

SUBTROPICAL RIDGE WILL STRENGTHEN OVER THE REGION ON FRIDAY.
DIABATIC HEATING FROM STRONG INSOLATION WILL EVENTUALLY WASH OUT THE
STALLED FRONTAL ZONE INVOF THE NC/VA BORDER...BUT NOT BEFORE SERVING
AS A FOCUS FOR ISOLATED/SLIGHT CHANCE CONVECTION FRIDAY AFTERNOON.
LOW-LEVEL THICKNESSES AND H8 (1430M AND 18-19C RESPECTIVELY)ARE
PROGGED TO BE ON PAR TO THURSDAY. HIGHS IN THE LOWER 90S. LOWS IN
THE UPPER 60S TO LOWER 70S.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 250 PM WEDNESDAY...

SUBTROPICAL RIDGE/BERMUDA HIGH PRESSURE OVER THE SOUTHEAST US WILL
REMAIN A FORMIDABLE PLAYER INTO THE WEEKEND WITH WARM AIR ALOFT
ACTING TO LARGELY SUPPRESS CONVECTION ON SATURDAY WITH A
CONTINUATION OF ABOVE NORMAL TEMPERATURES INTO THE LOWER TO MID 90S
SATURDAY AFTERNOON.

BY SUNDAY...AS THE SUBTROPICAL RIDGE AXIS BEGINS TO SLIDE EASTWARD
AND OUT OVER THE WESTERN ATLANTIC...RAIN CHANCES WILL BEGIN TO
INCREASE ACROSS WESTERN PORTIONS OF THE STATE VIA RING OF FIRE
CONVECTION PATTERN. RAIN CHANCES RETURN CWA WIDE MONDAY AND
TUESDAY...UNDER WEAKENING HEIGHTS AND COOLING TEMPS ALOFT WITH
SCATTERED DIURNAL CONVECTION FIRING ALONG A THERMAL TROUGH IN PLACE
EAST OF THE MOUNTAINS.

THE GFS REMAINS ON THE FAST SIDE OF MODEL GUIDANCE WITH BRINGING A
COLD FRONT THROUGH THE AREA TUESDAY NIGHT/EARLY WEDNESDAY...WHILE
THE EC IS NEARLY A FULL DAY BEHIND. FOR NOW WILL GO WITH THE SLOWER
TIMING...KEEPING CHANCE POPS THROUGH WEDNESDAY. HIGHS EARLY NEXT
WEEK IN THE UPPER 80S TO LOWER 90S.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
AS OF 845 PM WEDNESDAY...

VFR. UNDER THE INFLUENCE OF WEAKENING SFC HIGH PRESSURE CENTERED
OVER THE SOUTHERN APPALACHIANS...CLEAR AND GENERALLY CALM CONDITIONS
TONIGHT WILL YIELD TO SCT TO BRIEFLY BKN 4-7 THOUSAND FT CLOUD BASES
AND A LIGHT WEST TO SOUTHWEST SFC WIND AHEAD OF A COLD FRONT
APPROACHING FROM THE NORTH...ON THU. AN ISOLATED TO WIDELY SCATTERED
SHOWER OR STORM MAY ACCOMPANY THE FRONT AT NORTHERN TERMINALS
BETWEEN 22Z THU AND 04Z FRI.

OUTLOOK: SFC WINDS WILL BECOME N TO NE BEHIND THE FRONT THU NIGHT;
AND THERE IS A MEDIUM CHANCE OF THE DEVELOPMENT OF MVFR CEILINGS IN
NNE POST-FRONTAL FLOW FRI MORNING...MAINLY AT NORTHERN SITES. SCT TO
BKN HIGH MVFR-RANGE TO LOW-VFR RANGE CLOUD BASES WILL REMAIN
POSSIBLE THROUGH FRIDAY NIGHT...OWING TO THE STALL OF THE FRONT IN
THE VICINITY OF CENTRAL NC THROUGH EARLY SAT. THE PROBABILITY OF
PATCHY FOG WILL ALSO INCREASE BY THE WEEKEND...AS THE LOW LEVEL FLOW
ASSUMES A MORE SOUTHERLY (MOIST) COMPONENT WITH THE DISSIPATION/
NORTHWARD RETREAT OF THE FRONT.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...MWS
NEAR TERM...KRD
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...MWS



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