Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 221652
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1250 PM EDT FRI AUG 22 2014

.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL DIVE SOUTHEAST
INTO OUR REGION FROM THE OHIO VALLEY AND MIDWEST. A BACK-DOOR COLD
WILL SETTLE SLOWLY SOUTH THROUGH THE AREA ON SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1025 AM FRIDAY...

PERTURBED NORTHWESTERLY FLOW CONTINUES OVER THE REGION TODAY
BETWEEN A MID-LEVEL RIDGE OVER THE DEEP SOUTH AND A TROUGH OVER THE
NORTHEAST.  A LEAD...DECAYING DISTURBANCE CROSSING WV HS AIDING AN
AREA OF MOSTLY LIGHT SHOWERS NOW OVER SOUTHWESTERN VA.   AHEAD OF
THIS FEATURE...AMPLE SUNSHINE OVER CENTRAL NC WILL ALLOW TEMPS TO
RISE INTO THE LOW TO MID 90S...BASED ON H85 TEMPS OF 19-20C PER
REGIONAL RAOBS.  DEWPOINTS SHOULD AGAIN MIX OUT INTO THE MID/UPPER
60S...ESPECIALLY ACROSS THE SOUTHWESTERN AND WESTERN AREAS WHERE 925MB
DEWPOINTS ARE AT A RELATIVE MIN.  MLCAPE VALUES AREA FORECAST TO
RANGE FROM 1000 J/KG IN THE WEST TO NEAR 2000 J/KG IN THE EAST.  A
BELT OF STRONGER NORTHWESTERLY MID-LEVEL FLOW WILL SHIFT SOUTHEAST
ACROSS VA AND THE NORTHERN PORTIONS OF NC AS A SPEED MAX CROSSES THE
CENTRAL APPALACHIANS.  EFFECTIVE BULK SHEAR SHOULD REACH AROUND 25-
30 KTS NORTHEAST OF THE TRIANGLE THIS AFTERNOON AND EVENING...WHICH
COMBINED WITH MODERATE INSTABILITY WILL SUPPORT THE POTENTIAL FOR
SOME STRONG MULTI-CELL CLUSTERS.  THE BIGGEST UNCERTAINTY CONTINUES
TO BE WITH CONVECTIVE INITIATION AHEAD OF THE DISTURBANCE.  IF THE
SHOWERS AHEAD OF THE DISTURBANCE HOLD TOGETHER INTO THE NORTHERN
PIEDMONT IN THE NEXT 2-3 HOURS...THEY MAY LIMIT DESTABILIZATION.
HOWEVER... WITH TIME EXPECT ADDITIONAL STORMS TO POPS UP AND
PROPAGATE TOWARD THE SOUTH-SOUTHEAST TOWARD WHAT SHOULD BE MODEST
DCAPE ACROSS THE SOUTHERN TIER...FURTHER ENHANCING THE THREAT OF
SOME DAMAGING WIND GUSTS.

LINGERING SFC OUTFLOW AND SURFACE FRONT DROPPING SOUTH INTO THE AREA
WILL SUPPORT SMALL TO SLIGHT POPS OVERNIGHT. LOWS IN THE UPPER 60S
NE TO LOWER 70S SE.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 320 AM FRIDAY...

SATURDAY AND SATURDAY NIGHT: HIGH PRESSURE OVER NEW ENGLAND WILL
BEGIN TO RIDGE SOUTH DOWN THE MID-ATLANTIC SEABOARD WHICH SHOULD
PUSH THE BACK-DOOR FRONT SLOWLY SOUTH INTO THE AREA ON SATURDAY. AS
USUAL...TIMING OF THESE BACK-DOOR FRONTS THIS TIME OF YEAR IS
SUSPECT(USUALLY SLOWER IS BETTER)...WITH DIURNAL HEATING AND
RESULTANT DESTABILIZATION AIDING IN SCATTERED COVERAGE. THE LATE
ARRIVAL OF A SHORTWAVE TROUGH ROTATING SOUTHWARD DOWN THE BACK-SIDE
OF THE UPPER TROUGH SATURDAY NIGHT MAY EVEN SUPPORT A FEW ANAFRONTAL
SHOWERS OVERNIGHT.

COOLER ON SATURDAY WITH CLOUDS AND NELY FLOW NORTH OF THE FRONT.
HIGHS RANGING FROM LOWER/MID 80S NORTH TO LOWER 90S SOUTH. LOWS
SATURDAY NIGHT IN THE UPPER 60S TO LOWER 70S.

SUNDAY AND SUNDAY NIGHT: AS THE UPPER AIR PATTERN AMPLIFIES (RIDGE
BUILDING OVER THE MISSISSIPPI RIVER VALLEY...TROUGH DEEPENING ACROSS
THE WESTERN ATLANTIC) ON SUNDAY...CENTRAL NC WILL BE UNDER
NORTHWEST/NORTHERLY FLOW ALOFT. AT THE SURFACE...A COLD FRONT WILL
BE SHUNTED SOUTH OF THE REGION AS HIGH PRESSURE BEGINS TO RIDGE DOWN
FROM THE NORTHEAST. AS THIS OCCURS...DRIER AIR WILL FILTER INTO THE
REGION THROUGHOUT THE DAY...BUT SOME DEEP MOISTURE WILL REMAIN IN
PLACE...MOSTLY ACROSS THE SOUTH AND WEST WHERE PWAT VALUES ARE
PROGGED TO HOVER BETWEEN 1.5-1.75 INCHES THROUGH SUNDAY NIGHT. GIVEN
THIS AND THE LINGERING FRONT...AND THE POSSIBILITY OF ANY WEAK
DISTURBANCES MOVING OVER THE AREA WITHIN THE NORTHWESTERLY FLOW
ALOFT...WILL MAINTAIN SLIGHT CHANCE TO CHANCE POPS...HIGHEST ACROSS
THE SOUTH AND WEST. IN FACT...NORTHEASTERN PORTIONS OF THE FORECAST
AREA MAY STAY DRY. TEMPS WILL RANGE FROM NEAR 80 DEGREES TO THE MID
80S...WITH OVERNIGHT LOWS GENERALLY IN THE MID 60S.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 1250 PM FRIDAY...

AN AMPLIFIED UPPER PATTERN WILL PERSIST THROUGH EARLY NEXT WEEK...
WITH AN UPPER RIDGE GRADUALLY BUILDING EAST TOWARDS THE REGION. A
COLD FRONT WILL BE SUPPRESSED SOUTH OF THE AREA BY LATE SUNDAY AS
DRY AND COOLER SURFACE HIGH PRESSURE BECOMES FIRMLY ENTRENCHED
DOWN THE ATLANTIC COAST. THERE WILL BE A LINGERING CHANCE OF SHOWERS
SUNDAY AS THE FRONT SURGES SOUTH...FOLLOWED BY DRY CONDITIONS
THROUGH THURSDAY. THE UPPER RIDGE WILL DEAMPLIFY/FLATTEN OUT AS THE
NEXT UPPER TROUGH AND ASSOCIATED SURFACE FRONT APPROACHES THE AREA
LATE THURSDAY INTO FRIDAY...BRINGING INCREASING PRECIPITATION
CHANCES BY THE END OF THE WEEK.

POST FRONTAL CONDITIONS WILL BE PLEASANT...WITH CONSIDERABLY COOLER
TEMPERATURES AND LOWER HUMIDITY. LOW LEVEL THICKNESS VALUES WILL
FALL THROUGH EARLY NEXT WEEK...TO THE TUNE OF 30 METERS EQUATING TO
AROUND A 10 DEGREE COOLOFF. HIGHS SUNDAY THROUGH TUESDAY WILL BE
WELL BELOW...5-7 DEGREES...NORMAL WITH UPPER 70S TO LOWER 80S OVER
ALL BUT THE FAR SOUTHERN TIER WHICH MAY SEE MID 80S. TEMPS WILL BEGIN
TO MODERATE WEDNESDAY THROUGH FRIDAY AS THE UPPER RIDGE SHIFTS EAST...
WITH MID/UPPER 80S EXPECTED BY THE END OF THE WEEK. OVERNIGHT LOWS
WILL FOLLOW THE SAME PATTERN...WITH MOSTLY LOW TO MID 60S EARLY
NEXT WEEK WARMING TO MID AND UPPER 60S BY LATE WEEK.


&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AS OF 648 AM FRIDAY...

24-HR TAF PERIOD: VFR CONDITIONS SHOULD RETURN BY 13Z TO 14Z.
SHORTWAVE DISTURBANCES MOVING INTO THE AREA WITHIN THE NW FLOW ALOFT
WILL SUPPORT SHOWERS AND STORMS THIS AFTERNOON AND EVENING...WITH
THE BEST CHANCE AT THE RDU/RWI TERMINALS. ITS POSSIBLE THAT
CONVECTION COULD PERSIST WELL INTO OVERNIGHT HOURS...ESPECIALLY
ACROSS THE NE AS A COLD FRONT ATTEMPTS TO DROP SOUTH INTO THE AREA.

LOOKING AHEAD: DIURNAL CONVECTION IS EXPECTED AGAIN ON SAT...
ENHANCED BY THE PASSAGE OF A BACK DOOR COLD FRONT FROM THE NORTH/NE
SAT EVE/NIGHT. WIDESPREAD IFR CEILINGS ARE EXPECTED IN THE WAKE OF
THE BACKDOOR COLD FRONT SAT NIGHT/SUN MORNING...POSSIBLY PERSISTING
THROUGH THE DAY AND INTO SUN NIGHT.  DRY SURFACE HIGH PRESSURE
BUILDING DOWN THE MID-ATLANTIC SEABOARD WILL SECURE DRY VFR
CONDITIONS THROUGH EARLY NEXT WEEK.

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...CBL/BLS
SHORT TERM...CBL/KRD
LONG TERM...MLM
AVIATION...CBL/VINCENT



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