Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 220721
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
320 AM 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 OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 320 AM FRIDAY...

SHORTWAVE VORT DISTURBANCES DIVING SOUTH DOWN THE BACKSIDE OF THE
DIGGING UPPER TROUGH OFF THE MID-ATLANTIC COAST WILL CONTINUE TO
INFLUENCE THE WEATHER THROUGH SATURDAY. ASSOCIATED HEIGHT FALLS WILL
EVENTUALLY PUSH A COLD FRONT THROUGH THE AREA SATURDAY AND INTO
SATURDAY NIGHT.

TODAY AND TONIGHT: WEAKENING AREA OF CONVECTION OVER OHIO AND THE
BULK OF ITS REMNANT VORTICITY ENERGY IS FORECAST TO MOVE ACROSS
VIRGINIA LATE THIS MORNING AND THEN OFF THE DELMARVA COAST THIS
AFTERNOON. WHILE WEAKER ENERGY ALOFT COULD HELP TO SUPPORT
CONVECTION THIS AFTERNOON...APPEARS THAT SOUTHEASTWARD DRIFTING
OUTFLOW FROM STORMS IN CENTRAL/SOUTHERN VA WILL BE THE MAIN FOCUS
FOR CONVECTION LATE THIS AFTERNOON AND EVENING. THIS WILL HIGHEST
CHANCE POPS ACROSS THE NORTH/NORTHEAST TIER...WITH LOWER
CHANCE/SLIGHT CHANCE POPS ACROSS THE SOUTHERN ZONES OWING TO WEAKER
SUPPORT ALOFT AND WITH WHAT LIKELY BE INCREASING CIN AS WE MOVE INTO
THE EVENING AND OVERNIGHT HOURS. LINGERING SFC OUTFLOW AND SURFACE
FRONT DROPPING SOUTH INTO THE AREA WILL SUPPORT SMALL TO SLIGHT POPS
OVERNIGHT.

MODERATE TO STRONG DESTABILIZATION IS EXPECTED AGAIN ACROSS THE NC
COASTAL PLAN REGION WHERE BL DEWPOINTS SHOULD HOLD IN THE LOWER
70S...AWAY FROM THE DOWNSLOPE MIXING EFFECTS IN THE WEST. WITH A
BELT OF MODEST 35KT NWLY FLOW EXPECTED TO EXTEND ACROSS VA/NC...
COULD SEE A FEW STRONG TO SEVERE THUNDERSTORM CAPABLE OF PRODUCING
DAMAGING THUNDERSTORM WIND GUSTS.

HIGH RANGING FROM 90 NE TO 95 SOUTH. 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 /MONDAY THROUGH THURSDAY/...
AS OF 300 AM FRIDAY...

THE HIGHLY AMPLIFIED PATTERN WILL PERSIST THROUGH EARLY NEXT WEEK...
WITH THE UPPER RIDGE GRADUALLY BUILDING EAST TOWARDS THE REGION. THE
COLD FRONT WILL BE PUSHED WELL TO OUR SOUTH AS A SURFACE HIGH
PRESSURE RIDGE BECOMES FIRMLY ENTRENCHED OVER THE AREA. MUCH DRIER
AIR IS PROGGED TO BE IN PLACE...WITH PWAT VALUES EXPECTED TO FALL
BELOW 1 INCH. ALL OF THIS WILL LEAD TO MOSTLY DRY CONDITIONS THROUGH
AT LEAST THE MIDDLE OF NEXT WEEK. THE STRONG UPPER RIDGE WILL
FINALLY FLATTEN OUT/SHIFT OFFSHORE AS THE NEXT UPPER TROUGH/SURFACE
FRONT APPROACHES THE AREA LATE THURSDAY INTO FRIDAY...BRINGING
INCREASING PRECIP CHANCES BY THE END OF THE WEEK.

LOW LEVEL THICKNESS VALUES WILL GRADUALLY FALL THROUGH EARLY NEXT
WEEK AS THE UPPER TROUGH DEEPENS DOWN THE WESTERN ATLANTIC. IN
ADDITION...NORTHEASTERLY SURFACE FLOW WILL PERSIST AS HIGH PRESSURE
RIDGES INTO THE AREA FROM THE NORTHEAST. ALL OF THIS WILL RESULT IN
BELOW NORMAL TEMPS...WITH UPPER 70S TO LOW/MID 80S EXPECTED FOR
SUNDAY AND EARLY NEXT WEEK. TEMPS WILL BEGIN TO MODERATE TUESDAY AND
ESPECIALLY INTO WEDNESDAY/THURSDAY AS THE UPPER RIDGE SHIFTS EAST...
WITH MID/UPPER 80S EXPECTED BY THE END OF THE PERIOD. OVERNIGHT LOWS
WILL FOLLOW THE SAME PATTERN...WITH MOSTLY MID/UPPER 60S (MAYBE SOME
LOWER 60S IN THE COOLER LOCATIONS) FOR THE FIRST HALF OF THE PERIOD
AND THEN MORE IN THE WAY OF MID/UPPER 60S.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
AS OF 135 AM FRIDAY...

24-HR TAF PERIOD: AS DEBRIS CLOUD COVER SCATTERS OUT...MOSTLY MVFR
VFR FOG AND/OR LOW CEILINGS ARE EXPECTED TO DEVELOP OVERNIGHT
GIVEN VERY MUGGY/HUMID AIRMASS. THE EXCEPTION WILL BE AT FOG-PRONE
KRWI...WHERE A BRIEF PERIOD OF LIFR TO IFR CONDITIONS ARE POSSIBLE.

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
SHORT TERM...CBL/KRD
LONG TERM...KRD
AVIATION...CBL/VINCENT



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