Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 271943
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
342 PM EDT SUN JUL 27 2014

.SYNOPSIS...A SURFACE TROUGH WILL PERSIST OVER THE CAROLINAS THROUGH
TONIGHT. A STRONG COLD FRONT WILL CROSS THE AREA ON MONDAY...
BRINGING NOTICEABLY COOLER AND LESS HUMID AIR INTO THE AREA.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 340 PM SUNDAY...

AFTER A COOL START OWING TO ABUNDANT MULTI-LAYERED CLOUDS AND
RAIN...TEMPERATURES HAVE CLIMBED QUICKLY DURING THE PAST FEW HOURS
IN AN AREA OF CLEARING IN THE WAKE OF THE MORNING MCV...COINCIDENT
WITH THE ARRIVAL OF THE LEADING EDGE OF HOT/22C 12Z-OBSERVED H85
TEMPS AT KBNA. THE CONFIGURATION OF THE WAA REGIME DEVELOPING FROM
THE WESTERN CAROLINAS AND EARLIER RAIN-COOLED AIR WILL FAVOR THE
STRENGTHENING OF A NW TO SE-ORIENTED OUTFLOW BOUNDARY/EFFECTIVE
FRONT FROM THE TN VALLEY SOUTHEASTWARD ACROSS SOUTHERN VA/NORTHERN
NC. THIS BOUNDARY WILL SERVE TO ENHANCE WHAT NEAR TERM GUIDANCE
SUGGESTS WILL BE ALREADY STRONG LOW LEVEL SHEAR IN THE 250-400 MS/S2
RANGE CENTERED OVER SOUTHSIDE VA AND NORTH-CENTRAL NC...FROM JUST
PRIOR TO SUNSET THROUGH MIDNIGHT. MID-LEVEL/DEEP LAYER WINDS WILL BE
EQUALLY IMPRESSIVE...AS THE EXIT REGION OF AN UPSTREAM MID LEVEL JET
AT THE BASE OF THE UPPER MID WEST UPPER LOW EMERGES EAST OF THE
CENTRAL APPALACHIANS AND STRENGTHENS KGSO AND KRNK 12Z-OBSERVED MID
LEVEL FLOW OF ALREADY RESPECTABLE 35-40 KTS...INTO THE 45-55 KT
RANGE THIS EVENING. THE STRONGLY SHEARED ENVIRONMENT WILL SUPPORT A
CONDITIONAL PROBABILITY OF SEVERE THUNDERSTORMS OVER CENTRAL
NC...PARTICULARLY FROM LATE THIS AFTERNOON THROUGH MIDNIGHT.

IT IS PROBABLE THAT SCATTERED STORMS WILL DEVELOP INVOF THE OUTFLOW
BOUNDARY/EFFECTIVE FRONT FROM SOUTHWEST VA INTO THE NORTHERN NC
PIEDMONT...ON THE SOUTHERN FRINGE OF AN MCV MOVING ESE INTO WEST-
CENTRAL VA THIS AFTERNOON...AND AMIDST INCREASING LARGE SCALE LIFT
AHEAD OF THE UPPER LOW APPROACHING FROM THE UPPER MIDWEST. THE LAST
SEVERAL RUNS OF THE HRRR HAVE FINALLY PICKED UP ON THIS POTENTIAL.
WILL ADVERTISE A CHANCE OF STORMS MAINLY OVER THE NORTHERN HALF OF
THE FORECAST AREA (INVOF THE BOUNDARY) THROUGH THIS EVENING...WITH
AN ASSOCIATED CONDITIONAL PROBABILITY OF A MULTI-FACETED SVR RISK OF
DAMAGING WINDS...LARGE HAIL...AND EVEN AN ISOLATED TORNADO GIVEN THE
EXPECTED STRONG LOW LEVEL SHEAR CENTERED OVER THE NE PIEDMONT AROUND
00Z.

NWP GUIDANCE THEN SUGGESTS THAT STORMS OVER THE TN VALLEY THIS
AFTERNOON WILL DEVELOP SOUTHEASTWARD AND SPREAD ACROSS THE CENTRAL
APPALACHIANS LATE THIS EVENING...AND INTO CENTRAL NC AFTER LOW LEVEL
SHEAR DIMINISHES - AND WHEN CINH SHOULD BE MAXIMIZED - DURING THE
OVERNIGHT HOURS. ANY OVERNIGHT CONVECTION WOULD THEN POSE PRIMARILY
A THREAT OF DAMAGING WIND AND LARGE HAIL MAINLY OVER THE NW
PIEDMONT...BEFORE STORMS WEAKEN AS THEY MOVE SOUTHEAST INTO THE
REMAINDER OF CENTRAL NC. THOUGH THERE REMAINS OPPOSING SIGNALS FOR
STORM DEVELOPMENT/MAINTENANCE (IE. STRONG AND INCREASING FORCING FOR
ASCENT DOWNSTREAM OF THE DEEP UPPER LOW VERSUS STRONG CINH (NEAR 200
J/KG)...THE OVERWHELMING SIGNAL FROM NWP GUIDANCE IS FOR THE CINH TO
WIN OUT AND CAUSE STORMS TO DIMINISH INVOF HWY 64 BY LATE THIS
EVENING...SENDING ONLY A SURGING OUTFLOW BOUNDARY AND ASSOCIATED NW
WIND GUSTS OF 25-35 KTS (STRONGEST NORTH) SOUTH THROUGH THE
REMAINDER OF THE CENTRAL NC OVERNIGHT. REGARDLESS...IT WILL BE MUGGY
AND QUITE MILD OVERNIGHT...WITH LOWS GENERALLY IN THE MIDDLE 70S.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 325 PM SUNDAY...

NWP GUIDANCE CONTINUES TO SUGGEST DESTABILIZATION WILL BE LIMITED
AND CONFINED TO THE SANDHILLS AND COASTAL PLAIN...GIVEN THE FASTER
TREND NOTED IN NWP GUIDANCE WITH THE PASSAGE OF THE COLD FRONT
THROUGH ALL BUT THE SOUTHEASTERN THIRD OF THE FORECAST AREA BY 18Z
MON. INDEED...WESTERLY DOWNSLOPE FLOW WILL VEER THE SFC FLOW/LIMIT
CONVERGENCE AND AUGMENT DRY ADVECTION BEHIND THE FRONT (AND LIKELY
CAUSE THE FRONT TO ACCELERATE/MERGE WITH THE PRECEDING LEE
TROUGH)...AND CONSEQUENTLY CAUSE SFC DEWPOINTS TO MIX INTO THE LOWER
60S (AND EVEN SOME UPPER 50S POSSIBLE) OVER THE PIEDMONT - YIELDING
LITTLE BOUYANCY. TO THE EAST...IN THE PRE-FRONTAL AIR MASS OVER THE
SANDHILLS AND SOUTHERN AND CENTRAL COASTAL PLAIN...A RESERVOIR OF
UPPER 60S TO LOWER 70S SFC DEWPOINTS WILL REMAIN UNTIL THE FRONT
CROSSES THOSE AREAS DURING THE MID-AFTERNOON HOURS. MORE FAVORABLE
DIURNAL FRONTAL TIMING THERE WILL ALLOW FOR STRONG DIURNAL
HEATING/DESTABILIZATION/STEEPENING OF LOW LEVEL LAPSE RATES...
BENEATH A LINGERING PLUME OF STEEP MID LEVEL LAPSE RATES IN EXCESS
OF 7 C/KM. THESE EXPECTED STEEP LOW-MID LEVEL LAPSE RATES AMIDST
UNSEASONABLY STRONG MID LEVEL FLOW IN THE 40-50 KT RANGE - AND
ASSOCIATED LONG AND STRAIGHT FORECAST HODOGRAPHS AT KFAY AT TIME OF
FROPA AROUND 21Z - WILL SUPPORT A CONDITIONAL RISK OF DAMAGING WIND
GUSTS AND LARGE HAIL LIKELY FROM SPLITTING SUPERCELLS...PROVIDED
STORMS INDEED DEVELOP. THIS RISK WILL BE GREATEST ROUGHLY FROM
GOLDSBORO TO FAYETTEVILLE TO LAURINBURG AND ESPECIALLY POINTS
EAST...TO COASTAL AREAS.

LOW LEVEL THICKNESS VALUES AROUND 1425 METERS SUPPORT HIGH
TEMPERATURES IN THE MID-UPPER 80S NW TO LOWER-MID 90S SE. COOLER MON
NIGHT...WITH LOWS RANGING FROM LOWER 60W NW TO MID-UPPER 60 SE.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
AS OF 315 PM SUNDAY...

STRONGLY BLOCKED FLOW AROUND THE NORTHERN HEMISPHERE WILL LEAD TO A
RELATIVELY UNCHANGED WEATHER PATTERN FROM TUESDAY THROUGH THE END OF
NEXT WEEK.   THE TROUGH/RIDGE PATTERN OVER THE CONUS WILL AMPLIFY
WITH AN UNSEASONABLY DEEP UPPER TROUGH OVER THE EASTERN US.  IN THE
WAKE OF MONDAY`S SYSTEM...PW DROPS BELOW ONE INCH AND THE MEAN
TROUGH AXIS SETS UP NEARLY OVERHEAD.  DEWPOINTS ARE PROGGED TO DROP
WELL INTO THE 50S IN THE PIEDMONT...WITH THICKNESSES SUGGESTING
TEMPS 5-10 DEGREES BELOW NORMAL IN THE LOW TO MID 80S. THUS...
PRECIP CHANCES LOOK VERY SMALL THROUGH THURSDAY.  HEADING INTO NEXT
WEEKEND...MODELS SHOW ANOTHER SHORTWAVE REINFORCING THE UPPER TROUGH
OVER THE EASTERN CONUS...THOUGH ALSO SHIFTING THE TROUGH AXIS
WESTWARD TOWARD THE MIDWEST STATES. WITH AN FRONTAL ZONE/INVERTED
TROUGH LINGERING NEAR THE COAST OR SLOWLY DRIFTING
INLAND....MOISTURE RETURN AND A MORE FAVORABLE POSITION FOR
INFLUENCE FROM DISTURBANCES ROUNDING THE BASE OF THE TROUGH SHOULD
SLOWLY INCREASE CHANCES FOR PRECIP...WITH INCREASING CLOUD COVER
THROUGH THE WEEKEND.  HIGHS LOOK TO REMAIN A GOOD 5-10 DEGREES BELOW
NORMAL.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AS OF 205 PM SUNDAY...

SCATTERED SHOWERS AND STORMS...WHOSE PROBABILITY OF OCCURRENCE AT
ANY PARTICULAR TERMINAL IS ONLY AROUND 20 PERCENT...MAY FORM IN-SITU
OVER CENTRAL NC THIS AFTERNOON...IN ASSOCIATION WITH LIFT AHEAD OF A
MID LEVEL DISTURBANCE MOVING INTO SOUTH-CENTRAL VA...AND IN THE
VICINITY OF AN OUTFLOW BOUNDARY FROM NEAR KMTV TO KRDU TO KCTZ. IN
ADDITION...A BRIEF PERIOD OF MVFR CEILINGS WILL BE POSSIBLE ON THE
COOL SIDE OF THE OUTFLOW BOUNDARY (AT KRWI) THROUGH 20Z. ANOTHER
CLUSTER OF SHOWERS AND STORMS...THE ONE CURRENTLY DEVELOPING OVER
EASTERN KY...IS FORECAST TO SPREAD SOUTHEASTWARD AND INTO CENTRAL
NC...LIKELY IN A GRADUALLY WEAKENING STATE...BETWEEN 02-08Z. THE
RELATIVE BEST CHANCE OF STORMS WILL BE AT TRIAD TERMINALS...WITH
PROGRESSIVELY LOWER PROBABILITIES TOWARD KRDU/KRWI AND ESPECIALLY
KFAY. DESPITE THE PROBABLE WEAKENING OF THE STORMS AS THEY MOVE INTO
CENTRAL NC...A WELL-ORGANIZED OUTFLOW BOUNDARY AND ASSOCIATED
NORTHWESTERLY WIND GUSTS OF 25-35 KTS (STRONGEST AT KRDU/KRWI) MAY
SURGE ALL THE WAY SOUTH THROUGH CENTRAL NC OVERNIGHT.

A BREEZY WSW WIND EARLY MONDAY WILL VEER TO WEST OR WNW WITH THE
PASSAGE OF A PRONOUNCED COLD FRONT MONDAY AFTERNOON. THE FRONT IS
FORECAST TO BE A DRY ONE FOR MOST OF CENTRAL NC...WITH AROUND A 30
PERCENT CHANCE OF A STORM AT KRWI AND KFAY...AND HIGHER
PROBABILITIES TOWARD COASTAL AREAS.

PREDOMINATELY VFR CONDITIONS ARE OTHERWISE EXPECTED THROUGHOUT THE
FORECAST PERIOD...AS CANADIAN HIGH PRESSURE BECOMES CENTERED OVER
THE TN VALLEY AND CENTRAL APPALACHIANS THROUGH MID-WEEK.

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...BLS
AVIATION...MWS


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