Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 021418
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1015 AM EDT WED SEP 2 2015

.SYNOPSIS...A DISTURBANCE WILL DROP SOUTHEAST THROUGH THE AREA
TONIGHT THROUGH EARLY THURSDAY...BUT OTHERWISE DEEP HIGH PRESSURE
WILL HOLD OVER THE REGION THROUGH FRIDAY. A COLD FRONT WILL MOVE
SOUTHWARD THROUGH THE AREA LATE FRIDAY INTO SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM WEDNESDAY...

PLENTY OF SUNSHINE THIS MORNING ALTHOUGH IT`S BEING FILTERED
SOMEWHAT BY AREAS OF THIN MID-HIGH CLOUDS BLOWN OFF OF CONVECTION
OVER AND SOUTH OF THE LOWER MISS VALLEY. THE POTENT MID LEVEL WAVE
WE`VE BEEN WATCHING FOR THE LAST FEW DAYS OVER CENTRAL INDIANA IS
NOTED THIS MORNING OVER SE OHIO IS ON TRACK TO DROP SE INTO AND
THROUGH THE AREA LATER TODAY THROUGH TONIGHT. THE TIMING INDICATED
BY THE SPC SSEO / NSSL WRF / 3KM NAM CONUS NEST / NCAR ENSEMBLE
NEIGHBORHOOD PROBABILITIES ARE FAIRLY CLOSE TO THE EXISTING
FORECAST... BRINGING GOOD COVERAGE INTO THE EXTREME NORTHERN CWA
AFTER 19Z OR 20Z... THEN DROPPING TO THE SSE PEAKING IN COVERAGE
AROUND 00Z... THEN MOVING INTO THE SRN/SE CWA WHILE CONTINUING TO
WEAKEN BEFORE DISSIPATING AROUND OR SOON AFTER 06Z. HAVE MADE MINOR
TIMING DIFFERENCES AND HAVE INCREASED INITIAL COVERAGE IN THE 21Z-
03Z TIME FRAME ACROSS THE NORTH. HAVE ALSO ADDED IN LOW CHANCE POPS
IN THE YADKIN VALLEY LATE THIS AFTERNOON AS THE HRRR AND NSSL WRF
DEPICT MOUNTAIN CONVECTION DRIFTING INTO THE SW AND EXTREME WRN CWA
LATE. MODELS CONTINUE TO VARY ON INSTABILITY POTENTIAL WITH THE NAM
(AND IT`S SLIGHTLY HIGHER SURFACE DEWPOINTS) SHOWING MUCAPE VALUES
NEARLY A MAGNITUDE GREATER THAN THE GFS. DEEP LAYER SHEAR REMAINS
MARGINAL AT JUST 20-25 KTS... SO EITHER WAY DON`T EXPECT A GREAT
SEVERE THREAT... ALTHOUGH A FEW STORMS COULD GET STRONG GIVEN THE
DYNAMIC CONTRIBUTION FROM DPVA. THICKNESSES AND HRRR/GRIDDED LAMP/
LOCAL WRF GUIDANCE SUPPORT HIGHS OF 90-94. -GIH

ISOLATED-SCATTERED CONVECTION WILL SLOWLY WANE TONIGHT AS THE LOW
LEVEL AIR MASS UNDERGOES ITS NORMAL NOCTURNAL STABILIZATION. BULK OF
CONVECTION WILL DISSIPATE PRIOR TO 06Z THOUGH POTENTIAL FOR A FEW
SHOWERS TO PERSIST IN THE COASTAL PLAIN UP TO SUNRISE. MIN TEMPS 67-
73. -WSS

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 258 AM WEDNESDAY...

WEAK SUBSIDENCE BEHIND THE DEPARTING DISTURBANCE SHOULD INHIBIT
CONVECTIVE REDEVELOPMENT THURSDAY MORNING. HEATING OF THE AIR MASS
OVER CENTRAL NC SHOULD TRIGGER ISOLATED CONVECTION ABOUT ANYWHERE IN
THE MID-LATE AFTERNOON HOURS. ANOTHER UPPER DISTURBANCE...THOUGH
WEAKER THAN THE SYSTEM EXPECTED TONIGHT...WILL APPROACH FROM THE NW
LATE IN THE DAY AND CROSS CENTRAL NC THURSDAY NIGHT. THIS SYSTEM MAY
PROVIDE ENOUGH LIFT TO INITIATE/SUSTAIN A SHOWER OR TWO BUT FEEL
THAT MOST PLACES WILL REMAIN DRY THURSDAY NIGHT. MAX TEMPS THURSDAY
SHOULD BE COMPARABLE TO DAY...90-95 DEGREES...WITH MIN TEMPS THU
NIGHT 67-72.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 305 AM WEDNESDAY...

FRIDAY THROUGH SATURDAY NIGHT: A BACKDOOR COLD FRONT WILL SINK
SOUTHWARD THROUGH THE AREA ON FRIDAY INTO FRIDAY EVENING AS ANOTHER
WEAK IMPULSE IN THE NORTH-NORTHWEST TO NORTHWESTERLY MID LEVEL FLOW
MOVES ACROSS THE AREA. THIS WILL TRIGGER AT LEAST ISOLATED TO
SCATTERED SHOWERS AND SOME STORMS FRIDAY AFTERNOON INTO THE EVENING.
OVERALL DEEP FLOW CONTINUES TO BE QUITE WEAK. GIVEN THIS AND RATHER
WEAK TO MODEST INSTABILITY EXPECT LITTLE IN THE WAY OF A SEVERE
THREAT... WITH THE ONLY LIMITED THREAT FROM LOCALIZED.... MAINLY
URBAN... FLOODING AS PW/S ARE EXPECTED TO BE AROUND 1.75" OR SO ON
FRIDAY. HIGH TEMPS FRIDAY IN ADVANCE OF THE FRONT ARE EXPECTED TO
REACH INTO THE UPPER 80S TO LOWER 90S. SURFACE HIGH PRESSURE WILL
BUILD INTO THE AREA FROM THE NORTH/NORTHEAST ON FRIDAY NIGHT INTO
SATURDAY. HOWEVER... WE WILL LIKELY SEE SOME LINGERING PRECIP
CHANCES AS A WEAK MID LEVEL LOW DEVELOPS JUST TO THE SOUTH OF THE
AREA. THUS... EXPECT LOW POPS (SLIGHT CHANCE) IN THE NORTHEAST...
WITH THE HIGHEST POPS (CHANCE) IN THE SOUTHWEST. GIVEN NORTHEAST TO
EASTERLY LOW LEVEL FLOW... WE WILL LIKELY START THE DAY WITH A GOOD
BIT OF CLOUD COVER/LOW STRATUS. GIVEN THE COOLER AIR MASS FROM THE
NORTH AND EXPECTED CLOUD COVER... WILL GO WITH HIGHS ON SATURDAY IN
THE LOWER TO MID 80S (AND THIS MAY STILL BE TOO WARM IN SPOTS). LOWS
SATURDAY MORNING ARE EXPECTED TO BE IN THE UPPER 60S AND IN THE MID
TO UPPER 60S SUNDAY MORNING.

SUNDAY THROUGH TUESDAY: THE WEAK MID LEVEL LOW WILL CONTINUE TO
LINGER ACROSS THE SOUTHEAST U.S. DURING THIS TIMEFRAME WHILE SLOWLY
SINKING SOUTHWESTWARD... YET STILL EXTENDING INTO OUR AREA... ALONG
WITH AN INVERTED SURFACE TROUGH NEAR THE COAST TO EASTERN PORTIONS
OF OUR AREA. THIS WILL GENERALLY RESULT IN THE BEST CHANCES FOR
PRECIP TO THE SOUTH OF OUR AREA... BUT WE COULD SEE SOME ISOLATED TO
SCATTERED SHOWERS AND STORMS EACH DAY (MAINLY DIURNAL IN NATURE) AND
GENERALLY ACROSS EASTERN AND SOUTHEASTERN PORTIONS OF CENTRAL NC.
HIGHS WILL REMAIN IN THE 80S... COOLEST ON SUNDAY... WITH LOWS IN
THE 60S.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 705 AM WEDNESDAY...

THERE IS A HIGH LIKELIHOOD THAT VFR CONDITIONS WILL CONTINUE THROUGH
TONIGHT. THE EXCEPTION WILL BE ISOLATED-SCATTERED CONVECTION WHICH
WILL DEVELOP OR MOVE INTO CENTRAL NC FROM THE NORTH AFTER 18Z. THE
CONVECTION WILL BE SPARKED BY A SEWD MOVING UPPER LEVEL DISTURBANCE
WHICH WILL CROSS OUR REGION EARLY THIS EVENING. CONFIDENCE THAT
CONVECTION WILL OCCUR AT ANY ONE TAF SITES IS FAIRLY LOW BUT WILL
MENTION VICINITY SHOWER IN THE TRIAD TERMINALS THIS AFTERNOON...AND
NEAR KRDU AND KRWI EARLY THIS EVENING.

THE EXTENDED OUTLOOK SUGGEST MAINLY VFR CONDITIONS THOUGH COULD SEE
A BRIEF PERIOD OF EARLY MORNING FOG/STRATUS THURSDAY MORNING AND
FRIDAY MORNING. ALSO...COULD SEE SCATTERED CONVECTION DEVELOP FRIDAY
AFTERNOON INTO FRIDAY NIGHT AHEAD OF A SURFACE BOUNDARY WHICH
PROGRESS SOUTHWARD ACROSS THE AREA. THIS FEATURE MAY CAUSE UNSETTLED
WEATHER TO LINGER INTO SATURDAY WITH IMPROVING AVIATION CONDITIONS
EXPECTED BY SUNDAY.

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD/WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...WSS



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