-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 230031
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
824 PM EDT TUE JUL 22 2014

.SYNOPSIS...
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WEAK HIGH PRESSURE WILL LINGER OVER THE REGION INTO
THURSDAY. A COLD FRONT WILL MOVE ACROSS NORTH CAROLINA THURSDAY INTO
FRIDAY MORNING... THE STALL WELL SOUTH OF THE REGION SATURDAY.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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AS OF 824 PM TUESDAY...

ISOLATED SHOWERS HAVE GENERALLY DIED OFF IN THE PAST HOUR WITH THE
EXCEPTION OF THE SANDHILLS AND SOUTHERN COASTAL PLAIN REGION WHERE
SCATTERED SHOWERS AND THUNDERSTORMS CONTINUED AT MID EVENING. THE
THUNDERSTORMS HAVE VERY SMALL CORES WITH SOME LOCALLY INTENSE
RAINFALL. EVEN WITH THE SLOW MOVEMENT OF THESE STORMS... ONLY VERY
LOCALIZED DOWNPOURS WERE OCCURRING WITH NO REPORTED RUNOFF PROBLEMS
YET. THE AREAS AFFECTED EXTEND FROM NEAR SOUTHERN PINES TO
FAYETTEVILLE AND FORT BRAGG EAST TO NEAR CLINTON. IT APPEARS THAT
THESE STORMS ARE AGAIN LARGELY DIURNALLY DRIVEN. EXPECT THAT WITH
INCREASING CINH IN THE NEXT FEW HOURS... THEY WILL DIE OFF QUICKLY
AS WELL. OTHERWISE... THE ISOLATED SHOWERS WILL DIMINISH AS WELL.
THIS SHOULD LEAVE MOSTLY CLEAR TO PARTLY CLOUDY SKIES OVERNIGHT.
LOWS GENERALLY 68-73 N TO SE.
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&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
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AS OF 245 PM TUESDAY...

ON WEDNESDAY...LOOKS LIKE MORE OF A CONVENTIONAL SUMMERTIME
CONVECTIVE PATTERN WITH SOUTHWEST TO WESTERLY FLOW ALOFT ENHANCING
LEE TROFFING OVER THE AREA. MIXING WILL BE DEEPER TO PROVIDE BREAKS
IN THE CLOUDS TOMORROW AS WELL...ALLOWING HIGHS TO REACH THEIR
POTENTIAL IN THE LOW 90S. WE WILL REMAIN IN THE SOUPY AIRMASS...OF
COURSE...SO INSTABILITY WILL BE FAIRLY IMPRESSIVE...AROUND 1.5K
JOULES...SO POPS IN THE 40 PERCENT RANGE ARE IN ORDER...GRADUATED
SLIGHTLY HIGHER IN THE WEST WHERE DIFFERENTIAL HEATING SHOULD
PROVIDE EARLIER INITIATION...AND EAST OF THE SURFACE TROF AXIS.
SHEAR WILL BE MINIMAL...UNIDIRECTIONAL AROUND 15 KNOTS...SO ONLY A
MARGINAL SEVERE THREAT. CONVECTION WILL WANE WITH LOSS OF INSOLATION
AND WILL MAINTAIN A SLIGHT CHANCE OF A SHOWER OVERNIGHT. MINS
WEDNESDAY NIGHT WILL BE MILD IN LIGHT SOUTHWEST FLOW...72-75.

BOTH THE GFS AND THE NAM SHOW A WEAKENING MID-LEVEL WAVE MOVING
THROUGH CENTRAL NORTH CAROLINA THURSDAY AND THURSDAY NIGHT AS A
TROUGH AXIS ALOFT PUSHES SLOWLY EAST. MEAN MOISTURE INCREASES
THURSDAY WITH GOOD LIFT FORECAST BY THE GFS AND THE NAM.
PRECIPITABLE WATER VALUES INCREASE TO AT OR JUST OVER TWO INCHES
OVER MUCH OF CENTRAL NORTH CAROLINA THURSDAY...WITH THE HIGHEST
VALUES ALONG AND EAST OF U.S. 1. DYNAMICALLY...THE GFS FORECASTS THE
RIGHT ENTRANCE REGION OF A 60KT 300MB JET OVER CENTRAL NORTH
CAROLINA BY 18Z THURSDAY...AND THIS JET GRADUALLY MOVES EAST INTO
THURSDAY NIGHT. BUFR SOUNDINGS BECOME MOIST AND MORE UNSTABLE DURING
THE DAY NORTHWEST TO SOUTHEAST...AND IT APPEARS AT LEAST GOOD CHANCE
POPS FOR CENTRAL NORTH CAROLINA ARE WARRANTED...WHICH MAY BECOME
LIKELY CHANCES OVER TIME OVER MUCH OF THE AREA. 1000-500MB LAPSE
RATES ARE NOT REALLY HIGH BUT DECENT...TO 6.8C/KM...AND AS LOW-LEVEL
WINDS AT BOTH 850MB AND 925MB ARE FORECAST TO ACTUALLY DIMINISH SOME
DURING THE DAY FROM THE NORTHWEST...0-3KM SHEAR IS MODEST...MOSTLY
IN THE TEENS KNOTS TO AROUND 20KT TOWARD THE VIRGINIA BORDER. THE
BEST CAPE AROUND 18Z IS FORECAST BY THE GFS JUST WEST OF U.S. 1...
AROUND 900J/KG...SHIFTING EAST DURING THE AFTERNOON WITH THE BETTER
DOWNDRAFT CAPE CERTAINLY BETTER EAST OF U.S. 1. GIVEN A COMBINATION
OF THESE MODEST PARAMETER VALUES...SCATTERED-TO-NUMEROUS SHOWERS AND
THUNDERSTORMS WITH AN ISOLATED SEVERE WEATHER THREAT DUE TO WIND IS
A REASONABLE FORECAST. IN A RELATIVE SENSE...THE BETTER CHANCE OF
ISOLATED SEVERE WEATHER MAY BE ALONG AND EAST OF U.S. 1 DUE TO THE
COMBINATION OF GREATER INSTABILITY AND LOW-LEVEL WIND. THERE APPEARS
TO BE ENOUGH WIND AND SHEAR THAT STORMS SHOULD MOVE...POSING A LOCAL
FLOOD THREAT TO THE TYPICAL URBAN AND POOR DRAINAGE LOCATIONS WHERE
LOCAL TRAINING COULD OCCUR. 0-3KM HELICITY VALUES ARE LOW AND
ACTUALLY GET LOWER...INTO THE LOWER DOUBLE DIGITS...DURING THE DAY.

THE NAM IS A LITTLE FASTER WITH CLEARING AND INCREASING STABILITY
OVERNIGHT THURSDAY COMPARED TO THE GFS...BUT NOT GREATLY SO...SUCH
THAT CHANCES FOR PRECIPITATION BASED ON THE BUFR SOUNDINGS SHOULD
WANE IN THE TRIAD BY 03Z...BY 06Z TOWARD KRDU...AND BY 09Z TOWARD
INTERSTATE 95. DEPENDING ON THE DEGREE OF CLEARING...WITH THE
WEAKENING FRONT MAKING SLOW PROGRESS SOUTH THERE COULD BE SOME AREAS
OF FOG OVERNIGHT THURSDAY...BUT THE CONFIDENCE IN THIS DEPENDENT ON
THE OVERALL DIMINISHING CLOUD COVER IS NOT HIGH ENOUGH TO PLACE IN
THE FORECAST CURRENTLY. ON FRIDAY...ALTHOUGH THE WEAK SURFACE FRONT
SHOULD START TO GET HUNG UP NEAR THE SOUTH CAROLINA BORDER AND
TOWARD THE COAST...BUFR SOUNDINGS ESPECIALLY ON THE GFS BECOME
FAIRLY STABLE TO DEEP CONVECTION. PRECIPITABLE WATER VALUES CONTINUE
TO GRADUALLY DIMINISH...WITH VALUES APPROACHING AN INCH IN THE TRIAD
BY 00Z SATURDAY. BOTH THE NAM AND THE GFS FORECAST MINIMAL QPF
MAINLY ALONG AND EAST OF U.S. 1 FRIDAY AFTERNOON...AND GIVEN THE
PROXIMITY OF THE SURFACE FRONT AND SLOWLY DIMINISHING MOISTURE...
THERE MAY BE JUST ENOUGH INSTABILITY AND LIFT TO PROVIDE FOR
ISOLATED SHOWERS OR THUNDERSTORMS FRIDAY AFTERNOON MAINLY OUTSIDE
THE TRIAD...WHERE IT JUST SEEMS TOO STABLE FOR DEEP CONVECTION
FRIDAY AFTERNOON. NAM BUFR SOUNDINGS HAVE QUITE HIGH MOISTURE AROUND
850MB WHILE THE GFS IS SOMEWHAT LESS...AND BLENDING THEM SHOULD
RESULT IN SOME AREAS OF GOOD CU IN MUCH OF CENTRAL NORTH CAROLINA
FOR A TIME FRIDAY ESPECIALLY AWAY FROM THE TRIAD. HIGHS THURSDAY
MOSTLY A BLEND OF MOS...LEANING COOLER TOWARD THE TRIAD AND HIGHER
TOWARD I-95 FOR VALUES FROM THE UPPER 80S TO MID 90S. LOWS THURSDAY
NIGHT 67 TO 73...THEN HIGHS FRIDAY MOSTLY 85 TO 90...JUST A TOUCH
COOLER THAN 1000-850MB THICKNESSES WOULD IMPLY DUE MOSTLY TO THE
POTENTIAL FOR CU FOR A PERIOD THEN.
-- End Changed Discussion --

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...

FOR THE PERIOD FRIDAY NIGHT THROUGH TUESDAY...THE GFS AND THE ECMWF
ARE FAIRLY CONSISTENT IN MOVING THE UPPER-LEVEL TROUGH AXIS JUST
EAST OF CENTRAL NORTH CAROLINA OVERNIGHT FRIDAY INTO SATURDAY. BOTH
SETS OF GUIDANCE ALLUDE TO WEAK SHORTWAVE RIDGING SATURDAY NIGHT...
FOLLOWED BY A MID-LEVEL SHORTWAVE MOVING THROUGH SOMETIME ON SUNDAY
WITH THE TYPICAL TIMING DIFFERENCES OUT TO THE FIFTH DAY. AS AN
UPPER-LEVEL TROUGH DEEPENS OVER THE EASTERN UNITED STATES EARLY NEXT
WEEK...BACKING WINDS ALOFT MORE TO THE SOUTHWEST OCCUR. THE GFS AND
ECMWF ARE BOTH DRY FRIDAY NIGHT AND MOSTLY DRY SATURDAY BEHIND THE
TROUGH ALOFT AND UNDER WEAK HIGH PRESSURE ESPECIALLY EARLY SATURDAY
FOLLOWED BY WEAK SURFACE TROUGH DEVELOPMENT SATURDAY AFTERNOON. FOR
NOW...RETAINED THE SLIGHT CHANCE OF THUNDERSTORMS ALONG AND EAST OF
THE INTERSTATE 95 CORRIDOR FOR SATURDAY WITH THE ECMWF SHOWING THE
PRESENCE OF SOME MID-LEVEL MOISTURE...BUT GFS MODEL SOUNDINGS ARE
STABLE AND IF THE CURRENT TREND OF CHANCES BELOW CLIMATOLOGY
CONTINUES EVEN THESE SMALL CHANCES MAY EVENTUALLY BE REMOVED FROM
THE FORECAST.

1000-850MB THICKNESSES ARE WARMEST SUNDAY AND THAT MAY BE THE
WARMEST DAY OF THE LONG-TERM PERIOD BEFORE LOWERING HEIGHTS ALOFT
TAKE PLACE. THE ECMWF IS MUCH MORE MOIST AND UNSTABLE SUNDAY
COMPARED TO THE GFS AND WILL MAINTAIN THE CHANCES FOR SHOWERS AND
STORMS WITH THE HIGHER CHANCES ALONG AND NORTH OF U.S. 64 CLOSER TO
THE EXPECTED TRACK OF ANY MID-LEVEL SHORTWAVE AND AN APPROACHING
SURFACE FRONT. WITH THE DEEPENING TROUGH...BOTH THE GFS AND ECMWF
CURRENTLY MOVE THE SURFACE FRONT THROUGH CENTRAL NORTH CAROLINA
MONDAY INTO EARLY TUESDAY...LINGERING A SURFACE TROUGH NEAR THE
CAROLINA COAST.

WHILE CHANCES FOR PRECIPITATION INCREASE CLOSER TO CLIMATOLOGY EARLY
NEXT WEEK ESPECIALLY ON THE GFS...GENERAL QPF IS NOT TERRIBLY HIGH
AND THEN HIGHER RELATIVE TO THE REST OF CENTRAL NORTH CAROLINA ALONG
AND EAST OF U.S. 1. THIS COULD BE...IN PART...DUE TO MORE OF A
WESTERLY LOW-LEVEL FLOW ON FORECAST MODEL SOUNDINGS OVER THE WESTERN
PIEDMONT...AT LEAST FOR MONDAY. STILL...WILL FORECAST A CHANCE OF
SHOWERS AND THUNDERSTORMS THROUGHOUT CENTRAL NORTH CAROLINA MONDAY
WITH THE FRONT AND THEN A SLIGHT CHANCE IN THE TRIAD AND CHANCES
ELSEWHERE ON THE SEVENTH DAY...HIGHER THEN TOWARD KFAY AND
KGSB...BASED ON THE EXPECTED SURFACE FRONTAL POSITION AND THE
SOUTHWEST FLOW ALOFT.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 800 PM TUESDAY...

CURRENT ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DISSIPATE
AND WEAKEN WITH THE LOSS OF DAYTIME HEATING. THEN...CONDITIONS WILL
DETERIORATE ONCE AGAIN OVERNIGHT...WITH MVFR TO IFR VSBYS AND IFR TO
LIFR CIGS LIKELY AFTER 08Z. HOWEVER...IT IS POSSIBLE THAT CONDITIONS
WILL NOT BE AS BAD AS LAST NIGHT (ESPECIALLY VSBYS) SINCE MANY
LOCATIONS DID NOT RECEIVE RAINFALL TODAY. REGARDLESS...VFR
CONDITIONS SHOULD RETURN BY MID TO LATE MORNING ON WEDNESDAY.
THEN...ANOTHER AFTERNOON/EVENING OF WIDELY SCATTERED TO SCATTERED
CONVECTION IS EXPECTED TOMORROW...ALTHOUGH TRYING TO PINPOINT EXACT
TIMING AND LOCATION IS NEARLY IMPOSSIBLE THIS FAR OUT.

OUTLOOK...THE UNSETTLED WEATHER PATTERN WILL PERSIST THROUGH AT
LEAST THE END OF THE WEEK. A BETTER CHANCE OF MORE WIDESPREAD
CONVECTION IS EXPECTED ON THURSDAY/THURSDAY NIGHT AS A COLD FRONT
MOVES INTO THE AREA. THE FRONT MAY LINGER OVER (OR NEAR) THE AREA
THROUGH THE WEEKEND...LEADING TO MORE SHOWERS AND THUNDERSTORMS...
ESPECIALLY OVER THE SOUTHEASTERN HALF OF THE FORECAST AREA.

&&

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

&&

$$

SYNOPSIS..32
NEAR TERM...32
SHORT TERM...DJF
LONG TERM...DJF
AVIATION...KRD