Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 021132
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
732 AM EDT SUN AUG 2 2015

.SYNOPSIS...
AN AREA OF LOW PRESSURE OVER THE NORTHEAST GULF OF MEXICO THIS
MORNING WILL TRACK SLOWLY NORTHEASTWARD ALONG A NEARLY STATIONARY
FRONTAL ZONE OVER THE SOUTHEASTERN US THROUGH MON NIGHT...WHILE HIGH
PRESSURE WILL REMAIN CENTERED FROM THE TN VALLEY TO THE CENTRAL
APPALACHIANS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 350 AM SUNDAY...

THE LOW LEVEL FRONTAL ZONE...WHICH SEPARATED A DRIER AIR MASS OVER
THE PIEDMONT FROM A SUBSTANTIALLY MORE MOIST OVER COASTAL
AREAS...HAS NOCTURNALLY RETREATED INTO THE EASTERN SANDHILLS AND
SOUTHERN-CENTRAL COASTAL PLAIN OF NC THIS MORNING. MEANWHILE...1016
MB SURFACE HIGH PRESSURE WAS SITUATED FROM THE TN VALLEY TO THE
CENTRAL APPALACHIANS. THESE FEATURES ARE FORECAST TO MOVE LITTLE
TODAY...THOUGH DIURNAL HEATING/MIXING WILL LIKELY HELP DRIVE THE
FRONT...AND ASSOCIATED MOISTURE...LARGELY EAST OF THE RAH CWFA
THROUGH MID-AFTERNOON...BEFORE RETREATING WEST ONCE AGAIN WITH
NOCTURNAL COOLING BY THIS EVENING. ISOLATED SHOWERS AND STORMS WILL
BE POSSIBLE INVOF WHAT WILL BECOME ESSENTIALLY A MERGED FRONT AND AN
INLAND-RETREATING SEA BREEZE THIS AFTERNOON. THIS BOUNDARY WILL
BRING A RELATIVE HIGHEST CHANCE OF A SHOWER OR STORM (STILL LESS
THAN 20 PERCENT) TO THE NC COASTAL PLAIN BETWEEN 6-10 PM...WITH
OTHERWISE DRY AND MOSTLY CLEAR CONDITIONS...WITH CONTINUED LOW
RELATIVE HUMIDITY VALUES MAXIMIZED OVER THE PIEDMONT. GENERALLY
PERSISTENT HIGHS IN THE LOWER TO MIDDLE 90S...THOUGH WITH A FEW 88-
89`S POSSIBLE OVER THE FAR NORTHERN PIEDMONT WHERE SLIGHT COOLING
HAS OCCURRED IN ASSOCIATION WITH THE ARRIVAL INTO THE VIRGINIA/S OF
A REINFORCING LOW LEVEL FRONTAL ZONE PER 00Z/2ND 850-925 MB DATA.

FORECAST CONFIDENCE DECREASES LATER TONIGHT...AS A WEAK WAVE OF LOW
PRESSURE OVER THE NORTHEASTERN GULF OF MEXICO TRACKS SLOWLY UP THE
SOUTHEAST US COAST. MOIST SOUTHERLY FLOW AROUND THE LOW...DIRECTED
INTO THE EASTERN CAROLINAS...WILL LIKELY RESULT IN THE NORTHWARD
DEVELOPMENT/EXPANSION OF AN AREA OF LOW CLOUDS...AND EVEN A FEW
SHOWERS INTO THE SOUTHERN COASTAL PLAIN. THE ASSOCIATED LOW CLOUDS
MAY CREEP AS FAR WEST AS THE PIEDMONT PER THE 00Z/ECMWF... WHICH
INITIALIZED MUCH BETTER WITH LOW LEVEL MOISTURE VALUES THAN THE
DRIER/CLEARER GFS SOLUTIONS...THOUGH THE MOISTURE WOULD LIKELY BE
TOO SHALLOW AND CAPPED TO SUPPORT ANY PRECIPITATION THERE. LOWS
RANGING FROM THE MIDDLE 60S IN THE RESIDUALLY DRY/CONTINENTAL AIR
MASS OVER THE PIEDMONT...PARTICULARLY THE WESTERN HALF...TO AROUND
70 DEGREES OR SO OVER THE COASTAL PLAIN.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 415 AM SUNDAY...

MODEL SPREAD REMAINS RELATIVELY LARGE WITH THE TRACK AND SPEED OF
THE WAVE OF LOW PRESSURE FORECAST TO RIPPLE NORTHEAST ALONG THE
FRONT OVER THE EASTERN CAROLINAS MON AND MON NIGHT. GIVEN THE POORLY-
ANALYZED MOISTURE FIELDS IN THE GFS NOTED IN THE NEAR TERM...WILL
WEIGHT THE FORECAST TOWARD THE SLIGHTLY MORE WESTWARD TRACK AND
ASSOCIATED (MOSTLY) CLOUDIER AND WETTER CONDITIONS OVER THE COASTAL
PLAIN INDICATED BY THE 00Z/2ND ECMWF AND GEM. SUCH A SOLUTION WOULD
RESULT IN LESS HOT TEMPERATURES OVER THE COASTAL PLAIN...IN THE
UPPER 80S TO AROUND 90 DEGREES...TO LOWER 90S ACROSS THE REMAINDER
OF CENTRAL NC. IF THE DAY PROVES DRIER AND MOSTLY SUNNY AREA-
WIDE...PERSISTENCE HIGH TEMPERATURES IN THE LOWER TO MIDDLE 90S
WOULD AGAIN OCCUR. ANY LINGERING RAIN CHANCE SHOULD END OVER THE FAR
EASTERN NC COASTAL PLAIN BY MIDNIGHT...AS THE LOW LIFTS NE AND AWAY
FROM THE NC OUTER BANKS.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 245 AM SUNDAY...

THURSDAY AND WEDNESDAY: LOW PRESSURE OVER CANADA WILL LIFT NORTHWARD
AND UPPER LEVEL PATTERN OVER CENTRAL NC WILL BE VERY ZONAL WITH A
GRADUAL SHIFT TO WEST SOUTHWESTERLY FLOW BY WEDNESDAY. WITH THE JET
LIFTING NORTHWARD DURING THIS PERIOD AND MOST OF THE UPSTREAM
SHORTWAVE ACTIVITY REMAINING WELL TO THE NORTHWEST...EXPECT
GENERALLY DRY CONDITIONS DURING THIS PERIOD WITH THE OCCASIONAL
DIURNAL SHOWER POPPING UP ON SURFACE BOUNDARIES SUCH AS THE SEA
BREEZE. SOUTHWESTERLY SURFACE FLOW WILL KEEP TEMPERATURES UP WITH
HIGHS IN THE MID 90S AND LOWS IN THE LOW TO MIDDLE 70S.

THURSDAY THROUGH SATURDAY: THE FORECAST BECOMES MUCH MORE LOW
CONFIDENCE BY THE END OF THE WEEK BUT THERE ARE A FEW THINGS WE DO
KNOW FOR SURE. NUMBER ONE IS THAT MOISTURE WILL BE INCREASING
SIGNIFICANTLY OVER THE AREA. NUMBER TWO IS THAT SEVERAL SHORTWAVE
IMPULSES UPSTREAM WILL MAKE THEIR WAY INTO THE AREA OR AT LEAST
SKIRT CLOSE ENOUGH TO THE ARE TO AFFECT OUR WEATHER HERE IN CENTRAL
NC. THREE IS THAT ALTHOUGH MOISTURE IS INCREASING...INSTABILITY AND
SHEAR ARE NOT INCREASING ALL THAT MUCH...THEREFORE WHILE WE CAN
EXPECT INCREASE CONVECTIVE ACTIVITY BEGINNING ON THURSDAY THROUGH THE
WEEKEND...THE LIKELIHOOD OF SEVERE WEATHER IS STILL FAIRLY SMALL.

TOUGHER TO DETERMINE WILL BE THE TIMING OR EXACT LOCATIONS OF
CONVECTIVE ACTIVITY LATE IN THE WEEK. MODELS HAVE NOT BEEN
CONSISTENT AT ALL WITH TIMING THE LAST SEVERAL DAYS AND CONTINUE TO
FLUCTUATE. CURRENTLY...MODELS ARE PREDICTING THE FIRST SHORTWAVE TO
MOVE THROUGH ON THURSDAY. THERE WILL BE A GAP BETWEEN THE FIRST AND
SECOND SHORTWAVE WHICH IS DUE TO ARRIVE FRIDAY EVENING WHICH MAY
LINGER OVER THE AREA FOR A WHILE BEFORE POTENTIALLY DEVELOPING A
FULL ON SURFACE LOW ON SATURDAY AS IT SLIDES OFF OF THE EAST COAST.
INCREASED CLOUD COVER AND CONVECTIVE ACTIVITY WILL BRING
TEMPERATURES DOWN INTO THE MID 80S TO LOWER 90S DURING THIS PERIOD
BUT WITH THE INCREASED MOISTURE...RELATIVE HUMIDITIES WILL INCREASE.
LOWS DURING THE PERIOD UPPER 60S TO LOWER 70S.

&&

.AVIATION /12Z SUNDAY THROUGH WEDNESDAY/...
AS OF 730 AM SUNDAY...

MAINLY CLEAR SKIES ARE EXPECTED UNDER THE INFLUENCE OF AN
UNSEASONABLY DRY AIR MASS CENTERED OVER THE CENTRAL APPALACHIANS...
THOUGH SCATTERED TO BRIEFLY BROKEN CUMULUS CLOUDS --WITH BASES
BETWEEN 6 AND 8 THOUSAND FT-- ARE PROBABLE LATE THIS AFTERNOON AND
EVENING IN A MORE MOIST AIR MASS ALONG AND EAST OF A FRONTAL ZONE
OVER THE EASTERN CAROLINAS. WHILE A STRAY SHOWER OR STORM WILL ALSO
BE POSSIBLE OVER EASTERN NC...INCLUDING AT FAY AND RWI IN THE
SEVERAL HOURS SURROUNDING 00Z...THIS PROBABILITY IS TOO LOW TO
INCLUDE ANY MENTION IN THE TAFS.

A BRIEF PERIOD IFR-MVFR CEILINGS...AND SHOWERS...WILL BE POSSIBLE
LATE TONIGHT-EARLY MON AT FAY...AS AN AREA OF LOW PRESSURE TRACKS UP
THE SOUTHEAST US COAST. SOME OF THESE LOW CLOUDS MAY EXPAND AS FAR
NORTH AND WEST AS RWI AND RDU BY DAYBREAK.

OUTLOOK: A LINGERING CHANCE OF A SHOWER OR STORM WILL CONTINUE OVER
SOUTHEASTERN NC...INCLUDING AROUND FAY...AS THE LOW PRESSURE AREA
TRACKS ONLY SLOWLY NORTHEASTWARD THROUGH MON NIGHT. MVFR VISIBILITY
RESTRICTIONS WILL BE POSSIBLE TUE MORNING... PARTICULARLY EAST OF
INT AND GSO.

&&

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

&&

$$

SYNOPSIS...26
NEAR TERM...26
SHORT TERM...26
LONG TERM...ELLIS
AVIATION...26


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