Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 050044
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
843 PM EDT FRI SEP 4 2015

.SYNOPSIS...A BACK-DOOR COLD FRONT WILL APPROACH FROM THE NORTH LATE
TODAY...THEN PUSH SOUTHWARD THROUGH THE AREA TONIGHT...BEFORE
SETTLING TO OUR SOUTH ON SATURDAY. HIGH PRESSURE WILL EXTEND INTO
THE REGION FROM THE NORTH OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM FRIDAY...

A WEAK COLD FRONT OVER THE MID-ATLANTIC STATES WILL DROP SOUTH INTO
THE AREA LATE THIS EVENING. MOISTURE FLUX CONVERGENCE ALONG THE
FRONT COUPLED WITH WEAK SHORTWAVE IMPULSES EMBEDDED ON THE BACK
SLIDE OF THE DEPARTING SHORTWAVE TROUGH OFF THE SOUTHEAST COAST WILL
SUPPORT SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND
THROUGH THE EVENING.

DESPITE MODERATE INSTABILITY OF 1500-2000 J/KG OF MUCAPE...DEEP
LAYER SHEAR REMAINS VERY WEAK...LESS THAN 10 KTS. THUS...EXPECT A
NON-ZERO SEVERE THREAT. THE MAIN THREAT FROM ANY STORM WILL BE
LOCALLY HEAVY RAIN/SLOW MOVING STORMS OWING TO HIGH PWS OF
0.75-1.8" AND WEAK WINDS ALOFT. THE PRESENCE OF WEAK LIFT/FORCING ALOFT
COULD SUPPORT ISOLATED SHOWERS WELL INTO THE EARLY MORNING HOURS
SATURDAY...ESPECIALLY ACROSS THE WESTERN PIEDMONT AS DRIER AIR ALOFT
SPREADS INTO THE AREA FROM THE EAST.

NELY LOW-LEVEL FLOW AS SURFACE HIGH PRESSURE RIDGES SOUTH
DOWN THE MID-ATLANTIC REGION COULD SUPPORT AREAS STRATUS OVERNIGHT.
LOWS IN THE MID 60S TO AROUND 70.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 318 PM FRIDAY...

SHORTWAVE ENERGY EMBEDDED IN THE BROAD WEST-EAST ORIENTED MID/UPPER
LEVEL TROUGHINESS EXTENDING FROM THE SOUTHEAST US INTO WESTERN ATLANTIC
WILL PROVIDE THE FOCUS FOR MAINLY DIURNAL SCATTERED SHOWERS AS DEEP
FETCH OF EASTERLY MARITIME FLOW KEEPS A SEASONABLY MOIST AIRMASS(1.5-
1.75")IN PLACE ACROSS CENTRAL NC. EXTENSIVE NELY LOW-LEVEL CLOUDINESS
WILL KEEP TEMPERATURES AT OR JUST BELOW NORMAL. HIGHS RANGING FROM
UPPER 70S NW TO LOWER/MID 80S SOUTHEAST. LOWS SATURDAY NIGHT IN THE MID
TO UPPER 60S.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 300 PM FRIDAY...

TO START OFF THE PERIOD...A BROAD UPPER LOW WILL BE OVER THE SOUTHEAST
U.S. AND AN UPPER HIGH WILL BE OVER THE NORTHERN MID ATLANTIC. AT THE
SURFACE...HIGH PRESSURE WILL BE RIDGING DOWN THE SPINE OF THE
MOUNTAINS. ALL OF THIS WILL RESULT IN DEEP NORTHEASTERLY FLOW OVER THE
AREA WHICH WILL PUMP MOISTURE IN FROM THE ATLANTIC...WITH PWAT VALUES
PROGGED TO HOVER AROUND 1.6-1.7 INCHES. THIS COMBINED WITH ANY WEAK
UPPER DISTURANCES ROTATING AROUND THE BROAD UPPER LOW WILL LEAD TO
FAIRLY EXTENSIVE CLOUD COVER AND SCATTERED SHOWERS AND
THUNDERSTORMS...ESPECIALLY ACROSS THE EAST WHERE INSTABILITY WILL BE
BETTER. BY MONDAY...THE PATTERN IS NOT EXPECTED TO CHANGE ALL THAT
MUCH. ALTHOUGH...THE UPPER LOW WILL SLOWLY START TO SHIFT TO THE
SOUTH/WEST...THUS LOSING OUR MOISTURE FEED. HOWEVER...ENOUGH RESIDUAL
MOISTURE WILL BE AROUND FOR DIURNAL TYPE SHOWERS/STORMS. GIVEN ALL THE
CLOUDS AND PRECIP CHANCES...TEMPS WILL BE HELD DOWN...WITH GENERALLY
LOW/MID 80S ON SUNDAY AND A FEW DEGREES WARMER ON MONDAY. OVERNIGHT
LOWS WILL BE IN THE MID/UPPER 60S.

BY THE MIDDLE OF THE WEEK...THE AFOREMENTIONED UPPER LOW WILL SHIFT
EVEN FURTHER TO THE SOUTH/WEST...WHILE THE BERMUDA HIGH WILL DRIFT
TOWARDS THE SOUTHEAST COAST. AS A RESULT...DIURNAL TYPE CONVECTION WILL
OCCUR EACH DAY...WHILE TEMPS RISE TO ABOVE NORMAL ONCE AGAIN (MID/UPPER
80S TO NEAR 90 DEGREES). MODELS THEN SHOW A UPPER TROUGH/FRONT
APPROACHING THE AREA BY THE END OF THE WEEK. THEREFORE...PRECIP CHANCES
WILL GRADUALLY INCREASE LATE THURSDAY INTO FRIDAY...ALTHOUGH WILL NOT
GO TOO HIGH AT THIS TIME GIVEN THE TIMING WILL LIKELY CHANGE BETWEEN
NOW AND THEN.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AS OF 840 PM FRIDAY...

24 HR TAF PERIOD: CONVECTION HAS PUSHED TO THE SOUTH AND WEST OF
CENTRAL NC THIS EVENING... WITH GENERALLY DRY CONDITIONS EXPECTED
OVERNIGHT. EAST TO NORTHEASTERLY LOW LEVEL FLOW WILL OVERNIGHT INTO
SATURDAY AND WILL SUPPORT THE THE DEVELOPMENT OF STRATUS OVERNIGHT
(ESPECIALLY ACROSS THE PIEDMONT)... GENERALLY IFR/MVFR. EXPECT CIGS
WILL BEGIN TO SLOWLY LIFT AFTER DAYBREAK ON SATURDAY MORNING...
BECOMING VFR AT MOST SITES BY AT LEAST EARLY TO MID AFTERNOON...
THOUGH ITS POSSIBLE THAT KGSO AND KINT WILL ONLY IMPROVE TO HIGH END
MVFR CIGS ON SATURDAY. CHANCE OF SHOWERS AND PERHAPS AN ISOLATED
THUNDERSTORM OR TWO WILL BE POSSIBLE AGAIN TOMORROW AFTERNOON.
HOWEVER... CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE IN THE TAFS AT
THIS TIME.

OUTLOOK: DEEP FETCH OF EASTERLY MARITIME FLOW WILL SUPPORT EARLY
MORNING STRATUS AND SCATTERED SHOWERS AND STORMS THROUGH THE
WEEKEND. RAIN CHANCES SHOULD BECOME MORE CENTRALIZED TOWARD THE
COASTAL PLAIN MONDAY THROUGH WEDNESDAY.

&&

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

&&

$$

SYNOPSIS...BSD/26
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...WSS
AVIATION...77/CBL



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