Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 250216
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1016 PM EDT THU JUL 24 2014

.SYNOPSIS...A COLD FRONT WILL MOVE SOUTHWARD INTO CENTRAL NORTH
CAROLINA OVERNIGHT...THEN STALL NEAR THE SOUTH CAROLINA BORDER ON
FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1000 PM THURSDAY...

A S/W CROSSING THE CENTRAL APPALACHIANS WILL CONTINUE TO LIFT E-NE
INTO THE NORTHERN MID ATLANTIC OVERNIGHT. THE SURFACE FRONT
ASSOCIATED WITH THE S/W WAS DRIFTING SOUTHWARD ACROSS VA AT 01Z. A
PRE-FRONTAL TROUGH AHEAD OF THE SURFACE FRONT AIDED TO TRIGGER
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON
ACROSS CENTRAL NC. BY MID-EVENING..THE LINE OF CONVECTION HAD
DRIFTED SOUTHWARD INTO THE SOUTHERN COASTAL PLAIN AND SANDHILLS.
SHOWERS WITH A FEW ISOLATED THUNDERSTORMS WILL PERSIST WELL INTO THE
NIGHT ACROSS ROUGHLY THE SE HALF OF CENTRAL NC AS THE PRE-FRONTAL
TROUGH STALLS AND WAITS FOR THE APPROACHING SFC FRONT. AN ISOLATED
SHOWER OR THUNDERSTORM WILL BE POSSIBLE OVERNIGHT ACROSS THE NORTH
AS THE SFC FRONT CROSSES THE REGION. BY FRIDAY MORNING...SFC FRONT
SHOULD BLEND WITH THE SFC TROUGH THEN CONTINUE TO PUSH SOUTH AND
EAST AS SFC HIGH PRESSURE BUILDS INTO THE PIEDMONT.

MIN TEMPS OVERNIGHT SHOULD RANGE FROM THE LOWER 70S SOUTH TO THE MID-
UPPER 60S NORTH.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 305 PM THURSDAY...

FRIDAY AND FRIDAY NIGHT....THE MAIN UPPER TROUGH AXIS WILL MOVE EAST
OF THE AREA BY FRIDAY MORNING...WHILE THE ASSOCIATED RELATIVELY WEAK
COLD FRONT SLIPS SOUTH AND STALLS NEAR THE NC/SC BORDER.  HIGH
PRESSURE WILL BUILD QUICKLY ACROSS VA DURING THE DAY...WITH DRIER
MID-LEVEL AIR OVER MOST OF CENTRAL NC. THE AIRMASS DOESNT CHANGE
MUCH BEHIND THE FRONT...WITH DEWPOINTS ONLY DROPPING INTO THE MID
60S TO THE NORTHWEST AND HOVERING NEAR 70S IN THE SOUTH.  WEAK
INSTABILITY AND LEVEL CONVERGENCE IN THE VICINITY OF WHAT IS LEFT OF
THE FRONT MAY PRODUCE SOME VERY ISOLATED CONVECTION NEAR THE SC
BORDER.  HIGHS WILL BE IN THE MID 80S.  WEAK HIGH PRESSURE WILL BE
OFF THE VA COAST BY FRIDAY NIGHT...AND A LIGHT SOUTHEASTERLY RETURN
FLOW MAY PRODUCE SOME FOG AND LOW CLOUDS SATURDAY MORNING...SHOWN
MOST AGGRESSIVELY BY THE NAM.  LOWS IN THE MID/UPPER 60S.

SATURDAY AND SATURDAY NIGHT...A WEAK UPPER DISTURBANCE...POSSIBLY
EMANATING FROM CONVECTION NORTH OF THE SOUTHERN PLAINS RIDGE...WILL
SWING ACROSS THE AREA ON SATURDAY.  CURRENTLY...MODELS SHOW THE WAVE
DEAMPLIFYING AS IT CROSSES THE MOUNTAINS...AND THE EARLY DAY TIMING
WOULD ALSO BE UNFAVORABLE FOR CONVECTIVE INITIATION.  MOST OF
CENTRAL NC WILL REMAIN DRY...WITH THE EXCEPTION BEING THE FAR
SOUTHEAST CWA WHERE THE SEABREEZE MAY MAKE A RUN DURING THE
AFTERNOON.  WEST-SOUTHWESTERLY LOW-LEVEL FLOW WILL PROMOTE DEEPER
MIXING AND A WARMER DAY WITH HIGHS LIKELY IN THE LOWER 90S.  LOWS
SAT NIGHT WILL BE WARMER AS WELL IN THE LOWER 70S.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 305 PM THURSDAY...

SUNDAY THROUGH MONDAY NIGHT... A STRONG SHORTWAVE MOVING SOUTHEAST
OUT OF THE CANADIAN ROCKIES ON SUNDAY WILL BEGIN THE AMPLIFICATION
OF THE LONGWAVE PATTERN HEADING INTO NEXT WEEK.  CONVECTION PASSING
TO OUR NORTH ACROSS VA MAY BLEED SOUTH INTO MAINLY THE NORTHERN
PORTIONS OF THE AREA...PARTICULARLY SUNDAY EVENING BASED ON CURRENT
PROGS.  HOWEVER THE MAIN FORCING TO IMPACT CENTRAL NC WILL COME
MONDAY WHEN MODELS SHOW ADDITIONAL ENERGY...ACCOMPANIED BY STRONG
HEIGHT FALLS AND A BELT OF ENHANCED WESTERLIES...SWINGING ACROSS THE
AREA.  GIVEN THAT TEMPS ARE EXPECTED TO BE WELL INTO THE MID 90S ON
SUNDAY AND AT LEAST THE LOWER 90S ON MONDAY...INSTABILITY SHOULD BE
FAVORABLE AHEAD OF THE FRONT.  WHILE THERE IS STILL SOME UNCERTAINTY
AS TO HOW MUCH OVERLAP THERE WILL BE BETWEEN THE BEST INSTABILITY
AND STRONGEST SHEAR...THE SETUP LOOKS PRETTY GOOD FOR SEVERE WEATHER
AT DAY 5 IN LATE JULY.

TUESDAY THROUGH THURSDAY... MEDIUM RANGE ENSEMBLES SHOW AN
UNSEASONABLY DEEP UPPER TROUGH DEVELOPING OVER THE EASTERN US BY MID
WEEK WITH AN UPPER LOW CENTERED JUST SOUTH OF THE HUDSON BAY.  GIVEN
THAT BOTH THE GFS AND ECMWF SHOW THE SYNOPTIC FRONT REACHING THE
GULF OF MEXICO... CONFIDENCE IS HIGH THAT TEMPS WILL BE BELOW NORMAL
MUCH OF NEXT WEEK.  LOW-LEVEL THICKNESSES ARE PROGGED TO DIP BELOW
1390M...WHICH SUGGESTS HIGHS IN THE LOW/MID 90S AND LOWS IN THE
LOW/MID60S... POSSIBLY TOUCHING THE UPPER 50S IN THE COOLEST SPOTS.
THE AIRMASS CHANGE WILL ALSO BRING LOWER HUMIDITY...AND WITH
DEWPOINTS DROPPING INTO THE 50S THE CHANCES OF SHOWERS OR STORMS
WILL BE RELATIVELY LOW UNTIL RETURN FLOW DEVELOPS LATER IN THE WEEK.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AS OF 1010 PM THURSDAY...

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS EASTERN
PORTIONS OF CENTRAL NC THIS EVENING ARE EXPECTED TO WEAKEN FURTHER
AND SHIFT TO THE EAST AND SOUTH OF THE AREA BY AROUND 06Z.
HOWEVER... WITH A SLOW MOVING COLD FRONT SINKING SOUTHWARD THROUGH
THE AREA TONIGHT... WE CANT RULE OUT THE POSSIBILITY OF SOME
ISOLATED SHOWERS/STORMS DEVELOPING LATER TONIGHT. THE WEAKENING
SURFACE FRONT IS EXPECTED TO BEGIN TO STALL/WEAKEN FURTHER ACROSS
SOUTH/SOUTHEASTERN PORTIONS OF THE AREA FRIDAY MORNING. GIVEN THE
LACK OF ANY SIGNIFICANT AIRMASS CHANGE OVERNIGHT AND RAINFALL THIS
(THURSDAY) AFTERNOON/EVENING EXPECT WE WILL AT LEAST HAVE A THREAT
OF SUB-VFR CONDITIONS. CONFIDENCE IN SUB VFR CONDITIONS IS MEDIUM TO
HIGH IN THE PRE-DAWN TO AROUND DAYBREAK HOURS FRIDAY MORNING.
HOWEVER... CONFIDENCE IS LOW WITH REGARD TO HOW SEVERE THE
RESTRICTIONS WILL BE (THINKING MVFR TO IFR AT THIS TIME). THUS...
FOR NOW WILL GO WITH A TEMPO GROUP AT ALL TAF SITES IN THE 09-13Z
TIME FRAME... WITH THE POTENTIAL FOR SUB-VFR CONDITIONS TO DEVELOP
EVEN SOONER. IF WIDESPREAD SUB-VFR STRATUS/FOG DEVELOPS OVERNIGHT
THEN SUB-VFR CONDITIONS MAY LINGER UNTIL MID TO LATE MORNING
(ESPECIALLY DEPENDING ON THE ACTUAL PLACEMENT OF THE FRONT BY
DAYBREAK. ONCE VFR CONDITIONS RETURN ON FRIDAY... EXPECT GENERALLY
DRY CONDITIONS... WITH THE BEST CHANCE OF SEEING ANY SHOWERS AND
STORMS ACROSS THE SOUTHERN HALF OF THE AREA NEAR KFAY. CONFIDENCE IS
TOO LOW TO INCLUDE ANY MENTION OF PRECIP IN THE TAFS AT THIS TIME
THOUGH.

OUTLOOK: VFR CONDITIONS ARE GENERALLY EXPECTED TO CONTINUE FOR THE
WEEKEND... OUTSIDE OF ANY PATCHY MORNING SUB-VFR CONDITIONS. ANY
CONVECTION THIS WEEKEND IS EXPECTED TO BE QUITE ISOLATED AT BEST.
CHANCES FOR STORMS ARE EXPECTED TO INCREASE BY MONDAY THOUGH AS THE
NEXT MID LEVEL DISTURBANCE AND ASSOCIATED SURFACE FRONT APPROACHES
AND MOVES THROUGH THE AREA. VFR CONDITIONS ARE DRY WEATHER ARE
EXPECTED TO RETURN BY TUESDAY AGAIN.

&&

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

&&

$$

SYNOPSIS...VINCENT/WSS
NEAR TERM...WSS
SHORT TERM...BLS
LONG TERM...BLS
AVIATION...BSD



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