Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 290148
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
945 PM EDT THU APR 28 2016

.SYNOPSIS...A FRONTAL ZONE NEAR THE VIRGINIA NORTH CAROLINA BORDER
WILL SAG SOUTH INTO NORTH CAROLINA OVERNIGHT... THEN SHIFT BACK
NORTHWARD FRIDAY... BEFORE ONCE AGAIN DROPPING SOUTH THROUGH THE
REGION FRIDAY NIGHT. THE FRONT WILL THEN QUICKLY RETURN NORTHWARD AS
A WARM FRONT LATE SATURDAY AND SATURDAY NIGHT.

&&

.NEAR TERM /TONIGHT/...
AS OF 945 PM THURSDAY...

MUCH OF THE FORECAST AREA HAS BEEN WORKED OVER WITH GROWING MLCIN...
LEADING TO A DWINDLING SEVERE THREAT... ALTHOUGH A FEW POTENT STORMS
FROM RALEIGH DOWN EAST STILL WARRANT SOME ATTENTION WITH EFFECTIVE
SHEAR STILL FAVORABLE AT 35-45 KTS AND LINGERING INSTABILITY ALOFT
(MUCAPE STILL NEAR 1000 J/KG WITH 6.0+ C/KM MLLR)... AND ADDITIONAL
SUPPORT FOR ASCENT FROM WEAK UPPER DIVERGENCE MAXIMUM AND A WEAK
PASSING MID LEVEL WAVE. AS THESE FEATURES HEAD EASTWARD WITH
NOCTURNAL COOLING / STABILIZING AND SOME DRYING THROUGH THE
COLUMN... EXPECT THE DOWNWARD TREND IN CONVECTION COVERAGE AND
INTENSITY TO CONTINUE. WILL TREND POPS DOWN GRADUALLY WEST TO EAST
FOR THE NEXT SEVERAL HOURS... FOLLOWING THE CONSENSUS OF THE LATEST
HIGH-RES GUIDANCE AND OBSERVATIONS. THE RAIN-COOLED AIR SHOULD
CONTINUE TO DRAW THE SYNOPTIC FRONT SOUTHWARD THROUGH NRN NC
OVERNIGHT... DROPPING TEMPS DOWN TO LOWS IN THE UPPER 50S TO AROUND
60 NORTH OF HIGHWAY 64... WITH LOWER TO MID 60S TO ITS SOUTH. LOW
CLOUDINESS WILL CONTINUE TO SPREAD SOUTHWARD THROUGH CENTRAL NC LATE
TONIGHT... RESULTING IN CLOUDY SKIES ACROSS ALL BUT PERHAPS THE
EXTREME SOUTH BY DAYBREAK... WITH PATCHY FOG AS WELL. -GIH

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS OF 340 PM THURSDAY...

A BROAD UPPER LEVEL TROUGH WILL INITIALLY COVER THE LOWER 48
SATURDAY. THIS WILL TRANSITION TO AN AMPLIFIED RIDGE OVER THE
WESTERN U.S. AND AN TROUGH OVER THE EASTERN U.S. FORECAST CONFIDENCE
IS LOWER THAN NORMAL DUE TO THIS TRANSITION AS MODELS USUALLY HAVING
DIFFICULTY RESOLVING WHICH PARTICULAR S/W WILL CAUSE AN ENHANCED
CHANCE OF PRECIP TO A GIVEN REGION.

SINCE WEDNESDAY...THE MODELS HAVE SPED UP THE RETURN FLOW OF
MOISTURE INTO CENTRAL NC SATURDAY INTO SATURDAY NIGHT AS THE S/W
RIDGE SCOOTS QUICKLY EAST SATURDAY MORNING. THIS LOW LEVEL WARM AIR
ADVECTION COUPLED WITH A SERIES OF DISTURBANCES ALOFT WILL INCREASE
RAIN CHANCES SW-NE ACROSS CENTRAL NC SATURDAY AFTERNOON INTO
SATURDAY NIGHT. WHILE A SHORT-LIVED HYBRID/INSITU DAMMING EVENT MAY
OCCUR SATURDAY AFTERNOON-SATURDAY EVENING... MODEL GUIDANCE NOW
SUGGESTING THAT A WARM FRONT WILL LIFT ACROSS THE AREA SATURDAY
NIGHT...PLACING CENTRAL NC SOLIDLY IN THE WARM SECTOR ON SUNDAY.
THUS HAVE ADJUSTED MAX TEMPS UP SEVERAL DEGREES FROM EARLIER
FORECAST AND BACKED SFC WINDS TO A SWLY DIRECTION.

S/W IN THE NORTHERN STREAM WILL DRAG A WEAK COLD FRONT ACROSS
CENTRAL NC LATE MONDAY AND MONDAY NIGHT...BRINGING ANOTHER THREAT
FIR SCATTERED CONVECTION. NELY LOW LEVEL FLOW WILL ADVECT A COOLER
AND MORE STABLE AIR MASS TUESDAY LEADING TO PLENTY OF CLOUD COVER
AND COOLER DAYTIME TEMPS. -WSS

AMPLIFYING RIDGE OVER THE WESTERN CONUS WILL ALLOW FOR A DIGGING
TROUGH OVER THE EASTERN CONUS WITH A DEVELOPING UPPER LEVEL FEATURE
TO OUR SOUTH.  GFS SHOWS A SURFACE LOW PRESSURE SYSTEM DEVELOPING
OVER PORTIONS OF NORTHERN FL ON TUE AFTERNOON.  ECMWF SHOWS A MUCH
STRONGER BUT MUCH SLOWER DEVELOPING DISTURBANCE OVER THE MS VALLEY.
WITH THE CURRENT PATTERN AND SLOW MOVEMENT OF THE ECMWF... THE GFS
SEEMS TO BE THE MORE REALISTIC SOLUTION AT THIS TIME ALTHOUGH
CONFIDENCE IS LOW. THE LOW WILL LIKELY DEVELOP AND MOVE NORTHWARD
ALONG THE COAST FOR WED NIGHT INTO THU. GUIDANCE SUGGESTS EASTERLY
AND NORTHEASTERLY WINDS IN ASSOCIATION WITH THE LOW PRESSURE SYSTEM.
THE WEATHER PATTERN ASSOCIATED WITH THIS LOW COULD BRING SOME
ISENTROPIC UPGLIDE ALONG WITH INCREASE RAIN CHANCES FOR WED NIGHT
AND INTO THU MORNING WITH POPS TAPERING OFF AS THE DISTURBANCE MOVES
NORTHEASTWARD. TEMPS ARE CURRENTLY FORECASTED TO BE 5 TO 8 BELOW
CLIMO ON WED WITH INCREASING CLOUD COVER AND MOISTURE ADVECTION OFF
OF THE ATLANTIC.  THE COLD AIR ADVECTION ASSOCIATED WITH THIS COULD
BE LIGHT ENOUGH TO ALLOW FOR TEMPERATURES TO GET CLOSER TO CLIMO.
CLOUD COVER COULD LIMIT THE CURRENT FORECAST LOWS... HOWEVER GFS
SUGGESTS LOW LEVEL COLD AIR ADVECTION CONTINUING WED NIGHT. -JLB

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AS OF 815 PM THURSDAY...

CLUSTERS OF SHOWERS AND STORMS OVER THE NORTHERN PIEDMONT AND
NORTHERN COASTAL PLAIN WILL SLOWLY DIMINISH THROUGH 04Z/MIDNIGHT
LOCAL TIME. IN VICINITY OF THE HEAVIER SHOWERS AND STORMS...EXPECT A
BRIEF PERIOD OF MVFR CONDITIONS. AFTER 06Z...POCKETS OF MVFR/IFR
CEILINGS AND FOG WILL DEVELOP...MAINLY IN VICINITY OF KRDU AND KRWI.

ELSEWHERE...BRIEF INTERVALS OF MVFR/IFR FOG AND/OR CEILINGS WILL
OCCUR BETWEEN 09Z-13Z. AFTER 14Z...EXPECT CLOUD BASES TO LIFT AND
SCATTER BY MID-LATE MORNING AS DRIER AIR INFILTRATES THE
REGION...RESULTING IN VFR CONDITIONS.

THE OPTIMAL AVIATION CONDITIONS WILL BE SHORT IN DURATION AS A QUICK
RETURN FLOW OF MOISTURE WILL ADVANCE OVER THE PIEDMONT SATURDAY
MORNING. THIS WILL LEAD TO THICKENING LOWER CLOUD DECK AND SPOTS OF
LIGHT RAIN DEVELOPING SATURDAY AFTERNOON. ADVERSE AVIATION
CONDITIONS EXPECTED TO BE WIDESPREAD ACROSS CENTRAL NC SATURDAY
NIGHT THROUGH EARLY SUNDAY DUE TO LOW CLOUDS AND WIDESPREAD RAIN.

WARMER AIR WILL MAKE A RETURN SUNDAY AND MAINTAIN A THREAT OF
SCATTERED CONVECTION ALONG WITH PERIODS OF MVFR CEILINGS SUNDAY
AFTERNOON THROUGH TUESDAY.

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...HARTFIELD
SHORT TERM...CBL
LONG TERM...WSS/JLB
AVIATION...WSS


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