Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 271432
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1032 AM EDT WED MAY 27 2015

.SYNOPSIS...BERMUDA HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC
WILL PREVAIL THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1020 AM WEDNESDAY...

STRONG MID/UPPER LEVEL RIDGE OFF THE EASTERN SEABOARD MAY WEAKEN A
BIT WHILE DRIFTING EVER SO SLIGHTLY EASTWARD. MEANWHILE...BERMUDA
HIGH PRESSURE OVER THE WESTERN ATLANTIC WILL KEEP A WARM HUMID
AIRMASS IN PLACE.

SOME SHOWER ACTIVITY HAS DEVELOPED IN EASTERN SC AND SOUTHEASTERN NC
AND IS TRACKING TO THE NORTHEAST. THIS IS LIKELY IN RESPONSE TO A
WEAK DISTURBANCE WITHIN THE SOUTHEASTERLY FLOW ALOFT. THESE WEAK
DISTURANCES WILL BE THE MAIN TRIGGERS FOR ANY CONVECTION INTO THE
AFTERNOON AS WELL. HOWEVER...A LEFT-OVER OUTFLOW BOUNDARY FROM
CONVECTION OVERNIGHT ACROSS THE WESTERN PIEDMONT MAY ALSO SERVE AS A
FOCUS FOR CONVECTIVE INITIATION LATER TODAY. IN ADDITION...AN AREA
OF STRATUS ACROSS THE NORTHEAST PIEDMONT AND SANDHILLS HAS BEEN SLOW
TO BURN OFF THIS MORNING. SO DIFFERENTIAL HEATING ALONG THE
BOUNDARIES OF THIS AREA OF CLOUD COVER COULD ALSO SERVE AS A
TRIGGER. ALL OF THIS WILL LEAD TO SCATTERED AFTERNOON STORMS...WITH
SLIGHTLY HIGHER COVERAGE THAN PREVIOUS DAYS. WEAK/MARGINAL ML CAPE
BETWEEN 500-800 J/KG COUPLED WITH DEEP LAYER SHEAR OF 10-15 KTS WILL
FAVOR DISORGANIZED CONVECTION WITH LITTLE TO NO SEVERE THREAT.

MOISTURE WILL BE SLIGHTLY HIGHER TODAY AND GIVEN THE BETTER CLOUD
COVER AND SLIGHTLY HIGHER PRECIP CHANCES...HIGH TEMPS SHOULD BE A
COUPLE OF DEGREES LOWER THAN YESTERDAY. HIGHS ARE EXPECTED TO BE IN
THE LOW/MID 80S ACROSS THE NORTHWEST AND MID/UPPER 80S ACROSS THE
SOUTHEAST.

PRECIP SHOULD DIMINISH AFTER SUNSET...BUT PLENTY OF CLOUDS AND
MOISTURE WILL BE AROUND OVERNIGHT...KEEPING TEMPS FROM FALLING MUCH.
THEREFORE...OVERNIGHT LOWS ARE EXPECTED TO BE IN THE MID/UPPER 60S.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 300 AM WEDNESDAY...

MID AND UPPER-LEVEL FLOW BECOMES INCREASINGLY MORE WESTERLY ON
THURSDAY AS THE SHORTWAVE TROUGH OVER THE LOWER GREAT LAKES
PROGRESSES EASTWARD INTO SOUTHERN NEW ENGLAND THROUGHOUT THE DAY. IN
RESPONSE...MODELS HINT AT WEAK LEE-SIDE TROUGHINESS DEVELOPMENT
ACROSS THE WESTERN PIEDMONT...WHILE DRIFTING THE LINGERING VORTICITY
SHEAR AXIS EASTWARD INTO THE COASTAL PLAIN.

WITH CONTINUED SEASONABLY MOIST AIR IN PLACE...THESE TWO FEATURES
ALONG WITH DIURNAL DESTABILIZATION WILL SERVE AS A FOCUS FOR
SCATTERED CONVECTION THURSDAY AFTERNOON/EARLY EVENING.

PERSISTENCE TEMPERATURE FORECAST WILL BE FOLLOWED. HIGHS 83 TO 88.
LOWS IN THE MID TO UPPER 60S.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 315 AM WEDNESDAY...

THE UPPER LEVEL RIDGE AXIS ALONG THE EAST COAST WILL RETROGRADE
WESTWARD ON FRIDAY AS SURFACE HIGH PRESSURE ALSO EDGES BACK ACROSS
THE AREA. DRIER AIR WITHIN THE RIDGE SHOULD LEAD TO A SIGNIFICANT
REDUCTION IN INSTABILITY ACROSS THE EAST...WITH ONLY THE WESTERN
PIEDMONT FORECAST TO SEE ANY CAPE VALUES APPROACHING 1000 J/KG.
WITH MOISTURE AND INSTABILITY CONFINED TO THE WEST...MUCH OF THE CWA
WILL BE FREE OF CONVECTION AND JUST ISOLATED TO WIDELY SCATTERED
STORMS OVER THE WESTERN PIEDMONT.  COVERAGE WILL BE EVEN LESS ON
SATURDAY WITH THE UPPER RIDGE AXIS OVERHEAD...THOUGH MODELS HINT AT
SOME ACTIVITY ALONG THE SEABREEZE AS IT MAKES A MODEST PUSH INLAND.
LITTLE CHANGE IN THE AIRMASS AND EVEN A LITTLE WARMING ALOFT
SUGGESTS HIGHS CONTINUING IN THE MID AND UPPER 80S FOR THE MOST
PART. LOWS IN THE MID 60S.

FROM SUNDAY ONWARD...PRECIP CHANCES ARE EXPECTED TO INCREASE RATHER
DRAMATICALLY FROM NORTH TO SOUTH AS THE UPPER RIDGE AGAIN SHOWS
SIGNS OF WEAKENING IN RESPONSE TO A NORTHERN STREAM SHORTWAVE
CROSSING THE NORTHERN TIER OF THE US AND A COLD FRONT MOVES INTO THE
OHIO VALLEY/MID-ATLANTIC REGION. HOWEVER...THE DETERMINISTIC GFS AND
ECMWF RUNS DIFFER IN THE SOUTHWARD PUSH OF THE FRONT...WITH THE GFS
INDICATING THE FRONT WILL SETTLE SOUTH OVER NC BY MONDAY AND THE
ECMWF SUGGESTING THE FRONT WILL STALL TO OUR NORTH AS ANOTHER COUPLE
SHORTWAVES RIDE ALONG THE FRONTAL ZONE...ONLY TO THEN BE FOLLOWED BY
A BAGGING CUTOFF LOW SOMEWHERE OVER THE GULF COAST STATED BY
MIDWEEK.  NOT A LOT OF CONFIDENCE IN THE DETAILS...BUT WILL TEND TO
FAVOR THE ECMWF...WHICH IS THE SOMEWHAT LESS ACTIVE SOLUTION WITH
THE FRONT STALLING TO OUR NORTH.  IN EITHER SCENARIO... MONDAY
THROUGH WEDNESDAY COULD BE AN ACTIVE PERIOD WITH ABOVE NORMAL POPS
AND TEMPS A BIT CLOSER TO NORMAL.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 658 AM WEDNESDAY...

AREAS OF IFR AND MVFR CEILINGS SHOULD LIFT TO VFR BY 15-16Z. MAINLY
DIURNAL ISOLATED TO SCATTERED SHOWERS AND STORMS ARE EXPECTED THIS
AFTERNOON. BUT THIS PROBABILITY APPEARS TOO LOW TO MENTION IN THE
TERMINAL FORECAST AT THIS TIME.

BEYOND THE 00Z VALID TAF PERIOD...THE THREAT FOR RESTRICTIONS IN
EARLY MORNING FOG/STRATUS WILL CONTINUE THE WEEKEND AS BERMUDA HIGH
PRESSURE HOLDS OVER THE AREA. ISOLATED TO SCATTERED MAINLY AFTERNOON
AND EVENING THUNDERSTORMS ARE EXPECTED AGAIN ON THURSDAY. RAIN
CHANCES WILL BEGIN TO INTO THE WEEKEND AS UPPER LEVEL RIDGE
RETROGRADES WEST OVER THE AREA.


&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...KRD/CBL
SHORT TERM...CBL
LONG TERM...BLS
AVIATION...CBL


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