Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 270052
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
852 PM EDT TUE MAY 26 2015

.SYNOPSIS...THE WESTERN EXTENT OF BROAD SURFACE HIGH PRESSURE...AND
A SEASONABLY MOIST AIR MASS...WILL PREVAIL OVER THE REGION FOR THE
WORK WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 305 PM TUESDAY...

THE LATEST SURFACE ANALYSIS SHOWED THE WESTERN END OF HIGH PRESSURE
CONTINUING TO EXTEND OVER CENTRAL NORTH CAROLINA...WHILE WATER VAPOR
IMAGERY SHOWED WEAK MID-LEVEL VORTICITY AND AN INCREASE IN MID-LEVEL
MOISTURE OVER THE WESTERN CAROLINAS. PRECIPITABLE WATER VALUES HAD
INCREASED TOWARD INTERSTATE 95 AND EAST DURING THE DAY...SUCH THAT
THERE WERE FAIRLY UNIFORM VALUES AROUND 1.5 INCHES OVER CENTRAL
NORTH CAROLINA AS THE LATE AFTERNOON APPROACHED. SCATTERED
SHOWERS... AND ISOLATED THUNDER...OVER THE SOUTHERN COASTAL PLAIN
SHOULD GENERALLY DECREASE THIS EVENING AS GFS AND NAM BUFR SOUNDINGS
FORECAST LOW-LEVEL STABILITY INCREASING BY AROUND SUNSET. IN THE
MEANTIME...ISOLATED SHOWERS OR A VERY ISOLATED STORM MAY FIND THEIR
WAY ABOUT AS FAR NORTH AS U.S. 64 BASED ON A COMBINATION OF THE
LATEST RADAR TRENDS AND THE HRRR WRF. WHILE AN ISOLATED SHOWER VERY
LATE THIS AFTERNOON IS ALSO POSSIBLE OVER THE FAR WESTERN
PIEDMONT...SCATTERED SHOWERS MAY BE A BETTER POSSIBILITY OVER THE
WESTERN PIEDMONT AND TOWARD THE YADKIN RIVER LATER THIS EVENING WITH
THE APPROACH OF THE WEAK MID-LEVEL WAVE COINCIDENT WITH FORECAST
MOISTENING ON BUFR SOUNDINGS AND...AGAIN...HRRR WRF FORECASTS. 0-3KM
SHEAR ON THE SPC MESOANALYSIS...AND AS FORECAST BY THE NAM AND
GFS... IS LOW...SINGLE DIGITS KNOTS TO TEENS AT MOST...SO AS OF THIS
WRITING DO NOT EXPECT ANY STRONG...DEEP CONVECTION. THE GFS WOULD
SPREAD QPF FARTHER EAST THAN THE NAM AND THE HRRR WRF DEPICT...AND
BASED ON THE STABILITY EVEN ON THE KRDU...KFAY...AND KRWI GFS BUFR
SOUNDINGS OVERNIGHT...LEAN MORE TOWARD THE NAM AND RAP WHICH KEEP
MEASURABLE PRECIPITATION FARTHER WEST DURING THE OVERNIGHT HOURS.

AS ALSO NOTED IN THE AVIATION DISCUSSION BELOW...SREF MODEL
PROBABILITIES OF LOW CLOUDS ARE HIGH ESPECIALLY WEST OF INTERSTATE
95 OVERNIGHT. HOWEVER...THE STATISTICAL GUIDANCE IS NOT AS BULLISH
AND MODEL SOUNDINGS FROM THE GFS AND NAM DIFFER AS TO THE POTENTIAL
OF LOW CLOUDS LATE. SINCE LOW CLOUDS OCCURRED MAINLY TOWARD THE
YADKIN RIVER AND THE TRIAD EARLY THIS MORNING...THE OVERALL AIR MASS
HAS MOISTENED...AND 925MB WINDS SHOULD BE FAVORABLE OVERNIGHT WITH
VALUES OF 20 TO 30KT AS FORECAST BY THE GFS IN THE SOUTHWEST FLOW.
AS A RESULT...BELIEVE THERE WILL BE AREAS OF LOW CLOUDS LATE TONIGHT
CONTINUING INTO WEDNESDAY MORNING. OVERNIGHT LOWS 65 TO 70...SHY OF
ANY RECORD HIGH MINIMUM VALUES FOR MAY 27.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 305 PM TUESDAY...

INSTABILITY OVERALL INCREASES ACROSS CENTRAL NORTH CAROLINA
WEDNESDAY...WITH SURFACE-BASED CAPE RISING TO JUST OVER 1000J/KG
WHILE MLCAPE THROUGH THE LOWEST 3KM IS GENERALLY 500J/KG OR SO.
LIFTED INDICES ARE FORECAST TO BE SLIGHTLY LOWER COMPARED TO
TODAY... TO NEAR -5C WEDNESDAY AFTERNOON VERSUS ABOUT -3C.
ALOFT...THERE IS FORECAST WEAK AND BROAD DIFFLUENCE AND WEAK
CONVERGENCE AT 850MB...ALTHOUGH CERTAINLY THE NAM AND TO A LESSER
EXTENT THE GFS FORECAST MODEST LIFT OVER CENTRAL NORTH CAROLINA FOR
WEDNESDAY AFTERNOON. WINDS ALOFT ARE WEAK...AND ANY PIEDMONT TROUGH
SHOULD BE SOMEWHAT WEAK AS WELL...LEADING TO A DAY WHERE SCATTERED
MOSTLY DISORGANIZED SHOWERS AND THUNDERSTORMS SHOULD OCCUR AS THE
DAY PROGRESSES. ONCE AGAIN...0-3KM SHEAR IS LOW AND 850MB AND 925MB
WINDS ARE RELATIVELY LIGHT BY AFTERNOON...10 TO 20KT. HIGHS IN THE
80S.

OVERNIGHT...BUFR SOUNDINGS FROM BOTH THE NAM AND GFS SHOW INCREASING
STABILITY AS SURFACE HIGH PRESSURE IS FORECAST TO BUILD SOMEWHAT
BACK WEST. FOR THIS FORECAST WILL DIMINISH CHANCES EAST TO WEST AND
RETAIN A SLIGHT CHANCE OF SHOWERS IN THE OVERNIGHT HOURS ONLY TOWARD
THE YADKIN RIVER ESPECIALLY FOR FORECAST CONSISTENCY...BUT IF THE
NAM BUFR SOUNDINGS VERIFY IN PARTICULAR CENTRAL NORTH CAROLINA
SHOULD HAVE BELOW SLIGHT CHANCE POPS AFTER 06Z. LOWS IN THE MID TO
UPPER 60S.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
AS OF 210 PM TUESDAY...

THE REMNANT MOISTURE AND SHEAR AXIS FROM THE SYSTEM CURRENTLY OVER
THE MISS RIVER VALLEY WILL MOVE EAST AND BECOME CENTERED OVER
CENTRAL NC BY THURSDAY. WHILE THE BEST MID/UPR ENERGY WILL HAVE
LIFTED WELL TO OUR NORTH...THERE SHOULD BE ENOUGH MOISTURE AND
FORCING FOR AT LEAST SCATTERED AFTERNOON/EVENING SHOWERS/TSTMS.
INSTABILITY AND SHEAR VALUES SUGGEST SUB-SEVERE ACTIVITY.

THE UPPER RIDGE OFF THE EAST COAST WILL THEN REBUILD OVER THE
SOUTHEAST COASTAL REGION FRIDAY THROUGH THE WEEKEND...AND SHOULD
HELP LIMIT THE COVERAGE OF SHOWER/TSTM ACTIVITY OVER OUR AREA FRIDAY
AND SATURDAY.

A COLD FRONT CROSSING THE MIDWEST ON FRIDAY IS PROGGED BY THE LATEST
GFS TO DROP SOUTH ACROSS OUR AREA BY SUNDAY AND DISSIPATE OVER US BY
MONDAY. DESPITE THE LIFT PROVIDED BY THIS FRONT...MODELS SUGGEST THE
AFOREMENTIONED RIDGE OVER THE SOUTHEAST WILL KEEP THE BULK OF THE
MOISTURE JUST TO OUR NORTH.  NEVERTHELESS...THERE`S ENOUGH FORCING
AND MOISTURE TO WARRANT A DECENT CHANCE POP ACROSS OUR AREA LATE IN
THE WEEKEND INTO EARLY NEXT WEEK.

AS FOR TEMPS...PERSISTENCE IS THE BEST FORECAST AT THIS POINT WITH
LITTLE CHANGE IN THE AIRMASS. HIGHS IN THE MID TO UPPER 80S AND
LOWS IN THE MID 60S EACH DAY DURING THE PERIOD.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 830 PM TUESDAY...

VFR CONDITIONS ARE EXPECTED TO CONTINUE THIS EVENING... WITH LOW TO
MODERATE CONFIDENCE OF IFR/MVFR CONDITIONS EARLY WEDNESDAY
MORNING... POSSIBLY LINGERING TO NEAR NOON WEDNESDAY AT KGSO/KINT.
ISOLATED TO SCATTERED SHOWERS AND STORMS ARE EXPECTED ON WEDNESDAY
AFTERNOON AS WELL.

THE MID LEVEL RIDGE AXIS LOCATED NEAR THE COAST STILL HAD ENOUGH OF
AN INFLUENCE TO SUPPRESS SHOWERS AND STORMS FOR THE MOST PART ACROSS
THE AREA TODAY. HOWEVER... THIS FEATURE WILL CONTINUE TO SLOWLY
SHIFT EASTWARD AND ALLOW A MORE FAVORABLE AIRMASS TO SLOWLY SHIFT
FILTER INTO CENTRAL NC. IN FACT WE MAY SEE A WEAKENING BAND OF
SHOWERS AND STORMS CURRENTLY LOCATED ACROSS FAR SOUTHWESTERN NC AND
THE UPSTATE OF SC CONTINUE TO MOVE EAST AND NORTHWARD AND POSSIBLY
AFFECT KGSO/KINT (THOUGH IN A WEAKEN STATE) IN THE 04Z TO 08Z TIME
FRAME... WITH POSSIBLE MVFR CONDITIONS. ELSEWHERE OVERNIGHT... WE
CANT ENTIRELY RULE OUT A FEW SHOWERS... BUT PROBABILITIES ARE WAY
TOO LOW TO INCLUDE ANY MENTION OF CONVECTION IN THE TAFS.

GIVEN THE CONTINUED MOISTENING LOW LEVEL FLOW EXPECT WE WILL LIKELY
SEE SOME STRATUS AGAIN TONIGHT (MVFR/IFR CONDITIONS)... WITH THE
HIGHEST PROBABILITIES ACROSS THE WESTERN PIEDMONT... KGSO/KINT.
FURTHER EAST STILL THINK WE MAY SEE SOME MVFR/IFR CONDITIONS... BUT
CONFIDENCE IS NOT AS HIGH.

AFTER SUNRISE WEDNESDAY MORNING...ANY IFR CONDITIONS SHOULD LIFT AT
LEAST INTO MVFR RANGE BY MID MORNING... WITH CIGS EXPECTED TO BE IN
THE VFR RANGE BY EARLY AFTERNOON. SCATTERED SHOWERS AND STORMS ARE
EXPECTED TO DEVELOP/MOVE INTO THE AREA TOWARDS WEDNESDAY AFTERNOON
(GENERALLY ACROSS THE WESTERN PIEDMONT). THUS... GIVEN CONFIDENCE IN
SEEING SOME SHOWERS AND STORMS IS HIGHEST IN THE NW PIEDMONT... WILL
ONLY ADD A PROB30 GROUP AT KGSO/KINT FOR CONVECTION WEDNESDAY
AFTERNOON.

BEYOND THE 00Z VALID TAF PERIOD...LOW CLOUDS WILL BE POSSIBLE AGAIN
THURSDAY MORNING...THOUGH WITH A BETTER PROBABILITY TOWARD KFAY AND
KRWI RELATIVE TO THE REST OF CENTRAL NORTH CAROLINA. ISOLATED TO
SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS ARE ALSO
POSSIBLE. LOWEST CHANCES OF THOSE APPEAR TO BE SATURDAY WHEN THE AIR
MASS IS RELATIVELY MORE STABLE COMPARED TO OTHER DAYS.

&&

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

&&

$$

SYNOPSIS...DJF
NEAR TERM...DJF
SHORT TERM...DJF
LONG TERM...RAH
AVIATION...BSD/DJF



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