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000
FXUS62 KRAH 260705
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
305 AM EDT SUN MAY 26 2013

.SYNOPSIS...
CANADIAN HIGH PRESSURE WILL EXTEND ACROSS OUR REGION THROUGH THE
REST OF THE HOLIDAY WEEKEND.

&&

.NEAR TERM /TODAY/...
AS OF 250 AM SUNDAY...

TODAY: MID LEVEL CLOUDINESS AND EVEN SOME VIRGA...IN THE
ANTI-CYCLONIC STREAM OF A FRONTOGENETIC LOW-MID LEVEL WAA REGIME
FOCUSED OVER THE UPPER MIDWEST...WILL STREAM SOUTHEASTWARD ACROSS
CENTRAL NC THROUGH THE MORNING-MIDDAY HOURS. FORECAST GUIDANCE IS IN
GOOD AGREEMENT THAT THE BACK EDGE OF THIS MOISTURE AND ASSOCIATED
MOSTLY CLOUDY CONDITIONS WILL PIVOT SOUTHEASTWARD AND RESULT IN
MOSTLY SUNNY SKIES DEVELOPING FROM NW TO SE BETWEEN 14-18Z. THE
ABUNDANT SUNSHINE WILL SUPPORT RELATIVELY DEEP DRY ADIABATIC MIXING
AGAIN PER BUFR SOUNDINGS...OF AFTERNOON H85 TEMPERATURES FROM 8C NE
TO 10C SW. HIGHS IN THE MIDDLE TO UPPER 70S...WITH LOW HUMIDITY IN
THE 20-30TH PERCENTILE.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
AS OF 305 AM SUNDAY...

TONIGHT: DRY NORTHWEST FLOW ALOFT WILL PERSIST...WITH JUST SOME
PASSING CIRRUS FOR THE MAJORITY OF THE NIGHT. HOWEVER...NWP GUIDANCE
INDICATES A RENEWED SURGE OF MOISTURE IN THE H85-7 LAYER WILL STREAM
SOUTHEASTWARD ALONG THE QUASI-STATIONARY FRONTAL ZONE IN THAT
LAYER...FROM THE UPPER MIDWEST/NORTHERN PLAINS TO THE CAROLINAS...
AND RESULT IN SCT TO BKN 6-8 THOUSAND FT STRATO- ALTOCUMULUS TOWARD
DAYBREAK...MAINLY OVER THE WESTERN PIEDMONT. TEMPERATURES SHOULD
HAVE ALREADY COOLED TO NEAR OVERNIGHT MINIMUMS BEFORE ANY SUCH
INCREASING CLOUDINESS DEVELOPS...HOWEVER...SO WELL-RADIATIONALLY
COOLED LOWS IN THE 46 TO 53 DEGREE RANGE ARE EXPECTED.

MONDAY AND MONDAY NIGHT: A SURFACE FRONT WILL DEVELOP (BECOME
BETTER-DEFINED) INVOF THE NC/SC LINE MONDAY MORNING...THEN DIFFUSE
WITH TIME AMIDST BROAD SSE SURFACE FLOW AS IT GRADUALLY EDGES
NORTHEASTWARD INTO CENTRAL NC LATE IN THE DAY. BOUNDARY LAYER
MOISTURE SUPPORTIVE OF EVEN SHALLOW CONVECTION...IN THE MID 50S TO
AROUND 60 DEGREES...IS EXPECTED TO ARC ROUGHLY FROM KINT TO KHFF TO
KCTZ THROUGH THE DIURNAL HEATING CYCLE. AS SUCH...WILL MAINTAIN JUST
A SLIGHT CHANCE OF AN AFTERNOON SHOWER ALONG AND SOUTHWEST OF THAT
ARC. WE ADD ABOUT ANOTHER 10-15 METERS TO LOW LEVEL THICKNESSES...OR
ABOUT 2 C AT H85 VERSUS THOSE VALUES OF SUNDAY...WHICH SHOULD
TRANSLATE TO HIGHS IN THE UPPER 70S TO LOWER 80S.

VARIABLY CLOUDY AND NOT AS COOL MON NIGHT...WITH LOWS IN THE UPPER
50S TO AROUND 60 DEGREES. WILL MAINTAIN FORECAST CONTINUITY WITH A
SLIGHT SHOWER CHANCE...BUT CONFINED TO ALONG THE VA BORDER MON
NIGHT...INVOF THE DIFFUSING AND RETREATING SURFACE BOUNDARY AND
WHERE THE SREF MEAN HUNDREDTH OF AN INCH CONTOUR IS FORECAST.
HOWEVER...THIS TOO MAY ULTIMATELY BE OVERDONE GIVEN FORECAST BUFR
SOUNDINGS THAT DEPICT NEGLIGIBLE CAPE.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...

TUESDAY AND TUESDAY NIGHT...RIDGING ALOFT GRADUALLY INCREASES OVER
CENTRAL NORTH CAROLINA...WITH DECENT MOISTURE EARLY...PRECIPITABLE
WATER VALUES OF 1.5 INCHES AND A MODEST 850MB THETA-E RIDGE...
GRADUALLY DIMINISHING THROUGH 12Z WEDNESDAY. ANY WEAK SURFACE AND
850MB FRONTS SHOULD BE JUST NORTH OF CENTRAL NORTH CAROLINA AFTER
EARLY TUESDAY...AND AS SUCH THERE SHOULD BE GENERALLY WEAK FORCING
FOR LIFT DURING THE DAY WITH ONLY A WEAK SHORTWAVE POSSIBLE AROUND
THE TOP OF THE AMPLIFYING RIDING IN LINGERING NORTHWEST FLOW ALOFT.
NAM AND GFS BUFR SOUNDINGS SHOW SLENDER CAPE AT BEST...ALTHOUGH THE
GFS DURING THE AFTERNOON TUESDAY DOES SHOW ABOUT 750J/KG OF
MIXED-LAYER CAPE OVER MUCH OF CENTRAL NORTH CAROLINA...AND ABOUT
500J/KG OF CAPE FROM -10C TO -30C. GIVEN THE AVAILABLE INSTABILITY
AND MOISTURE...WILL RETAIN ISOLATED THUNDERSTORMS MAINLY TUESDAY
AFTERNOON...WITH THE HIGHER CHANCES RELATIVE TO THE REST OF CENTRAL
NORTH CAROLINA CONSISTENT WITH THE PREVIOUS FORECAST MAINLY ALONG
AND NORTH OF ABOUT KVUJ TO KGSB. CONCEPTUALLY...IT WOULD SEEM THAT
ALONG THE RETREATING DIFFUSE SURFACE BOUNDARY JUST TO OUR NORTH WILL
BE THE BETTER POTENTIAL FOR LOW-LEVEL CONVERGENCE...AND 1000-500MB
THICKNESSES...ALONG WITH GFS STORM-MOTION VECTORS SUGGEST THAT ANY
STORM MOTION WOULD BE MORE NORTH-TO-SOUTH THAN TYPICAL. WILL KEEP
THE MENTION OF ANY STRONG STORMS OUT OF THE HWO FOR NOW GIVEN THE
WEAK WIND FIELDS AND 0-3KM SHEAR...THE LATTER IN THE TEENS KTS
TUESDAY AFTERNOON. GFS BUFR SOUNDINGS SHOW WARMING ALOFT BETWEEN 00Z
AND 03Z WEDNESDAY SUCH THAT WITH THE ADDED LOSS OF DIURNAL
HEATING...ANY ISOLATED SHOWERS OR THUNDERSTORMS SHOULD DIMINISH
QUICKLY WITH SUNSET. THE STABILITY IS NOTED IN THE RAPID INCREASE IN
LIFTED INDICES AS WELL AFTER 00Z WEDNESDAY. HIGH TEMPERATURES
TUESDAY IN THE LOWER TO MID 80S...WITH OVERNIGHT LOWS TUESDAY NIGHT
59 TO 64.

WEDNESDAY THROUGH SATURDAY...THE TREND IN THIS PART OF THE
FORECAST...OVERALL...HAS BEEN FOR AMPLE RIDGING EARLY FOLLOWED BY A
GREATER WEAKNESS IN HEIGHTS ALOFT...WITH LOW PRESSURE OFF OF THE
EASTERN FLORIDA COAST AND OVER THE BAHAMAS GRADUALLY MOVING NORTH.
THE TREND OF THE LAST COUPLE OF VISIBLE RUNS OF THE ECMWF HAS BEEN
VERY CONSISTENT IN SLOWLY MOVING MID-LEVEL LOW PRESSURE NORTH ALONG
THE SOUTHEAST COAST. THE CANADIAN HAS BEEN MORE AGGRESSIVE IN MOVING
LOW PRESSURE NORTH...AND THE DGEX APPEARS TO BE A BLEND OF THE 12Z
ECMWF AND THE GFS...WHICH HAD A TREND OF A MUCH STRONGER RIDGE OVER
THE SOUTHEAST STATES. THE LATEST GFS IS STARTING TO SHOW MORE OF A
WEAKNESS OVER THE SOUTHEAST STATES...THOUGH STILL KEEPING ANY
MID-LEVEL LOW PRESSURE SUPPRESSED WELL SOUTH OF CENTRAL NORTH
CAROLINA UNDER STRONGER MID-LEVEL RIDGING.

GFS MOS ENSEMBLE POPS ARE VERY CLOSE TO ONE ANOTHER AND LOW CHANCE
CLIMATOLOGY TOWARD THE END OF THE LONG-TERM PERIOD...AND GIVEN SOME
POTENTIAL FOR A TREND OVER TIME OF MID-LEVEL LOW PRESSURE MOVING
FARTHER NORTH...THERE IS SOME URGE TO INTRODUCE AT LEAST A SLIGHT
CHANCE OF A SHOWER OR THUNDERSTORM IN THE FORECAST BY SATURDAY
AFTERNOON. WILL CONTINUE WITH A DRY FORECAST THROUGHOUT THIS PERIOD
FOR NOW UNDER STRONG MODEL CONSENSUS OF STABILITY AND RELATIVE
WARMTH ALOFT FOR THE MIDDLE AND END OF THE WORK WEEK...AND INTO
SATURDAY BASED ON THE UNCERTAINTY OF THE EVOLUTION OF MID-LEVEL AND
SURFACE LOW PRESSURE OUT NEAR THE SEVENTH DAY. THIS WILL ALSO
MAINTAIN A HIGHER DEGREE OF FORECAST CONSISTENCY AT THE END OF THE
FORECAST PERIOD. OTHER SENSIBLE WEATHER PARAMETERS WILL RETAIN CLOSE
CONTINUITY AS WELL...AND IT IS POSSIBLE THAT UNDER THE ORIENTATION
OF THE 850MB RIDGE LATE IN THE WEEK...WITH THE HIGHEST 850MB
TEMPERATURES IN CENTRAL NORTH CAROLINA FORECAST NEAR THE VIRGINIA
BORDER...MAXIMUM TEMPERATURES OVER AREAS SUCH AS THE NORTHERN
COASTAL PLAIN AND NORTHEAST PIEDMONT COULD RIVAL THE TYPICALLY
WARMER AREAS OF THE SANDHILLS AND SOUTHERN COASTAL PLAIN.

&&

 .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 135 AM SUNDAY...

THE PRESENCE OF CANADIAN HIGH PRESSURE WILL RESULT IN A CONTINUED
HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE 06Z TAF PERIOD. A BAND
OF LEFT-OVER MOISTURE FROM UPSTREAM PRECIPITATION IN NORTHWEST FLOW
ALOFT...AND ASSOCIATED MID CLOUDS AROUND 10 THOUSAND FEET...WILL
STREAM ACROSS CENTRAL NC THROUGH AROUND 15Z...WITH OTHERWISE JUST
PERIODS OF PASSING CIRRUS EXPECTED. LIGHT...GENERALLY NORTHERLY
WINDS THIS MORNING WILL BACK TO A MORE NORTHWESTERLY COMPONENT...BUT
STILL LIGHT...THIS AFTERNOON.

OUTLOOK: THE NEXT CHANCE OF SUB-VFR CONDITIONS WILL BE PATCHY LIGHT
(MVFR) FOG TUE MORNING...MAINLY AT KRWI AND KFAY...AND PERHAPS AGAIN
WED MORNING...AS LOW LEVEL MOISTURE GRADUALLY INCREASES AND DEEPENS
IN RETURN FLOW AROUND THE AFOREMENTIONED SURFACE HIGH EARLY TO MID
WEEK.

&&

.CLIMATE...
LOW TEMPERATURES ON THE 26TH ARE EXPECTED TO FALL SEVERAL DEGREES
SHY OF THE FOLLOWING RECORDS FOR THE DATE:

RECORD MIN TEMP/YEAR SET      MAY 26TH

RDU                           43 / 1979

GSO                           42 / 1930

FAY                           44 / 1988


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

&&

$$

SYNOPSIS...DJF
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...DJF
AVIATION...MWS
CLIMATE...RAH