-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 230723
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
322 AM EDT THU MAY 23 2013

.SYNOPSIS...
A TROUGH ALOFT AND ACCOMPANYING PRE-FRONTAL SURFACE PRESSURE TROUGH
WILL SETTLE INTO CENTRAL NC TODAY...FOLLOWED BY THE PASSAGE OF A
COLD FRONT TONIGHT. CANADIAN HIGH PRESSURE WILL THEN EXPAND ACROSS
OUR REGION THROUGH THE HOLIDAY WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 315 AM THURSDAY...

TODAY: AT THE BASE OF AN UPPER LOW MIGRATING THROUGH THE LOWER GREAT
LAKES...A NEUTRALLY-TILTED MID-UPPER TROUGH AXIS - AND ASSOCIATED
20-30 METER HEIGHT FALLS WILL PIVOT EASTWARD INTO CENTRAL NC TODAY.
MEANWHILE...MULTIPLE BOUNDARIES WILL BE PRESENT AND SERVE AS
CONVECTIVE TRIGGERS. MEANWHILE AT THE SURFACE...NWP GUIDANCE
SUGGESTS A PRONOUNCED PRE-FRONTAL TROUGH OVER WESTERN GA THIS
MORNING WILL DEVELOP EASTWARD INTO THE WESTERN CAROLINAS THIS
AFTERNOON...WHILE LEFT-OVER OUTFLOW FROM ONGOING CONVECTION OVER THE
PIEDMONT WILL ALSO SERVE AS A POSSIBLE FOCUS WITH DIURNAL HEATING.
THIS ONGOING CONVECTION SHOULD CONTINUE TO DIMINISH IN COVERAGE AND
INTENSITY AS IT EDGES SLOWLY EASTWARD INTO AN INCREASINGLY
STABLE/NOCTURNALLY-COOLED AIR MASS OVER CENTRAL NC.

SCATTERED TO NUMEROUS SHOWERS AND STORMS WILL CONSEQUENTLY LIKELY
INITIATE INVOF BOTH BOUNDARIES...ONE OVER THE EASTERN
PIEDMONT/SANDHILLS...AND THE OTHER OF HIGHER CONFIDENCE/
PREDICTABILITY OVER THE FOOTHILLS...WITH SOME TERRAIN ENHANCEMENT
PROBABLE WITH THE LATTER. STORM MOTION TO THE EAST NORTHEAST AT
10-15 KTS WILL ALLOW THIS LATTER CONVECTION THAT DEVELOPS TO OUR
WEST TO MOVE INTO THE WESTERN PIEDMONT MID-LATE AFTERNOON...THEN
EASTWARD ACROSS THE REMAINDER OF CENTRAL NC DURING THE LATE
AFTERNOON AND EVENING HOURS. MID LEVEL FLOW ON THE ORDER OF 20-25
KTS SUGGESTS MULTI-CELL STORM ORGANIZATION WITHIN A WEAKLY TO
MODERATELY UNSTABLE ENVIRONMENT OVER THE CAROLINAS...WITH STRONG
WIND GUSTS THE PRIMARY HAZARD. SOME TRAINING OF CONVECTION AND
ASSOCIATED QUICK ONE TO TWO INCHES OF RAIN WILL ALSO BE
POSSIBLE...PARTICULARLY BEFORE EVENING...WHEN FORECAST CORFIDI
VECTORS ARE SMALLEST. PROJECTED LOW LEVEL THICKNESSES OF 5-10 METERS
SHY OF THOSE OBSERVED ON WED...SUGGESTIVE OF HIGHS WITH PARTIAL
AFTERNOON SUNSHINE IN THE LOWER TO MIDDLE 80S.

TONIGHT: A COLD FRONT OVER THE WESTERN TN VALLEY THIS MORNING WILL
CREST THE APPALACHIANS THIS EVENING AND CROSS CENTRAL NC OVERNIGHT -
AROUND MIDNIGHT OR SO OVER THE WESTERN PIEDMONT...BETWEEN 4 AND 7 AM
IN THE COASTAL PLAIN. THE ARRIVAL OF A DRIER AIR MASS WITH FRONTAL
PASSAGE WILL HERALD THE END OF PRECIPITATION CHANCES...THOUGH
CONVECTIVE COVERAGE SHOULD ALREADY BE UNDERGOING A NOCTURNAL
DIMINISHING TREND WITH COOLING. AREAS OF FOG AND/OR LOW STRATUS ARE
ALSO PROBABLE PRIOR TO FRONTAL PASSAGE...MOST LIKELY AND LONGEST
OVER THE FAR EASTERN PIEDMONT/SANDHILLS AND COASTAL PLAIN. LOWS IN
THE LOWER TO MIDDLE 60S.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
-- Changed Discussion --
AS OF 310 PM WEDNESDAY...

A DEEP UPPER LEVEL TROUGH WILL SWING ACROSS CENTRAL NC FRIDAY AND
EXIT THE REGION FRIDAY NIGHT. MAY SEE A FEW INSTABILITY SHOWERS WITH
THE PASSAGE OF THIS SYSTEM HOWEVER MODEL RH CROSS SECTIONS DEPICT
THE AIR MASS DRYING OUT APPRECIABLY ABOVE 5000-8000FT BY EARLY
AFTERNOON. FOR NOW WILL LIMIT POPS TO SLIGHT CHANCE. OTHERWISE BRISK
NW FLOW WILL ADVECT COOLER MORE STABLE AIR INTO THE REGION.
SUSTAINED NW WINDS 10-15 MPH WITH GUSTS AROUND 25 MPH PROBABLE. THE
ARRIVAL OF THIS AIR MASS WILL RESULT IN COOLER CONDITIONS WITH
AFTERNOON MAX TEMPS IN THE LOWER 70S NORTH TO UPPER 70S FAR SE.

FRIDAY NIGHT...SKIES WILL CLEAR EARLY THOUGH A STEADY NW SFC WIND
WILL BE SLOW TO SUBSIDE. LOW LEVEL THICKNESSES CLUSTERING AROUND
1340M. HISTORICALLY...THIS SUGGEST MIN TEMPS NEAR 40-LOWER 40S.
FAVOR THE HIGH END OF THIS REGION DUE TO EXPECTED MIXING WELL INTO
THE NIGHT. MIN TEMPS 45-50.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 255 AM THURSDAY...

SATURDAY AND SUNDAY...

A TERRIFIC WEEKEND IS SHAPING UP AS CANADIAN HIGH PRESSURE WILL
BUILD SOUTH OUT OF THE GREAT LAKES INTO THE EASTERN CONUS. THIS WILL
RESULT IN CLEAR SKIES SATURDAY WITH DRY AND COOLER AIR IN PLACE.
UPPER FLOW WILL BE NORTHWEST AND MODEL CROSS SECTIONS SHOW THAT SOME
HIGH CLOUDINESS COULD MILDLY IMPEDE THE SUNSHINE ON SUNDAY. HIGHS
BOTH DAYS WILL BE MOSTLY IN THE MID 70S. MEANWHILE... SUNDAY
MORNINGS LOW TEMPERATURE WILL BE CONSIDERABLY BELOW NORMAL DUE TO
EXCELLENT RADIATIONAL CONDITIONS...IN THE 45 TO 50 DEGREE RANGE.

MONDAY THROUGH WEDNESDAY....

THE SURFACE HIGH PRESSURE MIGRATES OFFSHORE EARLY NEXT WEEK WHICH
WILL RESULT IN A GRADUAL WARMER AND MOISTER TREND INTO MIDWEEK. WE
WILL BE UNDER A BUILDING LOW AMPLITUDE UPPER RIDGE THROUGH THE
PERIOD WHICH WILL TEND TO SUPPRESS CONVECTION...ESPECIALLY WITH NO
EASILY IDENTIFIABLE FORCING OTHER THAN GENERALLY INCREASING
INSTABILITY WITH LEE TROFFING IN NORTHWEST FLOW AND POTENTIAL FOR
SOME INLAND PENETRATION OF SEA BREEZE CONVECTION IN THE EAST. AS
SUCH...WILL NOT MEDDLE WITH ONGOING SLIGHT CHANCE FOR LATE DAY
CONVECTION MONDAY THROUGH WEDNESDAY. TEMPS WILL BE ON THE UPTICK...
FROM 75 TO 80 ON MONDAY RISING TO 80 TO 85 ON WEDNESDAY...WITH MINS
FOLLOWING A SIMILAR TREND...FROM THE MID 50S MONDAY MORNING TO THE
LOWER 60S WEDNESDAY MORNING.


&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 205 AM THURSDAY...

A LINE OF SHOWERS AND ISOLATED STORMS THAT EARLIER AFFECTED THE
TRIAD TERMINALS WILL CONTINUE TO MOVE SLOWLY EASTWARD AT AROUND 10
MPH...AFFECTING THE KRDU AREA BETWEEN 8-10Z. A GRADUAL
WEAKENING/DISSIPATING TREND SHOULD OCCUR AS THE AIR MASS CONTINUES
TO STABILIZE WITH NOCTURNAL COOLING...HOWEVER...SO CONFIDENCE OF THE
CONVECTION REACHING THE KFAY AND KRWI AREAS IS LOW. OTHERWISE...A
CONTINUED MOIST AIR MASS WILL PROMOTE A HIGH CHANCE OF LIFR-IFR
CEILINGS THIS MORNING...THOUGH WITH RELATIVE LOWEST CHANCES - AROUND
60 PERCENT - AT TRIAD TERMINALS. THESE CEILINGS WILL LIFT AND
SCATTER TO VFR WITH HEATING THROUGH MIDDAY. HEATING OF THE MOIST AIR
MASS WILL ALSO CAUSE SCATTERED TO NUMEROUS SHOWERS AND STORMS TO
DEVELOP THIS AFTERNOON...AND THESE WILL LIKELY CONTINUE UNTIL A COLD
FRONT SWEEPS ACROSS CENTRAL NC FROM WEST TO EAST BETWEEN 04-06Z AT
TRIAD TERMINALS...TO 09-12Z AT EASTERN ONES. AREAS O FOG OR LOW
STRATUS WILL ALSO BE POSSIBLE AHEAD OF THE COLD FRONT...MOST LIKELY
AT KFAY AND KRWI BETWEEN 06-12Z.

VFR CONDITIONS WILL OTHERWISE PREVAIL IN CANADIAN HIGH PRESSURE
THROUGH THE HOLIDAY WEEKEND.

&&

.CLIMATE...
MORNING LOW TEMPERATURES ON THE 25TH AND 26TH ARE EXPECTED TO BE A
FEW DEGREES SHY OF RECORD MIN TEMPS FOR THE DATE.

RECORD MIN TEMP/YEAR SET      MAY 25TH            MAY 26TH

RDU                           43 / 1967           43 / 1979

GSO                           43 / 1956           42 / 1930


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

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...WSS
LONG TERM...MLM
AVIATION...MWS
CLIMATE...RAH