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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 221910
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
310 PM EDT WED MAY 22 2013

.SYNOPSIS...
-- Changed Discussion --
A MOIST SOUTHERLY WIND FLOW WILL PERSIST ACROSS CENTRAL NC THROUGH
THURSDAY. A COLD FRONT WILL CROSS THE REGION LATE THURSDAY AND
THURSDAY NIGHT. A CANADIAN HIGH PRESSURE SYSTEM WILL BUILD INTO THE
CAROLINAS FRIDAY AND LINGER OVERHEAD THROUGH THE HOLIDAY WEEKEND.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1015 AM WEDNESDAY...

QUIETER DAY TODAY AS CENTRAL NC SITS IN BETWEEN A SHORTWAVE SYSTEM
JUST OFF THE COAST AND A LARGER FRONTAL SYSTEM CURRENTLY STRETCHING
ACROSS THE MISSISSIPPI VALLEY THAT WILL CONTINUE TO PUSH EASTWARD
TODAY WITH THE PARENT LOW MOVING TOWARDS THE SOUTHERN GREAT LAKES.

FOR CENTRAL NC THE BIGGEST DIFFERENCE BETWEEN TODAY AND PREVIOUS
DAYS IS THE WEAKENING OF THE SHORTWAVE TROUGH AND THE PRESENCE OF
HIGH PRESSURE AT THE UPPER LEVELS OF THE ATMOSPHERE. IN ADDITION
PRECIPITABLE WATER VALUES HAVE RELAXED SOMEWHAT...NEAR 1.5 INCHES
WITH HIGHER VALUES SOUTH AND EAST AND DRIER CONDITIONS ACROSS THE
NORTHWESTERN PIEDMONT. CURRENT MVFR CEILINGS WILL GRADUALLY LIFT OUT
AND SET THE STAGE AGAIN FOR CUMULIFORM DEVELOPMENT LEADING TO
SHOWERS AND THUNDERSTORMS THIS AFTERNOON. COVERAGE OF STORMS SHOULD
BE LESS THAN PREVIOUS DAYS AND SURFACE BOUNDARIES WILL ONCE AGAIN BE
THE CATALYST. SEVERE PARAMETERS WILL ONCE AGAIN BE VERY WEAK
OUTSIDE OF THE INSTABILITY WITH SHEAR ONLY AT 10 KNOTS OR SO AND
WEAK LAPSE RATES NEAR 5.5 DEG/KM. ML CAPE VALUES ONLY PREDICTED TO
BE ABOUT 800 J/KG OR SO. THEREFORE NOT EXPECTING ANY SEVERE WX THIS
AFTERNOON BUT POP UP SHOWERS AND THUNDERSTORMS WILL STILL BE
POSSIBLE...ESPECIALLY NEAR SURFACE BOUNDARIES. HIGH TEMPERATURES
TODAY SHOULD BENEFIT FROM BETTER INSOLATION AFTER MVFR CEILINGS BURN
OFF. EXPECT MIDDLE 80S ACROSS THE CWA TODAY. THERE IS THE POTENTIAL
FOR MORE LOW STRATUS TONIGHT AFTER SUNSET WITH CEILINGS CLOSER TO
2000 FEET. LOWS IN THE MIDDLE 60S.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 308 AM WEDNESDAY...

COLD FRONT WILL CROSS THE AREA... ENTERING THE STATE FROM THE WEST
THURSDAY EVENING... AND WILL REACH THE COAST BY 12Z FRIDAY.
THUNDERSTORMS WILL DEVELOP IN THE MOIST AIRMASS IN ADVANCE OF THE
FRONT THURSDAY... AND MODEST INSTABILITY OF 500-1000 J/KG MLCAPE AND
0-6 KM BULK SHEAR VALUES OF 25 KTS WILL SUPPORT A FEW MULTICELL
CLUSTERS. BEST UPPER LEVEL FORCING REMAINS NORTH OF THE AREA... AND
WITH THE STRONGEST LOW LEVEL FORCING ASSOCIATED WITH THE FRONT NOT
MAKING IT THROUGH THE AREA UNTIL LATE THURSDAY... SEVERE POTENTIAL
IS LOW. HIGHS LOW TO MID 80S... LOWS IN THE 60S.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 310 PM WEDNESDAY...

FRIDAY THROUGH SATURDAY NIGHT...

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.

SATURDAY INTO SATURDAY NIGHT...CANADIAN HIGH PRESSURE OVER THE LOWER
GREAT LAKES WILL BUILD/EXTEND INTO OUR REGION SATURDAY INTO SATURDAY
NIGHT. THIS WEATHER SYSTEM WILL RESULT IN A DRY WEATHER PATTERN WITH
BELOW NORMAL TEMPS. AFTERNOON THICKNESSES PROJECTED TO BE ABOUT 35M
BELOW NORMAL...SUPPORTIVE OF TEMPS CLOSE TO 10 DEGREES BELOW NORMAL.
ALLOWING FOR WARMTH FROM LATE MAY SUN...EXPECT AFTERNOON HIGH TEMPS
IN THE MID-UPPER 70S. MOS GUIDANCE LIKELY TRENDING TOWARD
CLIMATOLOGY BY SATURDAY NIGHT. WITH SFC RIDGE OVERHEAD AND CORE OF
LOW LEVEL DRY ACROSS THE REGION...TEMPS SHOULD COOL QUICKLY INT EH
EVENING THEN STABILIZE. MODEL RH CROSS SECTIONS HINT AT INCREASING
MID-HIGH LEVEL CLOUDS OVERNIGHT INTO EARLY SUNDAY. FIRST GLANCE
SUGGEST THAT CLOUD COVERAGE MAY INITIALLY BE THIN AND SPOTTY SO
COULD SEE DECENT NOCTURNAL COOLING. FAVOR MIN TEMPS A FEW DEGREES
COOLER THAN PREVIOUS FORECAST WITH MIN TEMPS IN THE MID-UPPER 40S.

SUNDAY INTO MONDAY...DEEP UPPER LEVEL LOW OVER NORTHERN NEW
ENGLAND-CANADIAN MARITIME PROVINCES WILL MAINTAIN A NW FLOW OVER THE
FORECAST AREA SUNDAY. WEAK PERTURBATIONS IN THIS FLOW ALOFT WORKING
WITH AVAILABLE MOISTURE WILL LIKELY CAUSE AN INCREASE IN MID-HIGH
LEVEL CLOUDINESS SUNDAY INTO SUNDAY NIGHT...MORE SO ACROSS OUR WEST
AND SOUTH SECTIONS AND LEAST IN THE NE. A MODIFYING AIR MASS WILL
LEAD TO SLIGHTLY WARMER CONDITIONS WITH AFTERNOON TEMPS IN THE
MID-UPPER 70S...AND AND MIN TEMPS IN THE MID 50S. 00Z ECMWF SUGGEST
THAT THERE MAY BE ENOUGH AMPLITUDE TO AN APPROACHING MID LEVEL
TROUGH TO WARRANT A SLIGHT-SMALL CHANCE POP ACROSS CENTRAL NC MONDAY
AFTERNOON-MONDAY EVENING.

TUESDAY INTO WEDNESDAY...AN AMPLIFYING MID-UPPER LEVEL RIDGE OVER
THE EASTERN HALF OF THE U.S. WILL PLACE CENTRAL NC BACK INTO A
SUMMER-LIKE PATTERN WITH A SFC HIGH ANCHORED OFFSHORE BUT EXTENDING
WESTWARD INTO THE SE U.S. THIS SUGGEST A RETURN TO WARM AND SLIGHTLY
HUMID CONDITIONS WITH AFTERNOON TEMPS IN THE LOW-MID 80S AND MIN
TEMPS 60-65. CONVECTION APPEARS TO BE DIURNALLY DRIVEN...ADDED BY A
SEABREEZE TO SE AND  NW FLOW ALOFT SENDING CONVECTION OFF THE HIGHER
TERRAIN INTO THE WESTERN PIEDMONT. POPS NO HIGHER THAN SLIGHT
CHANCE-SMALL CHANCE AT THIS TIME...CONFINED TO THE AFTERNOON-EVENING
HOURS.
-- End Changed Discussion --

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 120 PM WEDNESDAY...

24 HOUR TAF PERIOD: AS OF 17Z MOST SITES ACROSS CENTRAL NORTH
CAROLINA WERE REPORTING VFR CONDITIONS WITH SOUTH SOUTHWESTERLY
WINDS 5-10 KNOTS GUSTING TO 15 KNOTS. EXPECT GUSTS TO CONTINUE
THROUGH SUNSET. AS FAR AS PRECIPITATION GOES THIS AFTERNOON...MOST
CONVECTION ON THE RADAR AT THIS TIME IS ASSOCIATED WITH THE SEA
BREEZE. AS HEATING CONTINUES AND OTHER BOUNDARIES FORM BASED ON
BREAKS IN THE CLOUDS...EXPECT FURTHER DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS THIS AFTERNOON. EASTERN SITES SUCH AS KRWI AND KFAY
WILL BE THE MOST LIKELY TO SEE STORMS THIS AFTERNOON. SUB-VFR
CONDITIONS WILL AGAIN BE POSSIBLE TONIGHT MAINLY AFTER 6Z IN THE
FORM OF LOW STRATUS WITH BASES AROUND 1000 FT. IT IS POSSIBLE THAT
WE WILL MAINTAIN MVFR CEILINGS THROUGH THE END OF THE TAF PERIOD.
FOR NOW HAVE CEILINGS BREAKING BETWEEN 14-16Z FROM WEST TO EAST BUT
HOVERING NEAR 3500 FT. AS FRONT APPROACHES THE THREAT FOR SHOWERS
AND THUNDERSTORMS WILL INCREASE GOING INTO THURSDAY AFTERNOON. WINDS
THURSDAY AFTERNOON WILL REMAIN LARGELY SOUTHWESTERLY NEAR 10 KNOTS
GUSTING TO 15-20 KTS.

LONG TERM: ADVERSE AVIATION CONDITIONS ARE EXPECTED TO PREVAIL
THROUGH EARLY FRIDAY MORNING AS THE FRONTAL SYSTEM MOVES THROUGH THE
AREA. FRIDAY WILL SEE A PROLONGED RETURN TO VFR CONDITIONS THROUGH
MONDAY MAKING CONDITIONS VERY FAVORABLE FOR GENERAL AVIATION THROUGH
THE EXTENDED MEMORIAL DAY WEEKEND.

&&

.CLIMATE...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

$$

SYNOPSIS...WSS
NEAR TERM...ELLIS
SHORT TERM...SEC
LONG TERM...WSS
AVIATION...ELLIS
CLIMATE...RAH