-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 222355
AFDRAH

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

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 PM WEDNESDAY...

CENTRAL NC CONTINUES TO SIT BETWEEN SURFACE HIGH PRESSURE OFF THE
COAST AND AN ADVANCING FRONTAL SYSTEM TO THE WEST. UPPER LEVEL
RIDGING OVER THE AREA AND DECREASED MOISTURE HAS LED TO A QUIETER
DAY TODAY AS FAR AS CONVECTION IS CONCERNED. AS OF 18Z THE CURRENT
RADAR SHOWS AN AXIS OF CONVECTION POPPING UP ALONG THE SEA BREEZE
FRONT WHICH IS CURRENTLY STILL EAST OF THE I-95 CORRIDOR. THIS WILL
SLOWLY ADVECT NORTHEASTWARD BUT IS NOT EXPECTED TO PROPAGATE TOO FAR
INLAND THIS AFTERNOON. OTHER WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS WILL BE POSSIBLE OVER THE NEXT COUPLE OF HOURS. SEVERE
PARAMETERS REMAIN LOW AND SEVERE WEATHER IS NOT EXPECTED THIS
AFTERNOON. WINDS REMAIN OUT OF THE SOUTH SOUTHWEST NEAR 10 KNOTS
GUSTING TO 15-20 KNOTS. HIGHS WILL TOP OUT IN THE MIDDLE 80S THIS
AFTERNOON.

FOR TONIGHT SHOWERS AND THUNDERSTORMS WILL END AFTER 00Z AND LOW
STRATUS IS ONCE AGAIN EXPECTED ACROSS THE CWA AS DEWPOINTS REMAIN
ELEVATED INTO THE MID 60S. CEILINGS SHOULD BE AROUND 1000 FEET
OVERNIGHT. LOW TEMPERATURES ARE EXPECTED TO BE IN THE LOW 60S.

&&

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

A COLD FRONT WILL APPROACH CENTRAL NC FROM THE WEST ON FRIDAY. AS A
DEEP 500 MB TROUGH DIGS SOUTHWARD THROUGH THE OHIO VALLEY. AS FAR AS
TIMING IS CONCERNED...SHOWERS AND THUNDERSTORMS AHEAD OF FRONT WILL
BEGIN TO AFFECT THE TRIAD BY LATE THURSDAY MORNING AND CONTINUE TO
PROGRESS SLOWLY EASTWARD ACROSS THE CWA BY AFTERNOON/EVENING. SEVERE
POTENTIAL WITH THIS SYSTEM WILL BE GREATER THAN THE PAST COUPLE OF
DAYS BUT STILL LOOKS VERY LOW. EFFECTIVE SHEAR WILL BE ABOUT 20
KNOTS SUGGESTING MORE LINEAR THUNDERSTORMS. THIS IS SUPPORTED BY THE
STRAIGHT HODOGRAPHS SHOWN BY NAM FORECAST SOUNDINGS. MID LEVEL LAPSE
RATES WILL BE WEEK ALTHOUGH 1000 ML CAPE OF THE TALL AND SKINNY
VARIETY COULD BE REALIZED BY AFTERNOON. LATER IN THE EVENT DYNAMICS
IMPROVE AS A 30 KNOT 850MB APPROACHES THE NORTHWEST. IT IS UNCLEAR
AT THIS TIME WHETHER OR NOT CONVECTION WILL BE TOO FAR TO THE EAST
TO TAKE ADVANTAGE OF THE INCREASED SHEAR. STORMS LINGERING BACK
TOWARDS THE WEST MAY BE ABLE TO TAKE ADVANTAGE OF AN INCREASED AXIS
OF DCAPE EXPECTED TO MOVE THROUGH THE CWA JUST AFTER 00Z FRIDAY.
THEREFORE IF WE DO ENCOUNTER SEVERE WEATHER TOMORROW...IT WILL MOST
LIKELY BE DAMAGING WINDS AND NOT HAIL. FOR NOW SPC HAS KEPT THE
RALEIGH AREA OUT OF THE SLIGHT RISK AREA FOR TOMORROW. PRECIPITABLE
WATERS WILL BE SIMILAR TO TODAY NEAR 1.5 INCHES BUT QPF WITH FRONTAL
PASSAGE IS ONLY EXPECTED TO BE BETWEEN A QUARTER AND A HALF OF AN
INCH WITH LOCALLY HEAVIER AMOUNTS POSSIBLE IN THUNDERSTORMS.
LOCALIZED FLOODING COULD BE AN ISSUE...ESPECIALLY IN URBAN AREAS
UNDER SLOW MOVING OR TRAINING THUNDERSTORMS. CLOUD COVER SHOULD
OVERSPREAD THE AREA FAIRLY EARLY TOMORROW AND THUS WILL TREND
TOWARDS THE COOLER MET GUIDANCE WITH HIGH TEMPERATURES. UPPER 70S IN
THE NORTHWEST TO LOW 80S SOUTHEAST. AS THE LOWER ATMOSPHERE BEGINS
TO DRY OUT LOW TEMPERATURES IN THE TRIAD SHOULD DIP INTO THE UPPER
50S IN THE NORTHWEST FOR THE FIRST TIME IN SEVERAL DAYS BUT FURTHER
TO THE SOUTHEAST LOWS WILL REMAIN IN THE MIDDLE 60S AS THE FRONT IS
EXPECTED TO FULLY MOVE THROUGH THE EAST UNTIL CLOSER TO 6Z ON FRIDAY.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
AS OF 750 PM WEDNESDAY...

SEABREEZE AND OUTFLOW GENERATED SHOWERS HAVE MOSTLY DISSIPATED IN
THE LAST HOUR...WITH MORE ROBUST CONVECTION JUST TO THE WEST OF KINT
CONTINUING TO MOVE SOUTHWEST TO NORTHEAST.  THERE IS NOT MUCH
EVIDENCE ON RADAR OF THESE CELLS MOVING EAST MAKING MUCH PROGRESS
EAST TOWARD KINT...SO WILL KEEP VCSH IN THE KINT TAF THROUGH 03Z.
THE MORE PROGRESSIVE AREA OF CONVECTION AND OUTFLOW IS STILL WEST OF
KHKY.  THE OVERALL WEAKENING TREND OF CONVECTION IS EXPECTED TO
CONTINUE THIS EVENING...WITH IFR/MVFR STRATUS EXPECTED TO DEVELOP
AFTER MIDNIGHT.

THE THREAT OF SCATTERED CONVECTION WILL CONTINUE ON THURSDAY AHEAD
OF AN UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT OVER THE MIDWEST
STATES.  MODEL GUIDANCE SUGGESTS SHOWERS MAY BE POSSIBLE AS EARLY AS
12Z NEAR KGSO/KINT...WITH MORE WIDESPREAD SHOWERS AND STORMS MORE
LIKELY THURSDAY AFTERNOON AS THE TROUGH AND COLD FRONT APPROACH FROM
THE WEST.  CEILINGS WILL BREAK BY MIDDAY THURSDAY...WITH CLOUD BASED
EXPECTED TO LIFT TO AROUND 3500-4000 FT THURSDAY AFTERNOON.

OUTLOOK...
A COLD FRONT MOVING THROUGH THE AREA LATE THURSDAY AND EARLY FRIDAY
WILL CONTINUE THE THREAT OF ADVERSE AVIATION CONDITIONS.  VFR
CONDITIONS ARE EXPECTED TO RETURN DURING THE DAY FRIDAY AND PREVAIL
THROUGH THE WEEKEND.
-- End Changed Discussion --

&&

.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...WSS
NEAR TERM...ELLIS
SHORT TERM...ELLIS
LONG TERM...WSS
AVIATION...SMITH
CLIMATE...RAH