Hail and Damaging Winds in North Carolina, May 20, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
245 PM EDT TUE MAY 20 2008

.SYNOPSIS...
A COLD FRONT WILL MOVE SOUTHEAST ACROSS CENTRAL NORTH CAROLINA EARLY
THIS EVENING ACCOMPANIED BY STRONG TO SEVERE THUNDERSTORMS. WEAK
HIGH PRESSURE WILL RESIDE WEST OF THE REGION WEDNESDAY AND
THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 PM TUESDAY...

ACTIVE CONVECTIVE WEATHER EXPECTED THROUGH 00Z AS A COLD FRONT
DRIFTS SE ACROSS THE FORECAST AREA. AIR MASS AHEAD OF BOUNDARY HAS
BECOME MODERATELY UNSTABLE WITH AN AXIS OF SURFACE LIFTED INDICES
-6/-7 C OVER THE REGION. 850-500MB WINDS REMAIN ROBUST WITH VAD WIND
PROFILES DEPICTING 35-50KTS OF WIND THROUGH THE COLUMN WITH 60-65KTS
BETWEEN 12000-14000FT. MID LEVEL LAPSE RATES ACROSS THE SOUTHERN
PIEDMONT INTO THE COASTAL PLAIN HOVERING BETWEEN 7-7.5 DEG C/KM
WHILE LOW LEVEL LAPSE RATES CLOSE TO 8-8.5 DEG C/KM. THIS SUGGEST
THAT STORMS SHOULD INTENSIFY AS THEY MOVE INTO CENTRAL NC FROM THE
W-NW. DUE TO LAPSE RATES AND FREEZING LEVEL AROUND 12000 FT...MAIN
SEVERE WEATHER THREAT WILL BE DAMAGING WINDS AND LARGE HAIL.

BY 00Z...EXPECT MAIN BAND OF CONVECTION TO LIE SOUTH OF HIGHWAY
64...EXITING THE REGION BETWEEN 03-05Z. SEVERE THREAT WILL DIMINISH
BETWEEN 00Z-02Z AS WINDS ALOFT SUBSIDE AND AIR MASS STABILIZES DUE
TO LOSS OF HEATING. DRIER MORE STABLE AIR WILL ADVECT ON W-NW FLOW
BEHIND THE EXITING SYSTEM. CLOUDS WILL GRADUALLY DIMINISHES FROM
WEST-TO-EAST AFTER 05Z. MOST AREAS SHOULD BE MOSTLY CLEAR/PARTLY
CLOUDY BETWEEN 09-12Z. MINS TONIGHT SHOULD RANGE FROM LOWER 50S
ACROSS THE NW AND FAR NORTH TO THE MID/UPPER 50S ELSEWHERE.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 250 AM TUESDAY...

ANOTHER BOUNDARY WILL MOVE THROUGH THE CWA WEDNESDAY... ALTHOUGH
MOISTURE IS LIMITED CAN NOT RULE OUT CHANCE OF AN ISOLATED SHOWER OR
TWO. OTHERWISE WEAK HIGH PRESSURE BUILDING OVER THE AREA AT THE
SURFACE... WITH OMEGA BLOCK ALOFT.

HIGHS IN THE 70S. LOWS MOSTLY IN THE 50S.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 330 AM TUESDAY...

VERY LITTLE CHANGE TO THE PREVIOUS FORECAST. A WARMING TREND WILL
COMMENCE IN THE LATTER HALF OF THE FORECAST WITH MAINLY DRY WEATHER
ANTICIPATED.

MEDIUM RANGE GUIDANCE IN GOOD AGREEMENT ON OPENING UP THE CLOSED
VORTEX OVER SOUTHEAST CANADA/INTERIOR NEW ENGLAND AND MOVING IT EAST
INTO THE CANADIAN MARITIMES BY THE WEEKEND WITH A SHARP RIDGE
PRESENT OVER THE CENTRAL PORTION OF THE COUNTRY. WE STAY IN A DEEP
NORTHERLY FLOW THROUGH THE FIRST HALF OF THE WEEKEND... WITH LOW
LEVEL THICKNESSES AVERAGING AROUND 20M BELOW NORMAL. THIS SHOULD
KEEP TEMPS A CATEGORY OR TWO BELOW CLIMO... GENERALLY MID TO UPPER
70S FOR HIGHS AND LOW TO MID 50S FOR LOWS... QUITE PLEASANT FOR LATE
MAY. ONE FLY IN THE OINTMENT IS A POTENTIAL SHORTWAVE DROPPING SOUTH
OUT OF CANADA AND INTO THE REGION LATE FRIDAY INTO EARLY SATURDAY.
THE ECMWF IS STRONGER WITH THIS ENERGY... ACTUALLY DEVELOPING A SFC
WAVE INVOF GA/SC BORDER ALONG A STALLED FRONT. IF THIS SCENARIO WERE
TO COME TO FRUITION... THEN THERE WOULD BE THE POSSIBILITY OF SOME
RAIN IN FAR SOUTHERN NORTH CAROLINA. HOWEVER... THE ECMWF HAS
TRENDED WEAKER AND FURTHER SOUTH WITH THE SFC LOW AND ALSO WEAKER
WITH THE 500 MB WAVE...CLOSER TO THE GFS/CANADIAN SOLUTION. GIVEN
THIS... WILL KEEP POPS OUT OF THE FORECAST FRI/SAT.

THE WARMUP BEGINS IN EARNEST ON SUNDAY AS THE MID LEVEL RIDGE OVER
THE CENTRAL UNITED STATES SLIDES EAST ACROSS OUR AREA. HIGH TEMPS
SHOULD CLIMB INTO THE LOW 80S SUNDAY AND BE WELL INTO THE MID 80S ON
TUESDAY AS 850 MB TEMPS AND LOW LEVEL THICKNESSES RISE ABOVE CLIMO.
WITH RIDGING OVERHEAD... DRY WEATHER WILL PERSIST.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AS OF 230 PM TUESDAY...

BAND OF CONVECTION HAS DEVELOPED ALONG A E-SE MOVING SURFACE
BOUNDARY. THIS BOUNDARY EXPECTED TO LIE ACROSS THE SOUTHERN
PIEDMONT...THROUGH THE SANDHILLS...THEN INTO THE CENTRAL/SOUTHERN
COASTAL PLAIN BY 00Z WED. EXPECT A BRIEF PERIOD OF MVFR/IFR
CONDITIONS WITH THE PASSAGE OF THE CONVECTION. WIND GUSTS NEAR THE
SURFACE WILL GUSTS AS HIGH AS 40-45 KTS IN VICINITY OF THE STORMS.
AWAY FROM THE STORMS...WIND GUSTS AROUND 30 KTS WILL BE COMMON.
EXPECT CONVECTION IN THE TRIAD VICINITY UNTIL 21Z. AROUND KRWI AND
KRDU...CONVECTION EXPECTED BETWEEN 20-23Z. IN KFAY...EXPECT
CONVECTION BETWEEN 21Z-00Z.

W-NW FLOW BEHIND THE SURFACE BOUNDARY AND THE EXITING MID LEVEL
TROUGH WILL USHER DRIER MORE STABLE AIR INTO THE REGION. THIS WILL
RESULT IN GRADUAL CLEARING FROM WEST-TO-EAST AFTER MIDNIGHT.

EXPECT VFR CONDITIONS WED. WILL SEE SCATTERED TO BROKEN CUMULUS
FIELD DEVELOP DUE TO HEATING WITH CLOUD BASES BETWEEN 4500-6000FT.
SURFACE WINDS WED GENERALLY 250-280 DEGREES WITH SPEEDS OF 10 KTS.

VFR CONDITIONS SHOULD PREDOMINATE WED NIGHT THROUGH SUNDAY AS A
BROAD UPPER LEVEL TROUGH MAINTAINS ITS INFLUENCE ALONG THE ATLANTIC
SEABOARD.

&&

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

&&

SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...RHJ
LONG TERM...JFB
AVIATION...WSS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE RALEIGH NC
1016 AM EDT TUE MAY 20 2008

NCZ007>011-021>028-038>043-073>078-083>086-088-089-211015-
PERSON-GRANVILLE-VANCE-WARREN-HALIFAX-FORSYTH-GUILFORD-ALAMANCE-
ORANGE-DURHAM-FRANKLIN-NASH-EDGECOMBE-DAVIDSON-RANDOLPH-CHATHAM-WAKE-
JOHNSTON-WILSON-STANLY-MONTGOMERY-MOORE-LEE-HARNETT-WAYNE-ANSON-
RICHMOND-SCOTLAND-HOKE-CUMBERLAND-SAMPSON-
1016 AM EDT TUE MAY 20 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

THERE IS A RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EARLY
THIS EVENING ACROSS CENTRAL NORTH CAROLINA. THE MAIN SEVERE
WEATHER THREAT WILL BE DAMAGING WIND GUSTS AND LARGE HAIL. AT THIS
TIME...THE SEVERE WEATHER APPEARS MOST LIKELY TO OCCUR BETWEEN 2
PM AND 9 PM...BEGINNING IN THE NORTHWEST PIEDMONT IN THE EARLY
AFTERNOON...THEN EXPANDING EAST INTO THE COASTAL PLAIN AND
SANDHILLS BY 5 PM. THE GREATEST INSTABILITY WILL LIKELY RESIDE
OVER THE SOUTHERN PIEDMONT...SANDHILLS AND COASTAL PLAIN...THUS
THIS REGION HAS THE HIGHEST RISK OF EXPERIENCING SEVERE STORMS.

AN INCREASINGLY MOIST AND UNSTABLE AIR MASS...A SLOW MOVING COLD
FRONT...AND THE APPROACH OF AN UPPER LEVEL DISTURBANCE WILL
PROVIDE THE NECESSARY INGREDIENTS FOR THE DEVELOPMENT OF SEVERE
THUNDERSTORMS THIS AFTERNOON AND EARLY THIS EVENING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION WILL LIKELY BE NEEDED IN THE
NORTHWEST PIEDMONT BY 2 PM...AND ACROSS THE REMAINDER OF CENTRAL
NORTH CAROLINA BY 4 PM. SPOTTERS SHOULD REPORT SEVERE WEATHER AS
SOON AS IT IS SAFE TO DO SO. PLEASE STAY TUNED FOR LATER WATCHES
AND WARNINGS.

WSS

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE RALEIGH NC
220 PM EDT TUE MAY 20 2008

NCZ021-022-201900-
FORSYTH-GUILFORD-
220 PM EDT TUE MAY 20 2008

...SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS NORTHERN FORSYTH AND
NORTHERN GUILFORD COUNTIES THROUGH 300 PM EDT...

AT 225 PM EDT...DOPPLER RADAR INDICATED SHOWERS AND THUNDERSTORMS
WITH VERY HEAVY RAIN STRETCHING FROM STOKESDALE WEST ACROSS NORTHERN
FORSYTH COUNTY. THESE STORMS WERE MOVING EAST AROUND 40 MPH AND WILL
AFFECT STANLEYVILLE AND SUMMERFIELD SHORTLY AFTER 230 PM...AND
NORTHERN SECTIONS OF THE TRIAD AREA BEWEEN 230 AND 300 PM.

GUSTY WINDS OF 30 TO 40 MPH...SMALL HAIL AND DANGEROUS
CLOUD-TO-GROUND LIGHTNING CAN BE EXPECTED WITH THESE STORMS. PEOPLE
ENGAGED IN OUTDOOR ACTIVITIES SHOULD SEEK SHELTER IF THUNDER IS
HEARD.

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