Flash Flood in North Carolina, May 13, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
304 PM EDT FRI MAY 13 2005

.SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)...
FADING WEDGE CURRENTLY OVER THE NC FTHILLS AND PIEDMONT WITH SCT CU
OVER THE UPPER SAVANNAH RIVER VALLEY...TEMPERATURE DIFFERENCE
REMAINS NEARLY 10 DEGREES FROM SOUTH TO NORTH. SH/TS DEVELOPING
ALONG THE SPINE OF THE APPALACHIANS THIS AFTERNOON. DEVELOPMENT OF
FUTURE STORMS SHOULD SPREAD ACROSS THE REMAINDER OF THE SOUTHERN AND
CENTRAL MTNS THIS AFTERNOON AND EVENING. THESE STORMS WILL LIKELY
RESULT IN POCKETS OF HEAVY RAIN AS ENVIRONMENT WILL YIELD PW OF 1.2
WITH STORM MOTIONS OF ONLY 5-10 KTS. BY LATE AFTERNOON...TCU FROM
CAE TO GVL SHOULD GROW INTO SCT SH/TS. CORFIDI VECTORS INDICATES
THAT THESE STORMS WILL SLOWLY TRACK NE TOWARD THE UPPER SAVANNAH
VALLEY. SREF SHOWS THAT THIS PORTION OF OUR CWA WILL REMAIN THE MOST
UNSTABLE WITH CAPES BUILDING TO 1500-2500 J/KG. GIVEN THE AMOUNT OF
INSTABILITY...A FEW SVR EVENTS ARE POSSIBLE THIS AFTERNOON AND
EVENING ACROSS THE SOUTHERN/CENTRAL NC AND SC MTNS EAST ALONG THE
SAVANNAH VALLEY. CONVECTION SHOULD QUICKLY DISSIPATE AROUND MIDNIGHT.

NEW ENGLAND HIGH PRESSURE WILL SLIDE SE TONIGHT OVER THE
ATLANTIC...RESULTING IN A WEDGE DECAYING RETURN FLOW SAT. MORNING
CLOUDINESS SHOULD RAPIDLY MIX OUT AND WILL GRID A PARTLY SUNNY DAY.
H5 HEIGHTS BEGIN TO FALL FROM THE WEST AND WITH TEMPS/DWPTS RUNNING
IN THE 80/60 RANGE. INSTABILITY WILL INCREASE ENOUGH FOR DEEP
AFTERNOON CONVECTION...ESPECIALLY IN AFTERNOON LEE SFC TROF. WILL
TIME CHC POPS IN THE MTNS EARLY WITH CHCS SPREADING INTO THE WESTERN
PIEDMONT BY LATE SAT AFTERNOON.

WILL FOLLOW NAM FRONTAL TIMING FOR DETAILS...ALTHOUGH THE GFS IS
FAIRLY SIMILAR. NAM BRINGS THE FRONT INTO WESTERN NC SAT
NIGHT...REACHING THE ESCARPMENT BY SUNRISE SUNDAY. BOTH THE NAM AND
GFS INDICATE THE A LINE OF SH/TS WILL ACCOMPANY THIS FRONT...EXITING
THE CWA BY SUN EVENING. NEW PACKAGE POPS WERE RAISED TO CATE ALONG
THE TN BORDER TO LIKELY EAST. DRY HIGH PRESSURE WILL MOVE INTO
CONTROL SUNDAY NIGHT AND MON.

&&

.LONG TERM (TUESDAY THROUGH FRIDAY)...
MDLS SHOWING RUN TO RUN INCONSISTENCY WITH UPPER TROF OVER EAST
COAST...SHORT WAVES DIVING INTO IT AND ASSOCIATED SFC WARM FRONT AND
LOW PRESSURE SYSTEMS. LATEST GFS HAS TRENDED TOWARD A MORE SRN WARM
FRONT AND LOW PRESSURE TRACK FOR WED AND THU...IN LINE WITH PREVIOUS
ECMWF AND HPC GUIDANCE. LOOKS LIKE PRECIP SHOULD HOLD OFF OVER OUR
CWFA UNTIL TUE WHEN BEST MOISTURE AND LIFT MOVE INTO THE AREA. BEST
MOISTURE AND LIFT REMAIN ACROSS THE NORTH CLOSER TO WARM FRONT AND
LOW TRACK. TRAILING COLD FRONT DOES MOVE THRU THE AREA LATE FRIDAY.
HOWEVER...GENERAL WLY FLOW PREVAILS PROVIDING LITTLE IF ANY GULF
INFLOW. THEREFORE...HAVE POP GRADIENT OF CHC NORTH TO SLIGHT CHC IN
LINE WITH GUIDANCE.

TEMPS START OUT BELOW NORMAL TUE RISING TO NEAR NORMAL WED THRU FRI.
TEMP GUIDANCE A LITTLE SUSPECT ACROSS THE NORTH WED/THU. NUMBERS
WERE WELL BELOW NORMAL...WHICH LOOKS TOO LOW EVEN WITH CLOUDS AND
PRECIP. WENT NEAR NORMAL FOR THESE AREAS.

&&

.AVIATION...
WEDGE BOUNDARY EVIDENT IN MSAS/LAPS DATA AND SAT PIX. COOL STABLE
AIR OVER NC FOOTHILLS/PIEDMONT BECOMING WARM AND UNSTABLE OVER MNTS
AND UPSTATE INTO NE GA. HAVE KEPT A SHORT PERIOD OF MVFR CIGS/VIS
XCPT AT KHKY/KCLT WHICH ARE MORE FIRMLY ENSCONCED IN THE WEDGE. SRN
AND WRN SITES ALSO HAVE THE POTENTIAL FOR TSRA AS ATMOS UNSTABLE AND
CONVECTION ALREADY FIRING OVER THE NC MTNS. KEPT KHKY/KCLT WITH MVFR
CIGS INTO THE EVENING AS LOW LEVEL MOISTURE REMAINS HIGH AND UPGLIDE
DEVELOPS.

WENT CLOSER TO THE NAM SOLN OVERNIGHT SINCE IT USUALLY DOES BETTER
IN WEDGE SITUATIONS. BRING ALL AFTERNOON VFR SITES BACK TO MVFR
ABOUT 02Z WITH VCSH AS LOW LEVEL MOISTURE INCREASES AND ISENTROPIC
UPGLIDE DEVELOPS. CIGS LOWER TO IFR FIRST AT KHKY...THEN KCLT
OVERNIGHT WHERE MOISTURE DEEPER AND ISENTROPIC LIFT BETTER. WENT
MVFR VSBY ALL LOCATIONS OVERNIGHT...BUT CANNOT RULE OUT ISOLATED
IFR. NAM SCOURS LOW LEVEL MOISTURE BY 14Z AS SWLY FLOW DEVELOPS AND
DRIER AIR MASS MOVES IN. ALL SITES VFR AT THAT TIME.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.
&&

SHORT TERM...NED
LONG TERM...RWH
AVIATION...RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
604 AM EDT FRI MAY 13 2005

GAZ010-017-018-026-028-029-NCZ033>037-048>059-062>072-082-
SCZ001>014-019-141015-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-CALDWELL-
ALEXANDER-IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-
BUNCOMBE-MCDOWELL-BURKE-CATAWBA-ROWAN-GRAHAM-NORTHERN JACKSON-
MACON-SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-POLK-RUTHERFORD-
CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION-
OCONEE MOUNTAINS-PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-
GREATER OCONEE-GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-
CHEROKEE-YORK-ANDERSON-ABBEVILLE-LAURENS-CHESTER-GREENWOOD-
604 AM EDT FRI MAY 13 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR UPSTATE SOUTH CAROLINA...
MUCH OF WESTERN NORTH CAROLINA... AND EXTREME NORTHEAST GEORGIA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY ACROSS
MUCH OF OUR FORECAST AREA...ALTHOUGH THE HIGHEST CHANCES OF RAIN
WILL EXIST ACROSS THE FAR WESTERN MOUNTAINS OF NORTH CAROLINA AS
WELL AS ALL OF NORTHEAST GEORGIA AND THE ADJACENT WESTERN AREAS OF
SOUTH CAROLINA...OR ROUGHLY ALONG AND WEST OF A LINE FROM CHEROKEE
AND FRANKLIN...TO WALHALLA...ANDERSON AND GREENWOOD. CHANCES OF
THUNDERSTORMS DECREASE SIGNIFICANTLY TODAY AS ONE HEADS NORTH INTO
THE NORTHERN FOOTHILLS AND NORTHWEST PIEDMONT OF NORTH CAROLINA.
WITH DAYTIME HEATING...ONE OR TWO STORMS IN THE FAR WESTERN FORECAST
AREA COULD BECOME STRONG AND IT IS POSSIBLE THAT PERHAPS STORMS
MAY APPROACH SEVERE STATUS IN THE FAR WEST. WIDESPREAD SEVERE
WEATHER IS NOT ANTICIPATED TODAY...HOWEVER.

WITH THE LOSS OF DAYTIME HEATING...ANY SHOWERS AND STORMS ARE
EXPECTED TO WEAKEN QUICKLY THIS EVENING. HOWEVER...SCATTERED
SHOWERS COULD AFFECT THE FAR WESTERN MOUNTAINS OF NORTH CAROLINA
AND PERHAPS THE MOUNTAINS OF NORTHEAST GEORGIA OVERNIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A MAJOR COLD FRONT IS FORECAST TO CROSS THE REGION SATURDAY NIGHT.
THIS WEATHER FEATURE WILL BE ACCOMPANIED BY SHOWERS AND
THUNDERSTORMS...ALTHOUGH SHOWERS AND STORMS SHOULD BE ONGOING LONG BEFORE
THE FRONT ITSELF CROSSES THE AREA. WIND SHEAR AND FORCING FOR STRONG
CONVECTION WILL BE A BIT GREATER...SO WE WILL HAVE TO WATCH THE
NEXT FEW RUNS OF DATA CLOSELY TO DETERMINE THE STRENGTH OF ANY
SEVERE WEATHER THREAT. THE FRONT IS EXPECTED TO BE CLOSE ENOUGH TO
OUR AREA SUNDAY MORNING TO PROVIDE SCATTERED SHOWERS FOR AREAS
ALONG AND ADJACENT TO INTERSTATE 77...WITH DRYING TREND FORECAST
FOR SUNDAY AFTERNOON. FAIR WEATHER IS THEN EXPECTED TO DOMINATE
THE FORECAST UNTIL ANOTHER FRONTAL SYSTEM APPROACHES WITH
SCATTERED SHOWERS AND THUNDERSTORMS IN THE WEST THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS COULD BE NEEDED LATER THIS AFTERNOON IN THE FAR WESTERN
MOUNTAINS OF NORTH CAROLINA AS WELL AS FAR WESTERN UPSTATE SOUTH
CAROLINA AND ALL OF EXTREME NORTHEAST GEORGIA IF STRONG STORMS DO
DEVELOP. SPOTTERS COULD ALSO BE NEEDED LATE SATURDAY AFTERNOON
INTO SATURDAY NIGHT AS THE FRONT BEGINS TO CROSS THE REGION.

44