Flash Flood in North Carolina, August 18, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
828 PM EDT WED AUG 17 2005

.SHORT TERM (REST OF TONIGHT)...
MINOR CHANGES TO TONIGHTS PACKAGE WITH CONVECTION RUNNING
PAST MIDNIGHT IN PIEDMONT OF THE CAROLINAS.  POPS INCREASED
IN EASTERN CWA AS OUTFLOW INDUCED LINE OF SHOWERS/THUNDERSTORMS
CONTINUES NORTHWARD UP I77. CONVECTION LINGERING IN MTNS SO
LIKE POPS WILL CONTINUE THERE.  LATEST MOS GUIDANCE CONTINUES
LIKELY AND HIGH POPS FOR THURSDAY SO NO CHANGES PAST TONIGHT.

&&

.PREVIOUS DISCUSSION...
(ISSUED 232 PM EDT WED AUG 17 2005)

SHORT TERM (TONIGHT THROUGH SATURDAY)...
AN EMBEDDED SHORTWAVE RIDING EAST OVER THE FLAT SOUTHERN RIDGE WILL
BRUSH THE NORTH CAROLINA MOUNTAINS TONIGHT. LOW LEVEL FLOW IS
EXPECTED TO BECOME INCREASINGLY UPSLOPE INTO THE EASTERN ESCARPMENT
OF THE MOUNTAINS AS WELL...WHICH COULD POSE A HYDRO PROBLEM WITH
PREVAILING LIGHT WESTERLY FLOW ABOVE 700 MB. SOUTHWEST MOUNTAIN
CONVECTION SHOULD CONTINUE TO BECOME INCREASINGLY WIDESPREAD BY
EVENING...WITH VERY SLOWLY MOVING OR NEARLY ANCHORED CELLS NEAR THE
BLUE RIDGE AND THE WESTERN FOOTHILLS. DIFFERENTIAL HEATING ALONG THE
STALLED FRONT IS ALSO KEEPING SOME THERMAL CONTRAST IN PLACE...AND
CONVERGENCE ALONG THE BOUNDARY SHOULD AID SCATTERED THUNDERSTORMS
OVER THE PIEDMONT THROUGH EVENING...WITH MORE NUMEROUS THUNDERSTORMS
OVER THE WESTERN UPSTATE...WHERE BOTH FRONTAL AND TERRAIN FORCING
COULD COME INTO PLAY.

ONGOING CONVECTION WILL BE MONITORED THROUGH ISSUANCE TIME...AND AN
SPS HIGHLIGHTING THE HEAVY RAIN POTENTIAL WILL LIKELY BE NEEDED. A
FLASH FLOOD WATCH REMAINS POSSIBLE...BUT THE THREAT AREA WILL BE
DIFFICULT TO PIN DOWN.

THE LOW LEVEL CONVERGENCE AXIS AND DEEPEST MOISTURE SHIFT BACK TO
THE WESTERN FRINGE OF THE MOUNTAINS ON THURSDAY. THE SURFACE FRONT
APPEARS TO HAVE NEARLY WASHED OUT ON THE NAM...WHILE DEEPER MOISTURE
FROM NC TO VA KEEPS WEAK THERMAL PACKING IN PLACE ACROSS THE CWFA ON
THE GFS. MORE ABUNDANT CLOUDS WILL KEEPS MAXES ONE TO TWO CATEGORIES
COOLER IN MOST LOCATIONS. SLOWLY MOVING THUNDERSTORMS COULD FURTHER
ENHANCE MOUNTAIN RAINFALL PROBLEMS FOR TOMORROW.

BOTH THE NAM AND GFS SHOW A H5 S/W RIPPLING WITHIN THE NW FLOW OVER
THE MID MISSISSIPPI VALLEY THU NIGHT. NAM DEPICTS THAT AN MCS WILL
ACCOMPANY THE S/W...HOWEVER THE FEATURE FADES AS IT CROSSES THE MTNS
15Z FRI. PLAN TO KEEP LIKELY TO HIGH CHC POPS WEST TO EAST ACROSS THE
CWA THU EVENING TO HANDLE DISSIPATING DAYTIME CONVECTION. BY FRI
AFTERNOON...CAPES SHOULD POOL TO 2K J/KG. FWC AND MET MOS SUPPORTS
CHC POPS RUNNING INTO FRI EVENING...WORDED FORECAST WILL USE 30%
POP.

LONG TERM (SATURDAY NIGHT THROUGH WEDNESDAY)...
ECMWF AND GFS SHOW S/W RIDGING BUILDING OVER THE CWA DURING THE DAY
ON SATURDAY AHEAD OF THE APPROACHING TROF. H85 TEMPS WARM TO 20C
FROM THE SW WITH WEAK DOWNSLOPE FLOW. I BELIEVE THAT SATURDAY WILL
BE THE WARMEST DAY OF THE WEEKEND AND EXTENDED PERIOD...WITH HIGHS
REACHING INTO THE 90-95 RANGE EAST OF THE MTNS. THE WARM TEMPS WILL
COMBINE WITH DWPTS IN THE L70S TO YIELD CAPES 2K-3K J/KG BY THE LATE
AFTERNOON. LITTLE IS SEEN AS A CONVECTIVE TRIGGER...HOWEVER RIDGETOP
CONVERGENCE SHOULD BE ENOUGH OF FOR INITIATION...STORMS SHOULD SPREAD
EAST OFF THE MTNS DURING THE AFTERNOON. NATURALLY...COVERAGE WILL BE
THE GREATEST OVER THE MTNS WITH LESSER AMOUNTS FURTHER EAST...WILL
USE CHC POPS.

CLOUD COVER SHOULD INCREASE MONDAY NIGHT OVER THE FA AS FRONTAL
BOUNDARY MOVES ACROSS KY/TN. THE COLD FRONT SHOULD ENCOUNTER THE
SOUTHERN APPALACHIANS MIDDAY SUN AND CONTINUE TO SLOWLY MOVE EAST
DURING THE REST OF THE DAY. GFS CONVECTIVE SCHEMES DO NOT GENERATE A
LARGE AMOUNT OF RAINFALL FROM THE EXPECTED CONVECTIVE LINE. WILL
CARRY HIGH CHC/LOW LIKELY POPS FOR THE MTNS WITH 40-30% EAST. GIVEN
THE TIMING OF THE FRONT...WILL KEEP TEMPS A FEW DEGREES COOLER THAN
EXPECTED ON SAT. CHC WILL REMAIN IN THE EAST SUN NIGHT AS FRONT
COMPLETES IT/S TRIP ACROSS THE FA.

MON THROUGH WED...CANADIAN HIGH PRESSURE WILL BUILD OVER THE
FA...WITH IT/S 1020+MB CENTER REMAINING NORTH OF THE WESTERN
CAROLINAS. GFS HAS BEEN INCONSISTENT WITH THE POSITION AND TIMING OF
THE FRONT POTENTIALLY STALLING OUT. GIVEN THE LATEST ECMWF/GFS/HPC
GUIDANCE I WILL FORECAST THE HIGH TO TOTALLY COVER THE FA DURING THE
PERIOD. TEMPERATURES SHOULD PAN OUT AROUND CLIMO WITH DWPTS RANGING
IN THE LOW TO MID 60S EAST OF THE MTNS...EVEN BETTER IN THE MTNS. I
KEPT A DIURNAL SLGT CHC EACH AFTERNOON AND EVENING.

AVIATION...
THUNDERSTORM COVERAGE WILL INCREASE ACROSS THE SOUTHWEST
MOUNTAINS...THREATENING KAVL THROUGH THE LATE AFTERNOON AND EVENING
HOURS. WITH LOW LEVEL EASTERLY UPSLOPE AND WESTERLY STEERING WINDS
ABOVE 700 MB...THUNDERSTORMS WILL LIKELY TRIGGER NEAR THE HIGHER
TERRAIN THROUGH THE EVENING HOURS. A SECONDARY MAXIMA OF
THUNDERSTORMS IS LIKELY ALONG THE WEAK FRONTAL BOUNDARY ORIENTED
WEST TO EAST ACROSS THE REGION. ASIDE FROM HIGHER COVERAGE NEAR
KAVL...TSRA SHOULD REMAIN IN THE VICINITY FROM KAND TO KGSP TO
KHKY...WITH SMALLER CHANCES NEAR KCLT. SOUTHEAST UPGLIDE AND UPSLOPE
FLOW SHOULD STEADILY PRODUCE LOWERING MVFR CIG OVERNIGHT...WITH
CONTINUED SCATTERED SHOWERS EXPECTED. THE OVERVIEW PERIOD SHOULD BE
A RELATIVE LULL...BUT WITH FAIRLY SOLID MVFR OR SLOWLY IMPROVING VFR
CIG BY NOON THU.

&&

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

SHORT TERM...VAD

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
621 AM EDT WED AUG 17 2005

GAZ010-017-018-026-028-029-NCZ033>037-048>059-062>072-082-
SCZ001>014-019-181030-
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 NC-
OCONEE MOUNTAINS-PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-
GREATER OCONEE-GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-
CHEROKEE-YORK-ANDERSON-ABBEVILLE-LAURENS-UNION SC-CHESTER-
GREENWOOD-
621 AM EDT WED AUG 17 2005

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS WILL ONCE AGAIN THREATEN THE REGION THIS
AFTERNOON AND TONIGHT. LOCALLY STRONG STORMS ARE POSSIBLE...
PRODUCING HEAVY RAIN...FREQUENT LIGHTNING AND GUSTY WIND.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A DAILY CHANCE OF THUNDERSTORMS CONTINUE INTO THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
835 PM EDT WED AUG 17 2005

SCZ007>009-013-014-180130-
CHEROKEE-CHESTER-SPARTANBURG-UNION-YORK-
840 PM EDT WED AUG 17 2005

...STRONG THUNDERSTORMS WERE AFFECTING CHEROKEE...CHESTER...
SPARTANBURG...UNION AND YORK COUNTIES...

AT 840 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS MOVING VERY SLOWLY ACROSS THE EASTERN PART OF
UPSTATE SOUTH CAROLINA. STROMS WERE MOVING VERY LITTLE BUT NEW
STORMS WERE DEVELOPING TO THE NORTH AND NORTHEAST.

PEA SIZE HAIL...AND WINDS 30 TO 40 MPH ARE POSSIBLE WITH THESE STORMS.

HEAVY RAINS WILL CAUSE PONDING ON ROADS AND MAY FLOOD SOME LOW LYING
AREAS SUCH AS DITCHES AND UNDERPASSES.

FREQUENT LIGHTNING IS OCCURRING WITH THESE STORMS. IF OUTDOORS...STAY
AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES. MOVE INDOORS IF
POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND DOORS AND AVOID
USING TELEPHONES UNLESS IT IS AN EMERGENCY. TRY TO UNPLUG
UNNECESSARY ELECTRICAL APPLIANCES BEFORE THE THUNDERSTORM APPROACHES.

RB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
856 PM EDT WED AUG 17 2005

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0400 PM     TSTM WND DMG     4 SSW GREENVILLE        34.79N 82.40W
08/17/2005                   GREENVILLE         SC   BROADCAST MEDIA

            FOX CHANNEL 21 REPORTED 7 TO 10 TREES DOWN ON DUKE STREET
            NEAR GREENVILLE MEMORIAL HOSPITAL. TIME OF EVENT WAS
            DERIVED FROM RADAR.

&&

OUTLAW