Flash Flood and Hail in South Dakota, July 23, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
337 PM CDT WED JUL 23 2008

.SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
THUNDERSTORMS BEGINNING TO DEVELOP OVER THE BLACK HILLS THIS
AFTERNOON WITH CU DEVELOPMENT FARTHER NORTH ACROSS THE WESTERN
DAKOTAS ALONG A DRY LINE. DEWPOINTS NEAR 70 NOTED ACROSS THE
WESTERN COUNTIES THIS AFTERNOON WITH LOW 50S DEWPOINTS WEST OF THE
DRY LINE. EXPECTING ADDITIONAL DEVELOPMENT ACROSS WESTERN AND
EVENTUALLY INTO CENTRAL SOUTH DAKOTA LATER THIS AFTERNOON AND INTO
THE EVENING HOURS. CLOUD COVER ACROSS THE EAST HAS KEPT
INSTABILITY AT BAY AND WILL AWAIT LLJ DEVELOPMENT OVERNIGHT FOR
ANY POSSIBLE THUNDERSTORM ACTIVITY. LAPS DATA SHOWING 2000-2500
J/KG CAPE ACROSS WESTERN CORSON AND WESTERN DEWEY COUNTIES WITH NO
CAP. CAPES DROP OFF SIGNIFICANTLY EAST OF THE MISSOURI WHERE CLOUD
COVER WAS PRESENT ALL DAY. HIGH PWATS FROM 1.50 TO NEARLY 2 INCHES
THIS EVENING INDICATES POTENTIAL FOR HEAVY RAIN WITH ANY
THUNDERSTORMS THAT DEVELOP. BEST INSTABILITY THIS EVENING LIES
ALONG THE MISSOURI RIVER VALLEY...WITH ELEVATED INSTABILITY
DEVELOPING LATER TONIGHT ACROSS THE EAST AS LLJ STRENGTHENS. ALL
IN ALL...A RATHER DIFFICULT CONVECTIVE FORECAST THIS
EVENING/OVERNIGHT THANKS IN PART TO THE CLOUD COVER TODAY. DID
BACK OFF FROM THE LIKELY POPS ACROSS THE EAST AND WENT WITH
GENERALLY 40 TO 50 PERCENT CHANCES. COULD SEE ADDITIONAL
THUNDERSTORM ACTIVITY TOMORROW AFTERNOON AS THE ACTUAL FRONTAL
BOUNDARY MOVES THROUGH THE AREA. BY THURSDAY AFTERNOON CAPE VALUES
APPROACH 2000-2500 J/KG ACROSS THE EASTERN CWA. DECENT SHEAR
VALUES ALSO RESIDE ACROSS THE EASTERN COUNTIES. BUMPED UP POPS
SLIGHTLY OUT OF THE SLIGHT CHANCE CATEGORY. FRONTAL BOUNDARY LOOKS
TO EXIT THE AREA TO THE SOUTHEAST BY THURSDAY EVENING BUT WILL
MAINTAIN SLIGHT CHANCE POPS NEAR THE FRONT INTO THURSDAY EVENING.

TEMPS WILL STAY ON THE WARM SIDE TOMORROW AS 850 MB TEMPS INCREASE
SLIGHTLY. WITH MORE SUNSHINE EXPECTED...WILL SEE HIGHS APPROACHING
90 DEGREES IN SOME AREAS THURSDAY AFTERNOON.

.LONG TERM...FRIDAY THROUGH WEDNESDAY
TRENDS IN UPPER LEVEL FLOW DURING THIS PERIOD CAN BE DEFINED AS
GENERALIZED RIDGING IN THE WEST WITH UPPER TROUGH IN THE
EAST...MARKED BY SEVERAL SHORTWAVES TRAVERSING THIS FLOW. WITH
LITTLE FAITH IN GUIDANCE ABILITY TO HANDLE SUBTLE FEATURES WITH
THIS TYPE PATTERN...HAVE FOCUSED ELIMINATING PRECIPITATION DURING
SEVERAL PERIODS AND IN CERTAIN AREAS...HOWEVER AM HAVING DIFFICULT
TIME NOT ADDING SLIGHT CHANCE/CHANCE ACROSS MUCH OF THE REGION
OVER THE LENGTH OF THE PERIOD. HAVE ALSO MADE MINOR ADJUSTMENTS TO
TEMPERATURE TRENDS OVER MAV/MEX GUIDANCE FOR WESTERN COUNTIES AS
RECENT WET TREND WILL SKEW FORECAST MAX GUIDANCE BASED OFF A DRIER
CLIMATOLOGY.

&&

.AVIATION...
RATHER COMPLEX AVIATION FORECAST FOR THE NEXT 24 HOURS WITH
SHOWERS SCATTERED ACROSS THE CWA...AND MAINLY VFR ISOLD MVFR
CIGS/VISBY. THESE CONDITIONS ARE EXPECTED TO PERSIST DURING THE
AFTERNOON HOURS WITH AN ISOLD CB AS WELL.  CB ACTIVITY IS
EXPECTED TO BECOME MORE WIDESPREAD DURING THE MID TO LATE
AFTERNOON ACROSS WESTERN SD AND BEGIN MOVING EAST...EFFECTING
KPIR/KMBG...BUT WILL LIKELY SEE A DECREASE IN ACTIVITY AS THIS
LINE MOVES TOWARD THE ATY/KABR TERMINALS LATE THIS EVENING. SYSTEM
WILL EVOLVE INTO A POSSIBLE HEAVY RAIN PRODUCER WITH BRIEF MVFR/IFR
CIGS/VISBY POSSIBLE AS IT MOVES THROUGH KABR/KATY AND POINTS EAST.
AS ALWAYS DURING THE SUMMER CONVECTIVE SEASON...AREAS THAT SEE
HEAVY RAINFALL TODAY COULD EXPERIENCE FOG DEVELOPMENT OVERNIGHT.
WE WILL ALSO SEE A SECOND FRONTAL FEATURE MOVE INTO THE REGION
THURSDAY...AND WITH PLENTY OF MOISTURE AROUND...MORE THUNDERSTORM
DEVELOPMENT FOR MUCH OF THE AFTERNOON.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

SHORT TERM...TMT
LONG TERM...CONNELLY
AVIATION...CONNELLY

WEATHER.GOV/ABERDEEN

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE ABERDEEN SD
414 PM CDT WED JUL 23 2008

SDZ003>005-009-010-015>017-033>037-045-048-051-242115-
CORSON-CAMPBELL-MCPHERSON-WALWORTH-EDMUNDS-DEWEY-POTTER-FAULK-
STANLEY-SULLY-HUGHES-HYDE-HAND-JONES-LYMAN-BUFFALO-
414 PM CDT WED JUL 23 2008 /314 PM MDT WED JUL 23 2008/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL SOUTH
DAKOTA AND NORTH CENTRAL SOUTH DAKOTA.

.DAY ONE...TONIGHT

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO
DEVELOP ACROSS WESTERN AND CENTRAL SOUTH DAKOTA INTO THE EVENING
HOURS. SOME STORMS MAY PRODUCE LARGE HAIL AND HEAVY RAIN ACROSS
CENTRAL SOUTH DAKOTA THIS EVENING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORMS ARE POSSIBLE AGAIN THURSDAY AFTERNOON...SOME OF
WHICH MAY BE SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY THIS EVENING ACROSS PORTIONS
OF CENTRAL SOUTH DAKOTA.

MNZ039-046-SDZ006>008-011-018>023-242115-
TRAVERSE-BIG STONE-BROWN-MARSHALL-ROBERTS-DAY-SPINK-CLARK-
CODINGTON-GRANT-HAMLIN-DEUEL-
414 PM CDT WED JUL 23 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL
MINNESOTA AND NORTHEAST SOUTH DAKOTA.

.DAY ONE...TONIGHT

THUNDERSTORMS ARE POSSIBLE OVERNIGHT ACROSS EASTERN SOUTH DAKOTA
AND WEST CENTRAL MINNESOTA. A FEW STORMS COULD BE SEVERE WITH
LARGE HAIL AND HEAVY RAIN POSSIBLE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORMS ARE POSSIBLE AGAIN THURSDAY AFTERNOON...SOME OF
WHICH MAY BE SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TONIGHT.

TMT