Severe Thunderstorm Warning 71, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
310 PM CDT MON JUN 23 2003

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...
12Z SOUNDING ANALYSIS CAPE (5K+) BY AWIPS SKEWED BY THE SONDE
APPARENTLY PENETRATING A THUNDERSTORM DURING FLIGHT.  18Z SOUNDING
ANALYSIS MORE REASONABLE.  RERUN OF THE 12Z ANALYSIS HAS A CAPE
SIMILAR TO THE LATER RUN.  SCAN STORM RELATIVE CAPES OF STORMS
MOVING THROUGH CWA THIS MORNING RANGED BETWEEN 1500 AND 3000...
DEPENDING ON STORM INTENSITY.

ETA FAMILY AND GFS IN NEAR AGREEMENT WITH QPF FORECAST.  LONG
TRAINING OF SHORTWAVES ALONG STATIONARY FRONT AFFECTING QPF OVER
CWA.  NO CHANGE TO CURRENT GRID VALUES.  JET AND UPPER LEVEL FLOW
PARALLELS FRONT.  NO KICKER EVIDENT TO ACCELERATE FRONT AWAY FROM
CWA.  MEANWHILE MOISTURE AND WIND CONVERGENCE (ESPECIALLY THE
PERSISTENT LOW LEVEL JET) AND THETA E LAPSE RATES CONTINUE UNSTABLE
ATMOSPHERE.  EXPECT SOME INCREASE IN STABILITY WHEN THE FRONT
FINALLY MOVES.  MEANWHILE CONVECTION CONTINUES TO FIRE IN WESTERN
ZONES ALONG OUTFLOW BOUNDARIES AT THE 925 AND 850MB ELEVATIONS.  FOR
NOW HAVE MOSTLY MID LEVEL SHOWERS AND CLOUDS...BUT THAT MAY CHANGE
IF TWO OR MORE BOUNDARIES COALESCE.

EXPECT ATMOSPHERE TO STABILIZE SOMEWHAT BY WEDNESDAY AS THE FRONT
DEFINITELY MOVES OUT OF THE REGION.  NEVERTHELESS WILL HAVE TO KEEP
A WEATHER EYE OUT FOR STRAY CONVECTION AND POSSIBLE SEVERE EVENTS.
MODELS EVENTUALLY START A COOLING AND DRYING TREND ABOUT WEDNESDAY
AS THEY MOVE A SURFACE HIGH AND UPPER RIDGE INTO THE REGION.  THIS
MAY BE FAST SINCE MODEL TREND HAS BEEN TO SLOW FEATURES DOWN EACH
RUN OVER THE PAST FEW RUNS.  MCNULTY

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
12Z GFS AND ETA CYCLES BOTH PLACE CWA IN DRY AREA ON THURSDAY. LEFT
EVENING WORDING IN FOR WEDNESDAY NIGHT PERIOD...WITH LAST OF
EXPECTED UVV FROM UPPER TROUGH AT THAT TIME. GOOD SUBSIDENCE AND
DRYING NOTED BY BOTH MODELS FOR WEDNESDAY NIGHT AND BETTER PART OF
THURSDAY. ETA MODEL IS 12 TO 18 HOURS FASTER THAN GFS IN BRINGING
BACK DOOR COLD FRONT THROUGH CWA FROM CANADA. ETA BRINGS FRONT
THROUGH THURSDAY AFTERNOON. GFS BRINGS FRONT THROUGH ON FRIDAY.
LEANING ON THE GFS FRONTAL POSITIONING HERE FOR NOW GIVEN RECENT
PROBLEMS MODELS HAVE HAD WITH CURRENT ULTRA SLOW FROPA. VERY COLD
MID-LEVELS AND NOT SO BAD LAPSE RATES WOULD SUPPORT SOMETHING IN THE
WAY OF COLD AIR INSTABILITY SHOWERS...EXCEPT THERE IS NOT ENOUGH
MOISTURE AROUND. KEEPING THURSDAY THROUGH EXTENDED DRY...WITH WAA
PATTERN SETTING UP OVER CWA BY SUNDAY. KEPT NE CORNER OF CWA A BIT
COOLER THAN THE REST OF CWA DAYS 4 AND 5 FOR ANY CAA AIR POSSIBLY
RESIDING OVER THAT AREA WITH BACK DOOR FRONT. DULY NOTED THE JET
STRUCTURE ALOFT WITH FROPA SCENARIO FOR FRIDAY...BUT AGAIN...SIMPLY
GOING WITH THE IDEA THAT LIMITED MOISTURE MAY GENERATE SOME
CLOUDS...BUT NOT ANYTHING IN THE WAY OF PRECIP. GFS GENERATING JUST
A FEW HUNDREDTHS OF AN INCH ON DAY 4 WITH 12Z RUN.

00Z MEX ENSEMBLES NUMBERS CONTINUE UPWARD TREND...ESPECIALLY OVER
WESTERN HALF OF CWA IN THE OUT PERIODS. AGAIN...MENTIONED THE
KEEPING OF COOLER MAX T VALUES OVER NE CWA AS SUCH. UPDATED THE
GRIDS...MADE SOME CHANGES.   DORN

.ABR...FLOOD WATCH FOR FAR NORTHEASTERN ZONES THIS AFTERNOON AND
TONIGHT.

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-241015-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
520 AM CDT MON JUN 23 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF CENTRAL...
NORTH CENTRAL AND NORTHEAST SOUTH DAKOTA...AS WELL AS
BIG STONE AND TRAVERSE COUNTIES IN MINNESOTA.

.DAY ONE...TODAY AND TONIGHT

A NEARLY STATIONARY FRONTAL BOUNDARY OVER EASTERN SOUTH DAKOTA WILL
LIKELY BE THE FOCUS FOR THUNDERSTORM DEVELOPMENT AGAIN THIS
AFTERNOON AND EVENING...ESPECIALLY IN AN AREA ALONG A LINE FROM
ABERDEEN TO REDFIELD EASTWARD TO THE MINNESOTA BORDER. SOME OF THESE
STORMS MAY BE SEVERE AND MAY CONTAIN VERY HEAVY RAINFALL. A FLOOD
WATCH IS IN EFFECT FOR ROBERTS...GRANT...BIG STONE AND TRAVERSE
COUNTIES WHERE HEAVY RAIN ALSO OCCURRED SUNDAY NIGHT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

MOIST AND UNSTABLE CONDITIONS OVER THE UPPER MIDWEST WILL ALLOW THE
CHANCE OF THUNDERSTORMS TO CONTINUE TUESDAY AND TUESDAY NIGHT. SOME
OF THE STORMS COULD BE SEVERE DURING THE AFTERNOON AND EVENING
HOURS. NO HAZARDOUS WEATHER IS EXPECTED WEDNESDAY THROUGH SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS LIKELY LATER TODAY OR TONIGHT...MAINLY EAST OF
A LINE FROM ABERDEEN TO REDFIELD.

PARKIN