Severe Thunderstorm Warning 12, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
250 PM CDT WED MAY 7 2003

.SHORT TERM...
MAIN FORECAST CONCERNS CONTINUE TO BE PRECIPITATION CHANCES
THROUGHOUT THE PERIOD. A WEAK UPPER RIDGE WILL SLIDE ACROSS THE
EASTERN PLAINS TONIGHT AHEAD OF AN APPROACHING TROUGH FROM THE WEST.
AT 19Z...A SURFACE LOW WAS LOCATED FROM EASTERN COLORADO TO
SOUTHEASTERN WYOMING WITH AN INVERTED TROUGH EXTENDING NORTHEASTWARD
INTO WESTERN SOUTH DAKOTA. THUNDERSTORMS HAD ALREADY BEGUN TO
DEVELOP ALONG THIS TROUGH IN FAR WESTERN SOUTH DAKOTA...AND EXPECT
THEY SHOULD HOLD TOGETHER AS THEY MOVE EAST...AS THE 19Z LAPS DATA
WAS INDICATING LIS OF -4 TO -6 AND CAPES AROUND 1700 J/KG IN THE FAR
WESTERN CWA. WILL KEEP THE CHANCE OF PRECIPITATION GOING INTO
THURSDAY AS THE UPPER WAVE PUSHES OVER WESTERN SOUTH DAKOTA...AND
THE INVERTED TROUGH MOVES VERY LITTLE. BY THURSDAY EVENING...THE
SURFACE LOW WILL BE APPROACHING IOWA...SO THE PRECIP SHOULD BECOME
MORE OF A WRAP AROUND/OVERRUNNING RAIN EVENT. THE SYSTEM WILL NOT BE
MOVING VERY QUICKLY...SO WILL KEEP LINGERING RAIN SHOWERS GOING INTO
FRIDAY. ANOTHER SURFACE LOW DEVELOPS OVER EASTERN COLORADO ON
FRIDAY...THEN TAKES JUST ABOUT THE SAME PATH TO THE
NORTHEAST...WHICH LOOKS TO KEEP THE CHANCE OF RAIN SHOWERS GOING
FRIDAY NIGHT AND SATURDAY AS WELL. DO NOT EXPECT ANY CONVECTION WITH
THIS SYSTEM AS IT WILL BE MOVING FASTER AND MODELS INDICATING THE
MAIN AREA OF INSTABILITY REMAINING SOUTH OF THE STATE.

TEMPERATURES SHOULD REMAIN BELOW NORMAL THROUGHOUT THE PERIOD AS
FALLING H85 TEMPS AND AN ABUNDANCE OF CLOUD COVER BEGINNING THURSDAY
MORNING WILL HELP KEEP THEM DOWN. LOOKING AT MAINLY 40S FOR LOWS AND
50S TO LOWER 60S FOR HIGHS.

.EXTENDED...
MEDIUM RANGE MODELS IN FAIR AGREEMENT TO START.  ECMWF AND GFS
DEVELOP DISPARITY ABOUT DAY 5 WITH THE ECMWF LAGGING GFS BY ABOUT 12
HOURS.  GENERAL POSITION OF NORTH CENTRAL PLAINS LOW SYSTEM TRACKS
ARE SIMILAR EVEN WITH THE TIMING DIFFERENCE.  GOOD DYNAMICS ALOFT
WITH INSTABILITY AND CONVECTIVE POTENTIAL FOR AT LEAST SHOWERS AND
POSSIBLY THUNDER ON SUNDAY.  EXPECT RATHER GUSTY WINDS AS THE LOW
SYSTEM WINDS UP WITH THE TIGHTEST GRADIENTS IN THE SOUTH DAKOTA
REGION.  WINDS GRADUALLY SLACKEN AS THE EXTENDED PERIOD PROGRESSES.
MONDAY AND TUESDAY TO BE DRY WITH NEAR OR SLIGHTLY BELOW NORMAL
TEMPERATURES.  PRECIP POTENTIAL RETURNS LATE ON DAY 7 (EARLY
WEDNESDAY).

.ABR...NONE.

PARKIN/MCNULTY

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-081045-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
550 AM CDT WED MAY 7 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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

WINDS WILL BECOME SOUTHEAST TODAY AND INCREASE TO 15 TO 30 MPH WITH
GUSTS TO 40 MPH. DRIVERS OF HIGH PROFILE VEHICLES TAKE CAUTION.
ALSO...SCATTERED THUNDERSTORMS ARE EXPECTED BETWEEN PIERRE AND
MOBRIDGE TODAY. NO STORMS ARE EXPECTED TO BECOME SEVERE...HOWEVER
ANY STORMS THAT FORM WILL BE SLOW MOVING...WITH THE POTENTIAL TO
PRODUCE HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

DORN