Damaging Winds in South Dakota, July 29, 2003

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
234 PM CDT TUE JUL 29 2003

...CONVECTIVE CHANCES THROUGH THE SHORT TERM ARE THE MAIN FORECAST
CONCERN...

SYNOPSIS...12Z UPPER AIR ANLYS INDCD BROAD MEAN TROF OVR THE ERN US
AND A SLIGHT RETROGRESSION OF THE WRN US RIDGE INTO NV. SHRTWV
ASSOCIATED WITH 60 KT H3 JET SEGMENT WAS MOVING THRU WRN SD...WITH
MAIN UPPER LVL CLOSED LO DROPPING S THRU CNTRL MANITOBA. CDFNT AT
H85 WAS LOCATED FM WRN ND SWWD INTO NRN WY WITH WRMFNT ACRS THE ERN
DAKOTAS. 18Z OBJECTIVE MSAS ANLYS INDCD SFC CDFNT FM ERN ND SWWD
INTO WRN SD WITH 2-4 MB PRES RISES BEHIND FNT. PREFRONTAL TROF
EXTNDD ACRS THE CNTRL DAKOTAS.

FORECAST...LATEST AREA 88-DS INDICATE RAPID THUNDERSTORM
DVLPMNT/INTENSIFICATION ACRS CNTRL SD. SECOND WEAKER LINE OF TRW
ASSOCIATED WITH THE CDFNT IN WRN SD ATTM. STORMS THUS FAR HAVE BEEN
MULTI-CELLED WITH MARGINALLY SVR HAIL AS LATEST MESO ANLYS SHOW ONLY
20-30 KTS OF DEEP LAYER SHEAR. ATMO ALONG AND AHEAD OF PREFRONTAL
TROF HAS BECOME MODERATELY UNSTABLE WITH MLCAPE OF 1500 J/KG. WITH
SUSTAINED CONVERGENCE ALONG CDFNT...AND DEGREE OF INSTABILITY WLD
EXPECT FAIRLY GOOD COVERAGE OF TRW IN WRN CWA THIS EVENING. HAIL
WILL BE THE MAIN THREAT AS STRNG MID LVL CAA ADVECTS ACRS THE WARM
SECTOR LOWERING WEB-BULB HEIGHTS TO 9-10 K FT. TRW WL PROGRESS E
ACRS THE CWA TONIGHT...BUT WITH LOSS OF INSULATION ATMO SHLD
STABILIZE SOME AFTER MIDNIGHT. WL CARRY LIKELY POPS W AND CHC SE.
ALTHOUGH SFC CDFNT WL CLR CWA WED MORNING...STRNG CYCLONIC FLOW
ALOFT WITH COOL MID LVL TMPS WL ALLOW FOR GOOD CU FIELD TO DVLP AND
MAYBE EVEN ISO TRW IN ERN CWA. AGREE WITH PREVIOUS FORECASTER THAT
STRNG LARGE SCALE SUBSIDENCE WL LIMIT DESTABILIZATION DURING THE
AFTERNOON AND THUS ONLY LO CHC POPS WARRANTED. SECONDARY PUSH OF CD
AIR COMES DOWN ON THURSDAY WITH A SHRTWV IN NW FLOW. DPS AROUND 60
DUE TO EVAPOTRANSPIRATION AND THE VERY COOL MID LVL TMPS WL ALLOW
FOR SOME INSTABILITY IN SRN CWA BY AFTERNOON. AS VERTICAL MOTION
ASSOCIATED WITH SHRTWV INTERACTS WITH INSTABILITY IN SRN FA...TRW WL
BE POSSIBLE. MAYBE EVEN A HAILER OR TWO.

EXTENDED...WL CONT WITH A DRY EXTNDD. MEDIUM RANGE MDLS ARE IN GOOD
AGREEMENT ON LARGE SCALE PATTERN IN THE 4-7 DAY TIME FRAME. UPPER LO
WL BE SLOW TO MV OUT OF THE GREAT LAKES OVR THE WEEKEND AND THUS THE
NW FLOW ALOFT WL CONT WITH TMPS AVERAGING NEAR OR SLIGHTLY BELOW
CLIMO. LITTLE CHC FOR MOISTURE RETURN AND NO FRONTAL BOUNDARIES WL
PRECLUDE MENTION OF PRECIP AT THIS TIME.

FCSTID = 15

.FSD...
IA...NONE.
MN...NONE.
NE...NONE.
SD...NONE

BOUSTEAD

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-IAZ001>003-
012>014-020>022-031-032-NEZ013-014-301200-

HAZARDOUS WEATHER OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
221 PM CDT TUE JUL 29 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA...
SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP IN SOUTH CENTRAL
SOUTH DAKOTA LATE THIS AFTERNOON...GENERALLY WEST OF THE JAMES
RIVER. THE THUNDERSTORMS WILL THEN SPREAD EAST OVER THE AREA THIS
EVENING. SOME OF THESE THUNDERSTORMS COULD BECOME SEVERE...WITH
THE MAIN SEVERE WEATHER THREAT BEING LARGE HAIL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE LIKELY AFTER 2 PM CDT WEST OF
INTERSTATE 29...AND AFTER 700 PM CDT EAST OF INTERSTATE 29.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.CRH.NOAA.GOV/FSD. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.