Severe Thunderstorm Warning 342, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
330 AM CDT MON JUL 12 2004

.DISCUSSION...
CRNT ROUND OF CONVECTION RAPIDLY WANING ALONG THE I 29 CORRIDOR...BUT
WITH MORE MOVG INTO THE NWRN CWA. THE FIRST ROUND OF CONVECTION WAS
CAUSED BY STRONG H7 CONVERGENCE AND THTE RIDGING OVR CNTRL AND E
CNTRL SD...BUT AS IT ENCOUNTERS THE MEAGER LOW LVL JET AND THTE ADV
OVER THE ERN CWA...IT IS NOT MAINTAINING WHATSOEVER. JUST BEHIND MID
LVL S/W RIDGE RIDER MOVG THRU THE AREA ATTN...MORE TS CONTS TO POP
IN N CNTRL SD...NOW EDGING INTO THE NWRN CWA. STRONG MID LVL THTE
CONTS TO SUSTAIN THIS ACTIVITY...COUPLED WITH THE GOOD LOW LVL JET
IN THAT AREA. WITH THE LOW LVL WINDS NOT PICKING UP OVER THE ERN
CWA...AM ALSO EXPECTING THAT ACTIVITY TO DIE OFF AS IT APPROACHES
THE I 29 CORRIDOR. WL WORD ZONES ACCORDINGLY.

SECOND S/W THEN MOVES INTO THE FA LATER THIS AFTN TO THE SOUTH OF
THE PARENT UPPER LOW IN S CNTRL CANADA. EARLY THIS MRNG...HORRIBLY
CAPPED OVR THE SRN CWA WITH H7 AIR APPRCHNG +14C. THE S/W WL BEGIN
TO BREAK DOWN SOME OF THIS AIR AS THE AFTN PROGRESSES AND CERTAINLY
THIS AFTN...TO A MORE TOLERABLE +10 TO +12C AT H7. STRONG
INSTABILITY EXISTS TDAY WITH GOOD DEEP LYR SHEAR FOR THIS TIME OF
YEAR. THEREFORE TS CHCS ARE DEFINITELY WARRANTED LATER TDAY AND TNGT
WITH THE PASSAGE OF THIS S/W. BELIEVE THE BEST CHCS FOR RAIN WL BE
ACRS SW MN WHERE THE COOLEST MID LVL AIR RESIDES. IN ADDN...TENDED
TO FOLLOW THE GFS QPF PATTERN MORE SO THAN THE ETA. ETA BEGINS TO
BREAK DOWN THE CAP AND DVLP LIGHT PCPN DEEP INTO THE CWA ERLY THIS
AFTN...WHICH HISTORICALLY IS WAY TOO FAST FOR THIS CWA FOR THIS TIME
OF YEAR. WITH FCST H85 TEMPS ON THE GFS/ETA...GUIDANCE TEMPS LOOKED
REASONABLE FOR TDAY AND TNGT. JUST WARM AND HUMID.

ON TUESDAY AND WEDNESDAY...SFC ANTICYCLONE BEGINS TO DRAIN DOWN FM
CANADA IN A NW TO SE ORIENTATION...STRONGLY CLIPPING THE NERN CWA.
WL SEE A DECREASE IN DEWPTS. WHAT IS INTERESTING IS THAT BOTH THE
GFS AND ETA CONT TO DVLP LIGHT PCPN IN A BAND WHICH STRETCHES FM
NEAR KSUX TO K9V9 TUE NIGHT AND WED. THIS IS ASSOCIATED WITH A LOW
LVL WIND SHEAR ZONE WRAPPING ARND THE HIGH PRES SYSTEM TO THE
N...AND ACCOMPANIED H85 FRONTOGENESIS. DEEP LYR MSTR IS MISSING WITH
THIS...SO DID NOT WANT TO GO ANY MORE THAN JUST CHC POPS ATTM. AS
MENTIONED...THE PCPN CHCS LINGER EVEN INTO WED AFTN OVER THE SRN
CWA. BUT AFTER WED MRNG...THE BEST FRONTOGENESIS WEAKENS SO DID NOT
WANT TO EXTEND THE PCPN PAST WED MRNG. H85 TEMPS COOL OFF IN THE TUE
NIGHT THRU WED NIGHT TIMEFRAME...SO HIGHS AND LOWS WILL BE PROBABLY
JUST ON THE COOL SIDE OF NORMAL.

&&

.FSD...WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&
MJF

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
514 AM CDT MON JUL 12 2004

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-131200-
AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA-
CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE-
DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON-
IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN-
LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN-
OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN-
SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON-
514 AM CDT MON JUL 12 2004

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

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS...MAINLY LATE THIS
AFTERNOON AND THROUGH MIDNIGHT ACROSS THE AREA. AT THIS
TIME...THE BEST CHANCES FOR SEVERE WEATHER APPEARS TO BE ALONG
AND NORTHEAST OF A BROOKINGS SOUTH DAKOTA TO WORTHINGTON
MINNESOTA LINE...WHERE TEMPERATURES IN THE MID LEVELS OF THE
ATMOSPHERE ARE A LITTLE COOLER. HAIL UP TO ONE INCH IN
DIAMETER...AND WIND GUSTS TO 65 MPH ARE THE PRIMARY THREATS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.
SPOTTER ACTIVATION WILL BE POSSIBLE AFTER
SPOTTER ACTIVATION WILL BE LIKELY AFTER

&&

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