Severe Thunderstorm Warning 334, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
912 PM CDT THU SEP 6 2001

LATEST ANALYSIS SHOWS THAT THE SFC FRONT HAS JUST MOVED THROUGH
CHAMBERLAIN AND MAY BE ENTERING FAR NW GREGORY.  SO IT APPEARS THAT
THE FRONTAL PROPAGATION HAS SLOWED.  RUC ALSO SHOWS THIS AND HAS
FROPA FOR FSD AND YKN AROUND 13Z FRI.  FOR AREAS N OF I-90 THIS IS
NOT GOOD FOR THE RAIN CHANCES SINCE 850 MB FLOW TURNS MORE SW AS THE
NIGHT PROGRESSES DECREASING THE DEPTH OF CONVERGENCE.  IN
ADDITION...THE UPPER WAVE MOVING INTO NEBRASKA WILL BEGIN TO FOCUS
MORE OF THE CONVECTION ALONG THE SRN PORTION OF THE FRONT IN
NEBRASKA AND FAR SOUTHERN SD.  THEREFORE...HAVE LOWERD POPS TO SCT
ALONG AND N OF I-90 IN SD.  ALSO WITH THE SLOWER MOVEMENT...HAVE
LOWERED POPS IN MUCH OF NW IA AND MUCH OF SW MN AND WORDED ANY PCPN
TO OCCUR TOWARD DAWN IN THESE AREAS.  WITH THE 850 MB FLOW REMAINING
MORE SRLY IN FAR SRN ZONES OVERNIGHT...BELIEVE FRONTAL CONVERGENCE
AND INSTABILITY WL ALLOW CONVECTION TO DEVELOP INTO THE MO VALLEY.
THEREFORE HAVE CONTINUED WITHE LIKELY OR CATEGORIAL POPS IN SD
COUNTIES ALONG MO RIVER AS FAR EAST AS SUX.

HAVE ALSO MADE A FEW CHANGES TO FRI.  FIRST...THE UPPER WAVE WL MOVE
NE TOWARD NW IA AND PORTIONS OF SW MN ON FRI.  AS THIS WAVE
INTERACTS WITH THE FRONT EXPECT SHRA/TSRA TO CONTINUE TO BE
WIDESPREAD IN THIS AREA...ESP THROUGH NOON.  THEREFORE HAVE UPPED
POPS FROM SUX TO SPW FOR FRI.  N OF I-90 IN SW MN HAVE LOWERED POPS
WITH IDEA THAT PCPN WL BE SCATTERED DUE TO SHALLOW CONVERGENCE AND
LESS FAVORABLE DYNAMICAL INTERACTION WITH UPPER WAVE.
FINALLY...SLOWED TIMING OF FRONT E OF I-29 BASED UPON OBSERVED AND
FCST MOVEMENT.

NEW ZFP OUT BY 220Z.

.FSD...NONE

SCHUMACHER