Severe Thunderstorm Warning 255, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
326 PM CDT MON AUG 25 2003

SUBTLE PCPN AND TEMP TRENDS WL BE PRIMARY CONCERN FOR NEXT SVRL
DAYS.  CURRENT SITUATION HAS VORT/SHEAR AXIS FM NE INTO SRN MN AND
WI PRODUCING BAND OF MID CLDS AND MID/HIGH BASED CONVECTION.  19Z
SFC ANLYS HAS A MYRIAD OF MINOR FEATURES BOTH SYNOPTIC AND
MESOSCALE.  TWO LOWS NOTED ACRS SD WITH PRIMARY BNDRY INTO MN.  TROF
ACRS NE AND OLD OUTFLOW BNDRY BTWN KCIN/KFOD AND KCSQ-KDSM. CURRENT
RUC TRENDS SUGGEST LOW CINS ARE EDGING NWD TWRD BETTER CNVGNC SO WL
MAY SEE SOME ISOLD SHRT LIVED SFC BASED DVLPMT TWRD NERN NE OR
SIOUXLAND AREA.  HWVR FEEL BETTER CHCS OVNGT WL BE NE AND E OF FA AS
THETA-E ADVCTN VEERS WITH INCRG LOW LVL JET.  THUS WL KEEP MENTION
OF CHC POPS ACRS NRN PTNS TNGT...MAINLY JUST EXTRAPOLATING WHATS
OCCURRING JUST TO OUR N AND W.

TMRW CVNGC WITH WEAK FNT COMES TOGETHER A BIT ACRS SERN IA DURING
PEAK HEATING...BUT DO NOT FEEL CNVG WL BE STG ENOUGH TO OVERCOME
CIN.  SIMILAR SIUTATION DRNG PEAK HEATING WED FOR SRN AND SWRN
PTNS.  CNVG NOT AS GOOD...BUT MID LVL TEMPS COOL A BIT.  HAVE GONE
WITH SILENT SLGT CHC MENTION IN ZNS...BUT REFLECTED IN GRIDDED
FCST.  FEEL THAT ANYTHING THAT DVLPS TOO ISOLD TO CARRY.  THIS
SHOULD BE WAMREST DAY FOR AWHILE AS LOW LVL TEMPS GRDLLY COOL.  HAVE
STAYED TWRD WRM END OF GUIDANCE...BUT GRDDLY COOLED INTO WED.

SOME TIMING DIFFERENCES EXIST...BUT MED RANGE MDLS AND ENSEMBLES IN
DECENT AGREEMENT WITH IA WX.  ECMWF HAS COME TO CONSENSUS ARND FM
YDAS SOLUTION.  OPERATIONAL GFS SEEMS LIKE OUTLIER...FASTER WITH
FROPA THAN ENSEMBLES AND OTHER MDLS SO WL FOLLOW THE SLOWER END OF
THINGS WHICH IS SUGGESTED BY ETA EXTENSION AS WELL.  THIS SCENARIO
CLOSE TO PREVIOUS THINKING AND RESULTS IN LTL CHG TO FCST.  HAVE
CHCS THU NWRN 2/3RDS...FA WIDE THU NGT AND THEN SERN PTNS INTO FRI.
CHCS MAINLY SFC BASED TO START...TRANSITIONING TO POST FNTL DRIVEN
MORE BY RIGHT ENTRANCE RGN AND ELEVATED QG FORCING.  RECENT GFS RUNS
HAVE ALSO HINTED AT ISENT LIFT LATE NEXT WEEKEND ASSOCD WITH
INVERTED TROF.  HWVR GFS HAS SHOWN POOR RUN TO RUN CONTINUITY IN
THIS TIME FRAME AND IS NOT SUPPORTED BY ENSEMBLES...SO WL LEAVE
SAT-MON DRY.  STAYED AOA GUIDANCE THRU PD...BUT NOT QUITE AS MUCH AS
PAST DAYS.

.DSM...NONE

SMALL

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-261100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1045 AM CDT MON AUG 25 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CAPABLE OF DAMAGING
WINDS AND LARGE HAIL TONIGHT...MAINLY FOR AREAS NORTH OF
POCAHONTAS...FORT DODGE AND WATERLOO.  A COLD FRONT WILL DROP SOUTH
INTO NORTHERN IOWA LATE THIS EVENING...PRODUCING SCATTERED
THUNDERSTORMS.  THESE STORMS WILL MOVE INTO EAST CENTRAL IOWA
THROUGH TUESDAY MORNING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE COLD FRONT WILL STALL OVER CENTRAL IOWA ALONG OR SOUTH OF
HIGHWAY 30 TUESDAY...WITH A CONTINUED SLIGHT RISK OF SEVERE
THUNDERSTORMS TUESDAY NIGHT ACROSS MAINLY THE EASTERN HALF OF
CENTRAL IOWA.

A HIGHER RISK OF THUNDERSTORMS AND SEVERE WEATHER WILL OCCUR LATE
WEDNESDAY NIGHT AND THURSDAY AS A MORE POTENT COLD FRONT DROPS
THROUGH THE REGION.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE TONIGHT IN NORTHERN IOWA...AND MORE
LIKELY WEDNESDAY NIGHT AND THURSDAY.
&&

MORE INFORMATION CAN BE OBTAINED AT WWW.CRH.NOAA.GOV/DMX (ALL LOWER
CASE).

KULA