Severe Thunderstorm Warning 37, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
425 AM CDT SUN MAY 4 2003

BUSY NIGHT SO THIS WILL BE SHORT.  THUNDERSTORMS BLEW UP IN NW
MO...SWRN IA AND ERN NE ON THE EDGE OF THE WAA AND ALONG AN 850MB
INSTABILITY AXIS.  AS THE STORMS LIFT NNE THEY MOVE INTO A LESS
FAVORED AREA...AT LEAST FOR NOW SO I WOULD NOT EXPECT TO SEE A LOT
OF SVR IN IA THROUGH 6 OR 7 AM...AT LEAST NOT MORE THAN AN ISOLATED
SEVERE STORM.  THE AFOREMENTIONED INSTABILITY AXIS FINALLY LIFTS
ACROSS IA LATER THIS MORNING FOR ELEVATED STORMS AND A RISK OF
HAIL.  AFTER A SHORT BREAK LATE MORNING INTO EARLY AFTERNOOON THE
WELL ADVERTISED SYSTEM LIFTS OUT OF THE PLAINS LIFTING A FRONTAL
BOUNDARY ACROSS IOWA.  EVERYTHING STILL APPEARS RIPE FOR AN OUTBREAK
DAY.  I HAVE MENTIONED TORNADOES IN THE ZFP OVER ABOUT THE SRN THREE
TIERS OF COUNTIES...WHERE THE MOST FAVORED AREA IS IN IA.  SOME
DIFFERENCES BETWEEN THE MODELS TO DEAL WITH.  THE GFS WANTS TO
DEVELOP A SQUALL LINE IN MO WITH DEF ZONE PRECIP IN NRN IA AND LESS
PRECIP OVER CENTRAL IA WHILE THE ETA IS MUCH MORE BULLISH.  BOTH
MODELS HOWEVERE GO BALLISTIC WITH INSTABILITY AND HELICITY VALUES
ARE OVER 700.  ITS GONNA BE AN ACTIVE DAY...ESPECIALLY OVER
SOUTHERN IOWA.

.DSM...NONE

FAB

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-041100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
345 PM CDT SAT MAY 3 2003

...SEVERE WEATHER WITH THE POTENTIAL FOR TORNADOES REMAINS FOR
SUNDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS KANSAS AND NEBRASKA
TONIGHT BEFORE MOVING INTO CENTRAL IOWA DURING THE EARLY MORNING
HOURS.  MOST OF THE THUNDERSTORMS SHOULD REMAIN WEST OF A LINE FROM
OTTUMWA TO NEWTON AND ALGONA THROUGH MORNING. LARGE HAIL WILL BE THE
PRIMARY THREAT FROM THESE STORMS IN ADDITION TO HEAVY RAINFALL.
RECENT RAINS HAVE MOISTENED SOILS CONSIDERABLY THEREFORE HEAVY RAINS
MAY LEAD TO RAPID RUNOFF AND QUICKLY FILL SMALL STREAMS AND CREEKS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THUNDERSTORMS WILL CONTINUE TO SPREAD ACROSS ALL OF CENTRAL IOWA ON
SUNDAY MORNING.  THE MAIN THREAT WILL REMAIN WITH LARGE HAIL AND
HEAVY RAINFALL THROUGH MIDDAY AS THE STORMS MOVE NORTHEAST.  BY
EARLY AFTERNOON...A WARM FRONT WILL BE LOCATED IN SOUTHERN IOWA WITH A
DRY LINE ENTERING SOUTHWEST IOWA.  INSTABILITY IS EXPECTED TO
INCREASE ACROSS THE SOUTHERN HALF OF IOWA DURING THE AFTERNOON AS
THE MORNING STORMS DIMINISH AND MOVE OUT OF CENTRAL IOWA. THE DRY
LINE AND WARM FRONT WILL BEGIN TO INTERACT BY MID AFTERNOON ALLOWING
STRONG TO SEVERE THUNDERSTORMS TO DEVELOP ACROSS SOUTHWEST IOWA AND
SPREAD EAST THROUGH THE STATE INTO THE EVENING AND OVERNIGHT.  THE
HIGHEST RISK OF SEVERE WEATHER WILL REMAIN ALONG AND SOUTH OF
INTERSTATE 80...WHERE LARGE HAIL...DAMAGING WINDS AND ISOLATED
STRONG TORNADOES MAY OCCUR.  FATHER NORTH...THE THREAT FOR TORNADOES
WILL DIMINISH SOME...HOWEVER THE THREAT FOR LARGE HAIL AND DAMAGING
WINDS WILL CONTINUE.  THIS STORM APPEARS TO BE SIMILAR TO THE
SYSTEMS OF APRIL 8, 2001 AND APRIL 11, 2001.  THOSE SYSTEMS PRODUCED
SEVERAL TORNADOES AND OTHER WIDESPREAD WIND AND HAIL DAMAGE ACROSS
CENTRAL IOWA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE TONIGHT...MAINLY WEST OF
INTERSTATE 35.  SPOTTER ACTIVATION IS LIKELY ON SUNDAY INTO SUNDAY
EVENING ACROSS ALL OF CENTRAL IOWA.

&&

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

COGIL