Severe Thunderstorm Warning 118, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
330 PM CDT MON AUG 9 1999

WX QUITE FOR TNGT WITH HI MOVG ACRS IA OVR NGT.  MAIN FEAT COMES
LATE WED INTO THU MRNG.  MDLS CONSISTENT WITH MVMT OF UPR LO AND STG
VMAX FOR THIS TIME OF YR.  MEAN RDG PSN TO THE W OF IA AND MVMTS OF
UPR LO AND SFC CONSISTENT WITH THIS PSN.  QUICK REBOUND OF MSTR
INDCTD BY ALL MDLS WITH PWATS UP TO 50 MM B WED EVE.  THETA-E AVCTN
STG OVR IA LATE IN DAY WED THRU 08Z THU AND VRY GUF LLJ FOR MID
AUG.  TSTMS SHUD BE WDSPRD AND WL GO CAT POPS N, LKLY CNTRL AND CHC
S WED NGT AFT INTRO CHC OVR W THIRD WED.  MNTND POPS MAINLY MRNG THU
AND A LOT CUD GO WRONG WITH THIS FCST BFR ALL IS SAID AND DONE.
INDICTNS OF 1ST DRY SLOT IN AVN FOR THU AFTN AND EVE BFR COLD AIR
WRAPS ARND FM THE NW INTO ERY FRI.  WL CARRY SOME POPS INTO FRI ERY,
BUT THEN DRY UNTIL LATE SUN WITH NXT SYS.  SHUD WRM UP OVR WKND WITH
PHASE 2 OF SUMMER GETTING INTO SWING.
DSM 02722   ALO 01865

.DSM...NONE

MS AUG 99

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-100200-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
401 PM CDT MON AUG 9 1999

HAZARD--WIDELY SCATTERED THUNDERSTORMS.  SOME MAY BE SEVERE WITH
DAMAGING WINDS AND LARGE HAIL.  BRIEF HEAVY RAINS AND ISOLATED
TORNADOES ARE ALSO POSSIBLE.

AREA OF CONCERN AND TIMING DETAILS--ALL OF CENTRAL IOWA BUT
PRIMARILY NORTH OF INTERSTATE 80.  STORMS MAY DEVELOP ACROSS
NORTHWEST IOWA AFTER 500 PM AND THEN MOVE INTO EASTERN PORTIONS OF
THE STATE OVERNIGHT.  THE PRIMARY THREAT OF SEVERE WEATHER WOULD BE
BEFORE MIDNIGHT.

METEOROLOGICAL COMMENTS--A FRONTAL BOUNDARY BRINGING IN DRIER AIR WAS
JUST ENTERING NORTHWEST IOWA THIS AFTERNOON AND MAY DEVELOP
THUNDERSTORMS LATE THIS AFTERNOON AND THIS EVENING.  MID LEVEL
TEMPERATURES REMAINED RATHER WARM HOWEVER AND THIS WAS PREVENTING
THUNDERSTORM DEVELOPMENT FOR THE TIME BEING.  THIS WARM LAYER ALOFT
MAY PREVENT STORMS FROM DEVELOPING AT ALL...BUT IF THEY DO FORM THEY
COULD BECOME SEVERE QUICKLY.  THE AIRMASS AHEAD OF THE FRONT WAS
QUITE UNSTABLE AND WIND SHEAR PROFILES WERE SUFFICIENT TO PRODUCE
ORGANIZED SEVERE THUNDERSTORMS...ESPECIALLY OVER NORTHERN IOWA.  IF
STORMS DO IN FACT DEVELOP...ALL FORMS OF SEVERE WEATHER ARE POSSIBLE
INCLUDING LARGE HAIL...DAMAGING WINDS AND TO A LESSER EXTENT
TORNADOES.

PRECAUTIONS--ALTHOUGH NOT A CERTAINTY...SPOTTER DEPLOYMENT MAY BE
NEEDED THIS EVENING.   THE WEATHER SITUATION COULD CHANGE RAPIDLY SO
PEOPLE WITH OUTDOOR CONCERNS SHOULD MONITOR LATER NATIONAL WEATHER
SERVICE FORECASTS AND STATEMENTS FOR UPDATED INFORMATION...AND BE
READY TO MOVE TO SAFE SHELTER QUICKLY.

SMALL

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-101100-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
800 PM CDT MON AUG 9 1999

HAZARD--WIDELY SCATTERED THUNDERSTORMS.  SOME MAY BE SEVERE WITH
DAMAGING WINDS AND LARGE HAIL.  BRIEF HEAVY RAINS AND ISOLATED
TORNADOES ARE ALSO POSSIBLE.

AREA OF CONCERN AND TIMING DETAILS--ALL OF CENTRAL IOWA BUT
PRIMARILY NORTH OF HIGHWAY 20.  STORMS ACROSS SOUTHERN MINNESOTA
WILL MOVE SOUTHEAST INTO NORTH CENTRAL AND NORTHEAST PORTIONS OF THE
STATE OVERNIGHT.  THE PRIMARY THREAT OF SEVERE WEATHER SHOULD END BY
MIDNIGHT.

METEOROLOGICAL COMMENTS--A FRONTAL BOUNDARY BRINGING IN DRIER AIR WAS
MOVING INTO NORTHWEST IOWA THIS EVENING.  THE AIRMASS AHEAD
OF THE FRONT WAS QUITE UNSTABLE AND WIND SHEAR PROFILES WERE
SUFFICIENT TO PRODUCE ORGANIZED SEVERE THUNDERSTORMS...ESPECIALLY
OVER NORTHERN IOWA.  STORMS WHICH HAVE ALREADY FORMED IN SOUTHERN
MINNESOTA WILL MOVE INTO NORTHERN IOWA THIS EVENING WITH ALL FORMS
OF SEVERE WEATHER POSSIBLE INCLUDING LARGE HAIL...DAMAGING WINDS AND
TO A LESSER EXTENT TORNADOES.

PRECAUTIONS--SPOTTER DEPLOYMENT MAY BE NEEDED THIS EVENING.   THE
WEATHER SITUATION COULD CHANGE RAPIDLY SO PEOPLE WITH OUTDOOR
CONCERNS SHOULD MONITOR LATER NATIONAL WEATHER SERVICE FORECASTS AND
STATEMENTS FOR UPDATED INFORMATION...AND BE READY TO MOVE TO SAFE
SHELTER QUICKLY.

COGIL

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-101100-

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
800 PM CDT MON AUG 9 1999

HAZARD--WIDELY SCATTERED THUNDERSTORMS.  SOME MAY BE SEVERE WITH
DAMAGING WINDS AND LARGE HAIL.  BRIEF HEAVY RAINS AND ISOLATED
TORNADOES ARE ALSO POSSIBLE.

AREA OF CONCERN AND TIMING DETAILS--ALL OF CENTRAL IOWA BUT
PRIMARILY NORTH OF HIGHWAY 20.  STORMS ACROSS SOUTHERN MINNESOTA
WILL MOVE SOUTHEAST INTO NORTH CENTRAL AND NORTHEAST PORTIONS OF THE
STATE OVERNIGHT.  THE PRIMARY THREAT OF SEVERE WEATHER SHOULD END BY
MIDNIGHT.

METEOROLOGICAL COMMENTS--A FRONTAL BOUNDARY BRINGING IN DRIER AIR WAS
MOVING INTO NORTHWEST IOWA THIS EVENING.  THE AIRMASS AHEAD
OF THE FRONT WAS QUITE UNSTABLE AND WIND SHEAR PROFILES WERE
SUFFICIENT TO PRODUCE ORGANIZED SEVERE THUNDERSTORMS...ESPECIALLY
OVER NORTHERN IOWA.  STORMS WHICH HAVE ALREADY FORMED IN SOUTHERN
MINNESOTA WILL MOVE INTO NORTHERN IOWA THIS EVENING WITH ALL FORMS
OF SEVERE WEATHER POSSIBLE INCLUDING LARGE HAIL...DAMAGING WINDS AND
TO A LESSER EXTENT TORNADOES.

PRECAUTIONS--SPOTTER DEPLOYMENT MAY BE NEEDED THIS EVENING.   THE
WEATHER SITUATION COULD CHANGE RAPIDLY SO PEOPLE WITH OUTDOOR
CONCERNS SHOULD MONITOR LATER NATIONAL WEATHER SERVICE FORECASTS AND
STATEMENTS FOR UPDATED INFORMATION...AND BE READY TO MOVE TO SAFE
SHELTER QUICKLY.

COGIL