Damaging Wind in Iowa, August 22, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
232 AM CDT WED AUG 22 2001

POPS AND EFFECT OF RESULTING CLOUD DEBRIS AND POTENTIAL FOR RAIN
COOLED AIR ALL PRODUCING A TOUGH FORECAST THIS MORNING...

SEASONABLY STRONG UPPER RIDGE ACROSS CENTRAL CONUS THIS MORNING WITH
MAIN BRANCH OF WESTERLIES ALONG CANADIAN BORDER. WEAKER BUT STILL
IMPORTANT BRANCH ROUNDING BASE OF S/W TROF IN DESERT SOUTHWEST WITH
JET STREAK FROM NEW MEXICO INTO WRN KS.  LEFT EXIT REGION OF THIS
JET STREAK MAY BE HELPING CONVECTION ALONG IN KS/SRN NEB...THOUGH
NOT VERY WELL.  MEANWHILE TOWARD NE IA INTO SE MN AND WI...SMALL MCS
GOING ON NOSE OF 50 KT LLJ.  AT 80H TONIGHT...WARM FRONT ALONG IA/MN
BORDER WHILE LATEST SFC ANALYSIS PLACES SFC FRONT ALONG A KSPW TO
KDBQ LINE FROM WEAK SFC LOW IN KSUX VCNTY.  SOME WEAK TROFFINES
NOTED OVER KS/NE AREAS TOO.  SFC DEWPOINTS PUSHED WELL INTO THE 70S
TUES AFTERNOON...BUT HAVE SINCE DECREASED SEVERAL DEGREES.

ETA SEEMS OVER AGRESSIVE WITH BACK BUILDING ARX AREA MCS THIS
MORNING AND RESULTANT OUTFLOW BOUNDARY/WARM FRONTAL INTERACTION THIS
AFTERNOON OVER CEN IA.  SUSPECT...LIKE NCEP/SPC...THAT MOST ACTION
WILL BE ALONG/N OF WARM FRONT TODAY...HOWEVER CANT DISCOUNT FACT
THAT KS/NE CONVECTION MAY MAKE IT INTO SRN CWA...ESPECIALLY DURING
MORNING HOURS.  SHOULD ANY CONVECTION GET GOING...IT SHOULD RAPIDLY
BECOME SEVERE (WIND/HAIL/TORNADO IN THAT ORDER OF GREATEST TO LEAST
THREAT) DURING DAYTIME ESPECIALLY IF CLOUD DEBRIS DONT INHIBIT
WARMING TOO MUCH.  OF COURSE AS ALWAYS THERES THE CAPPING PROBLEM
IN THE WARM SECTOR TO WORRY ABOUT. PROGS DONT INDICATE A LOT OF
WARMING...BUT ITS THERE NONETHELESS AT 70H.  ALL IN ALL...WILL
DECIDE RIGHT AT PRESS TIME ON POP VS COVERAGE WORDING.
OTHERWISE...WINDS TOUGH WITH CONVECTION AND BOUNDARIES.  LIKEWISE
TEMPS...BUT EXPECT WARMEST SOUTH AROUND WARMEST GUID...WHILE IN
NORTH WILL GO WITH COOL GUID.

TONIGHT...MAY CONTINUE TO SEE SUPRESSION OF FRONT/OB A BIT...BUT
STILL CHC POPS ACROSS CWA. 30 VS 40 N TO S.  TEMPS LOOK GOOD.

THURSDAY...EXPECT S/W RIDGING TO PUSH TO THE NORTH PER PROGGS.
LIKELY TO SEE SOME DRIER GR. LAKES. AIR PUSH INTO NE HALF OF STATE.
WILL ATTEMPT TO GO DRY NE OF A KFOD GO KAWG LINE.  TEMPS MAY BE A
BIT MORE HOMOGENEOUS ON THURS...WITH POTENTIAL FOR CLOUDS/PRECIP IN
SOUTH WHILE COOLER/DRIER AIR PUSHES INTO NE.

THURSDAY NIGHT...GREAT BASIN TROF PUSHES INTO PLAINS. SHOULD SEE A
COMBINATION OF SYNOPTIC OR SUB SYNOPTIC SCALE LIFT COINCIDE WITH
NIGHTTIME LLJ.  A BROAD BRUSH OF 40 POPS LOOKS GOOD FOR NOW.

.DSM...NONE

SEARCY

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
534 AM CDT WED AUG 22 2001

A FRONTAL BOUNDARY DRAPED ACROSS NORTHERN IOWA THIS MORNING SHOULD
SLOWLY PUSH SOUTHWARD INTO CENTRAL SECTIONS OF THE STATE BY LATE
THIS AFTERNOON OR EARLY THIS EVENING...AND INTO SOUTHERN PORTIONS OF
IOWA TONIGHT.  MOISTURE WILL CONTINUE TO POOL ALONG THE FRONT
TODAY...AS A COMBINATION OF SURFACE HEATING AND UPPER LEVEL
DISTURBANCES COME TOGETHER TO CREATE SCATTERED SHOWERS AND
THUNDERSTORMS PERIODICALLY THROUGH THURSDAY MORNING.  MID AND HIGH
LEVEL CLOUDS FROM CONVECTION OVER THE PLAINS EARLY MAY INHIBIT LOW
LEVEL WARMING SOMEWHAT...DECREASING THE POTENTIAL FOR WIDESPREAD
SEVERE THUNDERSTORMS TODAY AND TONIGHT.  ALTHOUGH LOW LEVEL FLOW IS
STRONG EARLY THIS MORNING...ITS DIRECTION FROM THE SOUTHWEST IS NOT
OVERLY CONDUCIVE FOR STRONG CONVERGENCE.  THE FLOW IS EXPECTED TO
WEAKEN SOMEWHAT BY MID MORNING...WHICH WILL ALSO LESSEN THE CHANCES
FOR WIDESPREAD SEVERE WEATHER.  HOWEVER...WITH AN EAST...WEST
BOUNDARY IN THE AREA...MOISTURE...AND SOME INSTABILITY...THERE DOES
EXIST AT LEAST LOW CHANCES OF SEVERE WEATHER.

SEE SITE SPECIFIC DETAILS BELOW FOR MORE INFORMATION.

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-222300-
ADAIR-ADAMS-APPANOOSE-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-
CALHOUN-CARROLL-CASS-CERRO GORDO-CLARKE-CRAWFORD-DALLAS-DAVIS-
DECATUR-EMMET-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-
HARDIN-HUMBOLDT-JASPER-KOSSUTH-LUCAS-MADISON-MAHASKA-MARION-
MARSHALL-MONROE-PALO ALTO-POCAHONTAS-POLK-POWESHIEK-RINGGOLD-
SAC-STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE-WEBSTER-
WINNEBAGO-WORTH-WRIGHT-
INCLUDING THE CITIES OF...ALGONA...AMES...ATLANTIC...BOONE...
CARROLL...CENTERVILLE...CHARITON...CRESTON...DENISON...DES MOINES...
ESTHERVILLE...FORT DODGE...GRINNELL...INDIANOLA...IOWA FALLS...
KNOXVILLE...LAMONI...MARSHALLTOWN...MASON CITY...NEWTON...
OSKALOOSA...OTTUMWA...PELLA...PERRY...WATERLOO...WAVERLY AND WEBSTER
CITY
524 AM CDT WED AUG 22 2001

* EVENT TIMING... ANYTIME TODAY OR TONIGHT...BUT PRIMARILY BETWEEN
NOON AND MIDNIGHT.

* THREAT CATEGORIES...
     TORNADO.......... VERY LOW.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... LOW.
     FLASH FLOODING... LOW.

* SPOTTER ACTIVATION OUTLOOK... LOW.

* ANY STORMS THAT DO FORM WILL MOVE FAIRLY SLOWLY.  WITH RAINFALL
RATES INTENSE FOR SHORT PERIODS OF TIME IN THE STRONGEST
THUNDERSTORMS...SOME LOCALLY HEAVY RAINFALL MAY OCCUR.

SEARCY

-------------------------------------------------------------------

THREAT KEY:
    TORNADO.......... ANY TORNADO OCCURRENCE
    DAMAGING WINDS... WINDS >= 58 MPH
    LARGE HAIL....... HAIL >= 3/4 INCH DIAMETER
    FLASH FLOODING... FLOODING CAUSED BY HEAVY RAINS WITHIN 6 HOURS
                      OF RAIN EVENT. POSES THREAT TO LIFE OR
                      PROPERTY.

THREAT CATEGORY KEY:  PROBABILITY OF THREAT OCCURRING WITHIN 25
                      MILES OF POINT WITHIN FORECAST AREA
    NONE....... NOT EXPECTED.  LESS THAN 5% ( 2% FOR TORNADOES)
    LOW........ 5-15% (2-15% FOR TORNADOES)
    MODERATE... 25-35%
    HIGH....... 45% OR GREATER

SPOTTER ACTIVATION OUTLOOK KEY:
    NOT EXPECTED
    LOW........ ACTIVATION POSSIBLE BUT NOT LIKELY
    MODERATE... POSSIBILITIES ABOUT 50-50
    HIGH....... ACTIVATION LIKELY

FOR MORE INFORMATION ON PROBABILISTIC SEVERE WEATHER OUTLOOKS...GO
TO THE STORM PREDICTION CENTER WEBSITE AT
WWW.SPC.NOAA.GOV/PRODUCTS/OUTLOOK/PROBINFO.HTML .