Severe Thunderstorm Warning 293, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
300 AM CDT SUN JUL 8 2001

OVERALL PATTERN SHIFT TO A MORE AMPLIFIED UPPER RIDGE OVER THE
ROCKIES UNDERWAY AND STILL FORECAST BY MODELS INTO MIDWEEK.
RESULTANT NORTHWESTERLY FLOW ALLOWS STUBBORN FRONTAL BOUNDARY TO
SLOWLY SAG SOUTH INTO N MO EARLY IN THE WEEK. MODELS CONTINUE TO
AGREE ON LARGER SCALE FEATURES BUT CONTINUE TO STINK ON THE QPF.
APPEARS AVN IS LESSOR OF ALL EVILS BASED ON CURRENT RADAR
IMAGERY.

IN GENERAL ALL MODELS FOCUS FRONTAL RELATED WEAK LOWER LEVEL THETA-E
CONVERGENCE AND BAND OF UVV OVER THE SOUTHERN HALF OF THE CWA...
WHICH SHIFTS SOUTH OF THE AREA LATER MONDAY. LAYER OF ELEVATED WARM
CAPPING TEMPERATURES HAS COOLED A LITTLE BIT BUT MODELS CONTINUE TO
DEPICT A FAIR AMOUNT OF NEGATIVE AREA ON FORECAST SOUNDINGS OVER
AREA. AS A RESULT WILL CONTINUE TO KEEP POPS ON THE LOW SIDE.

WILL BASE FIRST PERIOD OF FORECAST ON CURRENT CONVECTIVE COMPLEX
OVER CENTRAL NEBRASKA. NORTH PLATTE RADAR SHOWING SOME ADDITIONAL
DEVELOPMENT/STRENGTHENING UP TOWARD KONL. THIS CLUSTER SHOULD
CONTINUE TO MOVE EAST IN DEEP LAYER WESTERLY FLOW ALONG NORTHERN
EDGE OF THERMAL RIDGE AND ELEVATED CONVERGENCE ZONE. IF THE SYSTEM
HOLD TOGETHER IT WOULD MOVE INTO THE WESTERN CWA MID TO LATE
MORNING. WILL NEED TO ADD LOW POPS SOUTH WITH THIS IN MIND. IN
ADDITION...JUST GETTING SOME INITIAL AC DEVELOPMENT OVER CENTRAL IA.
APPEARS BEST CHANCE FOR PRECIPITATION WILL BE CENTRAL AND SOUTH BUT
WILL MAINTAIN LOW POPS NORTH DUE TO UNCERTAINTY IN LOW CONFIDENCE
FORECAST.

DRIER AIR MOVING INTO THE NORTH SHOULD SHUT DOWN LOW PRECIPITATION
CHANCES COME MONDAY WHILE BEST CONVERGENCE AXIS SHIFTS INTO THE FAR
SOUTH.

MOS CONTINUES TO LOOK OK ON TEMPS. CONVECTIVE DEBRIS WILL PLAY HAVOC
ON TEMPS AND HEAT ADVISORY TODAY. IF CLOUDS THIN ENOUGH CURRENT
CONFIGURATION LOOKS OK. ALTHOUGH DAYTIME HEAT INDICES WILL CONTINUE
TO BE HIGH OVER WEST CENTRAL IA...ENOUGH NIGHTTIME COOLING HAS
OCCURRED TO KEEP THEM JUST UNDER CRITERIA. WILL LEAVE HEAT ADVSRY AS
IS THOUGH IF CONVECTION AND DENSE MID/HIGH LEVEL CLOUDINESS OVER
NEBRASKA LINGERS INTO SW IA THROUSGH THE EARLY AFTERNOON...ADVSRY
CRITERIA WILL NOT BE MET.

.DSM...HEAT ADVY THRU SUN ALG S OF I80.

JAW

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
600 AM CDT SUN JUL 8 2001

SYNOPSIS
A WEAK FRONTAL BOUNDARY WILL PERSIST ACROSS THE AREA TODAY. THE
BOUNDARY WILL EDGE SLIGHTLY FURTHER SOUTH TONIGHT. A VERY MOIST AND
UNSTABLE AIR MASS WILL REMAIN OVER CENTRAL AND SOUTHERN IOWA WHILE
SLIGHTLY MORE STABLE AIR HAS FILTERED INTO NORTHERN IOWA.

A SMALL THUNDERSTORM COMPLEX WILL MOVE NORTHEAST OUT OF NEBRASKA
THIS MORNING AND MOVE INTO THE NORTHWEST DES MOINES COUNTY WARNING
AREA BETWEEN 8 AND 9 AM. THESE THUNDERSTORMS SHOULD DIMINISH IN
INTENSITY AS THEY MOVE EAST ACROSS NORTHERN IOWA. HOWEVER THERE DOES
REMAIN A LOW THREAT OF STRONG STRAIGHT-LINE WINDS IN EXCESS OF 50
MPH AS THE STORMS MOVE OVER NORTHWEST IOWA.

ADDITIONAL THUNDERSTORMS MAY DEVELOP NEAR THE FRONT OVER CENTRAL
IOWA THIS AFTERNOON AND EVENING DURING THE PEAK HEATING OF THE DAY.
THE THREAT FOR ADDITIONAL THUNDERSTORM DEVELOPMENT WILL SHIFT INTO
THE SOUTHERN HALF OF IOWA LATE TONIGHT. ONCE AGAIN...THE MAIN THREAT
FROM THESE STORMS WILL BE GUSTY WINDS AND LOCALLY HEAVY RAINFALL.

SEE SITE SPECIFIC DETAILS BELOW FOR MORE INFORMATION.

IAZ004>007-015>017-091100-
CERRO GORDO-EMMET-HANCOCK-KOSSUTH-PALO ALTO-WINNEBAGO-WORTH-
INCLUDING THE CITIES OF...ALGONA...ESTHERVILLE AND MASON CITY
600 AM CDT SUN JUL 8 2001

* EVENT TIMING... 8 AM THROUGH NOON.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... LOW.
     FLASH FLOODING... NONE.

* SPOTTER ACTIVATION OUTLOOK... LOW.

IAZ023>028-033>039-044>050-057>062-070>075-091100-
ADAIR-AUDUBON-BLACK
HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CASS-CRAWFORD-DALLAS-
FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HARDIN-HUMBOLDT-JASPER-
MADISON-MAHASKA-MARION-MARSHALL-POCAHONTAS-POLK-POWESHIEK-SAC-STORY-
TAMA-WARREN-WEBSTER-WRIGHT-
INCLUDING THE CITIES OF...AMES...ATLANTIC...BOONE...CARROLL...
DENISON...DES MOINES...FORT DODGE...GRINNELL...INDIANOLA...IOWA
FALLS...KNOXVILLE...MARSHALLTOWN...NEWTON...OSKALOOSA...PELLA...
PERRY...WATERLOO...WAVERLY AND WEBSTER CITY
600 AM CDT SUN JUL 8 2001

* EVENT TIMING... 4 PM THROUGH 8 PM AND AGAIN AFTER 2 AM.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... LOW.
     FLASH FLOODING... LOW.

* SPOTTER ACTIVATION OUTLOOK... LOW.

* ADDITIONAL DETAILS... ISOLATED STORMS MAY MOVE ACROSS AREAS
ALONG AND NORTH OF HIGHWAY 20 THIS MORNING. IT APPEARS THAT A LITTLE
BETTER THREAT FOR MORE WIDESPREAD THUNDERSTORM DEVELOPMENT WILL
OCCUR THIS AFTERNOON AND EARLY EVENING.

IAZ081>086-092>097-091100-
ADAMS-APPANOOSE-CLARKE-DAVIS-DECATUR-LUCAS-MONROE-RINGGOLD-TAYLOR-
UNION-WAPELLO-WAYNE-
INCLUDING THE CITIES OF...CENTERVILLE...CHARITON...CRESTON...LAMONI
AND OTTUMWA
600 AM CDT SUN JUL 8 2001

* EVENT TIMING... AFTER 2 AM.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... LOW.
     LARGE HAIL....... LOW.
     FLASH FLOODING... LOW.

* SPOTTER ACTIVATION OUTLOOK... LOW.

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

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 .