Severe Thunderstorm Warning 291, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
325 AM CDT SAT JUL 7 2001

BIGGEST PROBLEMS WILL BE THE HEAT IN THE SHORT TERM AND CONTINUATION
OF THUNDER CHANCES THROUGH THE WEEKEND.

FLAT UPPER RIDGE CENTERED OVER THE SOUTHERN PLAINS BECOMES MORE
AMPLIFIED THROUGH 60 HOURS...RESULTING IN A TRANSITION BACK TO
NORTHWEST FLOW AND SLIGHTLY LOWER HEIGHTS. AREA WILL REMAIN ABSENT
OF ANY DIRECT INFLUENCE BY SHORT WAVE TROUGHS. ONE SUCH SHORT WAVE
WILL MOVE ACROSS THE NORTHWEST GREAT LAKES TODAY. THIS MAY GIVE THE
FRONT IN OUR AREA A LITTLE NUDGE TO THE SOUTH BUT THE GREATEST PUSH
WILL BE THROUGH THE GREAT LAKES. MODELS MAINTAIN FRONTAL BOUNDARY
ACROSS THE AREA INTO SUNDAY. MODELS DEPICT WEAK CONVERGENCE ALONG
THIS FEATURE. WHILE SURFACE BASED INSTABILITY REMAINS QUITE HIGH...
SO DOES THE CONVECTIVE INHIBITION. FORECAST MODEL SOUNDINGS WHICH
ARE IN MUCH BETTER AGREEMENT DO COOL THE H85-7 LAYER TONIGHT AND
SUNDAY THOUGH. THIS MAY BE ENOUGH TO ALLOW A FEW STORMS TO DEVELOP
ALONG THE BOUNDARY. BY LATE TODAY INTO SUNDAY H85-7 WINDS BECOME
QUITE LIGHT. IF ANY STORMS DO FORM...THEY WILL BE SLOW MOVERS AND
COPIOUS RAIN PRODUCERS WITH PRECIPITABLE WATER REMAINING AROUND 2
INCHES. CERTAINLY DO NOT LIKE CARRYING SEVERAL PERIODS OF LOW
POPS...HOWEVER I JUST CANNOT RULE OUT A THUNDERSTORM SO WILL
MAINTAIN LOW POPS IN THE FORECAST. WILL DRY THE NORTH OUT TONIGHT
AND SUNDAY AS FRONT SAGS A LITTLE TO THE SOUTH.

NEXT PROBLEM FOR THE SHORT TERM IS THE HEAT. MOST ALL TEMPS OVER THE
SOUTHERN HALF OF THE CWA REMAIN IN THE LOWER 80S AS OF 3 AM. THESE
READING COUPLED WITH EXPECTED HEAT INDICES AOA 105 DEGREES THIS
AFTERNOON WILL PROMPT A HEAT ADVISORY TODAY ACROSS THE SOUTH. SOME
HINT OF SLIGHTLY LOWER DEW POINTS TONIGHT AND A LITTLE COOLER MIN
TEMPS.

COORD WITH KOAX KDVN

.DSM...HEAT ADVISORY TODAY FOR ABOUT THE SOUTHERN HALF OF THE CWA.

JAW
N

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
600 AM CDT SAT JUL 7 2001

SYNOPSIS
A WEAK COLD FRONT WILL SLOWLY MOVE SOUTH INTO CENTRAL IOWA BY LATE
TONIGHT. A VERY MOIST AND UNSTABLE AIRMASS WILL REMAIN OVER MUCH OF
CENTRAL IOWA IN ADVANCE OF THE FRONT. A WARM LAYER OF AIR SHOULD
TEND TO INHIBIT THUNDERSTORM DEVELOPMENT THROUGH MUCH OF THE
DAY. BY TONIGHT...THIS WARM CAPPING LAYER OF AIR WILL COOL SLIGHTLY.
CONVERGENCE ALONG THE FRONT MAY INITIATE A FEW THUNDERSTORMS.
ALTHOUGH THUNDERSTORMS CANNOT BE RULED OUT ANY TIME TODAY...IT
APPEARS THE BEST CHANCE FOR THUNDERSTORM DEVELOPMENT WILL BE LATER
THIS AFTERNOON THROUGH THE OVERNIGHT HOURS.

ANY THUNDERSTORMS THAT DO DEVELOP WILL BE CAPABLE OF PRODUCING VERY
HEAVY RAINFALL...IN EXCESS OF TWO INCHES. A SMALLER THREAT WILL BE
GUSTY WINDS IN EXCESS OF 50 MPH AND SOME HAIL.

SEE SITE SPECIFIC DETAILS BELOW FOR MORE INFORMATION.

IAZ023>028-033>039-044>050-057>062-070>075-081>086-092>097-081100-
ADAIR-ADAMS-APPANOOSE-AUDUBON-BLACK
HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CASS-CLARKE-CRAWFORD-DALLAS-
DAVIS-DECATUR-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HARDIN-
HUMBOLDT-JASPER-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-
POCAHONTAS-POLK-POWESHIEK-RINGGOLD-SAC-STORY-TAMA-TAYLOR-UNION-
WAPELLO-WARREN-WAYNE-WEBSTER-WRIGHT-
INCLUDING THE CITIES OF...AMES...ATLANTIC...BOONE...CARROLL...
CENTERVILLE...CHARITON...CRESTON...DENISON...DES MOINES...FORT
DODGE...GRINNELL...INDIANOLA...IOWA FALLS...KNOXVILLE...LAMONI...
MARSHALLTOWN...NEWTON...OSKALOOSA...OTTUMWA...PELLA...PERRY...
WATERLOO...WAVERLY AND WEBSTER CITY
535 AM CDT SAT JUL 7 2001

* EVENT TIMING...

* 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 .

CENTRAL IOWA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
825 AM CDT SAT JUL 7 2001

SYNOPSIS
A WEAK COLD FRONT WILL SLOWLY MOVE SOUTH INTO CENTRAL IOWA BY LATE
TONIGHT. A VERY MOIST AND UNSTABLE AIRMASS WILL REMAIN OVER MUCH OF
CENTRAL IOWA IN ADVANCE OF THE FRONT. A WARM LAYER OF AIR SHOULD
TEND TO INHIBIT WIDESPREAD THUNDERSTORM DEVELOPMENT THROUGH MUCH OF
THE DAY. A SMALL CLUSTER OF ISOLATED THUNDERSTORMS WILL RAPIDLY MOVE
EAST ACROSS NORTHERN IOWA THROUGH LATE MORNING. THESE STORMS WILL
HAVE THE POTENTIAL TO PRODUCE STRONG STRAIGHT-LINE WINDS.

BY TONIGHT...THE WARM CAPPING LAYER OF AIR ALOFT WILL COOL SLIGHTLY.
CONVERGENCE ALONG THE FRONT MAY INITIATE A FEW ADDITIONAL
THUNDERSTORMS. ANY THUNDERSTORMS THAT DO DEVELOP TONIGHT WILL BE
CAPABLE OF PRODUCING VERY HEAVY RAINFALL...IN EXCESS OF TWO INCHES.
A SMALLER THREAT WILL BE GUSTY WINDS IN EXCESS OF 50 MPH AND SOME
HAIL.

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>097-081100-
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
825 AM CDT SAT JUL 7 2001

* EVENT TIMING... UNTIL 1 PM NORTH OF HIGHWAY 30. AFTER 1 PM SOUTH
OF HIGHWAY 30.

* THREAT CATEGORIES...
     TORNADO.......... NONE.
     DAMAGING WINDS... MODERATE.
     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 .

$$