Severe Thunderstorm Warning 102, NWS Des Moines, IA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1245 PM CDT TUE JUN 23 2009

...UPDATED 18Z AVIATION AND PUBLIC DISCUSSION...

.SHORT TERM...
STORMS NOW FIRING ALONG OLD OUTFLOW AND MCS THAT ENTERED NW IA LATE
MORNING. INSTABILITY AXIS SUGGESTS SOME SE TURNING DURING THE
AFTERNOON HOURS TODAY. CURRENT WW TO US 30...BUT MAY NEED SOME
ADJUSTMENTS LATER IN AFTERNOON GIVEN CORFIDI VECTORS SHOWING A MORE
SOUTHERLY COMPONENT DURING THE LATE AFTERNOON AND EVENING HOURS.
HAVE RAISED POPS AND THUNDER SOUTH INTO THE AFTERNOON AND EARLY EVE.
HEAT ADV CONTINUES...THOUGH STORMS WILL TAKE SOME OF THE HEAT AWAY
NORTH...LEFT IT GOING FOR THE PRE-ENVIRONMENT WHICH REMAINS QUITE
HOT. /REV

..PREVIOUS SHORT TERM...TODAY
ISOLATED CONVECTION CONTINUES TO PERCOLATE OVER WESTERN IA IN
VICINITY OF BAND OF 850 MB THETA-E ADVECTION AND 100 MB MLCAPES OF
2500 J/KG. THE FORCING AND HIGH INSTABILITIES WILL REMAIN OVER THE
SOUTHWESTERN FORECAST AREA THEREFORE WILL INTRODUCE ISOLATED THUNDER
MENTION. BIGGER CONCERN FOR CONVECTIVE CHANCES IS CURRENT MCS ACROSS
WESTERN NEBRASKA. IF THE MCS GETS ROOTED IN AND BEGINS TO FOLLOW
EASTWARD POINTING CORFIDI VECTORS...IT COULD END UP IN IOWA BY THIS
AFTERNOON. ANOTHER SCENARIO COULD BE A DECAYING MCS OR REMNANT MCV
ARRIVING DURING PEAK HEATING WHEN HIGH INSTABILITY AND LITTLE CIN
REMAINS...REFIRES AND FOLLOWS THE INSTABILITY AXIS RIGHT INTO
CENTRAL IA.  DO FAVOR THUNDER REACHING THE FORECAST AREA BEFORE 00Z
AND GIVEN MULTIPLE SCENARIOS AND TIMEFRAMES THIS COULD HAPPEN...HAVE
INCREASED POPS OVER THE NORTHWEST HALF.

REGARDING HEAT INDEX POTENTIAL. EXPECT A SIMILAR DAY TO MONDAY WITH
HIGHER DEW POINTS OVER THE CENTRAL AND SOUTH WHERE DEW POINTS WILL
BE IN THE LOWER TO MID 70S AND HIGHS IN THE LOWER TO MID 90S. THIS
WILL RESULT IN HEAT INDEX VALUES OF 105 TO 110. FARTHER NORTH...DEW
POINTS REMAIN LOWER AND ARE CURRENTLY IN THE MID TO UPPER 60S.
SOUNDINGS SUGGEST MIXING WILL LIMIT MAX DEW POINTS TO AROUND 70.
ANOTHER FACTOR IS POTENTIAL BLOW OFF CLOUD COVER FROM NEBRASKA
CONVECTION TO LIMIT HIGHS ACROSS PORTIONS OF THE NORTH. CURRENT
FORECAST HEAT INDEX READINGS ARE 100-103 AND BELOW ADVISORY
CRITERIA. DESPITE THIS...WILL MAINTAIN INHERITED ADVISORY SINCE IT
IS ALREADY OUT AND THIS IS THE WARMEST AND MOST HUMID IT HAS BEEN TO
DATE THIS YEAR.

.LONG TERM...TONIGHT THROUGH MONDAY
THE MAIN FOCUS THIS PERIOD WILL BE THE NEAR TERM WITH POTENTIAL FOR
SEVERAL ROUNDS OF HEAVY RAIN AND ISOLD SEVERE WEATHER THROUGH
WEDNESDAY. THE INITIAL CONCERN IS ONE OR MORE THUNDERSTORM COMPLEXES
TONIGHT ACROSS IOWA. THE GFS DRIVES AN OVERNIGHT MCS ACROSS
SOUTHERN MINNESOTA...DESPITE INDICATIONS OF A SOUTHWARD PUSH WITH
THE CORFIDI VECTORS AND INSTABILITY AXIS AT 06Z. CONCEPTUALLY...THE
NAM12 AND LOCAL 3.5KM WRF MAKE MORE SENSE IN DRIVING THE MCS(S)
SOUTH INTO THE HEART OF THE FORECAST AREA WITH ATTENDANT WIND/HAIL
THREAT ALONG WITH VERY HEAVY RAIN. WOULD ALSO THINK THE UPPER RIDGE
WOULD KEEP STORMS FROM MOVING THAT FAR EAST. BASED ON THE NAM/WRF
SOLUTIONS...HAVE MADE SOME SIGNIFICANT UPWARD ADJUSTMENTS IN
POPS...ESPECIALLY TONIGHT AND WEDNESDAY. JUST HOW FAR SOUTH ANY
COMPLEXES DRIVE TONIGHT WILL BE A KEY FACTOR IN HOW WIDESPREAD THE
FLASH FLOOD THREAT IS. INCREASING CIN WITH TIME COULD WEAKEN STORMS
OVERNIGHT AS THEY MOVE INTO SOUTHERN IOWA. FOR NOW HAVE STAYED NEAR
TO SLIGHTLY ABOVE HPC QPF...WHICH KEEPS THE HEAVIEST RAIN NORTH OF
HIGHWAY 30. CURRENT 12 INCH SOIL MOISTURE ANOMALIES ARE HIGHEST OVER
EASTERN AND SOUTHERN PORTIONS OF THE CWA. MATCHING UP SOIL MOISTURE
WITH HEAVIEST RAIN POTENTIAL...THE NORTHEAST COUNTIES WOULD HAVE THE
HIGHEST OVERALL THREAT OF FLASH FLOODING OVERNIGHT. HOWEVER...IF THE
HEAVY RAIN IS SUSTAINED FARTHER S/SE...THE RISK WOULD INCREASE. ON
WEDNESDAY...A BOUNDARY WILL LIKELY STALL OUT ACROSS IOWA FOLLOWED BY
THE ARRIVAL OF ANOTHER SHORT WAVE TROUGH. MORE SEVERE STORMS AND
HEAVY RAIN ARE POSSIBLE...ALTHOUGH THERE IS MUCH LESS CONFIDENCE IN
THE DETAILS. HAVE AGAIN TRENDED POPS UPWARD WEDNESDAY AND WEDNESDAY
NIGHT. FLASH FLOODING EVENTS HAVE BEEN VERY INFREQUENT DURING THE
RECENT WET PERIOD...BUT PORTIONS OF THE CWA WILL LIKELY NOT BE AS
FORTUNATE THROUGH WEDNESDAY.

THE HEAT ADVISORY MAY HAVE TO BE EXTENDED OVERNIGHT TONIGHT INTO
WEDNESDAY...MAINLY SOUTH OF INTERSTATE 80...WHERE CURRENT
TEMP/DEWPOINTS PUSH HEAT INDEX VALUES NEAR TO SLIGHTLY ABOVE 105
DEGREES WEDNESDAY AFTERNOON. NO CHANGES MADE TO THE EXTENDED
PERIOD...FRIDAY THROUGH MONDAY.

&&

.AVIATION...23/18Z
LINE OF CONVECTION NOW MOVING ACROSS THE NORTHERN AREAS AND WILL
IMPACT KFOD...KMCW...AND KALO FOR THE AFTERNOON HOURS. HAVE ADDED
VRB25G40KT GUSTS WITH TSRA EXPECTED AS THE LINE PASSES EAST. PSBL TO
SEE 50KT GUSTS WITH SOME OF THE STRONGER STORMS. FARTHER
SOUTH...STORMS NOT AS LIKELY EARLY ON BUT CONTINUED CHANCES FOR SOME
THUNDER AT KDSM DURING THE 20-22Z PERIOD THIS AFTERNOON. OVERNIGHT
TNT ANOTHER CHANCE FOR STORMS AND WILL LEAVE FOR EVENING SHIFT TO
PIN DOWN MOST FAVORED AREAS...THOUGH NORTHERN AND CENTRAL AREAS LOOK
TO BE MOST FAVORABLE AT PRESENT./REV

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY UNTIL 7 PM CDT TUESDAY ALONG AND SOUTH OF I-80 HEAT
ADVISORY NOON-7 PM CDT TODAY NORTH OF I-80.

&&

SHORT TERM...DONAVON/REV
AVIATION...COGIL
LONG TERM...KINNEY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
442 AM CDT TUE JUN 23 2009

IAZ057>062-070>075-081>086-092>097-241100-
AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-POWESHIEK-CASS-ADAIR-MADISON-
WARREN-MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS-MONROE-WAPELLO-
TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS-
442 AM CDT TUE JUN 23 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND
SOUTHERN IOWA....SOUTH OF HIGHWAY 30.

.DAY ONE...TODAY AND TONIGHT

VERY HOT AND HUMID CONDITIONS WILL PERSIST TODAY. A HEAT ADVISORY
IS IN EFFECT FOR THE AREA THROUGH THIS AFTERNOON. PLEASE REFER TO
THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR
FURTHER DETAILS.

ISOLATED NON SEVERE THUNDERSTORMS WILL CONTINUE THIS
MORNING...MAINLY WEST OF INTERSTATE 35. ADDITIONAL STORMS ARE
POSSIBLE TONIGHT. A FEW STORMS COULD BE SEVERE...WITH ISOLATED 60
MPH WIND GUSTS THE MAIN THREAT.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

HOT AND HUMID CONDITIONS WILL PERSIST WEDNESDAY...WITH AFTERNOON
HEAT INDEX VALUES AROUND 105 DEGREES.

MORE THUNDERSTORMS ARE EXPECTED WEDNESDAY INTO THURSDAY MORNING.
ISOLATED SEVERE STORMS AND LOCALLY HEAVY RAINFALL ARE POSSIBLE...ESPECIALLY
WEDNESDAY NIGHT. ADDITIONAL THUNDERSTORM CHANCES ARRIVE FRIDAY
NIGHT INTO THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED AT VARIOUS TIMES TONIGHT
THROUGH WEDNESDAY NIGHT.

IAZ004>007-015>017-023>028-033>039-044>050-241100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-
442 AM CDT TUE JUN 23 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND
NORTHERN IOWA...ALONG AND NORTH OF HIGHWAY 30.

.DAY ONE...TODAY AND TONIGHT

VERY HOT AND HUMID CONDITIONS ARE EXPECTED THIS AFTERNOON. A HEAT
ADVISORY IS IN EFFECT FOR THE AREA THIS AFTERNOON. PLEASE REFER
TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES
FOR FURTHER DETAILS.

ISOLATED NON SEVERE THUNDERSTORMS ARE POSSIBLE THIS MORNING...MAINLY
WEST OF INTERSTATE 35. ADDITIONAL STORMS ARE EXPECTED LATE THIS AFTERNOON
AND TONIGHT. A FEW STORMS COULD BE SEVERE...WITH ISOLATED 60 MPH
WIND GUSTS THE MAIN THREAT. LOCALLY HEAVY RAINFALL IS EXPECTED...AND
ISOLATED FLASH FLOODING CANNOT BE RULED OUT.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

MORE THUNDERSTORMS ARE EXPECTED WEDNESDAY INTO THURSDAY MORNING.
ISOLATED SEVERE STORMS AND LOCALLY HEAVY RAINFALL ARE POSSIBLE...ESPECIALLY
WEDNESDAY NIGHT. ADDITIONAL THUNDERSTORM CHANCES ARRIVE FRIDAY
NIGHT INTO THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED AT VARIOUS TIMES TONIGHT
THROUGH WEDNESDAY NIGHT.

KINNEY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
142 PM CDT TUE JUN 23 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0137 PM     HAIL             8 N FENTON              43.33N 94.43W
06/23/2009  E0.88 INCH       KOSSUTH            IA   LAW ENFORCEMENT

&&

LEE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
242 PM CDT TUE JUN 23 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0238 PM     TSTM WND GST     2 WNW CLARION           42.75N 93.77W
06/23/2009  M69 MPH          WRIGHT             IA   AWOS

            CLARION AIRPORT AWOS

&&

SMALL

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