Severe Thunderstorm Warning 398, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
648 PM CDT TUE JUL 15 2008

UPDATED FOR 00Z AVIATION DISCUSSION

.SHORT TERM /TONIGHT/...
PRIMARY FORECAST CONCERN IS COVERAGE AND MAGNITUDE OF CONVECTION
TONIGHT. WAA BTWN SFC AND 700 MB HAS ERODED CAP AND MOISTURE
ADVECTION BTWN SFC AND 850 MB HAS ENHANCED INCREASING INSTABILITY
THIS AFTERNOON. STORMS HAVE BEGUN TO BREAK OUT ACROSS NORTHEASTERN
NE WHERE INSTABILITY IS EVEN HIGHER. AS THE LOW-LEVEL WAA REACHES A
STATIONARY BOUNDARY IN SD/SOUTHERN MN THUS DECREASING CINH IN THAT
AREA MORE ORGANIZED STORMS ARE EXPECTED TO BREAK OUT THIS EVENING.
WITH STEERING FLOW JUST NORTH OF WEST...SOME OF THE STORMS FROM
NE/SD/MN WILL PROPAGATE INTO OUR AREA BY TONIGHT. SHEAR IS MARGINAL
BUT SUFFICIENT FOR ISOLATED SEVERE WEATHER...PRIMARILY HAIL AND
WIND...WITH THIS RISK BEING MORE OR LESS CONFINED TO NORTHERN AND
NORTHWESTERN IOWA. HAVE INCLUDED SLIGHT CHANCE AND CHANCE POPS FOR
THESE AREAS AS IT IS BELIEVED THAT INSTANTANEOUS COVERAGE WILL BE
FAIRLY LOW...AND WILL LEAVE SEVERE STORM MENTION OUT OF THE ZONES AS
ANY SEVERE STORMS ARE EXPECTED TO BE ISOLATED.

.LONG TERM...
THE FOCUS FROM WEDNESDAY ON WILL BE HEAVY RAIN AND FLOODING
POTENTIAL ACROSS THE FORECAST AREA.  THE VARIOUS MODELS AND
ENSEMBLES ARE COMING INTO BETTER AGREEMENT REGARDING THE POTENTIAL
FOR...LOCATION OF...AND TIME FRAME FOR THE FIRST SHOT OF HEAVY RAIN.
THE LATEST ECMWF/NAM/CANADIAN AND GFSENS ALL POINT TO THURSDAY
THURSDAY NIGHT INTO FRIDAY LOOKS TO BE PROBLEMATIC. WITH PWAT/S AOA
2 INCHES IN THE NORTHWEST...DEEP MOISTURE SOUNDINGS WITH TALL SKINNY
CAPE AND RELATIVELY WEAK STEERING FLOW...AND CORFIDI VECTORS
INDICATING POTENTIAL FOR SLOW MOVING AND/OR BACK BUILDING
STORMS...ALL INGREDIENTS APPEAR PEGGED FOR A SUBSTANTIAL RAIN EVENT.
INITIAL THOUGHTS ARE A GENERAL 1-2 INCH RAIN ACROSS THE NORTHWEST
HALF THROUGH THE DAY ON FRIDAY...WITH LOCALLY HIGHER AMOUNTS AROUND
4 OR SO. HEAVY RAIN MAY PERSIST INTO FRIDAY NIGHT AND SATURDAY...AND
GRADUALLY SPREAD SOUTHWARD ACROSS THE STATE. CONFIDENCE IN THIS
SECOND ROUND OF HEAVY RAIN OCCURRING IS LOWER AT THIS TIME. WILL
ISSUE HYDROLOGIC OUTLOOK (DSMESFDMX) TO HIGHLIGHT THREAT. CURRENT
FLASH FLOOD GUIDANCE AND UPPER SOIL MOISTURE INDICATE WE CAN TAKE
SOME PRETTY GOOD RAIN...BUT THE MORE EXTREME AMOUNTS AND/OR RAINFALL
RATES WILL LIKELY LEAD TO SOME INCIDENTS OF SHORT TERM FLASH
FLOODING. THERE WILL ALSO LIKELY BE SOME THREAT FOR SVR HAIL/WIND
THURSDAY LATE AFTERNOON AND EVENING...AND POSSIBLY AGAIN FRIDAY INTO
THE WEEKEND. THE NORTHWEST COUNTIES ARE OUTLOOKED IN SWODY3.

LOOKING AHEAD...ONLY MINOR CHANGES MADE TO SUNDAY THROUGH TUESDAY.
AT LEAST SOME PARTS OF THE STATE CAN EXPECT MORE CONVECTION AT TIMES
THROUGH THE PERIOD...ALTHOUGH DETAILS ARE TOUGH TO PIN DOWN. WARM
AND MUGGY CONDITIONS WILL PERSIST.

&&

.AVIATION...16/00Z
PREDICTING THUNDERSTORM CONDITIONS WILL BE A BIT DIFFICULT TONIGHT
DUE TO WEAK FORCING. TWO AREAS APPEAR MORE LIKELY. FIRST BEFORE 06Z
WOULD BE WEST OF KDSM...AND THEN AFTER 03Z NORTH NEAR THE MN BORDER.
STORMS WILL BE ISOLATED AND SHORT LIVED...SO HAVE CONTINUED TO HOLD
OFF PUTTING TSRA IN THE TAFS. AFTER 12Z...ALL CONVECTION AND DEBRIS
SHOULD BE CLEARING OUT FOR THE REMAINDER OF WED.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

LONG TERM...KINNEY
SHORT TERM...LEE
AVIATION...JUNGBLUTH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
350 PM CDT TUE JUL 15 2008

IAZ004>007-015>017-023>028-033>038-044>047-057-058-161100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-CRAWFORD-CARROLL-GREENE-BOONE-
AUDUBON-GUTHRIE-
350 PM CDT TUE JUL 15 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND
NORTHERN IOWA...NORTH OF A LINE FROM AUDUBON TO BOONE TO WAVERLY.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP LATE THIS
AFTERNOON INTO TONIGHT. A FEW SEVERE STORMS ARE POSSIBLE THROUGH
THE EVENING WITH THE MAIN THREAT BEING WINDS OF UP TO 65 MPH AND
HAIL UP TO NICKEL SIZE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THERE IS A CHANCE OF THUNDERSTORMS EVERY DAY FROM WEDNESDAY INTO NEXT
MONDAY. WIDESPREAD THUNDERSTORMS ARE EXPECTED THURSDAY NIGHT INTO
FRIDAY...WITH LOCALLY HEAVY RAINFALL POSSIBLE. MOST LOCATIONS CAN
EXPECT RAINFALL AMOUNTS OF 1 TO 2 INCHES...WITH ISOLATED HIGHER
AMOUNTS OF 4 INCHES OR MORE NOT OUT OF THE QUESTION. THE HEAVY
RAIN THREAT COULD LINGER FRIDAY NIGHT INTO SATURDAY. SOME SEVERE
STORMS ARE ALSO POSSIBLE...ESPECIALLY THURSDAY NIGHT THROUGH
FRIDAY...MAINLY IN THE FORM OF LARGE HAIL AND DAMAGING WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THROUGH THIS EVENING.

IAZ039-048>050-059>062-070>075-081>086-092>097-161100-
BLACK HAWK-STORY-MARSHALL-TAMA-DALLAS-POLK-JASPER-POWESHIEK-CASS-
ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS-
MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS-
350 PM CDT TUE JUL 15 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL AND
SOUTHERN IOWA...SOUTH OF A LINE AUDUBON TO BOONE TO WAVERLY.

.DAY ONE...TONIGHT

WIDELY SCATTERED NON-SEVERE THUNDERSTORMS ARE POSSIBLE NEAR THE
INTERSTATE 80 CORRIDOR.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THERE IS A CHANCE OF THUNDERSTORMS EVERY DAY FROM THURSDAY NIGHT INTO
NEXT SUNDAY. SCATTERED TO WIDESPREAD THUNDERSTORMS ARE EXPECTED
THURSDAY NIGHT THROUGH FRIDAY. LOCATIONS FROM WATERLOO THROUGH
AMES TO NEAR ATLANTIC CAN EXPECT RAINFALL AMOUNTS UP TO AN INCH
THROUGH THE DAY ON FRIDAY...WITH LESSOR AMOUNTS TO THE SOUTH.
ADDITIONAL LOCALLY HEAVY RAINFALL IS POSSIBLE FRIDAY NIGHT INTO
SATURDAY. A FEW SEVERE STORMS ARE ALSO POSSIBLE...ESPECIALLY
FRIDAY INTO SATURDAY...MAINLY IN THE FORM OF LARGE HAIL AND DAMAGING
WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE FRIDAY AFTERNOON INTO SATURDAY.

KINNEY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
628 PM CDT TUE JUL 15 2008

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

0627 PM     TSTM WND GST     1 S DOW CITY            41.91N 95.49W
07/15/2008  E60 MPH          CRAWFORD           IA   FIRE DEPT/RESCUE

&&

STEACHOU

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