Special Weather Statement, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
142 PM CDT Wed Aug 24 2016

.SHORT TERM.../Tonight/
Issued at 142 PM CDT Wed Aug 24 2016

Concern today/tonight will be coverage and evolution of expected
convection along/ahead of the weak cold front. Currently the front
resides northeast to southwest across central Iowa and will continue
to slowly progress further south/southeast before stalling out in
southern Iowa/northern Missouri. While the front itself is suspect
with regard to triggering convection, a shortwave remains on track
to traverse the state this evening coincident with the front helping
provide necessary lift.

Severe weather parameters remain meek through Iowa, with best
opportunities remaining south into Missouri. However, with decent
recovery in southeast Iowa this afternoon, a small window for a
severe storm or two remains possible with hail and damaging winds
most likely. Primary severe threat through the evening will be
damaging winds associated with any MCS development, as hinted by at
least some guidance solutions, or collapsing cells. Bigger concern
remains potential for heavy rainfall through southern/southeast
Iowa. Should front stall in the vicinity, set up appears ideal for
training storms with storm motions parallel to the slow
moving/stalled front and broad lift with the front and shortwave.
Localized totals of 2-3 inches or more would not be surprising,
possibly creating flooding concerns, as seen by the active flash
flood watch over the area. Fortunately, areas most likely to see
heavy rainfall this evening/overnight have been relatively dry the
last few days and should be able to handle a fair amount of
rainfall.

.LONG TERM.../Thursday through Wednesday/
Issued at 142 PM CDT Wed Aug 24 2016

Not many changes to the going grids with mainly dry conditions
expected initially. Cold front moving through the CWA today to stall
out across the south tonight and may have some lingering activity
across the south into early Thursday. Expect though most of the
activity and additional development will be south of the CWA with
the front pushing into MO Thursday. Weak energy continues to push
northeast aloft with additional development in vicinity of the
stalled out boundary into Thursday nigh and Friday, but again should
remain south of state. By Friday night, boundary starts to lift
northward through the state Friday in advance of a stronger
shortwave trough lifting out of the southern Rockies. Strong
southerly flow and moisture into the state, should allow for an
expansion of thunderstorm chances across the state Friday
night/early Saturday. Sfc low to move through Saturday with a main
upper level trough moving through the northern Plains toward Iowa
bringing additional chances for convection later Saturday with
another cold frontal passage. Front then stalls out near the
southern portion of the state into Missouri early next week.

As for temperatures cooler temps into the 70s expected for Thursday
into Friday and warming up again into the low to mid 80s for
Saturday behind the warm front and ahead of the cold front moving
through later in the day. Not a big push of cool air behind the
front late Saturday, so temps stay closer to the seasonal averages
into next week.

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1233 PM CDT Wed Aug 24 2016

Line of MVFR/IFR CIGs continues to move across the state with
surface front, dropping sites below VFR for 3-4 hour periods. Line
nearly through KFOD, a couple hours remaining for KMCW and
approaching KALO. Those 3 sites will go VFR once through. KDSM and
KOTM will deal with both low CIGs associated with front, and
expected convection this afternoon/evening. In both instances,
MVFR conditions likely from convection, but have withheld for now
waiting for coverage/timing to show itself.

&&

.HYDROLOGY...
Issued at 142 PM CDT Wed Aug 24 2016

Abundant moisture and possible training of cells will lead to the
potential for flash flooding across southern Iowa tonight.
Efficient rainfall production is anticipated with higher rainfall
rates possible. Warm cloud depths not as deep as in previous days,
but still sufficient to produce the higher rainfall rates. Current
trend in the high-res models also suggesting some of the heavier
rain potential pushing further south of the area into northern MO,
however threat still enough to warrant keeping the flash flood
watch for far southern Iowa tonight.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 7 PM CDT this evening through Thursday
morning for Adams-Appanoose-Clarke-Davis-Decatur-Lucas-Mahaska-
Marion-Monroe-Ringgold-Taylor-Union-Wapello-Wayne.

&&

SHORT TERM...Curtis
LONG TERM...Beerends
AVIATION...Curtis
HYDROLOGY...Beerends

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
440 PM CDT WED AUG 24 2016

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>073-251100-
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-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-
440 PM CDT WED AUG 24 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TONIGHT...MAINLY IN CENTRAL
TO SOUTHERN IOWA. LOCALIZED HEAVY RAINFALL IS EXPECTED ALONG WITH
THE POSSIBILITY OF SMALL HAIL AND GUSTY WINDS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORM CHANCES RETURN TO THE AREA FRIDAY NIGHT THROUGH THE
WEEKEND. THE SEVERE AND HEAVY RAIN THREATS LATE IN THE WEEK
WILL BE BETTER DETERMINED IN LATER FORECASTS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT LIKELY TONIGHT.

IAZ074-075-081>086-092>097-251100-
MARION-MAHASKA-ADAMS-UNION-CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-
RINGGOLD-DECATUR-WAYNE-APPANOOSE-DAVIS-
440 PM CDT WED AUG 24 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TONIGHT

HEAVY RAIN REMAINS POSSIBLE TONIGHT.  A FLASH FLOOD WATCH IS IN
EFFECT FOR THE AREA TONIGHT. PLEASE REFER TO THE NATIONAL WEATHER
SERVICE WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER DETAILS.

IN ADDITION...AN ISOLATED STORM MAY BECOME SEVERE WITH GUSTY WINDS
AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORM CHANCES RETURN TO THE AREA FRIDAY NIGHT THROUGH THE
WEEKEND. THE SEVERE AND HEAVY RAIN THREATS LATE IN THE WEEK
WILL BE BETTER DETERMINED IN LATER FORECASTS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TONIGHT.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
502 PM CDT WED AUG 24 2016

IAZ071-072-242245-
MADISON IA-ADAIR IA-
502 PM CDT WED AUG 24 2016

...RAPIDLY INTENSIFYING STORM MAY PRODUCE UP TO DIME SIZE HAIL
AND HEAVY DOWNPOURS...

AT 502 PM CDT...DOPPLER RADAR WAS TRACKING STRONG THUNDERSTORMS ALONG
A LINE EXTENDING FROM NEAR GREENFIELD TO 6 MILES SOUTHWEST OF
WINTERSET. MOVEMENT WAS NORTHEAST AT 35 MPH.

DIME SIZE HAIL WILL BE POSSIBLE WITH THESE STORMS.

LOCATIONS IMPACTED INCLUDE...
WEST DES MOINES...WINTERSET...EARLHAM...ORIENT...PATTERSON...
MACKSBURG...BADGER CREEK STATE PARK AND WINTERSET-MADISON COUNTY
AIRPORT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THESE STORMS...AND MAY
LEAD TO LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH
FLOODED ROADWAYS.

THESE STORMS MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO
STATIONS AND AVAILABLE TELEVISION STATIONS FOR ADDITIONAL INFORMATION
AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.

&&

LAT...LON 4116 9451 4150 9418 4151 9379 4139 9379
      4116 9401
TIME...MOT...LOC 2202Z 232DEG 30KT 4126 9438 4126 9407

KOTENBERG