River Flood Warning 48, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
614 AM CDT Fri May 24 2019

.DISCUSSION.../Today through Thursday/
Issued at 613 AM CDT Fri May 24 2019

Convective trends remain the primary forecast focus and will
remain so through the Memorial Day weekend into at least the
middle of next week. Overall the models are in decent agreement
through that time with a continued active pattern. Southwest flow
aloft will transition to minor ridging late in the weekend and
then back to southwest flow again early next week allowing for
only brief breaks from convection.

At onset, the situation is volatile with tremendous 0-1km
shear/SRH across southern Iowa just north of a northern MO warm
front. Objective analysis suggests the instability environment is
marginal, but radar trends suggests otherwise with a very healthy
QLCS advancing into the forecast area in strong effective shear.
Thus expect the MCS to maintain itself for a while at least with
all modes of severe weather possible. The only thing holding the
severe potential back for now seems to be the lack of cold pool
generation and/or getting rooted low enough.

Later today the warm front and weak surface low over eastern NE
are expected to advance northward through IA with a considerable
airmass changes across the state. It will be humid with MLCAPEs
reaching around 2K j/kg with 40-50kts of 0-6km shear. The surface
flow will be broad southwesterly, with little convergence, but the
lingering thermal discontinuity across NE/KS early this morning
should advance into the state and potentially aid convective
initiation. This will combine with any remnant MCVs from overnight
convection upstream and other weak synoptic waves in the
southwest flow to trigger additional convection over central and
southeast IA with severe weather possible, This will likely
transition into a heavy rain threat into the night south and east.
There will be strong 850MB moisture transport into the convection
and with the mean wind parallel to the convective axis, and
opposite the low level inflow, the convection may train over
similar areas with minimal Corfidi Vectors as well. Precipitation
waters will be approaching 2 inches with 3.5km warm cloud depths
so 1-3 inch rains are certainly possible, with locally higher
amounts much like occurred this morning. Thus have issued a Flash
Flood Watch to account for this possibility.

The convection should exit to the south and east and weaken into
Saturday morning, but a weak synoptic front will linger SW to NE
across the state again Saturday. The thermodynamic environment
will be even greater by peak heating with MLCAPEs pushing 3K j/kg
and 50kts of deep shear. Thus additional severe weather with large
hail and damaging winds are possible. Low level winds appear too
weak and veered for much tornado potential. The heavy rain threat
does not appear as great with this round however as the deeper
moisture will be pushed just to the south and east with the low
level jet into the night veering to WNW into the early morning
hours and staying south.

This should lead into a break Sunday before a more coherent short
wave lifts into the MO Valley Sunday Night into Monday. We will
then see another repeat cycle of nocturnal, possibly severe, MCS
and then potentially additional peak heating severe convection
into Monday. The tornado potential will be in or near Iowa, but
dependent on where the warm front lays out. This will likely
transition into yet another round of nocturnal convection Monday
Night with more heavy rain potential. Large scale forcing
attendant to the long wave trough is expected to produce
significant convective into Tuesday and Tuesday Night before there
is finally some light at the end of the tunnel toward drying out
and a flip to NW flow into the end of the next work week.

&&

.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1151 PM CDT Thu May 23 2019

Showers and thunderstorms moving into TAF locations from the west.
Expect cigs to drop to MVFR with local IFR cigs in heavier showers.
MVFR vsbys will accompany tsra with local IFR vsbys in stronger
storms.  Latest models suggest a break in precip during the day
though isold shra may linger then redevelopment south and east aft
25/00Z.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from this afternoon through Saturday morning
for IAZ050-061-062-072>075-081>086-092>097.

&&

DISCUSSION...Small
AVIATION...FAB

Hazardous Weather Outlook
National Weather Service Des Moines IA
421 AM CDT Fri May 24 2019

IAZ050-061-062-072>075-081>086-092>097-250930-
Tama-Jasper-Poweshiek-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
421 AM CDT Fri May 24 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

A Flash Flood Watch is in effect for this area. Please refer to
the National Weather Service website at weather.gov/desmoines for
further details.

Thunderstorms are expected throughout today. A few storms may be
strong to severe, with large hail and damaging winds the primary
threat. Heavy rainfall may lead to flash flooding and river
flooding.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Outside of a brief break around Sunday, periodic thunderstorm
chances are expected into early next week, including Memorial
Day. Severe weather primarily in the form of large hail, damaging
wind gusts, and moderate to heavy rainfall will be possible at
times. Flash flooding and river flooding risks will increase
through the weekend.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed off and on through the Memorial Day
weekend, especially today, Saturday, and Monday.

IAZ004>007-015>017-023>028-033>039-044>049-057>060-070-071-250930-
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-Audubon-Guthrie-Dallas-Polk-Cass-Adair-
421 AM CDT Fri May 24 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Thunderstorms are possible today, especially towards central and
to southeastern Iowa. A few storms may be strong to possibly
severe, with large hail and damaging winds the main threats. Heavy
rainfall may also increase flash flooding and river flooding
risks.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Outside of a brief break around Sunday, periodic thunderstorm
chances are expected into early next week, including Memorial
Day. A few storms may be strong to possibly severe. Flash
flooding and river flooding risks will increase through the
weekend.

A River Flood Warning remains in effect for the West Fork Des
Moines River near Estherville for the foreseeable future. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed off and on through the Memorial Day
weekend, especially today, Saturday, and Monday.

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
107 AM CDT Fri May 24 2019

IAZ071-072-082-240630-
Adair IA-Union IA-Madison IA-
107 AM CDT Fri May 24 2019

...Line of Storms May Produce Dime to Nickel Size Hail and
Strong Winds..

At 107 AM CDT, Doppler radar was tracking a strong thunderstorm near
Green Valley Lake, or 8 miles north of Creston, moving northeast at
50 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Creston, Winterset, Green Valley Lake, Orient, Lorimor, Macksburg,
Green Valley Lake State Park, Creston Municipal Airport and
Winterset-Madison County Airport.

LAT...LON 4126 9444 4146 9400 4116 9397 4116 9401
      4110 9402 4098 9445
TIME...MOT...LOC 0607Z 239DEG 43KT 4118 9440

Kotenberg

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Special Weather Statement
National Weather Service Des Moines IA
234 AM CDT Fri May 24 2019

IAZ038-039-049-050-061-062-240800-
Black Hawk IA-Tama IA-Poweshiek IA-Grundy IA-Jasper IA-Marshall IA-
234 AM CDT Fri May 24 2019

...Line of Storms May Produce Strong Winds of 40 to 50 mph...

At 234 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles northwest of Marshalltown to near Rock
Creek Lake. Movement was northeast at 55 mph.

Wind gusts up to 50 mph will be possible with these storms.

Locations impacted include...
Marshalltown, Toledo, Tama, Traer, Reinbeck, Conrad, Meskwaki Casino,
Rock Creek Lake, Gladbrook, Le Grand, Garwin, Gilman, Albion,
Chelsea, Montour, Laurel, Clutier, Elberon, Beaman and Haverhill.

LAT...LON 4192 9230 4173 9295 4212 9310 4245 9254
      4205 9230
TIME...MOT...LOC 0734Z 232DEG 51KT 4208 9304 4176 9288

Kotenberg

Special Weather Statement
National Weather Service Des Moines IA
307 AM CDT Fri May 24 2019

IAZ060-061-073-074-240845-
Marion IA-Jasper IA-Polk IA-Warren IA-
307 AM CDT Fri May 24 2019

...Line of Storms May Produce Brief Winds in Excesss of 40 mph...

At 305 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Iowa State Fairgrounds to 9 miles
southeast of Avenue Of The Saints Event Center. Movement was east at
40 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Des Moines, Newton, Indianola, Altoona, Pleasant Hill, Knoxville,
Carlisle, Bondurant, Mitchellville, Colfax, Monroe, Pleasantville,
Prairie City, Adventureland Amusement Park, Iowa Speedway, Prairie
Meadows, Iowa State Fairgrounds, Knoxville Raceway, Lake Red Rock and
Milo.

LAT...LON 4175 9292 4126 9301 4122 9363 4167 9355
TIME...MOT...LOC 0805Z 265DEG 34KT 4162 9352 4119 9369

Kotenberg

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
359 AM CDT FRI MAY 24 2019

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

0359 AM     HEAVY RAIN       9 SW CUMBERLAND         41.17N 94.97W
05/24/2019  M4.18 INCH       CASS               IA   PUBLIC

            MEASURED BY HOME WEATHER STATION.

0358 AM     HEAVY RAIN       6 NNE CARBON            41.13N 94.79W
05/24/2019  M4.22 INCH       ADAMS              IA   PUBLIC

            MEASURED BY HOME WEATHER STATION.

&&

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