River Flood Warning 67, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
556 AM CDT Fri Jun 21 2019

.DISCUSSION.../Today through Thursday/
Issued at 310 AM CDT Fri Jun 21 2019

MCS currently ongoing across south central Nebraska with additional
activity developing further west as a 50+ kt low level jet(LLJ)
continues to fuel the storms. The LLJ will shift further east this
morning and will bring increasing instability to southwest Iowa and
should help the MCS to maintain intensity as it reaches central and
south central Iowa. Several of the CAM solutions are weakening the
currently leading edge of the thunderstorms with the western new
development overtaking the lead storms as it reaches the forecast
area. Another area of storms may develop in advance of the MCS into
central Iowa where increasing elevated instability along a stronger
push of theta-e advection centered around 750 mb. These storms could
develop a large hail threat given increasing instability and
steepening lapse rates aloft. These storms should rapidly move east
through the area this morning but could produce local rainfall
amounts of 1-2 inches. Another concern that is being hinted at by
the CAMs and fits the situation is the development of a wake low
this morning with the most favored region being north of Highway 30.
The threat for a broad area of easterly winds in excess of 50 kts
will be the primary threat. Should the wake low develop, a High Wind
Warning may be necessary.

CAM solutions continue to suggest quick thunderstorm redevelopment
this afternoon in central and south central Iowa. There seems to be
a narrow window for this to occur before the elevated mixed
layer(EML) intensifies and caps the region. Model raw precipitation
chances look much too high later this afternoon and into the early
evening with the EML in place. A more plausible scenario is
increasing saturation below the EML that could lead to broad stratus
development and possibly drizzle. For this reason, have also lowered
high temperatures today with the low level saturation not allowing
for much warming. Thus after this mornings convection, the severe
weather threat is quite conditional.

The LLJ cranks back up towards midnight and combined with the
arrival of another impulse lifting through the southwest flow, may
be sufficient for additional thunderstorm development. The EML
intensifies once again late tonight into Saturday and may maintain
much of the day and keep the area storm free. Do have chance pops in
the forecast but that is to mainly capture and potential development
late in the afternoon. A more likely scenario is redevelop again
overnight as another strong short wave arrives along with the
increasing LLJ. The primary upper level system will eject out of the
intermountain west Sunday and Sunday night and will bring additional
showers and thunderstorms to the state, possibly lingering into
Monday morning. This activity could produce additional severe storms
and locally heavy rainfall. The heaviest rainfall potential today
through Sunday night is still projected over the southern half of
Iowa where 1 to 3 inches of rain are possible with the usual locally
higher amounts. Conditions for efficient rainfall rates are possible
at times during the period with PWATs increasing to near 2 inches at
times along with warm cloud depths over 12 kft. Therefore, despite
the general rainfall amounts mentioned, a few areas with heavy
rainfall rates could experience flash flooding and rises on local
streams.

Little chance beyond Monday. The biggest feature for the extending
is the building upper ridge into the Central and Northern Plains
which likely will bring more summer like heat to the state by the
mid to late part of the week. High temperatures in the 90s certainly
will be possible across portions of the state.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 552 AM CDT Fri Jun 21 2019

Thunderstorms will move across the area this morning. The storms
may contain small hail and gusty winds. An area of stronger winds
may develop on the backside of the storms near KMCW/KFOD by late
morning. MVFR to local IFR cigs are expected as the storms depart.
Additional redevelopment is possible near KDSM/KOTM late afternoon
and evening. A few patches of fog and IFR/MVFR cigs will persist
through much of the night.

&&

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

DISCUSSION...Donavon
AVIATION...Donavon

Hazardous Weather Outlook
National Weather Service Des Moines IA
349 AM CDT Fri Jun 21 2019

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-220900-
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-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
349 AM CDT Fri Jun 21 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Thunderstorms will move across the area this morning. Quarter
sized hail and damaging wind gusts in excess of 60 mph are
possible. Additional storms are possible especially especially
over southern Iowa late this afternoon and overnight with a few
severe storms possible.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Additional rounds of storms are anticipated over the weekend
mainly Saturday night into Monday. A few severe storms and locally
heavy rainfall will be possible during the period.

.SPOTTER INFORMATION STATEMENT...

Spotter activation might be needed at times over the next several
days.

Special Weather Statement
National Weather Service Des Moines IA
705 AM CDT Fri Jun 21 2019

IAZ047-048-059>061-073-074-211300-
Story IA-Boone IA-Marion IA-Jasper IA-Polk IA-Dallas IA-Warren IA-
705 AM CDT Fri Jun 21 2019

...GUSTY WINDS 40 to 50 MPH AND SMALL HAIL POSSIBLE...

At 704 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Perry to near Waukee to 8 miles south of
Avenue Of The Saints Event Center. Movement was northeast at 35 mph.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Des Moines, Ames, West Des Moines, Ankeny, Urbandale, Johnston,
Clive, Indianola, Altoona, Waukee, Boone, Norwalk, Pleasant Hill,
Grimes, Perry, Nevada, Adel, Windsor Heights, Carlisle and Bondurant.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

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.

&&

A Severe Thunderstorm Watch remains in effect until 1000 AM CDT for
south central and central Iowa.

LAT...LON 4116 9379 4151 9379 4150 9390 4190 9416
      4216 9365 4186 9330 4116 9317
TIME...MOT...LOC 1204Z 237DEG 30KT 4188 9408 4156 9386 4118 9374

Beerends

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