Hail and Damaging Wind in Iowa, August 11, 2023

Area Forecast Discussion
National Weather Service Des Moines IA
636 AM CDT Fri Aug 11 2023

...Updated for the 12z Aviation Discussion...

.DISCUSSION.../Today through Thursday/
Issued at 357 AM CDT Fri Aug 11 2023

Key Messages:

- Storms ending over the east early this morning.
- Additional storms possible with greatest chances over far
  southern Iowa.
- A few strong storms possible Sunday afternoon and evening.

An area of thunderstorms is moving across the state from west to
east this morning and these are associated with a region of strong
theta-e advection and upper short wave. Thus far, the storms have
remained below severe limits though wind gusts of 30 to 40 mph have
been common in the Highway 20 to Highway 30 corridor. Outflow
dropping south has led to some briefly stronger updrafts over
southern Story county and into northeast Polk and western Jasper but
these have mostly resulted in melting small hail along with gusty
winds along the outflow. Some areas also had one to two inches of
rainfall with that focus on the redevelopment areas along the
outflow in Story and Jasper counties. These storms will move east of
the area in the next few hours.

Today will be mostly dry as the temperature and dew point spread
combined with a relatively dry surface to 700 mb layer cap surface
based convection. There is moisture above 700 mb and in some areas
this is modest MUCAPE with parcels lifted from that level. Isolated
storms may occur over central and northern Iowa very late this
afternoon and overnight. Greater chances are possible over south
central Iowa and into Missouri with the low level jet focused into
that region that may activate increasing MUCAPES > 2000 J/kg. PWAT
values will approach 2 inches so where the development occurs,
efficient warm rain processes are possible with warm cloud depths
near 13 kft. That said, attm, the main focus looks to be just south
into northern Missouri with the NAM farther north than other
solutions with the main precipitation core.

Beyond the next 24 hrs, the next main weather maker is a strong
short wave cluster that will be moving through the upper level
westerly/slightly northwesterly flow. This system will evolve into
an upper closed low as it moves into the Upper Midwest on Sunday.
Thunderstorms are possible from late Saturday night through Sunday
evening with a few strong storms possible especially along the cold
front. The timing of the cold front as of now looks to be late
Sunday afternoon and into the evening.

Monday will be cooler with highs in the 70s as the state is within
the cyclonic region of the departing upper low. A few showers and
isolated storms could occur within that cyclonic flow and at the
moment, that potential is not well represented in this forecast.
Will continue to monitor this period for possible PoP increase.
Temperatures should again gradually warm through mid-week and back
into the 80s followed by another system late in the week.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 633 AM CDT Fri Aug 11 2023

VFR conditions for much of the period with some passing mid-level
clouds through the day today. There is the potential for a few
storm late this afternoon and overnight. Chances at any one
location is low enough to preclude from mention in the terminals
but will add if confidence increases. The wind will become
southwest to west and could be breezy at times today.

&&

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

DISCUSSION...Donavon
AVIATION...Donavon

Hazardous Weather Outlook
National Weather Service Des Moines IA
505 AM CDT Fri Aug 11 2023

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-121015-
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-
505 AM CDT Fri Aug 11 2023

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Chances for showers and storms return early this evening with
some stronger storms possible, mainly in the east.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Storm chances return for Sunday with strong storms possible. Large
hail and strong wind gusts are the primary hazards.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.