Severe Thunderstorm Warning 159, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
306 PM CDT Fri Aug 19 2022

.DISCUSSION.../Tonight through Friday/
Issued at 304 PM CDT Fri Aug 19 2022

Key Messages:

-Severe Storms This Afternoon and Evening
-More Storms Tomorrow With Slightly Reduced Severe Threat
-Relatively Quiet and Seasonal Through Beginning of the Week

The surface low to our north has begun to make it's way south into
the state as the first of the storms associated with it have started
to impact most of central Iowa. The passage of this low tonight and
tomorrow will be the main show within this forecast period with
conditions quieting down significantly in it's wake.

The first of the impacts from this system will be through this
afternoon and evening as surface heating erodes the cap and
scattered storms fire off in southern and central Iowa. In addition,
more stratiform showers and storms will begin to track into northern
Iowa with the low and it's associated cold front. However, the
greatest severe threat will be with the central and southern storms
where the environment is more favorable for organized
development. Cool air aloft with steep low level lapse rates will
provide sufficient instability to these storms and promote strong
updrafts. Favorable speed shear will also assist in the
organization of these updrafts, making the atmosphere conducive
for strong storms this afternoon. In addition to storm
organization, low melting levels and dry low levels will help
promote severe hail and strong cold pools, resulting in damaging
wind gusts. This environment will also support funnel cloud
development below stronger updrafts. The severe threat with storms
in northern IA is a bit lower, but a few strong storms are still
possible there as well. Scattered storms are expected to continue
through the night but the severe threat should diminish later this
evening.

Tomorrow's storms should pose less of a severe threat than this
evening's, however funnel cloud development is again possible with
sufficient instability in the low levels. However, with relatively
high LCLs the tornado threat is low. A few stronger storms do still
remain possible, but will be somewhat limited by the weak
instability and low shear profiles. These showers and storms will
fester through most of the day but chances begin to diminish in the
afternoon and evening as the low departs to the east. Following this
system, the weather will quiet down with cool and dry conditions on
Sunday. This pattern will continue through the beginning of the week
with seasonal temperatures and mostly dry conditions. Showers return
to the forecast on Wednesday with off and on chances through the end
of the week, however it's a bit too early to lock down any
specific details regarding the late week rain.

&&

.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 100 PM CDT Fri Aug 19 2022

Ceilings should be mostly VFR this afternoon with some scattered
clouds at MVFR heights. Showers and storms moving in from the
north could also lead to lower ceilings for sites impacted.
Confidence is fairly low on exact location of showers and storms,
but all sites in the area could potentially see some vicinity
lightning or showers through the evening. Tomorrow morning,
ceilings and visibility could drop into IFR, but have kept TAFs
MVFR for now and will re-assess at next issuance. Patchy fog is
also possible in the northwest, but is also not yet reflected in
the TAFs.

&&

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

DISCUSSION...Dodson/Hahn
AVIATION...Dodson/Donavon

Hazardous Weather Outlook
National Weather Service Des Moines IA
1113 AM CDT Fri Aug 19 2022

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-201615-
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-
1113 AM CDT Fri Aug 19 2022

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Scattered thunderstorms are expected again today. A few strong to
severe storms will be possible this afternoon into the evening
with large hail and damaging wind gusts the primary threats.
There may also be some funnel clouds with a few of the storms
today.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Scattered, mainly non-severe, thunderstorms will continue into
Saturday. Gusty winds and perhaps a few funnel clouds may also
occur.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed this afternoon and evening.

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