Severe Thunderstorm Warning 152, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
1147 PM CDT Sun Jul 16 2023

...Updated for the 06z Aviation Discussion...

.DISCUSSION.../Tonight through Sunday/
Issued at 230 PM CDT Sun Jul 16 2023

Key Messages:

-Surface smoke expected to gradually diminish overnight.
-Isolated to scattered showers/storms into tonight, some
 marginally severe.
-Quiet and relatively pleasant mid-summer weather to end the work
week.

Convection in area of warm advection and theta-e advection remained
mostly south and west of the area this morning into early afternoon.
Some shower activity did clip the far southwest but with minimal
impact.  Meanwhile, smoke from Canadian fires remains relatively
widespread across the state into this afternoon although with some
signs of improvement.  This has also once again kept afternoon highs
from reaching the overall potential that otherwise would have
occurred. A cold front will approach and move into northern Iowa by
this evening and this may produce some isolated convection with main
concern from gusty winds and possibly some hail across the north.
Meanwhile, a moisture gradient exists over central Iowa this
afternoon along with the higher instability and this may also act as
a focus for convection into the evening and overnight as the front
approaches. Some CAM members have continued to show widely scattered
storms by mid evening near along this gradient (near I80
corridor) with the threat gradually shifting south overnight as
the front pushes through the state. Given better instability with
this convection, an isolated storm may produce some marginally
severe hail along with gusty winds. The advance of the front
should also help dissipate the smoke overnight with visibilities
and air quality improving by daybreak on Monday.

Quiet weather is expected on Monday into Monday night across central
Iowa with cool temperatures and low humidity as a thermal trof
passes just northeast of the area.  Warm advection and moisture
transport increase late Monday night into Tuesday morning across the
Missouri River valley with convection increasing during the early
morning hours.  The bulk of the activity is expected to remain west
of the area through Monday night where the focus of the low level
jet remains.  By Tuesday morning, the theta-e push enters southwest
Iowa with convection spreading into the southwest forecast area.
While some threat remains for showers and storms farther northeast,
any precipitation should be lighter and more scattered with the bulk
of moisture streaming into the convective complex across the
southwest into midday.  The convection is also expected to remain
elevated with any severe threat originating from marginally severe
hail.  Heavy rain remains possible as well with a decent moisture
fetch feeding into the convection.  Lingering scattered showers
remains possible into Tuesday evening across much of the area,
however the main focus of the low level jet will be just southeast
of Iowa where deeper convection is expected from northeast Missouri
into Illinois.

Iowa is between systems on Wednesday morning with a relative lull in
forcing across the state and limited precipitation threat.  A cold
front does sweep through the state late in the day providing the
focus for some isolated convection as cooler air arrives. Relatively
tranquil weather is then expected into Thursday and Friday with cool
northerly surface flow.

&&

.AVIATION.../For the 06Z TAFS through 06Z Monday night/
Issued at 1134 PM CDT Sun Jul 16 2023

Visibilities from smoke will gradually improve from MVFR to VFR
tonight as a frontal boundary moves through the state. Expecting
showers and thunderstorms to increase in coverage across the
south. Thus, have VCTS and VCSH mentions for KDSM and KOTM early
Monday morning. Confidence is low for any direct impacts to these
terminals, but expect reduced visibilities and low ceilings with
any storms that form. Winds will generally be from the north early
in the period before becoming light and variable towards the end
of the period.

&&

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

DISCUSSION...Cogil
AVIATION...Castillo/Small

Hazardous Weather Outlook
National Weather Service Des Moines IA
833 PM CDT Sun Jul 16 2023

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-180145-
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-
833 PM CDT Sun Jul 16 2023

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

A few strong storms are possible, especially central and south,
with strong wind gusts and hail the primary threats.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Additional thunderstorm chances exist much of Tuesday with strong
to severe storms possible, mainly across the southwest third of
the forecast area.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed tonight and again Tuesday.

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