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263
FXUS63 KDMX 050820
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
320 AM CDT Sun May 5 2024

.KEY MESSAGES...

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-Strong to severe thunderstorms Monday later afternoon and
 overnight into early Tuesday. Damaging wind and perhaps few
 tornadoes are the primary hazards. Pockets of locally heavy
 rain also possible.

-Active pattern continues late week with additional
 thunderstorm chances.
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&&

.DISCUSSION...
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Issued at 318 AM CDT Sun May 5 2024

Surface high pressure has settled across the area early this
morning, resulting in calm winds and clear skies (excepting the high
cirrus blowing across southern Iowa from the complex impacting the
southern plains overnight). This has allowed for patchy fog to
develop early this morning, primarily in low lying areas. More
widespread fog development is not anticipated this morning but
patchy dense fog will likely continue through sunrise. High pressure
will continue to influence the area throughout the day as it slides
east, allowing for abundant sunshine and generally quiet conditions.

Our attention then turns to a robust upper level trough swinging
across the Rockies on Monday. Early impacts come in the form of a
tightening pressure gradient across the area which will induce
breezy winds out of the southeast ahead of the approaching system.
By late afternoon/early evening the leading edge of the trough
nudges into western Iowa. Initial environment into SW Iowa includes
around 1000-1500 J/kg of MLCAPE with 40-50+ kts of 0-6 km shear. Low
level hodographs continue to show nicely swept areas and SRH remains
around 200 m2/s2 to start. With lackluster lapse rates, hail is not
a big concern. And while CAPE may not support sustained severe
storms, damaging winds would be the primary concern with a
linear storm mode. The tornado risk is also worth keeping an
eye on, hinging mainly on whether storms can remain surface
based versus becoming elevated through the overnight. While the
low- level jet will help to maintain storms overnight,
instability diminishes further east and would expect to see
diminishment into Tuesday morning. At the same time, a
widespread 1-1.5" of rain is anticipated with embedded locally
higher amounts pushing 2+" possible. Given the progressive
nature of storms, flash flooding shouldn`t be a problem, however
recent heavy rains in the last week could leave localized areas
more susceptible to hydro problems.

The rest of the week will see additional storm chances as the main
trough axis passes across the area. How exactly this plays out is
less certain as models diverge in handling of these interacting
systems.
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&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1157 PM CDT Sat May 4 2024

Main change is the decrease confidence in fog for sites
overnight. Have removed fog mentions for all but KFOD. Patchy
fog cannot be ruled out given clear skies and calm winds.
Otherwise, VFR with light winds becoming easterly during the
daylight hours.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Hagenhoff
AVIATION...Jimenez