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683
FXUS63 KDMX 152054
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
354 PM CDT Sat Jun 15 2024

.KEY MESSAGES...

 
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- Some strong to severe thunderstorms remain possible late
   this afternoon into evening, mainly west with all hazards
   possible. Although severe threat decreases with eastward
   extent, heavy rain potential will continue into the night as
   storms move northeastward with time into Sunday morning.

 - Very warm and humid Sunday and Monday with highs near to in the
   90s and heat indices nearing or in the 95-100 degree range
   at times.

 - Off and on chances for showers and storms later Sunday north and
   again at times this week. Chances for locally heavy rain or
   stronger storms will remain at times as well.
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&&

.DISCUSSION...
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Issued at 323 PM CDT Sat Jun 15 2024

Rest of Today Through Sunday:

Decaying MCS brought varying amounts of rain to a good portion of
the CWA this morning with some areas seeing a few rounds of showers
or a few storms with lightning as some storms developed just behind
the main line in parts of northern and southern Iowa. By late
morning into midday, clearing started to occur over parts of
southwest Iowa extending back into eastern Nebraska, northwest
Missouri, and northeast Kansas where a prominent outflow boundary
was traversing southward as well.

9Z analysis had the shortwave crossing through central
Nebraska/Kansas with a very slow moving warm front draped through
east central NE into northeast KS with temperatures near to in the
90s with dew points in or near the 70s along the boundary. As
generally expected, temperatures have remained lower through much of
central Iowa so far today thanks to the showers this morning and
lingering cloud cover. In saying this, we still have a few more
hours of peak heating that will allow temperatures to continue to
warm, especially over central to western Iowa where the most
clearing has occurred. Moisture will continue to increase as
well, especially over western Iowa where low to mid-level
moisture transport is highest. Both of these things should
continue to decrease the remaining CAP while also increasing
instability values through the rest of the afternoon hours, as
seen in east central Nebraska where MLCAPEs have climbed to
2000-2500 J/kg. Although it is unlikely we will quite climb that
high in our western area, MLCAPEs may be able to reach or near
1000-2000 J/kg by around 00Z paired with marginal effective bulk
shear of around 25-30 knots. All this being said, there remains
a window for some strong to severe storms tonight. The most
favorable area appears to be just outside of our CWA, but cannot
completely rule out potential for a few supercells to reach our
area bringing a large hail or tornado threat initially, with
damaging wind gusts also a concern as well. Some hi- res
guidance continues to kick off some near-severe gusts as storms
congeal and move into west central Iowa, but overall uncertainty
remains high in how the event will play out and overall
severity of storms as they move into our CWA with most guidance
suggesting a weakening trend as storms move into central Iowa.

Although storms are expected to weaken with time tonight, showers
and storms continue to fester through much of the overnight not
ending until Sunday morning in the east thanks in part to the LLJ.
Pwats of 1.5-2" with favorable warm cloud depths will keep a heavy
rain threat going through the night with rain amounts of 1-2" and
isolated 2-3+" possible for areas that receive repeated rounds of
storms.

Behind the morning showers moving out, increasing heat and humidity
will be the main story on Sunday as temperatures reach near to into
the 90s and heat indices top out in the upper 90s in many areas
central to south on Sunday afternoon. Extent of heat may depend on
how fast any lingering cloud cover moves out, with additional cloud
cover possible in northern Iowa later in the day, potentially
helping to keep temperatures north down slightly. The aforementioned
warm front boundary to the southwest today will lift through the
rest of the area tonight stalling out to the north tomorrow.
Multiple rounds of storms are possible to the north Sunday night
that we will have to continue to monitor. Guidance remains uncertain
in if any storms will dive far enough south into Iowa but will
continue to monitor trends as some potential for stronger
storms could exist if they propagate far enough south. SPC`s Day
2 Marginal to Slight Risk captures this potential.

Beyond Sunday, Iowa will be between an amplifying ridge over the
eastern U.S. and a digging trough over the northwest U.S. Hot
and humid conditions will continue to start the week as
temperatures on Monday remain in the upper 80s to 90s with heat
indicies well into the 90s again. Little relief is expected at
night with lows in the 70s, which may challenge some high
minimum temperature records on Monday and/or Tuesday morning.
There will also be multiple opportunities for additional storms
this week, notably Tuesday into Wednesday as the front stalled
out up north dives back south. Winds will also be breezy through
the next several days which may help mitigate some of how the
heat feels. Uncertainty increases again later in the week with
additional details on any storm threats to come.
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&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1245 PM CDT Sat Jun 15 2024

VFR conditions ongoing across much of the area as a decaying MCS
continues to push through the area with lingering showers near
KMCW early this afternoon with a few potentially nearing KOTM as
well. Additional storms still expected to develop west late this
afternoon into the evening before spreading east to northeast
with time through the evening and overnight hours. Confidence in
timing and direct impacts to TAF sites remains low due to
uncertainty in exactly where storms form and how they track, but
general trends give more confidence for impacts to
KFOD/KMCW/KALO at some point into the night, with lesser
confidence in extent of impacts at KDSM or KOTM. Updates are
likely in rain/tstorm mentions, timing, and potential lower CIG
or VIS impacts as storms form and start to move east/northeast.
Winds out of the south to southeast also remain gusty this
afternoon with higher gusts certainly possible during storms.

&&

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

&&

$$

DISCUSSION...KCM
AVIATION...KCM