135
FXUS63 KDMX 151753
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1253 PM CDT Tue Jul 15 2025

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Warm and humid conditions continue today, cooler temperatures
  in the 70s on Thursday.

- Storm chances return to western Iowa late tonight (overnight)
  into Wednesday morning. A few strong storms possible with
  gusty winds the primary threat. Conditional threat for
  additional strong storms later Wednesday into Wednesday night,
  but will depend on morning activity.

- Drier to end the week before additional storm chances return
  at times into the weekend.

&&

.UPDATE...
Issued at 358 AM CDT Tue Jul 15 2025

Expectations for a quiet day remain today, though will see moisture
advection increase as Iowa sits in the warm sector in relation to a
developing low pressure system into Nebraska and Kansas this
evening. The cold front per guidance still looks to generally sag
into southern Minnesota into north/northwest Iowa and eastern
Nebraska late tonight into early Wednesday, with a 30-35 knot low
level jet nosing into Kansas. As the front gradually sinks southward
into Iowa Wednesday morning, an MCV will track along the boundary
across Iowa, which per CAM guidance is still somewhat varied on the
path and speed that this system will take. Generally speaking,
scattered showers and storms look to move into western Iowa around
midnight and track eastward, with instability values around 1000-
1500 and shear values around 25-30 knots that are favorable to
produce isolated strong to severe storms should any mature enough,
considering these storms will gradually lose steam with eastern
extent as the environment looks less conducive. Some CAM guidance
points to further development over northern into northeast Iowa into
the mid-late morning hours as heating increases, which could keep
the potential for isolated severe weather, with damaging winds
looking to be the main threat. Into the afternoon to evening, the
frontal boundary is slated to generally be somewhere over southern
Iowa, with recent guidance suggesting that the boundary would
be close to the IA/MO border, with redevelopment of scattered
showers and storms in the early evening, gradually pushing out
of the state Thursday morning as high pressure over the
Dakotas/Minnesota takes over the region. The question still
remains on the extensiveness of potential severe weather with
the evening activity, as it will still depend on how well the
atmosphere recovers following the morning activity. A close eye
will be kept on trends to better determine the potential outcome
of the later activity. For now, a conditional severe threat
remains reasonable, with a more broad-brushed Marginal Risk
across Iowa to include at least some chance for isolated severe
weather. The heavy rain potential remains highest with the
scattered activity Wednesday evening into early Thursday given
PWATS of 1.75-2 inches and warm cloud depths overhead, with 1-2
inches of rainfall possible in far southern to eastern Iowa,
where a Slight Risk for Excessive Rainfall is in place per WPC
guidance.

&&

.DISCUSSION...
Issued at 303 PM CDT Mon Jul 14 2025

Fog was quick to burn off this morning leaving mostly clear skies
across the state. Few weather concerns through the rest of today
into much of Tuesday with the exception of the heat and humidity
with temperatures in the mid to upper 80s this afternoon but when
paired with dew points in the 60s to 70s, has resulted in heat
indicies back in the upper 80s to 90s. Similar warm and humid
conditions are expected on Tuesday though moisture off the
Gulf increases into Wednesday as flow turns more southwesterly.

Although timing and strength discrepancies remain, there is decent
agreement in the CAMs and deterministic models of MCS development in
NE Tuesday evening that pushes eastward towards the Missouri River
late in the evening to early overnight hours. A 30-40 knot LLJ will
favorably sustain the activity through NE with the uncertainty lying
in what happens as the storms cross into Iowa. The parameter space
remains most favorable in western Iowa (pending storm arrival time)
where some risk for strong to damaging wind gusts could be
maintained before storms continue to diminish with eastward extent.
The Day 2 SPC Marginal (Level 1 of 5) Risk area covers this threat
well into early Wednesday morning.

Additional storms are forecast at times on Wednesday but are fairly
dependent on the mesoscale details following the MCS progression
into/though Iowa into Wednesday morning. Activity lingering longer
on Wednesday morning may push the surface boundary further south
towards the IA/MO border into Wednesday afternoon/evening with storm
development occurring far south to even south of the IA/MO
border. A MCS that decays faster with additional clearing and
heating/instability may allow storms to then develop further
north into Iowa in the warm sector ahead of the front. Although
instability in the warm sector of central to southern Iowa
blossoms on Wednesday afternoon into early evening, the better
shear lags behind the front. As such, uncertainty remains fairly
high Wednesday but some strong to severe storms may be possible
and conditions will continue to be monitored closely. The SPC
Day 3 Marginal (Level 1 of 5) Risk area again covers this threat
well, albeit the threat remains a bit conditional at this
point. The LLJ is not as robust on Wednesday night into
Thursday, but may help maintain some rain/storms over far
southern Iowa into the night.

With continuing maturing crops and a couple dry days now, the hydro
threat overall remains low, but exists nonetheless with some locally
heavy rain possible Wednesday as pwats reach between 1.5 and 2" with
favorable warm cloud depth. Precipitation amounts of 1-2" may occur
over portions of central into southern Iowa into early Thursday
morning, but location and amounts are highly dependent on where
shower/storms occur, as noted above.

Quiet conditions return for portions of Thursday into Friday as high
pressure returns before additional chances for showers/storms return
for the weekend. Cooler temperatures in the 70s to 80s will also be
in place behind the front on Thursday and Friday before temperatures
start to warm again especially into early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1242 PM CDT Tue Jul 15 2025

VFR conditions ongoing and expected to continue through much of
the night. Scattered diurnal cu will diminish tonight but clouds
will be on the increase west to east late tonight into early
Wednesday. Shower/storm chances also increase in western Iowa
near to after 06Z but confidence in showers/storms maintaining
to most sites too low at this time to include any precip
mentions overnight except at KFOD. Started with shower mentions
for KFOD with uncertainty as well in strength of activity as it
reaches the terminal. Additional showers/storms possible after
the overnight activity into Wednesday morning (and again
afternoon/evening) but coverage and timing remain far too
uncertain to address at this time. Some gusty winds out of the
south this afternoon will decrease tonight with winds shifting
to be out of the west to northwest ahead to behind the passing
boundary Wednesday.

&&

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

&&

$$

UPDATE...Bury
DISCUSSION...05
AVIATION...05