789
FXUS63 KDMX 171123
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
623 AM CDT Thu Jul 17 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Drier & cooler Today

- Multiple rounds of showers/storms Friday and this weekend with
  potential for heavy rain and severe weather at times. Marginal
  Severe Risk Friday-Saturday, and Slight Risk (Level 2 of 4)
  ERO for Friday-Sunday.

&&

.UPDATE...
Issued at 346 AM CDT Thu Jul 17 2025

Lingering shower and storm activity this morning is focused just
about completely into MO where the frontal boundary that recently
passed across Iowa is now located. At this time, only a few showers
are just barely skirting the IA/MO border, with only minimal
rainfall amounts expected before the front tracks further south and
east out of the region near and after sunrise today. High pressure
sinking into the region will continue to bring widespread subsidence
and drier air across the state, with northerly surface flow keeping
temperatures cooler today as highs are only expected to make it in
the low to mid 70s.

Upper level zonal flow will remain into the central CONUS Friday,
though in the lower levels, southwesterly flow is expected to
gradually overspread across Iowa through the day. Increasing theta-e
advection, especially by the afternoon and especially evening will
bring pooling moisture and warmer temperatures back into the state.
A mid-level shortwave within the larger scale flow per guidance
looks to arrive near Iowa into the afternoon, though another system
to the south of the state will also be near. Models generally
develop spotty convection over the state, with moderate instability
and shear overhead, though forcing looks to be on the weaker side. A
few strong to severe storms may occur with this activity, with wind
looking to be the main hazard. However, a more defined boundary with
the aforementioned shortwave looks to sag somewhere into northern
Iowa late Friday into Saturday, dropping a MCS through the state
through the morning hours. Given better forcing with the boundary
and presence of a 35-40 knot low level jet reaching into the state,
as well as moderate instability values of 2000+ J/kg and shear
values of 35+ knots, a higher potential for at least isolated severe
storms would at least be in place with this system, though track and
coverage are still quiet uncertain given model differences that
still remain. Again, wind looks to be the primary severe weather
hazard with DCAPE values over 1000+ J/kg. The SPC has placed much of
Iowa in a Marginal Risk for severe weather, which is fair at this
time. The potential for heavy rain also remains in play Friday into
Saturday morning, given PWATS near 2 inches, along with deep warm
cloud depths, which is highlighted by a Slight Risk for Excessive
Rainfall into northern and eastern Iowa. Details are expected
to gradually come into better focus over the next few forecast
packages. The weekend still holds a decent signal for more on
and off showers and storms at times, with additional chances for
a least some potential for severe weather Saturday and heavy
rain at times throughout the weekend.

&&

.DISCUSSION...
Issued at 228 PM CDT Wed Jul 16 2025

Surface low continues to push eastward early this afternoon into
northeast Iowa/southwest Wisconsin with the associated surface cold
front already largely through the area as of early afternoon. This
has resulted in quite pleasant temperatures having already arrived
in much of the area with temperatures in the 70s to low 80s. The
lingering rain from the MCV this morning in the north/northeast has
also largely diminished into early this afternoon with just a few
showers or sprinkles remaining north central to northeast. With the
location of the front and associated warm sector, storm chances for
the afternoon and evening have pushed southward into Missouri and
considerably diminished PoPs as a result. Some may see a brief
shower or sprinkle still this afternoon, but otherwise a largely
pleasant afternoon and evening are in store for much of the area.
CAMs still suggest late evening shower/storm development along the
elevated boundary which was forecast to be in southern Iowa with
many of the evening/overnight runs but 12Z data has pushed this
boundary further south as well keeping most of the precipitation
chances right along to south of the IA/MO border as well. Although
pwat values reach between 1.5-2" with favorable warm cloud depths
and the corfidi vectors pointing in line with the boundary in
southern Iowa, the LLJ is not particularly robust tonight nor in a
favorable location, and instability values also wane through the
evening hours. All this being said, there could be some locally
heavy rain with any showers/storms that develop far south late
tonight (after 10 pm), but given antecedent drier conditions,
continuing maturing crops, and more capacity in southern Iowa, the
hydro threat for the night has also diminished given forecasted
rainfall amounts are largely all less than 1" with higher amounts
into northern MO. Should some locally heavy rainfall occur north of
the border, some localized ponding could occur, but overall the
hydro and severe risk through the night are both low with any rain
far south ending into early Thursday morning.

Temperatures tonight and Thursday will both be cooler with lows
tonight in the 50s to low 60s and highs on Thursday in the 70s.
Similar temperatures are expected into Friday, though afternoon
temperatures warm a bit more southwest into the low 80s as the
surface high which moves in early Thursday pushes off to the east on
Friday returning low to mid-level flow out of the south to southwest
respectively allowing for the warming temperatures but also a stream
of moisture off the Gulf which largely persists through the weekend.
Multiple shortwaves will move through the region at times from later
Friday through the weekend within the upper zonal flow to start the
weekend before upper ridging develops into Sunday. This will bring
the return of periodic shower and storm chances through the weekend
though location and timing remain more uncertain with guidance not
in good agreement. Overall, better rain/storm chances look to be
overnight into early morning Friday night through Sunday night with
some drying through the midday periods Saturday and Sunday. Will
continue to evaluate the severe threat with time as guidance comes
into better agreement but setup favors multiple rounds of heavy rain
as noted in the WPC Excessive Rainfall Outlooks (EROs) for days 3-5
(Friday-Sunday).

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 623 AM CDT Thu Jul 17 2025

Low ceilings remain across the terminals due to low stratus,
with IFR/MVFR conditions this morning that will gradually
improve through the day with the departing system to the south.
VFR conditions are expected to return across the all terminals
by late morning/early afternoon, with KOTM later into the
evening. Otherwise, winds out of the north/northeast will be
generally light, with an occasional gust to 10-15 knots.

&&

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

&&

$$

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