483
FXUS63 KDMX 092325
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
625 PM CDT Tue Jul 9 2024

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

* A few scattered showers/thunder north this evening.

* Expanding/more widespread showers/thunder Wednesday.

* Low-end scattered shower/thunder chances at times Sat/Sun - best
  east.

* Heat builds in late week/weekend - HI Values into 100s by Sun

&&

.DISCUSSION...
Issued at 255 PM CDT Tue Jul 9 2024

Beryl remnants continue to slowly churn NE into/through the region,
with its center currently working through the MO/IL/KY/TN
intersections. With regards to sensible weather, precip from Beryl
will only just clip far SE Iowa today/tonight and expanded cloud
cover into central Iowa will suppress high temperatures a degree or
two today.

Otherwise quiet overall conditions may be briefly disrupted by a few
scattered shower/thunder opportunities over northern Iowa later this
afternoon and evening with a combination of sunshine/deep mixing and
little to no cap. With very weak wind profiles, these would be
transient and short live in nature with only real risk being
lightning.

More widespread opportunities for showers/thunder will begin to
present themselves late overnight as a stronger compact shortwave
rides southward through the mean flow, on the backside of the
exiting Beryl remnants. This has been well advertised and continues
to be well resolved in guidance, so have generally kept with near
likely PoPs, but have hesitated to go much higher with expectation
of hi-res/CAM depictions predominantly scattered in nature. Similar
to yesterday and potential showers/thunder later today, little
expectation for much more than some moderate to heavy rain and
lightning. Strongest updrafts may produce some small hail with
MUCAPE depictions around 2000 J/kg, but unlikely anything will be
able to sustain long enough or tap into full CAPE potential to
produce a notable severe threat with continued weak wind profiles
and moist profiles overall. As previous discussion noted, a
landspout may be possible with supportive low level stretching
progged, especially with likely outflows around to help product
areas of vorticity.

Wednesday will be the end of the most notable precipitation
opportunities across the area within the going forecast. Though as
the area remains supplanted within NW large scale flow, compact
embedded shortwaves may produce periodic opportunities for a few
scattered showers and storms, as noted within deterministic synoptic
models at times Friday through Sunday. Very hard to latch onto
anything of note at this time with timing and location variances, so
have kept with the low end NBM PoPs at this time. Of more not
through the weekend will be the building heat as western heat dome
begins to ooze into the central CONUS. Bulk of the heat remains
expected to stay W/SW of the area, but enough will build in by late
weekend to see highs rise into the low to mid 90s and heat index
values into the lower 100s deg F. This is all well aligned within
NBM with MaxT spreads of only a couple/few degrees through the
weekend. Uncertainty grows substantially into next week though with
spreads reaching 10 to 12 degrees or so with guidance uncertain on
evolution of northern stream shortwaves and heat dome evolution.
Another aspect to casually watch is Td`s may be a little low given
all the recent moisture and peak agriculture ET ongoing this time of
the year. Low 70s Td`s are bad enough already, but could be closer
to mid-upper 70s at times. Primary consequences there would be
possibly suppressing MaxTs a degree or two, but also pushing heat
index values closer to 110 deg F. Regardless, be prepared for
uncomfortable temperature and humidity conditions this weekend and
into early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 619 PM CDT Tue Jul 9 2024

VFR conditions currently prevail over the area. Only concern
through the TAF period is the increasing potential for
scattered to widespread shra/tsra from mid to late morning
tomorrow lasting through afternoon. Have included mention of
shra and some vcts at terminals where probabilities of occurance
are highest, however timing and the extent of any categorical
impacts still remains questionable at this time and will need
refined with future TAF updates.

&&

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

&&

$$

DISCUSSION...Curtis
AVIATION...Martin