350
FXUS63 KDVN 301130
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
630 AM CDT Tue Jun 30 2026

.KEY MESSAGES...

- Extreme Heat Warning continues through Wednesday evening with
  ongoing prolonged period of hot and very humid conditions.
  Daily peak heat index values of 100 to 110 and nighttime low
  temperatures only dropping into the mid to upper 70s.

- Increasing thunderstorm chances into midweek and onward
  (including the July 4th weekend), with the resultant cloud
  cover potentially having an impact on high temperatures, but
  the very humid conditions will remain.

 &&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 250 AM CDT Tue Jun 30 2026

The Extreme Heat Warning continues. Synoptic scale feature
placement of the brunt of the ridge axis aligned from the lower
MS RVR/TN Valley to the eastern OH RVR Valley and WV. This would
make for a slow migration eastward of the northwest flank ring
of fire storm track edging closer to us but brunt of the CWA may
be spared until late in the week and the weekend. The far
northwest and northern CWA may be brushed by convection sooner
than that such as late tonight into early Wed morning. Back to
the heat, with the NBM and high temps underachieving yesterday
in the high humidity, will go just a degree or two warmer at
most sites for highs today. This will make for widespread highs
in the low to mid 90s, but the sfc DPTs are having no problem
getting elevated and expect another day of mid to upper 70
values. Of course this will support heat index readings of a 100
to 108 degrees with pockets of higher values and the ongoing
need for heat headlines.

As for the ongoing MCS acrs northeast NE into far northwest IA
this morning, only the ECMWF brings a portion of this into the
DVN CWA along and north of I-80 this morning. All other CAMs
migrate this activity east-northeastward acrs southern MN into
WI today and will cautiously play it that way, but of course
will watch the upstream trends through the end of the shift
whether to make changes on the fly.

Tonight...LLJ convergence on an elevated boundary with possible
short wave rippling in southwesterly steering flow acrs the
northwest half of IA will look to generate elevated showers and
storms in a scattered west-east linear coverage pattern acrs the mid
MO RVR Valley and acrs far northern IA/southwest WI late tonight.
Most of this may remain just to the north of the local CWA but
will have to have at least some low CHC POPs along the Hwy 20
corridor before they lift north by mid Wed morning.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 250 AM CDT Tue Jun 30 2026

Wednesday...As mentioned above, the latest ensembles and upper
jet progs suggest the active southwesterlies edge closer to the
western and northern side of the DVN CWA through mid week,
before the flow will look to flatten and become more progressive
acrs the north half of the CONUS by late week. Besides maybe
some decaying debris spilling in acrs the west and north at
times, feel the EML and lingering ridge centered off acrs the OH
RVR Valley will maintain the mainly precip-free regime for one
more day through Wed evening. Thus, with low to mid 90s still
fcst with the ongoing high humidity, the Extreme Heat Warning
will be allowed to ride acrs the entire area through Wed
evening. After that, too much uncertainty about convection and
associated debris/cool pools interrupting the heat acrs at least
portions of the local area to extend the heat headlines further
at this time. From mid Wed evening on into the early Thu
morning hours, there appears the potential for a portion of an
MCS to move into or form acrs the northwestern quarter to third
of the DVN CWA and will have to have POPs to account for this.
With all the available CAPE, and mature storm system moving into
the area may be strong to severe with damaging winds until they
maybe move more to the east and encounter the stouter EML and
linger upper ridge lobe that would commence storm decay.

Thursday through Monday...The general pattern of flattened flow and
broader zonal storm track acrs the upper mid CONUS may result in an
unsettled period over the Holiday weekend with occasional rounds of
showers and storms with passing even subtle short waves and probable
MCV`s. There will be a lot of dry hours mixed in as well. At the
beginning of this longer range period, the latest ensembles suggest
a stronger ridge-riding short wave upper trof to ignite a SD/NE
MCS Thu evening with longer range thermal thickness steering
guides taking at least a portion of this system into the CWA
late Thu night into Friday morning...probably the northern half
of the CWA and that`s driving SPC`s day-3 outlook risk areas.
Details that far out still tough to call at this point, and it
may be more of a far northern IA/MN/WI show into early Friday.
Then it`s day by day convective-wise for the rest of the period
with one day`s activity affecting the next day lay out with
lingering outflow boundaries and synoptic fronts, something the
models won`t handle well close in, let alone this far out. The
clouds, debris, and outflow could hinder ambient temp warm up
into the 90s helping the cause to limit the need for more heat
headlines, but the humidity and high sfc DPTs will unfortunately
still be there for a very muggy holiday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 630 AM CDT Tue Jun 30 2026

VFR conditions are expected throughout the TAF period. Some
lingering low-level moisture under a temperature inversion has
led to a stratus deck formation around 5 to 7 kft, extending
from GGL northeast towards DBQ. Eventually, this deck should
dissipate later this morning as the inversion mixes out. When it
does, expect another period of gusty south-southeast winds,
gusting to around 25 knots this afternoon.

As winds weaken overnight, we will have to keep an eye on the
potential for at least marginal low-level wind shear tonight
after midnight for BRL, MLI, and CID, given a persistent
southwesterly flow aloft.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Extreme Heat Warning until 10 PM CDT Wednesday for IAZ040>042-
     051>054-063>068-076>078-087>089-098-099.
IL...Extreme Heat Warning until 10 PM CDT Wednesday for ILZ001-002-
     007-009-015>018-024>026-034-035.
MO...Extreme Heat Warning until 10 PM CDT Wednesday for MOZ009-010.

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Schultz