232
FXUS63 KDVN 300752
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
252 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
maybe 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, 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. But 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
effecting the next day lay out with lingering outflow boundaries and
synoptic fronts, something the models won`t handle well close in,
let along 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 /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1240 AM CDT Tue Jun 30 2026

Generally a VFR TAF cycle through Tuesday evening. Just a low
chance for a few showers and thunderstorms to get into the VCNTY
of the DBQ site Tuesday evening but will hold off even a PROB30
for now. South to southwesterly sfc winds to be gusty again on
Tuesday up to 25 KTs.

&&

.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...12