364
FXUS63 KDVN 271908
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
208 PM CDT Mon Jul 27 2026

.KEY MESSAGES...

- Oppressively hot and humid through this evening, with heat
  indices in many locations peaking around 105-115 degrees.

- Thunderstorms are possible this afternoon into the evening,
  though there remains some uncertainty due to capping
  inversions. Some of these storms may be strong to severe with
  damaging winds the main hazard if well-organized convection
  develops. A Slight Risk (level 2 of 5) for severe weather
  remains for areas along and east of the Mississippi River.

- Some mid-week relief from the heat and humidity comes behind
  a cold front tonight, although smoke from Northwest U.S. and
  Canadian fires may spread over the area that could continue
  through Tuesday.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 207 PM CDT Mon Jul 27 2026

Mid-day upper air flight shows several small capping inversions
aloft. These caps, along with likely subsidence behind the MCS
along Lake Michigan, are acting to suppress convective
development across the area so far.

Peak heating along any boundaries or theta-e gradients should
force isolated to low-end scattered (20-40%) coverage of
diurnal storms along/ahead of the cold front. These storms will
quickly dissipate with sunset, leaving the remainder of the
overnight hours muggy but dry.

The question after midnight is will any smoke approach the surface
due to post-frontal mixing or remain aloft. Some solutions
suggest yes while others say no. So, we will do a middle of the
road solution and do a partial mix-down with the idea some
areas may experience some smoke for a few hours but a majority
of it remains aloft.

Tuesday will be a bit cooler and definitely less humid, with
dew points in the upper 60s to lower 70s. Net result will be
peak afternoon heat indices in the upper 80s to lower 90s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 202 PM CDT Mon Jul 27 2026

Tuesday night through Thursday will continue to be on the dry side,
thanks to an area of high pressure/subsidence that`s progged to
develop over the western Great Lakes, along with an upper-level
ridge over the Great Plains region. Temperatures will remain
seasonably warm, with high temperatures forecast for Wednesday and
Thursday in the middle to upper 80s, and nighttime lows in the
middle 60s.

As we go through the day Thursday, the aforementioned upper ridge
begins to break down, with a mid-level shortwave trough embedded in
the zonal flow. A quasi vertically-stacked upper low will accompany
the trough, which will help further support large-scale forcing over
our region. Likely chances of showers and thunderstorms (50-70%)
look to increase late Thursday night into Friday. At this time,
strong to severe storm potential for this period appears to be
pretty low, given meager instability and deep-layer shear magnitudes
(20-30 knots). The latest machine-learning severe probs from NSSL,
NCAR, and CSU all show very small values, if anything. More likely,
this bout of precipitation appears to bring beneficial rainfall to
the area, with the latest NBM exceedance probabilities of a half
inch of total rainfall through 12z/7 AM Saturday around 40 to 60%
across the area. With the precipitation and cooler air mass building
in, temperatures look to be cool even further for the end of the
week, with highs warming to around 80 degrees for Friday and
Saturday - a welcomed sign for those looking for relief from the
heat.

Saturday and Sunday: there could be some lingering chances of
showers/storms Saturday morning before the aforementioned stacked
upper low moves out and another high pressure system builds in,
bringing drier conditions to the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1215 PM CDT Mon Jul 27 2026

The morning inversion has eroded but has been replaced by
multiple capping inversions aloft. Thus convection will be
suppressed until the caps can be over come; most likely during
peak heating. Thus isolated to scattered (15-35%) coverage is
possible along and ahead of the cold front from 20z/27 through
02z/28 across eastern Iowa and northern Illinois. After 02z/28
convection will dissipate but haze from wildfire smoke will be
possible.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...Schultz
AVIATION...08