754
FXUS63 KDVN 300715
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
215 AM CDT Sun Aug 30 2026

.KEY MESSAGES...

- Heat and humidity will build across the area, especially
  Monday through Thursday. Heat indices of 95 to 100 are
  expected with areas south of I-80 possibly exceeding 100. How
  hot it gets will be dependent upon where potential
  showers/storms develop.

- With heat building into the area, a near daily risk of showers
  and storms are possible depending upon where the edge of the
  heat dome is located.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 214 AM CDT Sun Aug 30 2026

Nocturnal convection with scattered (20-40%) coverage will continue
through sunrise as the LLJ reaches its peak of 40-50 knots at 5 kft
AGL. The CAMs are not handling this very well but if one looks under
the hood the signals are there for convection.

Of interest is convection in central Nebraska which is being
supported by an upper level disturbance. Interestingly, the CAMs
bring the remnants or reinvigorate said convection into the area
late this morning and into the afternoon for areas north of I-80. IF
this scenario is correct then the northern third of the area will be
cooler for much of the day.

Cloud cover from the Plains convection will help suppress
temperatures somewhat today, but like yesterday, there should be a
respectable pop in temperatures late this afternoon.

Tonight will start out quiet, but as the LLJ slowly strengthens
during the evening a new round of nocturnal convection will develop
that will generally favor areas along/north of I-80.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 147 PM CDT Sat Aug 29 2026

The main focus for the long-term forecast period continues to be on
building heat and humidity, especially for Monday through at least
Wednesday before relatively cooler conditions return by the end of
the week. For areas that avoid any precipitation during this period,
confidence is higher for very warm and muggy conditions. The latest
ECMWF EFI/Shift of Tails values for high temperatures Monday through
Wednesday are in excess of 0.9 (even some values over 0.95 in
isolated spots), along with Shift of Tails values around 1. This
suggests high confidence in anomalously warm high temperatures,
although not extreme values based on the lower Shift of Tails. In
terms of heat headlines, we will need to watch this closely, given
the LREF ensemble exceedance probabilities of heat indices of 100
degree or warmer is around 30 to 50% for areas along and south of
Highway 92 for Wednesday and Thursday. The probabilities of heat
indices of 95 degree or warmer goes up drastically, to around 60 to
90% over most of our forecast area. Additionally, overnight lows
might not dip below 75 degrees Monday night through Wednesday night,
so this would continue stress from the heat - even at night. There
is potential for some record warm low temperatures during this
period. See the Climate section below for the current records. We
will hold off on headlines for now, but Heat Advisories may be
needed next week.

With all of this said, it bears repeating that any showers or storms
that develop will help to limit temperatures, and therefore, heat
indices. Ultimately, this appears most likely for areas along and
north of Highway 30, where both NBM and LREF ensemble probabilities
of measurable rainfall are 40 to 60%. In terms of strong to severe
storms, there are some signals in the various machine-learning
severe probs for at least a limited potential on Wednesday and
Thursday as the mid-level ridge becomes more zonal for a time and a
weak cold front sweeps through the area during that time with
appreciable instability. Something for us to keep an eye on, but
with it being further out, confidence isn`t particularly high on
severe weather at this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1240 AM CDT Sun Aug 30 2026

Nocturnal convection is beginning to develop as the LLJ is
reaching its peak of 45-50 knots. LLWS across eastern Iowa and
northern Illinois is a given through 14z/30 BUT continued wind
gusts at the surface is starting to suggest the lower atmosphere
may not decouple and thus make the LLWS more marginal. 20-40%
coverage of SHRA/TSRA can be expected through sunrise with the
potential of a larger shield of rain with embedded TSRA moving
into eastern Iowa after 15z/30. More LLWS is being suggested
after 00z/31.

&&

.CLIMATE...
Issued at 139 PM CDT Fri Aug 28 2026


Record Warm Low Temperatures:

August 31:
KDBQ: 74/2000
KMLI: 75/2000

September 1:
KDBQ: 73/1937
KMLI: 75/1913

September 2:
KDBQ: 74/2011
KMLI: 77/1913

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...08
LONG TERM...Schultz
AVIATION...08
CLIMATE...Gross