497
FXUS63 KDVN 202336
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
636 PM CDT Wed May 20 2026

...Updated for 00z Aviation...

.KEY MESSAGES...

- The remainder of the work week will be cooler than normal with
  a chance of rain just before the weekend.

- A pattern change this weekend will bring warmer than normal
  temperatures to the area next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 158 PM CDT Wed May 20 2026

Dry easterly flow will keep temperatures cooler than normal tonight
into Thursday. A passing upper level disturbance may or may not
produce some sprinkles on Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 158 PM CDT Wed May 20 2026

Thursday night through Friday night
Assessment...high (>80%) confidence of a storm system. Low (20-30%)
confidence on rainfall.

The remainder of the work week will be characterized by cooler than
normal temperatures.

Timing differences continue regarding the system just before the
weekend. What has changed over the past 24 hours are two items; 1)
the track has shifted further east into the Ohio Valley, 2) the
result of point 1 is that prolonged easterly flow that is deep and
dry remains in place across the area.

The net result of these changes is that several deterministic model
runs are strongly suggesting Thursday night and the first part of
Friday morning could end up being dry across the area.

The model consensus is slowly trending this way by delaying the
highest rain chances (55-70%) until late Friday morning through
Friday evening. Additionally, the QPF is lowering as a result of the
dry easterly flow. Most areas will see 0.25 inch or less with some
areas potentially seeing up to one half inch. I would not be
surprised if QPF amounts lower further over the next 1.5 days.

Sunday through Wednesday
Assessment...a certainty (>95%) of warmer than normal temperatures

The holiday weekend still looks to be mainly dry although a rogue
diurnal shower or thunderstorm cannot be ruled out.

As mentioned yesterday the flow pattern changes with southwest flow
aloft developing as an upper level ridge develops on the east coast.
The net result is temperatures climbing above normal starting Sunday
and continuing through next week.

Starting Tuesday humidity levels will be much more noticeable and
uncomfortable as dew points climb into the mid 60s. The increased
moisture combined with the very warm temperatures and passing upper
level disturbances is expected to result in mainly diurnal
convection both Tuesday and Wednesday afternoon and evening. Right
now the model consensus has rain chances at 15 to 30 percent.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 625 PM CDT Wed May 20 2026

VFR conditions and easterly winds gusty at times is anticipated for
the TAF cycle.

A boundary off Lake Michigan was moving westward through northern
Illinois currently. The latest runs of the HRRR and RAP models
bring this boundary to the river terminals (DBQ, MLI, BRL) by around
03z-04z, and suggest a directional shift more easterly along with
gusts of around 20 kt that may be more persistent within the first
couple of hours after the boundary moves through before becoming more
sporadic. The boundary is shown to weaken toward CID and thus
confidence is too low for any sustained gustiness to include mention.
Toward 12z and through 15z-18z there is a very low signal in some
of the guidance for some MVFR ceilings potentially advecting in from
parts of Indiana and/or developing off Lake Michigan and working
westward toward the terminals. Latest SREF and HREF probabilities
for ceilings or only 20-30%, particularly near MLI and BRL, which
suggest potentially Indiana being more the source region that needs
to be monitored, where there is currently some patchy MVFR conditions
over the central part of the state and more IFR in the far southern
portions. The cloud bearing winds do increase toward 15 kt tonight, but
typically the threshold is around 20+ kt for increased probability of
reaching the terminals. All of this to say the confidence is too low
for any mention of MVFR ceilings, but something to keep an eye on.
Easterly winds on Thursday may initially be gusty to 20 kt after
daybreak for a bit, then subside before potentially turning gusty once
again in the afternoon but confidence with persistence precludes mention
for now.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...McClure

NWS DVN Office Area Forecast Discussion