Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

928
FXUS63 KDVN 041928
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
228 PM CDT Sat Jul 4 2026

.KEY MESSAGES...

- Isolated to scattered storms can be expected through Sunday.
  Heavy rain, lightning and gusty winds are the primary risks.

- Humid conditions will continue through much of the coming
  week. There will be dry periods the first half of next week
  with mainly isolated to scattered (20-50%) coverage of storms
  the second half of next week.

- Rises are occurring on area rivers. Refer to the hydro section
  for more information.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 220 PM CDT Sat Jul 4 2026

A convectively induced upper level disturbance has developed new
convection mainly east of the Mississippi. This convection will grow
upscale as it moves further east through the afternoon and evening.
Some of the stronger storms will be capable of damaging winds and
possibly hail.

West of the Mississippi downward motion has temporarily suppressed
any diurnal convection but as daytime heating continues, diurnal
convection with a 10-25% coverage will develop through sunset.

The atmosphere has slightly less than 2 inches of water in it but
any storm that develops will be capable of producing heavy rainfall
and high rainfall rates.

With the risk of heavy rain and that various areas have seen heavy
rainfall over the past 48 hours, the flood watch was extended into
the evening hours and also expanded into the I-88 and I-80 corridors
of Illinois.

Once sunset occurs, most convection will dissipate. However, the
models continue to show negative theta e lapse rates through the
night. Thus isolated showers or even a thunderstorm are possible
through sunrise Sunday.

On Sunday isolated showers and some thunderstorms will be possible
through the day as theta e lapse rates remain negative. The key
message is that while there is a risk of storms, there will be many
hours of dry weather. Additionally, progged profiles indicate the
overall atmospheric moisture levels will continue to trend downward
thus lowering the overall risk of locally heavy rainfall.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 220 PM CDT Sat Jul 4 2026

Sunday night through Wednesday
Assessment..high (>80%) confidence of humid conditions continuing

The models show northwest flow developing across the CONUS which
will bring temperatures down to near normal for the first half of
July. The humid conditions will continue but not to the excessive
conditions of last week.

There will be weak disturbances moving through the flow aloft
through Wednesday. While the model consensus has dry conditions, a
rogue diurnal shower or storm during peak heating each day cannot be
ruled out.

Wednesday night through Saturday
Assessment...high (>80%) confidence of continued humid conditions.
Low (15-25%) confidence regarding rain chances.

The humid conditions will continue the second half of the week with
a potential uptick in the humidity Wednesday night into Thursday.
The various model solutions have a system passing to the north of
the area that will push a cool front through the area. While there
are some timing differences, late Wednesday night into Thursday
evening looks to be the most likely time any rain would be seen.

Not all areas will see rain but overall coverage on the rain looks
to be 30-50 percent.

Beyond Thursday evening, the model consensus has a daily risk of
rain driven by the diurnal cycle. However, overall coverage will be
low at 15-25 percent.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1224 PM CDT Sat Jul 4 2026

Convectively induced vort max will initiate SHRA/TSRA along and
east of the Mississippi this afternoon/evening. Overall
environment suggests a low probability of a TAF site being
impacted. However, a prob30 was included for all TAF sites this
afternoon and into the evening. CAMs are struggling to handle
the weak forcing but appear to be keying in on areas east of the
Mississippi as the primary focus for storms. After 03z/05
isolated SHRA/TSRA will be possible through the night and into
Sunday morning.

&&

.HYDROLOGY...
Issued at 220 PM CDT Sat Jul 4 2026

Rounds of heavy rainfall the past 60 hours and additional heavy
rain across Minnesota and Wisconsin are causing area rivers to
rise over the next two weeks. Most rivers will experience
within bank rises. However, parts of some rivers are forecast to
go into flood.

The Wapsipinicon River from Anamosa down to the mouth is
forecast to go into flood. Minor flooding is expected near
Anamosa with moderate to potentially major flooding near De
Witt.

The Iowa River at Marengo is expected to go into minor flood. A
flood watch is in effect for the Cedar River near Conesville
which may go into flood next week.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch until 10 PM CDT this evening for IAZ040>042-
     051>054-063>068-076>078-087>089.
IL...Flood Watch until 10 PM CDT this evening for ILZ009-015>018-
     024.
MO...None.

&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...08
HYDROLOGY...08