Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

021
FXUS63 KDVN 182322
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
622 PM CDT Thu Jun 18 2026

.KEY MESSAGES...

- Besides a few nuisance light shower chances this evening and Friday
  evening, generally cooler and benign weather through Saturday
  before storm chances increase again by Sunday.

- The cooler than normal temperature regime still looks to continue
  for much of next week.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 215 PM CDT Thu Jun 18 2026

Tonight...Looking at water vapor imagery(WV), a few channeled
looking short waves were notice embedded in low amplitude
northwesterlies acrs SD into western IA ATTM. These waves may
combine with late afternoon heating to produce isolated to wdly
sctrd high based showers and possibly even a thunderstorm through
mid evening from southwest MN down acrs central into eastern IA, and
will include low POPs for this potential. Then a bout of short wave
upper ridging to bring about clearing and calm conditions late night
into Friday morning. Low temps tonight to cool below normal again
down in the 50s.

Friday...With a passing bout of ridging, much of the day to be
decent with less CU than today(Thu) and warming profiles for highs
in the mid 70s to around 80 for much of the area. Then ongoing
northwesterly steering flow aloft will usher another clipper-like
wave down out of the northern plains and acrs MN/WI(western GRT LKS)
through Friday evening. Moisture return remains limited, but
appearing to be a little more substantial wave on the ensembles, it
should still kick up sctrd showers and some thunderstorms acrs MN
into WI late Friday afternoon and into the evening. Some of this
activity may get down into at least the north half of the DVN CWA
Friday evening, but QPF amounts look light(tenth of an inch or less)
and besides maybe some small hail, the storm support is not severe
looking.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 215 PM CDT Thu Jun 18 2026

The weekend will bring our next measurable chance for rain Late
Saturday night through Sunday as a shortwave moves through the
region. Late Saturday into early Sunday, a shortwave will
translate through the central Plains, accompanied by a surface
low off the lee of the Rockies. Low level moisture advection
will provide a steady stream of moisture as PWATs of 1-2 inches
flood northward. Widespread rainfall is expected throughout
Sunday, with NBM probabilities showing a 50-70% chance of
24-hour rainfall exceeding 1 inch by Monday morning. In addition
to the potential for heavy rainfall, current guidance suggests
that there will be some instability with these showers, which
would allow for some thunderstorms. At this time, the track of
the low and uncertainty in timing make severe potential unclear,
but is something to monitor in the coming days.

Past Sunday, ridging behind the shortwave will keep us in northwest
flow as high pressure builds into the mid-Mississippi Valley. This
will continue the trend of cool temperatures for mid-June as it
lingers in place for a day or two until midweek. By midweek,
guidance suggests that another system may be possible, though a wide
range of solutions, including some that keep high pressure rooted
over us, keep the most likely scenarios unclear at this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 615 PM CDT Thu Jun 18 2026

Passing upper level disturbance will bring a risk of an isolated
SHRA/TSRA through 03z/19 with KDBQ/KCID having the better
chances. Otherwise winds to drop under 10 knots after sunset.
Another weak upper level disturbance on Friday will bring
another round of isolated SHRA/TSRA after 20z/19.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...Ellingworth
AVIATION...08