Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

843
FXUS63 KDVN 042338
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
538 PM CST Thu Dec 4 2025

...00z Aviation Update...

.KEY MESSAGES...

- Continued very cold this evening into early Friday morning
  with wind chills in the single digits and teens below zero!

- Snow chances increasing Saturday night into Sunday morning,
  with 40-70% probabilities of 2+" north of Highway 34.

- Active northwest flow next week, with several clippers
  tracking near the area.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 230 PM CST Thu Dec 4 2025

After record low temperatures for some locations this morning,
we`ll be a little "warmer" tonight due to steady southerly winds
limiting decoupling near the surface. Temperatures will likely
fall quickly this evening into early tonight, then slowly rise
late as the southerly flow becomes established. Latest forecast
has lows in the single digits above and below zero, coldest in
the eastern counties. Wind chills again will be quite cold with
min values in the single digits and teens below zero...brrr!

A mid-level shortwave will track across the Midwest on Friday
with an attendant surface trough expected to move through
eastern Iowa and northwest Illinois during the late evening to
overnight period. This system is moisture starved, but could
result in patchy light snow/flurries across the northern to
northeast counties, or even a little freezing drizzle due to a
loss of in-cloud ice (precip chances: 10-20%). Overall, it looks
like a low probability and little to no impact event.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 230 PM CST Thu Dec 4 2025

Saturday-Sunday: A clipper system is expected to impact the area
Saturday night into Sunday morning. NBM probabilities for
accumulating snow have continued to trend higher, now between
40-70% for 2"+ (roughly north of Highway 34). And the
probabilities for 4"+ are between 20-40% near and W/NW of the
Quad Cities. The EC ensemble has been consistent in showing a
band of 0.20-0.30"+ of QPF and other model guidance as been
trending toward the wetter and slightly stronger EC scenario.
Saturday`s forecast highs are in the mid/upper 20s, with colder
values in the teens/20s expected Sunday behind the clipper.

Early Next Week: Cold start to the work week Sunday night, with
another 1034mb surface high overhead. These temperatures will
not be as cold as the current air mass this morning, with 850mb
temps 4C warmer. Still could see a few locations with sub- zero
lows Monday morning. Two more clippers to track over the upper
Midwest (one Monday night-Tuesday and another 24hrs later) with
a general consensus keeping any appreciable snow potential north
across MN/WI. We would instead see a warm draw of above
freezing temps move into the CWA Tuesday and Wednesday, with a
rain/snow mix possible. LREF (100 member ensemble) is showing
40-70% probabilities of 850mb temps above 0C Tuesday and
Wednesday supporting above freezing highs. Continue to monitor
the forecast for any updates and trends with these passing
systems.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 533 PM CST Thu Dec 4 2025

A VFR TAF period into early Friday morning, but will have to
watch for a wing of stratocu moving in from the west at CID and
DBQ that may be close to MVFR heights. Sfc winds will trend
south and increase to 8-12 KTs as the overnight goes and into
Thu morning. With southwesterly LLJ winds of 35 to 40 KTs, there
may be some marginal LLVL wind shear from 08z through 14z Friday
morning. Then sfc south to southwest sfc winds may get a bit
gusty by late morning. Then there will be the potential for MVFR
stratocu moving in from the west as the afternoon progresses and
into early Friday evening, especially at CID and DBQ.

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...Uttech/Gross
AVIATION...12