Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

874
FXUS63 KDVN 190040
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
640 PM CST Thu Dec 18 2025

.KEY MESSAGES...

- A strong storm system will continue to bring very windy
  conditions across the area this afternoon and evening, along
  with falling temperatures. A Wind Advisory remains in effect
  for the entire area through midnight tonight.

- Scattered snow showers are expected to continue into this
  evening. Some of the snow showers could generate visibilities
  near zero at times, with accumulations up to 1.0 inch possible
  in the most intense showers. Additionally, falling
  temperatures are expected to create icy road conditions for
  the evening commute, especially in places that see snow
  accumulations. A Winter Storm Warning has been issued for
  parts of eastern Iowa and Rock Island County until 10 PM.

- A very cold morning is expected Friday morning, with wind
  chill values expected to fall to the single digits and teens
  below zero, especially for areas along and north of Interstate
  80.

- Mainly dry conditions are expected through the first half of
  next week, with large temperature swings over the weekend.

&&

.UPDATE...
Issued at 625 PM CST Thu Dec 18 2025

An FGEN band at 925 MB is forecast to move southeastward across
eastern Iowa this evening and gradual weakening as it
approaches the Mississippi River. This will allow narrow bands
of intense snow showers to continue through the evening hours.
The 00 UTC DVN sounding shows an inversion at 850 MB with wind
speeds at the base of the inversion near 45 knots. Any snow
showers moving across the area will have the potential for winds
to gust to 45 to 55 MPH and cause blowing snow and the
potential for visibilities to be near zero for brief periods of
time. There will also be rapid changes in visibility over short
distances. Additionally, the elongated nature of these
convective snow showers will allow snow to occur for up to 1
hour leading to accumulations of up to 1 inch. Temperatures have
fallen into the teens across the area increasing the potential
for a flash freeze with any precipitation that has melted on
untreated roadways. For these reasons, a Winter Storm Warning
was been issued until 10 PM CST for areas along and north of
Interstate 80 in eastern Iowa plus Rock Island County in
Illinois. The wind advisory remains in effect until Midnight.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 217 PM CST Thu Dec 18 2025

After a rainy morning/early afternoon across the area, attention
then turns to the west and northwest as a secondary, more potent
cold front is on its way. This front should bring increasing chances
(20 to 50%) of snow showers between 4 PM and 10 PM today. As of 2 PM
this afternoon, we are seeing wind gusts increasing ahead of the
boundary to around 35 to 45 mph over eastern Iowa. These wind gusts
will only expand further across the area this afternoon, and the
Wind Advisory remains in effect area-wide through midnight tonight.

Back to the snow showers: one concern we have is that the snow
showers will be moving through during the evening commute time
frame, and combined with the strong wind gusts, this should lead to
reduced visibilities under the showers. Upstream over northwest
Iowa, we`re seeing visibility reductions less than a mile in some
spots, but the latest RAP/NAM guidance suggests that the better FGEN
forcing should remain north of our area. This, along with limited
surface-based instability, should keep our threat for snow squalls
low. While visibilities here may not be as bad as they are in
northwest Iowa, there could still be some reduced visibilities, and
with plummeting temperatures (as fast as 3 degrees cooling per
hour!), any remaining wet and untreated roadways could become icy.
In short, travel conditions for the evening commute could be
treacherous, so use extra caution if out traveling tonight. As far
as snow accumulations are concerned, they likely won`t be much due
to the brief nature of the snow showers, but some locations could
see up to a half inch as the soundings suggest ample saturation
within the dendritic growth zone aloft that could generate a light,
fluffy snow accumulation but enough to make things slick!

Eventually, the snow showers will come to an end late this evening,
along with the winds gradually tapering off through the overnight
into Friday morning. Temperatures and wind chills will be quite cold
in the morning, with lows dipping to the single digits north and the
teens south, with wind chills in the single digits and teens below
zero (coldest along and north of Interstate 80). These values aren`t
low enough to warrant a cold headline, but it will still feel quite
cold so make sure to bundle up!

The rest of the day Friday will feel seasonably cool, with dry
conditions, thanks to a surface high pressure ridge axis progged to
sweep through the area mid-day Friday. Southerly return flow will
help temperatures rebound nicely from the morning lows, with highs
in the lower 20s northeast to the lower/middle 30s southwest.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 217 PM CST Thu Dec 18 2025

Friday night through the rest of the weekend: we will see a few
systems pass near or over the local area, but a lack of moisture
will keep precipitation chances at bay. The first system will remain
north of the area where the better moisture will stay. For us, this
will only result in some cloudy skies overnight. The other system is
progged in the form of a weak cold front, which looks to sweep
through the area during the day Saturday. Again, higher moisture
should remain north of the area, so only some cloudy skies are most
likely to result from the fropa.  Temperatures will warm up to the
mid/upper 30s north to the mid 40s south for highs Saturday. Another
cold night looks possible Saturday night in the wake of the front,
with lows dipping to the lower teens north with some isolated single
digit lows, to the lower 20s south.

Monday through Wednesday: model solutions differ quite a bit
regarding precipitation chances for the early part of next week, so
not much confidence in this. However, confidence is much higher for
a warming trend, with the LREF ensemble probabilities of daytime
highs above freezing around 70-90+ percent for Monday through
Wednesday. Given the significant snow melt over the area these last
few days and no major winter systems expected from now through mid-
week next week, prospects look very good for a Brown Christmas this
year.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 523 PM CST Thu Dec 18 2025

An intense storm system continues to track across the Upper
Midwest to start the TAF period. There are widespread MVFR
ceilings to start the period. West to northwest winds sustained
near 25 to 30 knots with gusts up to 40 to 45 knots are
possible through 06 UTC. Snow showers, especially at KCID and
KDBQ, will result in possible IFR visibilities with blsn and
gusts up to 45 to 50 knots through 4 UTC. Northwest winds are
forecast to begin to diminish from west to east after 06 UTC
with gusts up to 30 knots. Ceilings are forecast to lift to MVFR
by 06 UTC and then to VFR after 09 UTC. Wind gusts further
diminish below 20 knots after 12 UTC. Winds will further drop
below 10 knots after 18 UTC.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Wind Advisory until midnight CST tonight for IAZ040>042-
     051>054-063>068-076>078-087>089-098-099.
     Winter Storm Warning until 10 PM CST this evening for
     IAZ040>042-051>054-063>068.
IL...Wind Advisory until midnight CST tonight for ILZ001-002-007-
     009-015>018-024>026-034-035.
     Winter Storm Warning until 10 PM CST this evening for ILZ015.
MO...Wind Advisory until midnight CST tonight for MOZ009-010.

&&

$$

UPDATE...Cousins
SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Cousins