Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

684
FXUS63 KDVN 060704
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
204 AM CDT Mon Apr 6 2026

.KEY MESSAGES...

- Cold high pressure will bring chilly weather through Tuesday with
  a freeze expected tonight.

- An accumulating snow is expected to graze our southwestern
  counties late tonight.

- There are occasional chances for light rain and snow/mix
  through Tuesday night (20-50%).

- More significant rainfall and higher coverage still possible  by
  late week.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 203 AM CDT Mon Apr 6 2026

Cold, seasonally strong high pressure is moving into the area this
morning as a cold front reached the Quad Cities around 1 AM.  Very
little moisture has allowed this to be mainly a dry FROPA, though a
couple weak showers did pass through the north 1/2 of the area late
last evening, and due to cold air aloft, a lightning strike was
recorded in far northern Dubuque County.

Northwest winds will continue today, with an increase in mid clouds
expected through the day as Frontogenetic processes begin to develop
on the southwest flank of the high pressure area, mainly over the
Missouri Valley through tonight. This F-gen is forecast to
intensity, with saturation increasing aloft tonight.  It will
interact with the cold high pressure to bring a narrow swath of
accumulating snow to portions of Iowa and Missouri/western Illinois,
with the question being exactly where does this narrow band reach
the ground. There are around half the guidance which show this band
impacting  our southern counties while the other half show it
remaining south of the CWA.  This mainly comes down to how models
are handling a dry layer, about the lowest 5000 ft, shown in model
soundings. This dry wedge and dry advection in that layer will
continue to be a resistance to saturation through Tuesday.  This is
typical for F-gen bands, and one major reason they`re often very
narrow, as saturation is not complete either side of the band. I do
think it will at least temporarily saturate in our southwest
corner, with pops peaking around 80% late tonight, and
accumulations around 1 inch expected. The NBM 1 inch
probabilities remain in the 20-40, while WPC guidance for over 1
inch is found in the 75-90th percentile, with nearly dry in the
lowest 50%. Thus, there is statistical support showing this
event being on the lower end for our area, despite some
deterministic models dropping 3+" of snow in our southwest.

Temperatures tonight continue to be coldest in the north 1/2, where
cloud cover will be thin at times, with lows in the lower 20s. South
of I-80, under thick cloud cover, temperatures will be near
freezing, possibly a little below at times.  Though areas along and
south of a line from Keokuk County to Louisa County are "on" for
frost/freeze headlines, I`m unable to coordinate a headline at this
time with surrounding WFOs, which correctly address low confidence
due to the marginal nature of the low temps near freezing, cloud
cover, and precipitation falling (mainly as snow).  Today`s day
shift will have some time to still get a freeze warning out if
needed.

Tuesday, a cold start to the day, cloud cover, and some light
rain/snow will keep the day rather cold, in the lower to mid 40s,
though winds do not appear strong that day, generally southeast at
8 to 15 mph.


&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 203 AM CDT Mon Apr 6 2026

Wednesday through Friday...Continued warming and with better
moisture return off the western Gulf as this mid to late week period
progresses. If precip moves out, Wed could be mild as warm sector
south winds increase and help boost high temps into the mid to upper
60s. Ensemble upper jet patterns lean toward upper troffiness
developing acrs the northern and central plains, while a LLVL
boundary organizes and pushes acrs the upper Midwest acting as a
precip focal point later Wed into Thu. Then signs of this feature
eventually laying out along west-to-east tightening LLVL
baroclinicity and flattened westerly steering flow into Fri and even
Saturday. This boundary will continue to be a convergent focus for
southerly warm moist conveyor to impinge upon and over for more
robust precipitation events for the late week timeframe, but where
this front lays out is still uncertain with several of the latest
run ensemble members more robust with northerly ridging shunting the
boundary further to the south of the DVN CWA.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1216 AM CDT Mon Apr 6 2026

A dry frontal passage will bring northwest winds of 12 to 25 kts
the next few hours before dropping down to around 10-12 kts for
the early morning hours today. Increasing mid clouds is expected
today, but otherwise VFR weather with winds gusting a bit during
the daytime hours, then becoming northerly tonight, with clouds
thickening up ahead of a snow event, that appears to be falling
southwest of all terminals into Tuesday morning.

&&

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

&&

$$

SHORT TERM...Ervin
LONG TERM...12
AVIATION...Ervin