Crystal Lake, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

107
FXUS63 KDVN 162326
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
526 PM CST Tue Dec 16 2025

.KEY MESSAGES...

- Rain likely Wednesday night and early Thursday, with strong
  winds developing Thursday. There is a 40-60% chance of wind
  gusts over 40 mph.

- Dry conditions late week and into the weekend, with roller-coaster
  temperatures.

- Above normal temperatures are likely next week ahead of the
  Christmas holiday.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 124 PM CST Tue Dec 16 2025

Plentiful sunshine was seen today allowing for a good view of
the current snowpack on GOES 19 satellite imagery. All but the
far southwest portions of the CWA (south of Memphis MO) has
snow on the ground, with the snow-free line roughly from
Centerville, IA to Quincy, IL. Southerly winds ahead of an
approaching cold front has allowed much of the area to see temps
above freezing already as of Noon. Highs should top out in the
mid to upper 30s this afternoon for most, with a few readings in
the lower 40s in northeast MO, southeast IA, and west central
IL.

Tonight...a cold front currently near Sioux Falls will move
through and with a dry atmosphere in place shown on our 18z
sounding, am only expecting an increase in high clouds. Lows
will be warmer than in previous days with readings only dropping
into the mid to upper 20s. Taking a look at fog potential,
given poor model performance this morning, dry BL, and winds
above 7kts, kept fog out of the forecast. Better signal is in
central IA close to the incoming surface ridge axis.

Wednesday...another mostly sunny day will be seen, as surface
ridge slides east. Afternoon highs will be similar to today,
with readings reaching the upper 30s to lower 40s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 124 PM CST Tue Dec 16 2025

Wednesday night-Thursday...a storm system approx 650 mi off the
Pacific northwest coast currently will track near the US-
Canada border and drop southeast into the upper Midwest
Wednesday night and Thursday. This system will drag a strong
cold front through the CWA Thursday, with rising temps ahead of
the fropa Wednesday night. Favorable moisture return evident by
PWs rising into the 0.6-0.7" range (near 90th percentile per
SPC climatology) and strong forcing along and behind the front
will result in a 5-8 hr period of precipitation at any one
location. QPF totals have risen some with this forecast, with
rain amounts between 0.20-0.35" possible. Thermal profiles and
ptype progs continue to show rain as the dominant ptype and
have continued that in the forecast. A rain-snow mix may occur
in the afternoon/evening hours north of Hwy 20, as colder air
moves in. Pavement and surface temps near or just above freezing
will prevent any accumulation. Lastly, some wrap around snow
showers will be possible Thursday night mainly north of Hwy 30,
as the system exits the area. Little to no accumulation is
expected at this time.

Attention then turns to the wind potential post frontal. Forecast
soundings continue to show 40 kts at the top of the mixed layer and
combined with a tightening pressure gradient will result in
windy conditions Thursday afternoon and evening. An interesting
trend in the latest LREF (100 member ensemble) is to shift the
probabilities of the strongest gusts (45+ mph) to our west over
central IA. Conversely, the NBM still shows 40-45 mph peak winds
over much of the area. We still have some time to iron out the
details for a possible wind headline decision and will continue
to message strong winds and falling temps are likely Thursday.

Friday-Sunday...zonal flow to bring a period of above freezing temps
and dry conditions ahead of another cold front Saturday. Moisture
will be lacking with this front as shown with 1000-500mb RH
progs, so only anticipating an increase in clouds with the fropa
Saturday. A 1035mb surface high will build into the Midwest
Sunday, pushing temps back closer to normal.

Early Next Week...a broad 588 dm upper ridge will set up shop across
the southern CONUS centered over southern TX. Building heights aloft
and warmer 850mb temps (rising into the 6-10C range by Tuesday) will
result in a warming trend leading up to Christmas. For MLI, the
latest LREF has 72% of its members with highs above 40 degrees for
Tuesday Dec 23rd and I suspect this may increase further in later
model runs. While the snowpack has indeed compacted with SWEs around
1" in most locations and avg snowpack temp less than 23 deg per
latest NOHRSC analysis, I believe we will see some substantial
melting before Christmas. We can still dream of a white
Christmas, but prospects are not looking good for at least the
southern half of the CWA.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 514 PM CST Tue Dec 16 2025

Winds will slowly turn from southerly this evening to the west
and northwest overnight as a cold front moves through the
eastern Iowa TAF sites tonight with speeds around 10 knots.
Winds are forecast to become light and variable for a short
period between 14 and 18 UTC Wednesday with winds turning to
the southeast after 18 UTC. Skies and visibility are forecast to
remain VFR through the period with mid and high clouds moving
across the area with the front. There is a low chance for fog
and MVFR visibilities at DBQ after 12 UTC on Wednesday.

&&

.CLIMATE...
Issued at 1204 PM CST Tue Dec 16 2025

A broad and anomalous 500mb ridge (588 dm or 99th percentile
per climatology for late December) will be across the central
CONUS next week. The 8-14 day temperature outlook from the
Climate Prediction Center shows 85-90% combined probabilities of
near/above normal temperatures for the December 23rd-29th time
frame. Normal highs for this period are in the lower 30s and
normal lows are in the middle teens. Should see some substantial
melting take place before and during Christmas across the
forecast area.

&&

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

&&

$$

SHORT TERM...Gross
LONG TERM...Gross
AVIATION...Cousins
CLIMATE...Gross