DeKalb, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

964
FXUS63 KLOT 022116
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
316 PM CST Mon Feb 2 2026

.KEY MESSAGES...

- There is a chance (40%) for a very narrow band (or bands) of
  accumulating snow late tonight, currently favoring areas south
  of a Rockford to Chicago to Valparaiso line.

- Lake effect snow showers may meander near the Indiana and
  Illinois shores of Lake Michgian Tuesday into early Wednesday
  morning (30% chance).

- Temperatures may warm above freezing Thursday and more likely
  Friday then cool again heading into the weekend.

- A pattern change toward warmer temperature (highs and lows
  both above freezing) may materialize by the middle of next
  week.

&&

.DISCUSSION...
Issued at 315 PM CST Mon Feb 2 2026

Much of the area has been blanketed in low-level stratus all
day paired with intermittent flurries thanks to the cloud layer
being situated near/into the DGZ. As a result, temperatures have
only warmed a few degrees today in the mid-upper 20s. However,
some areas west of I-39 have managed to clear out this afternoon
allowing temperatures to warm into the lower 30s in spots. It
is possible further erosion of the edge of the cloud layer may
occur prior to sunset. Expect the flurries to also gradually
wane heading into the evening hours as the cloud layer continues
to thin.

Looking ahead to the overnight hours, a clipper system
currently pushing through the Dakotas into Minnesota is expected
to move toward and across northern Illinois into Indiana late
tonight into early Tuesday morning (~11 PM - 6 AM CST). The
majority of hi-res guidance shows hints of this feature holding
together into the area but only show streaky dustings of snow.
Suspect they are struggling to resolve this smaller scale
feature amidst limited moisture advection into the area.
However, forecast vertical profiles within this potential band
appear supportive of a brief window when sufficient saturation
within the DGZ paired with steep lapse rates could result in a
quick burst of snow and a axis of 0.5-1" of accumulations (maybe
even locally higher) within a narrow band. Low to mid- level
frontogenesis appears somewhat ephemeral and could be indicative
of one or more very narrow bands occurring rather than one lone
band, and confidence in where remains low overall. Based on the
trajectory of snow upstream, it currently favors areas along a
line from Sterling to Kankakee to Rensselaer. Have kept snow
chances a bit more broad brushed than what will likely end up
occurring for now.

As the clipper departs to the east Tuesday morning, northerly
low-level flow sets up over the area. This will allow low-level
convergence to set up over southern Lake Michigan which could
set the stage for an extended period of (mainly light) lake
effect snow showers into northwest Indiana (at times meandering
into northeast Illinois) Tuesday through early Wednesday
morning. Inversion heights are not especially high, but with
sufficient lift within the DGZ could support accumulations up to
0.5-1" to locally higher. Dry conditions are expected across
the rest of the area away from the lake. Temperatures Tuesday
and Wednesday will remain cooler, with highs only in the 20s
amidst weak northwesterly cold air advection.

Northwest flow will remain in place aloft late week with
multiple waves expected to dive across the region which could
lead to occasional periods of snow. Confidence in the timing and
strength of these features remains on the lower side, but
keeping an eye on Thursday morning, again Thursday night Another
wave dives through Thursday. As confidence increases in the
timing of these features, higher snow chances may become
warranted than the current blended guidance.

Temperatures will gradually warm through the end of the work
week with highs potentially in the mid 30s to around 40 by
Friday, though there remain differences with respect to just how
warm we end up. Stay tuned. This "warmth" will be rather short
lived with a strong cold front expected to push through late
Friday with high temperatures back into the 20s to around 30
over the weekend.

Petr


Next week:

Looking toward next week, ensemble model guidance exhibits a
strengthening signal that the exceptionally persistent
northwesterly upper-level flow pattern that has thus far
defined winter across the central/eastern United States may
temporarily break. As a result, ensemble mean temperatures
trend notably upward by the middle of next week and beyond, with
both high and lows above the freezing mark. Indeed, the CPC
temperature outlooks for the middle of February favor the above
average category across much of the central US.

Also have to point out a growing signal for a southwest-flow
synoptic scale cyclone somewhere east of the Rocky Mountains in
the February 11-14 timeframe, with both the GEFS/EPS already
favoring our area being on the warm side. Should a cyclone
actually develop and we end up on the warm side, could easily
envision forecast focus trending toward hydrology concerns
considering the frost depth of just deeper than 13 inches at our
office isn`t going to vanish anytime soon.

Borchardt

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1202 PM CST Mon Feb 2 2026

Key Messages:

- MVFR ceilings will continue to be observed this afternoon
  before scattering out.

- There is roughly a 25-35% chance for a period of snow to be
  observed overnight tonight.


MVFR stratus continues to blanket the area early this
afternoon. Some flurries have been leaking out of this cloud
deck as well, and this may continue to be the case while the
stratus remains in place. Between the back edge of the stratus
approaching the terminals and the stratus thinning/eroding, a
return to VFR conditions is likely this evening. However,
lake-induced MVFR stratocumulus will make an inland surge
sometime tomorrow morning, bringing a renewed period of MVFR
ceilings to GYY, MDW, and possibly ORD tomorrow.

There also remains about a 25-35% chance for snow at the
terminals overnight tonight as a mid/upper-level shortwave
disturbance dives into the region. There is an increasing
likelihood that there will be a narrow corridor somewhere in the
area where the snow comes down at a fairly decent clip --
enough to reduce visibility lower than presently advertised in
the going TAFs. However, the greatest likelihood for this
appears to be south and southwest of the terminals, so only have
visibility reductions down to MVFR in the going PROB30 groups
at this time.

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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