Champaign, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

184
FXUS63 KILX 171919
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
219 PM CDT Thu Apr 17 2025

.KEY MESSAGES...

- A cold front will bring scattered thunderstorms to central
  Illinois Friday evening. There is a slight risk (level 2 of 5)
  for severe thunderstorms with damaging wind gusts and large hail
  the primary concerns (15% within 25 miles), but an isolated
  tornado cannot be ruled out (2% within 25 miles).

- As the severe threat diminishes Friday night, attention will
  turn to flooding concerns as heavy rain develops. Middle 50th
  percentile precip amounts through the weekend range from 0.75 to
  2.50 inches with some localized swaths over 3.00 possible (90th
  percentile forecast).

&&

.DISCUSSION...
Issued at 214 PM CDT Thu Apr 17 2025

Afternoon water vapor imagery shows a very dry mid level air mass
and elevated mixed layer lifting northeast across OK/KS which
guidance depicts overspreading central Illinois overnight into
Friday morning. Soundings show very steep lapse rates that are
nearly dry-adiabatic especially within the 800-600mb layer. This
is atop an incredibly strong capping inversion. MLCIN in excess of
600 J/kg will be in place to start the day Friday and is expected
to persist most of the day across central Illinois very
effectively capping the warm sector and preventing deep
convection. It`s not until the arrival of a cold front Friday
evening that guidance begins to erode the cap. Scattered storms
should eventually be able to form Friday evening, and parameter
space is supportive of severe weather once the cap breaks.
Moderate instability around 1000-1500 J/kg MLCAPE and strong deep
layer shear of 45-50 kt will allow for rotating updrafts with
initially discrete storms. Forcing along the front appears weak
Friday evening with the surface low pulling away across the Great
Lakes and a col area moving into central Illinois late in the
evening. Given the modest synoptic scale forcing and antecedent
cap, it appears that upscale growth will be slow if much at all.
CAMs generally depict scattered clusters of storms over the area.
Storm coverage will increase late in the evening and overnight,
especially south of I-72, in response to a low level jet along the
lower to mid Mississippi Valley overspreading southern Illinois.

Frontal boundary is expected to meander over the southern half of
the state over the weekend and will serve as the focus for
additional rounds of showers and storms. The heaviest period of
rain is expected to be Friday night into Saturday morning
associated with the aforementioned LLJ. Cloud bearing flow
(850-300mb) and deep layer shear vectors are both parallel to the
quasi-stationary surface front indicating that training storms
will be possible. HREF LPMM through Saturday morning shows some
localized swaths of 1.5-2.0 inches with additional rain expected
later Saturday and Sunday.

NBM 72-hour mean QPF from Friday through Monday morning ranges
from around 1.25 along the I-74 corridor to 1.50-2.00 inches
along our southern CWA boundary (Beardstown to Lawrenceville).
90th Percentile indicates that there is some potential for some
higher end rainfall amounts of over 3.00 inches of rain through
the weekend. RFC 6-hour flash flood guidance generally ranges
between 2.5-3.0 inches.

Early next week, departing low pressure over the Great Lakes will
usher in colder air across the Upper Midwest and into central
Illinois while, at the surface, high pressure builds across the
region. This will allow for a dry but slightly cooler start to the
upcoming week. Highs will top out around 60 degrees Monday, but
should begin to warm back up Tuesday and Wednesday as the ridge
axis shifts to our east allowing southwest flow to overspread the
area. Models begin to diverge by the middle of next week, but
another area of low pressure and attendant cold front is expected
sometime in the Wed/Thu timeframe bringing the next chance for
precip to the area.

Deubelbeiss

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1231 PM CDT Thu Apr 17 2025

At 1730z (1230 pm CDT), radar shows an area of showers lifting
northeast across central and eastern IL. These showers could bring
a brief period of MVFR visibility to any terminal, but they`re
expected to evacuate the TAF sites over the next couple hours with
even some breaks in VFR cloud cover arriving by late
afternoon/evening. LLWS was considered for tonight as a LLJ
results in south winds increasing to 40-50 kt at just 2kft AGL,
but this was ultimately not added to the TAFs given stiff
southerly surface winds around 20kt. Winds regain their gustiness
tomorrow morning with gusts over 30 kt in the forecast by the end
of the forecast period.

Bumgardner

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$