800
FXUS63 KILX 252312
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
612 PM CDT Fri Apr 25 2025

.KEY MESSAGES...

- The next significant chance for thunderstorms will arrive early
  next week as a cold front approaches from the west. There is a
  15% chance for severe weather northwest of a Litchfield to
  Hoopeston line Monday night...and everywhere east of the
  Illinois River during the day Tuesday.

- In addition to the storm chances, it will become windy and very
  warm ahead of the front on Monday...with the latest guidance
  suggesting a high probability (60-90% chance) for wind gusts
  greater than 30mph.

&&

.DISCUSSION...
Issued at 228 PM CDT Fri Apr 25 2025

...Scattered Convection This Afternoon/Evening...

18z/1pm surface analysis shows a slow-moving cold front extending
from southern Michigan southwestward into Missouri. While the bulk
of the precip that tracked across the area this morning has pushed
east of the I-57 corridor and decreased in areal coverage, new
convection is beginning to form along the front from just south of
Lewistown to near Jacksonville. Given partial sunshine heating
temperatures into the lower to middle 70s and surface dewpoints
hovering in the 60s, SPC mesoanalysis indicates SBCAPEs have risen
into the 1000-1500J/kg range. Weak convergence along the boundary
and deep layer shear of less than 30kt will be mitigating factors
for vigorous convection: however, think this band of scattered
showers and thunderstorms will continue to work its way eastward
across the area...generally impacting locations along/south of a
Lewistown...to Bloomington...to Hoopeston line between now and
about 8-9pm. After that, the showers will push into Indiana and
dissipate by late evening.

...Windy and Much Warmer Conditions on Monday...

As high pressure pushes eastward into the Ohio River Valley,
southeasterly return flow will commence on Sunday. Some CAMs
suggest a few WAA showers will be possible across the W/SW CWA:
however, these will be fighting a dry low-level airmass and will
not amount to much even if they do occur. As the high shifts
further east and a cold front approaches from the west, a
tightening pressure gradient will lead to increasing winds on
Monday. The 00z Apr 25 LREF is showing a high probability (60-90%
chance) for southerly wind gusts exceeding 30mph everywhere north
of the I-70 corridor by Monday afternoon. Both the LREF and NBM
indicate a strong signal for wind gusts over 30mph on Monday and
in the 25-30mph range into Tuesday as well. With sunshine and
strong southerly winds, the 570dm 1000-500mb thickness line is
progged to surge northward into the area...supporting Monday
afternoon highs in the lower to middle 80s.

...Severe Weather Risk Monday Night...

The approaching cold front will interact with a highly unstable
(GFS SBCAPEs 2000-3000J/kg) and strongly sheared (GFS 0-6km bulk
shear greater than 50kt) environment to trigger a line of severe
convection across western Wisconsin into Iowa by late Monday
afternoon/evening. This convection will then translate eastward
into the Illinois River Valley after dark and will likely continue
eastward to the I-57 corridor toward dawn Tuesday. While the
storms will be undergoing some degree of diurnal weakening, ample
wind energy in the environment will keep the risk of at least
scattered severe wind gusts alive across a good portion of the
KILX CWA. The latest SPC outlook highlights locations along/west
of a Litchfield to Hoopeston line...and this still looks good
based on the latest data.

...Severe Weather Risk Tuesday Afternoon/Evening...

The big question for Tuesday will be exactly where convection will
re-develop ahead of the cold front/outflow boundary during the
afternoon. The GFS continues to suggest initiation will be across
the heart of central Illinois: however, the 12z ECMWF is showing
things setting up a bit further south...perhaps along the I-70
corridor. Will need to keep a close eye on where the storms
eventually fire, because deep-layer kinematics associated with the
right entrance region of a 110-120kt 300mb jet streak across the
Great Lakes will be favorable for significant synoptic lift. In
addition, strong convergence along the cold front will support
vigorous updrafts and the subsequent risk for large hail and
damaging wind gusts from mid-afternoon into the evening.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 612 PM CDT Fri Apr 25 2025

MVFR cigs are expected to spread over the central IL terminals
from the northwest this evening, lingering into Saturday morning.
Although timing continues to have uncertainty, start of MVFR looks
to be anywhere from before 00Z at KBMI to 03Z at KDEC, and end
looks to be around 15Z-17Z. Winds N 10-15 kts with gusts around 20
kts this evening, decreasing to 10-12 kts and shifting to NNE
overnight.

37

&&

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

$$