268
FXUS63 KILX 061929
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
Issued by National Weather Service Chicago IL
229 PM CDT Fri Jun 6 2025

.KEY MESSAGES...

- Despite daily rain chances through Monday, most of central
Illinois will experience below normal rainfall over the next 7 days.
The exception will be in areas near and south of I-70 where there is
a chance (30-50%) for above normal rainfall. Normal rainfall this
time of year is about 1 inch per week.

- Any storms that do develop between now and Sunday have a low risk
(< 5% probability) of producing severe weather and/or flash flooding.

- Residual near-surface smoke will linger through the weekend,
becoming more formidable again by next week.

&&

.DISCUSSION...
Issued at 229 PM CDT Fri Jun 6 2025

Short-term model guidance remains in excellent agreement with the
timing and placement of two distinct low-amplitude shortwave
impulses pushing across Illinois today and Saturday.  The first of
these disturbances will lift along the I-70 corridor this afternoon
and support scattered showers and thunderstorms.  The second
disturbance will push across central IL later Saturday afternoon
into the evening hours, offering greater coverage of showers and
perhaps a little more zest, too.  With both cases, we will need to
monitor upstream trends for signs of a decaying MCS/MCV, which could
augment an otherwise underwhelming shear profile and bring forth a
marginal severe weather risk.

Additional showers and storms are then forecast later Sunday evening
as an upper-level low descends into the Upper-Mississippi Valley and
Great Lakes regions, ultimately helping to push a cold front through
central and southeast Illinois.  Once again, CAPE profiles appear
relatively tall and skinny, and the front itself looks poised to
push through the bulk of our area at a diurnally unfavorable time
factors that might limit storm coverage.  On the other hand, deep-
layer shear should get a boost from a mid-level jet core sagging
into the region.  A quick glance at the hodograph and orientation of
the shear vectors with respect to the forcing suggests a storm mode
of multi-cell clusters with a tendency to want to grow upscale into
linear segments. Without a more robust CAPE profile or a ripping low-
level jet veering in ahead of the front, its hard to imagine the
marginal risk for severe weather pushing east of a Taylorville-to-
Champaign line.

The signal for showers then bleeds into Monday afternoon as some
wrap-around moisture on the backside of the departing upper-level
low supports diurnally-driven, stratocu-type showers. Despite the
daily chances for rainfall through Monday, both blended (NBM) and
ensemble (LREF) guidance point to below-normal rainfall over the
next 7 days across central and southeast Illinois.  Normal rainfall
for this time of year is about 1 inch per week, and the guidance
only suggests a low probability (15-30%) of exceeding this amount
across much of central Illinois.  The exception is near and south of
I-70 where there is a medium (30-50%) probability of exceeding 1
inch over the next 7 days.

A stretch of dry and seasonably warm weather is anticipated from
Tuesday through Thursday once the upper-level low opens and lifts
out of the Great Lakes region.  This feature will be replaced by a
high-pressure ridge that will build across the central US through
midweek.  Daily afternoon highs will be in the low-to-mid 80s with
overnight lows in the low 60s each day beneath the ridge.

Rain chances then creep back into the forecast by late next week,
with global deterministic guidance showing semblance of a slow-
moving disturbance lifting out of the Southern Plains and meandering
through the Mid-Mississippi Valley.  While thunderstorms cannot be
ruled out, relatively weak shear should limit the potential for
widespread organized, severe convection.

As an important aside, the pesky near-sfc smoke that has blanketed
the region over the past 2-3 days looks to finally disperse or mix
out by Monday morning behind the cold front, but only briefly.
Another round of impactful smoke looks positioned to enter our area
later Monday.  Deep northwest flow behind the departing disturbance
promises to bring a higher concentration of smoke into our region by
Tuesday, then becoming trapped beneath surface high pressure on
Wednesday and Thursday.

MJA

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 106 PM CDT Fri Jun 6 2025

The main avn weather concerns for the 18Z TAF period include:

* Patchy MVFR cigs and vsbys this afternoon

* A potential for showers later this afternoon, primarily at
  SPI, DEC, and CMI

* MVFR vsbys associated with fog possible overnight into early
  Saturday

Patches of MVFR cigs are floating around parts of the area this
afternoon, but are gradually thinning out. We`ve been seeing
intermittent vsby reductions to MVFR associated with wildfire
smoke. Reduced vsbys will remain possible through the period,
primarily during the daytime.

A system of showers is expected to move across central and
southern IL this afternoon and early evening. Scattered showers
will be possible at the TAF sites, mainly SPI, DEC, and CMI.
After the rain moves away, fog is expected to develop and stick
around into early Saturday. Vsby reductions should be largely
limited to MVFR. SPI, DEC, and CMI see the highest chances for
MVFR vsbys tonight. All sites are expected to return to VFR by
mid-morning once the fog burns away.

Meanwhile, light and rather variable winds this afternoon will
take hold of a NE direction this evening while remaining light.
Direction will veer to ESE by late Saturday morning and remain
below 10 kt into the afternoon.

Doom

&&

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

&&

$$