339
FXUS63 KILX 092305
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
605 PM CDT Thu May 9 2024

.KEY MESSAGES...

- A threat for isolated lightning strikes will persist through
  the middle of this evening south of I-74.

- A low-end lightning threat will accompany a line of showers
  crossing central Illinois from late Friday evening into early
  Saturday morning.

- In the Monday-Tuesday time frame, there is a 20-40% chance of
  greater than a half inch of rainfall in 24 hours. Should this
  occur, one impact would be additional runoff into area rivers
  already running high.

&&

.DISCUSSION...
Issued at 313 PM CDT Thu May 9 2024

A frontal boundary which was nearly stationary this morning has
lifted northward slightly early this afternoon, with winds along
I-74 backing somewhat in response. Around 250-750 J/kg of MLCAPE
resides along a narrow axis from about Lincoln to Mattoon-
Charleston where the sky has cleared somewhat, and we have seen a
handful of showers reaching 40-50 dBZ or so with a few lightning
strikes. The threat for lightning should persist no later than
mid-evening as the frontal boundary pushes southward, MLCAPE
decreases and the atmosphere stabilizes.

A 500-mb short wave trough diving southward out of the upper
Midwest helping to drive some of this afternoon and evening`s
shower activity should pivot east into Indiana by early Friday
morning. Weather during the day should be fairly quiet, with the
next mid-level short wave and associated mid-level jet coming out
of the upper Midwest on Friday evening. An associated weakening
line of showers is forecast to move through central Illinois from
northwest to southeast from late Friday evening through early
Saturday morning, with around 100 J/kg of MUCAPE forecast by the
HRRR indicating at least some probability of lightning especially
Friday evening.

Look for breezy northwest winds gusting to 20-30 mph on Saturday
behind the departing short wave trough. Temperatures kick up a
notch on Sunday under short wave ridging as a mid-level low moves
out of the Colorado Rockies into the high Plains. This low is
responsible for a chance of fairly widespread rainfall in the
Monday-Tuesday time frame. The probability of SBCAPE > 250 J/kg
and sfc-500 mb shear is below 5%, with severe weather
probabilities low. Enough CAPE should be around to support some
thunder, however. NBM probabilities show about a 20-40% chance of
greater than a half inch of rain in a 24 hour period in the
Monday-Tuesday window.

Notable model variability exists in timing and strength of troughs
beyond Tuesday. Though mid-range precip chances are included
throughout Wednesday and Thursday, there`s a decent chance of at
least one dry period occurring in that stretch.

AAT

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 605 PM CDT Thu May 9 2024

Band of MVFR to occasionally IFR ceilings has been sagging
southward this evening, associated with a cold front that roughly
extends from KIJX-KDNV. Lower visibilities have generally been
associated with heavier showers immediately north of this front.
General trend for the next several hours will be for ceilings to
remain below 2,000 feet in most areas except for KPIA, where more
of an increase to 5,000 feet is imminent. However, HREF guidance
hints at some potential for IFR ceilings (30-50%) after 08Z. More
of a general improvement is expected after 15Z.

North/northeast winds overnight will generally trend more toward
the northwest Friday morning.

Geelhart

&&

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

$$