812
FXUS63 KILX 220906
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
406 AM CDT Sun Sep 22 2024

.KEY MESSAGES...

- Beneficial rainfall is expected over central and southeast IL
  today through Tuesday morning. Between 1 and 2 inches is
  expected from I-72 south, with locally higher amounts possible
  south of I-70. Between a half and 1 inch of rain is expected
  north of I-72.

- Cooler temperatures are expected this week following 8
  consecutive days of summerlike heat. Dry conditions return to
  central and southeast IL Tuesday night through Wednesday night.
  There is now a 20-30% chance of showers Thursday into next
  weekend.


&&

.DISCUSSION...
Issued at 400 AM CDT Sun Sep 22 2024

A large area of showers with a few embedded thunderstorms was
moving eastward into central IL early this morning, as was as far
east as highway 29 from Peoria to Springfield. Some weakening
trends noted in convection past few hours and expect this to
continue as it tracks into eastern IL during this morning. A cold
front over central WI into far southeast Iowa and nw MO will push
se to near the IL river by early afternoon and nearing I-70 by
sunset. A broken band of convection is forecast to develop along
and ahead of the cold front near the IL river valley early this
afternoon and push into southeast IL this evening. SPC day 1
outlook keeps marginal risk of severe storms south of CWA this
afternoon/early evening over southern MO and southern IL where
instability will be greater. Ample clouds today along with rain
chances to bring cooler temperatures with highs in the lower 70s
nw of the IL river and upper 70s to near 80F in southeast IL. This
will be a nice break from the heat we had past 8 days with highs
in the upper 80s to mid 90s since Sep 14th.

Convection chances to lower as the night wears on with mainly
isolated chances overnight with main energy/lift focused sw of our
area. Lows tonight range from mid to upper 50s from I-55 nw to the
mid 60s in southeast IL from I-70 southeast. Monday we will be on
the cool side of the front to our south with highest pops (50-60%) in
our southern counties and slight chances from I-74 north by Mon
afternoon. SPC day2 marginal risk of severe storms Monday
afternoon and evening is in far southern IL from Murphysboro to
Evansville south. Highs Monday mostly in the lower 70s with upper
60s even possible sw of Springfield. Highs near 75F at
Lawrenceville.

Low pressure near central AR around dawn Monday to lift ne along
the front into the mid MS river valley by sunset Monday and near
southeast IL by dawn Tue as upper level trof/low digs into the
upper MS river valley and east central plains by Tue afternoon.
This will likely spread another wave of convection ne over central
and southeast IL during Mon night and Tue morning, and lingering
chances of showers in eastern IL Tue afternoon. Seasonably cool
day again on Tue with mostly cloudy to overcast skies and rain
chances especially in the morning, with highs around 70F in
central IL and low to mid 70s in southeast IL. Have generally dry
and seasonably cool conditions Tue night through Wed night though
nearby upper level trof may keep more low clouds around and
isolated light showers (pops less than 20%).

Models diverge with evolution of upper level pattern during 2nd
half of the week as a strong cutoff low appears to affect the
southern and southeast states. Latest GEM and Ecmwf models now
bring cutoff low far enough north with qpf over central/se IL Thu
into this weekend, while GFS is drier with upper level ridging
into IL late this week. Blended models have 20-30% chance of
showers Thu through this next weekend with highs in the 70s and
lows in the 50s.

07

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1145 PM CDT Sat Sep 21 2024

Large area of rain and storms west of the Mississippi River will
move east overnight, though thunder extent is expected to be more
questionable the further east it gets. Will include a thunder
mention at KPIA/KSPI for now, and monitor trends for the next few
hours for potential expansion eastward. Currently think the
thunder threat should be out by about 12Z in these areas. By 18Z,
the bulk of the steadier rain should scatter out, but additional
showers will remain a threat into the afternoon as the cold front
moves across the TAF sites. Can`t rule out some additional thunder
in the 21-24Z period, but confidence is too low to include at
this point.

Once the rain begins, ceilings are expected to quickly drop to
below 2,000 feet, where they largely will remain into the evening.
Getting to the end of the forecast period, latest HREF guidance
suggests 40-60% chances of IFR ceilings by 03Z from KBMI-KCMI,
with some lower potential at KDEC.

Geelhart

&&

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

$$