539
FXUS63 KILX 231046
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
546 AM CDT Sun Jun 23 2024

.KEY MESSAGES...

- After a cool-down today and Monday, hot weather will briefly
  return on Tuesday when afternoon heat index readings exceed 100
  degrees.

- Thunderstorm chances come back into the picture by late
  Tuesday...with the latest guidance suggesting a Slight Risk
  (15-30% chance) for severe weather along and north of the I-72
  corridor.

&&

.SHORT TERM...(Today through Monday)
Issued at 339 AM CDT Sun Jun 23 2024

08z/3am radar imagery shows a line of thunderstorms extending from
Danville to Shelbyville. These storms will continue to track eastward
and will exit into Indiana within the next 3-4 hours. After that,
am expecting cooler/drier conditions across the board today.
Thanks to northwesterly winds behind a departing cold front and at
least partial cloud cover through midday, high temperatures will
be several degrees cooler than in recent days with readings
primarily topping out in the middle to upper 80s. As high pressure
builds overhead and winds become light/variable, radiational
cooling will help low temperatures tonight drop into the lower to
middle 60s. Another pleasant summer day will be on tap for Monday
with highs in the upper 80s to around 90 degrees and low relative
humidity values.

Barnes

.LONG TERM...(Tuesday through Saturday)
Issued at 339 AM CDT Sun Jun 23 2024

As the high shifts off to the east, a warm front will lift
northward through central Illinois Monday night. Models have been
suggesting the potential for widely scattered thunderstorms
along/north of the boundary...particularly late Monday night into
Tuesday morning. Have therefore added 20 PoPs along/north of the
I-74 corridor. Stronger forcing will be present further north in
conjunction with a short-wave trough tracking through the Northern
Plains, which could potentially lead to the formation of an MCS
across Wisconsin into far northern Illinois/Indiana.

With the warm front well to the north and southwesterly winds in
place, a hot/humid airmass will return to central Illinois on
Tuesday. NBM guidance continues to be too warm based on the
projected thermal profile and the potential for convective debris
from the early morning MCS, so have once again undercut those
numbers to feature highs in the lower to middle 90s. With surface
dewpoints progged to reach the lower 70s, afternoon heat index
values will climb to near Heat Advisory criteria in the 100-105
degree range.

While a few thunderstorms will be possible during the day Tuesday,
it appears a much better chance for convection will materialize
Tuesday night as a cold front drops southward into the moderately
unstable/sheared environment. While precise details are still not
clear, confidence is growing for another round of strong to
potentially severe thunderstorms...with the highest probability
for severe focusing along/north of the I-72 corridor.

The front will drop southward through the region late Tuesday
night into Wednesday. Once it passes, another airmass change will
bring cooler/less humid conditions back. High temperatures will
drop into the 80s for Wednesday/Thursday before returning to the
90s by Friday/Saturday.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 546 AM CDT Sun Jun 23 2024

10z/5am obs show a cold front has passed just east of I-55. Winds
will remain SW at 5-10kt at both KDEC/KCMI for the next hour or
two before veering to NW after FROPA. NW winds will then increase
and gust 18-22kt at all terminals from late morning through the
afternoon before decreasing to less than 10kt by sunset. Skies
have partially cleared behind the departing front: however, patches
of MVFR ceilings are drifting southward into central Illinois.
Based on satellite trends and the HRRR forecast, have included a
period of MVFR at all sites before clearing the low clouds from
west to east later this morning. Have scattered the MVFR ceiling
at KPIA/KSPI by 15z, then further east to KCMI by 17z. After that,
mostly clear skies will prevail through the remainder of the 12z
TAF period.

Barnes

&&

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

$$