265
FXUS63 KILX 221041
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
541 AM CDT Sat Jun 22 2024

.KEY MESSAGES...

- Strong to severe thunderstorms are possible tonight...with the
  highest probability of damaging wind gusts and hail focused
  along and northwest of a Jacksonville to Bloomington line.

- After a brief cool-down on Sunday, temperatures will once again
  climb early next week. Heat index readings will exceed 100
  degrees by Tuesday.

- A second cold front will arrive Tuesday night into Wednesday,
  bringing another chance for much-needed rainfall.

&&

.SHORT TERM...(Today through Sunday)
Issued at 343 AM CDT Sat Jun 22 2024

Low pressure currently over Nebraska will track northeastward into
the Great Lakes, pulling a cold front into central Illinois tonight.
Given the trajectory of the low, the front will not have a strong
southward push and will instead gradually sag into the area. The
airmass ahead of the boundary across eastern/southern Iowa will
become moderately unstable/sheared this afternoon...with HREF ensemble
mean SBCAPEs of 2000-3000J/kg and 0-6km bulk shear increasing to
30-35kt. As a result, scattered thunderstorms will initiate across
this area...then congeal into a broken line as they push across
the Mississippi River into west-central Illinois this evening.
CAMs have slowed the arrival of the convection by a couple of
hours...with consensus suggesting thunderstorms reaching the far
NW KILX CWA around Galesburg between 7pm and 9pm. Given favorable
instability/shear parameters, a risk for large hail and damaging
wind gusts will initially accompany the storms. However, as the
activity drops further southeastward, the atmosphere will decouple
and become more stable with time. The severe risk will therefore
diminish later in the evening, with only a 5-10% chance of a
severe wind gust reaching the I-72 corridor around midnight. Areal
coverage of storms will continue to decrease overnight as they
push into an even less favorable environment south of I-72. Storm
total rainfall tonight will be greatest along/north of a Rushville
to Bloomington line where amounts of 0.75 to locally greater than
1 inch will be likely. Amounts will rapidly decrease further
southeast with locations along/south of a Taylorville to Paris
line only picking up 0.25 or less.

Scattered showers/thunder may linger and/or re-develop across
east-central and southeast Illinois on Sunday before the cold
front settles into the Ohio River Valley: however, am not
expecting any substantial rainfall from the few showers that
persist on Sunday. The main story will be the slightly cooler/less
humid conditions as highs drop into the upper 80s to around 90
degrees.

Barnes

.LONG TERM...(Monday through Friday)
Issued at 343 AM CDT Sat Jun 22 2024

After a warm/dry day on Monday, another cold front will drop into
the region by Tuesday. With temperatures spiking back into the
middle 90s and dewpoints climbing into the lower 70s ahead of the
boundary, peak afternoon heat index values will exceed 100 degrees.
As the front arrives, another round of scattered strong convection
will be on tap Tuesday night into Wednesday. After that, upper troughing
over the Great Lakes will bring a more substantial cool-down for
the end of next week as highs drop into the middle to upper 80s
Wednesday through Friday.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 541 AM CDT Sat Jun 22 2024

Main aviation forecast challenge will be predicting the areal
coverage and timing of convection ahead of a cold front late this
evening. Latest CAMs have slowed the approach of a broken line of
storms by 1-3 hours from prior runs. Based on trends, have
included predominant thunder at KPIA between 03z and 06z and at
KBMI between 04z and 07z. Have opted to maintain PROB30 thunder at
the remaining terminals as the storms will tend to weaken and
decrease in areal coverage the further southeast they track into
central Illinois. Once the front passes, a band of MVFR ceilings
will settle southward late tonight into Sunday morning. Based on
HRRR timing, have added MVFR at KPIA after 08z...then further
south to KDEC/KCMI by 10z. SW winds will increase and gust 20-25kt
from late morning through this evening. After FROPA, winds will
veer to NW and decrease to 10-15kt overnight.

Barnes

&&

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

$$