885
FXUS63 KILX 231945
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
245 PM CDT Thu May 23 2024

.KEY MESSAGES...

- There is a slight risk (level 2 of 5) for severe weather for all
  of central and southeastern Illinois for tomorrow. These storms
  could produce damaging winds and large hail.

- There is a 80-100% chance of thunderstorms on Sunday. These
  storms have the potential to be severe, with a 15-30% chance for
  severe weather that day.

&&

.DISCUSSION...
Issued at 245 PM CDT Thu May 23 2024

There are a few rounds of low pressure systems and it associated
frontal passages over the coming days. The first of which arrives
tomorrow morning. A cold front is expected to move through central
and southeastern Illinois late morning/early afternoon tomorrow,
bringing along severe weather potential. A brief surface high
pressure will set up for Saturday before the next low pressure
system passes to the north/northwest of the CWA Sunday. This low
will bring its associated cold front through the area in the
afternoon to evening hours. This system on Sunday will have the
greatest risk for severe weather.

This forecast cycle will put a lot of focus on what is coming
tomorrow. The models are being difficult and not agreeing on timing
or how the storms will move through the CWA. They do agree on storm
type, however. It will move through as a QLCS but whether it will be
a broken line or not is up for debate. The HRRR and NAM 3km differ
in timing somewhat, with the NAM 3km being a bit slower. The line
will enter our western border between 15z and 17z. The HRRR has the
QLCS moving through as solid line that goes across the entire CWA.
Whereas the NAM 3km shows a broken line. The northern portion of the
line propagates across the CWA (north of I-72), with the southern
portion developing slightly later as the first line exits the state
around 21z. This second line stretches further south along our
entire CWA. The HRRR shows the activity exiting Illinois around 23z
but the NAM 3km shows it lingering longer to around 4z. The chances
of redevelopment behind the front is basically non existant at this
time.

Temperatures tomorrow get up into the low to mid 80s. In more
mesoscale news, the storms should be surface based. The HREF 12z run
shows a 50-60% chance of greater than 3000 J/kg of SBCAPE ahead of
the front. There is a brief cap in the morning that quickly erodes
by mid morning. DCAPE values associated with the system shows 1000-
1500 J/kg. There appears to be an inverted V signature on the 18z
HRRR soundings ahead of the front. The hazards most likely to impact
central and southeast Illinois with this round of severe weather is
primarily hail and severe wind. The wind threat is the highest risk
for tomorrow, which the inverted V soundings and high DCAPE values
support. PWAT values max out around 2 inches but the fast moving
nature and training isn`t expected will limit the flooding threat.
Localized higher amounts could occur.

Saturday a high pressure settles of the area briefly, providing us a
short break before the next round of severe weather on Sunday.
Sunday another low pressure system is progged to move just
north/northwest of the CWA, bringing the next chance for severe
weather. There is a 15-30% chance for severe weather, with the
greatest risk down in southeastern Illinois. Timing of the system is
sort of uncertain currently but it looks to move through Sunday
morning into the afternoon in a linear storm mode. This round is
looking more impressive than the system expected tomorrow afternoon.

Memorial Day, Monday, looks to be windy and pretty dry. A few pop up
showers aren`t completely ruled out but basically dry. Stay tuned as
the holiday weekend gets closer and this first system gets out of
the picture for more detailed information.

Copple

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1250 PM CDT Thu May 23 2024

VFR conditions will prevail across the central IL airport through
Friday morning, and generally dry conditions expected. SE winds of
5-10 kts with a few gusts 15-20 kts into mid afternoon will be
fairly light tonight. Winds then veer south and increase to 12-17
kts with gusts 20-25 kts after 15Z/10 am Fri. Scattered to broken
cumulus clouds with bases of 4-7k ft will occur along I-72 this
afternoon. Fair skies are expected tonight across the central IL
airports with mid/high clouds increasing during Friday morning.
Patchy fog possible late tonight though coverage appears too
limited to mention in TAFs. A broken line of convection will
track eastward toward the IL River valley and by near PIA by 18Z/1
pm Fri and VCTS added to PIA after 17Z. Main line of convection
to move eastward over central IL airport Friday afternoon just
after this TAF period and likely have stronger impact on PIA and
BMI.

07

&&

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

$$