861
FXUS63 KILX 021951
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
251 PM CDT Thu May 2 2024

.KEY MESSAGES...

- Concern remains for some strong to locally severe storms through
  sunset, primarily west of I-55.

- While some quieter periods are expected during the weekend, an
  active weather pattern re-establishes itself early next week.


&&

.DISCUSSION...
Issued at 251 PM CDT Thu May 2 2024

Isolated convection has begun to fire early this afternoon near
Peoria, along a subtle surface boundary. Latest SPC mesoanalysis
shows close to 1500 J/kg of surface based CAPE across much of
central Illinois, with steep low level lapse rates of around 8.5
C/km. Already have received some pea size hail reports with the
Peoria cell. On a broader scale, numerous thunderstorms continue
to develop over central Missouri and are traveling northeast. A
general expansion northeast along the Illinois/Iowa border is
expected over the next few hours, with storms becoming numerous
over west central Illinois. Area remains in a Level 1 severe risk
this afternoon and early evening, with some brief wind/hail risks.
High-res models show some general weakening after sunset, though
PoP`s will remain high over the eastern half of the forecast area
through about 3-4 am. Timing of the overall system appears to have
sped up though, and rain chances on Friday were significantly
lowered and primarily limited to near/east of I-57.

Overall, the upper air pattern over the coming days has not
changed in the morning model suite. As the upper low over
southern Saskatchewan lifts northeast, a larger low will track
into northern California/Nevada this weekend, before ejecting into
the Plains on Monday. The international models keep the closed
low more or less intact through the period, while the GFS opens it
up for a time. Net effect of this will be periods of showers and
thunderstorms into the middle of next week. There are some signs
of extended drier periods Friday night, and again later in the
weekend, with more of an increase in PoP`s as the low moves into
the Plains and gets more wound up. Tuesday remains a period of
concern for potential for strong storms, with a number of European
ensemble members featuring CAPE values upwards of 1500 J/kg.
Overnight CSU machine learning probabilities also highlight
Tuesday as a concern.

Geelhart

&&

.AVIATION...  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1223 PM CDT Thu May 2 2024

Main concern in the shorter term will be with timing of convective
development. Initial development is expected along the IL/IA
border toward 20-21Z with storms moving east, though some
weakening will take place after 00Z. While some of the heavier
storms may produce some brief MVFR visibility or ceilings,
confidence levels are not high enough yet to introduce a TEMPO
period.

Later on, a more sustained period of ceilings below 3,000 feet
will accompany the cold front following the rain. This should be
moving into KPIA as early as 06-07Z, though not reaching KCMI
until closer to 11-12Z. Morning HREF guidance suggests a 2-3 hour
period of IFR conditions isn`t out of the question (30-50%
probability), so this will need to be monitored.

Geelhart

&&

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

$$