017
FXUS63 KILX 022303
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
603 PM CDT Sun Jun 2 2024

.KEY MESSAGES...

- Showers and storms return for the start of the new week with the
  potential for severe storms on both Monday and Tuesday.

- A cooler and drier period looks favorable late in the week
  through the weekend.

&&

.DISCUSSION...
Issued at 249 PM CDT Sun Jun 2 2024

Shortwave upper ridging is positioned over the area today with a
broad associated surface high situated over the Midwest states.
Pesky low stratus lingers over a good chunk of the area this
afternoon, with gentle east-northeast winds slowly eroding it. Areas
near and west of the Illinois River are mostly clear aside from some
diurnal cumulus. High temperatures for today have been lowered by
several degrees where 2 pm readings are still in the upper 60s
underneath the cloud deck. High temperatures this afternoon should
peak in the middle 70s to low 80s with the highest where clouds were
quicker to erode.

Zonal flow sets up overhead for the start of the new week, with what
looks like a more active period with several chances for showers and
storms. The remnants of a decaying MCS will approach from the west
Monday morning, falling apart just before or as it reaches the
forecast area as it encounters a more stable airmass. An outflow
boundary left behind from this feature will act as a forcing
mechanism for any thunderstorm development later in the day, though
this looks to lay out over northern Illinois. Another MCS
southwest of here will track across the south-central Plains
states tonight, leaving a remnant MCV somewhere over the lower
Missouri Valley by Monday morning. This feature will lift
northward with a shortwave trough, approaching the Middle
Mississippi Valley Monday afternoon. Southerly flow ahead of these
mesoscale features will bring in a much warmer and moist airmass
with dewpoints climbing well into the 60s. Moderately strong
instability will quickly build by Monday afternoon with values
looking to top out between 1500- 2000+ J/kg. However, wind shear
will be rather weak due to the lack of mid to upper jet support.
Despite this, CAMs show thunderstorms developing by mid to late
afternoon over Missouri/west-central Illinois with the MCV and
another area over northwest parts of Illinois along the outflow
boundary. The MCV may act to locally enhance wind shear, but the
overall lack of wind shear should prevent storms from maintaining
organization. Any storms that do develop will pose a threat for
isolated large hail and damaging wind gusts.

A stronger upper wave will track from the Pacific Northwest into the
northern Plains on Tuesday, sending a cold front toward the Midwest
states later Tuesday night into Wednesday. Continued southerly flow
ahead of the system will lead to another day of moderately strong
instability with dewpoints climbing into the 70s. Upper jet
support will once again be displaced to our west/northwest,
resulting in relatively weak wind shear. Previous day`s convection
may also play a role in any outcomes for Tuesday, with the 12Z
run of the NAMnest suggesting the remnants of Monday`s MCV
bringing another round of storms as early as Tuesday morning.
Additional thunderstorms appear possible later Tuesday night into
Wednesday with FROPA, but instability looks to decrease some by
then due to loss of daytime heating. Tuesday is another day that
bears watching for severe potential.

The upper pattern becomes more northwesterly by the end of the week
as the strong upper wave occludes and becomes somewhat stationary
over the northern Great Lakes Region. Precipitation chances become a
little more unknown in the extended due to differences in
progression of the upper wave and any shortwaves rippling through
the flow aloft, but a drier period does appear to be favored.

NMA

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 603 PM CDT Sun Jun 2 2024

Lingering stratocu at KDEC/KCMI will dissipate shortly, leaving
mainly VFR conditions for the remainder of the forecast. One
exception is the development of fog tonight over eastern IL.
Confidence is currently low that it will expand as far west as
KCMI/KDEC, so added a tempo group for MVFR visibility late. There
are low probabilities of IFR/LIFR visibilities for KCMI/KDEC
should the fog become more dense/widespread than currently
expected. Scattered TSRA will be around Monday afternoon, with
coverage low enough for a PROB30 group at all central IL
terminals. Impacts would be brief gusty winds and IFR conditions.


25

&&

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

$$