169
FXUS63 KILX 031453
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
953 AM CDT Mon Jun 3 2024

.KEY MESSAGES...

- Showers and thunderstorms this afternoon (50-60% chance) for
  areas west of I-57. There is a threat for isolated strong to
  severe storms this afternoon (hail and stronger winds).

- More storms and showers late tomorrow afternoon into the
  overnight hours ahead of a passing cold front. There is another
  threat for strong-to-severe storms late tomorrow.

- A drier pattern sets up for the end of the week.

&&

.UPDATE...
Issued at 949 AM CDT Mon Jun 3 2024

Latest geocolor satellite imagery shows mid-level convective debris
and cirrus clouds stirring across much of the Midwest, while strong
thunderstorms continue across portions of Oklahoma. Flow across the
region remains weak, with the 12z raob only suggesting 15 kt of 0-
6km bulk shear; however, instability will climb this afternoon with
HREF mean bringing SBCAPE values to 1500-2500 J/kg by 2pm near and
west of I-55. With mixing of drier air aloft to the surface this
afternoon, forecast soundings take on a bit of a (rather shallow)
inverted V look, with steep low level lapse rates aiding in sub
cloud-base evaporation of downdrafts in any thunderstorms that
develop.

The big question is: will thunderstorms develop? At this
point, the presence and location of a forcing mechanism is unclear,
however the abundance of clouds and isolated, light showers upstream
across Iowa and Missouri suggests there`s some type of forcing
mechanism out there. The 12z CAMs are virtually all dry here, but
several have convection just to our west near the IL/IA/MO state
lines, so we`ll need to keep a close eye on things though at this
point I think our area might just escape with a storm-free
afternoon. The level 1 of 5, marginal, risk from SPC seems
reasonable, as it covers the potential for localized, near-severe
wind gusts with the collapse of any pulse storm that fires...but
also implies the low (5-15%) potential for storms to materialize
at all in central IL.

Temperatures and dewpoints were updated using a blend of the 12z
HRRR and NBM, which brought highs up a degree or two across our
west (to the 86-89 degF range) where the better afternoon mixing
is forecast.

Bumgardner

&&

.DISCUSSION...
Issued at 300 AM CDT Mon Jun 3 2024

Some patchy fog is occuring across central Illinois this morning..
Dewpoint depressions are 0 for many locations which is mixed with
clear skies and light winds. The morning sun will erode the areas
experiencing fog this morning. A shortwave is expected to move
through central Illinois today, bringing isolated strong to severe
thunderstorms and some showers. There is a MCV trekking across the
middle Mississippi Valley that could influence how long-lived the
storms are.

There is more than sufficient instability (1500-3000 J/kg SBCAPE) to
support thunderstorms this afternoon. The bulk shear values,
however, are nonexistent (10-15kts) with unimpressive mid-level
lapse rates (~6.5 C/km). The storms that do develop will be short-
lived and pulsey without the shear to keep them alive, unless the
passing MCV can locally increase the wind shear. They could be
capable of marginally severe hail and stronger wind gusts as they
collapse (DCAPE values near 1000 J/kg). The 06z HRRR and 00z NAMNest
is showing the main area of interest being west of I-57.

Tuesday will look quite similar to this afternoon in terms of pop up
type thunderstorms, except there is weaker instability in the
afternoon (1000-1500 J/kg SBCAPE). The 06z HRRR is showing the
development of the afternoon storms/showers being east of the
Illinois River valley. The main threat for severe weather looks to
come late evening into the overnight hours tomorrow ahead of the
cold frontal passage on Wednesday. However, we are not expecting it
to be widespread.

For the remainder of the week, a drier pattern sets up for a few
days. There is a small chance (10-25%) of any rain over the weekend.
Highs will hang around the upper 70s to low 80s through Sunday.

Copple

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 544 AM CDT Mon Jun 3 2024

There is some fog in central Illinois this morning, affecting
BMI/DEC/CMI. Once the fog erodes (after 14z), today will be a VFR
kind of day. There is a 20-40% chance of showers and thunderstorms
this afternoon (after 18z), but the location of where they will pop
up is uncertain. I have chosen to leave out mention of SHRA/VCSH or
any TS due to the uncertainty for this TAF cycle.

Copple

&&

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

$$