283
FXUS63 KILX 031915
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
215 PM CDT Wed Jul 3 2024

.KEY MESSAGES...

- Scattered showers and storms are possible (30-50 percent) mainly
  south of I-70 late this afternoon into the evening. A few storms
  could be strong to severe with damaging wind gusts the primary
  hazard.

- A couple rounds of showers and storms are expected Thursday; one
  during the morning and a second during the late evening and
  overnight. There is increasing confidence in a relative lull in
  precip coverage during the late afternoon and evening.

&&

.DISCUSSION...
Issued at 209 PM CDT Wed Jul 3 2024

This afternoon, synoptic cold front is located roughly near the
I-55 corridor, while effective front from earlier convection just
barely clips the southeastern forecast area near Lawrenceville.
Temps jump from the low 80s north of the effective boundary to
around 90F south. Anticipate this to be the main focus of
convection as we head into the mid to late afternoon hours. Latest
RAP suggests around 1500J/kg or higher MLCAPE is in place on the
warm side of the boundary, but deep layer shear is marginal/sub-
marginal around 20-30kt. Storms should begin to increase in
coverage in this vicinity by late afternoon or early evening, and
a few could be strong to marginally severe. Latest HRRR keeps this
activity a county or two south of the forecast area which lines
up well with current location of the front.

Overnight into Thursday morning, a pair of shortwave troughs will
move across central Illinois resulting in an increase in showers and
a few storms. Weakening surface front will likely stay stalled
across portions of southern Illinois with weak/negligible
instability in place north of the front across central Illinois
which will keep the threat for severe storms out of the local
area.

After the shortwave exits central Illinois early Thursday
afternoon, there is growing confidence in a relative lull in
precip later Thursday afternoon and at least early evening before
a stronger shortwave digs across the Upper Midwest later Thursday
evening into Friday. Despite passage of the weaker shortwave
midday Thursday, mid level height falls will persist across
central Illinois through the day in advance of the next deeper
wave, contributing to at least some spotty convection during the
afternoon/early evening, but coverage should be fairly isolated at
this point, and should allow many locales to kick off their
Independence Day celebrations. By mid to late evening, moderate
instability (MUCAPE 1000-1500 J/kg) begins to lift back north into
portions of central Illinois coinciding with the arrival of the
deeper wave / closed 500mb low into the Midwest. Storm coverage
will increase in response. Unfavorable diurnal timing should keep
the severe threat low Thursday night into Friday morning, but a
few stronger storms are possible, especially west of I-55, with
seasonably strong deep layer shear overspreading central Illinois.

As upper wave begins to depart the region Friday, strong cold air
advection will overspread central Illinois in its wake and scour out
some of the low level moisture. There will be a brief respite from
the precip chances once this occurs and will persist into Friday.
Temps will be lower, too, with afternoon highs generally in the
upper 70s to lower 80s Friday and Saturday. Surface ridge axis will
shift across the area Saturday afternoon with return flow
overspreading the area Sunday. Heat and humidity will begin to creep
back up in response and broad upper troughing over the Great
Plains will be in place with several shortwaves ejecting across
the region Sunday through the first half of next week bringing
additional chances for showers and storms.

Deubelbeiss

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1204 PM CDT Wed Jul 3 2024

A slow moving cold front will settle south of I-70 and serve as the
main focus for showers and thunderstorms the rest of today. Some
patchy lingering MVFR ceilings in place now will scatter back to VFR
over the next hour or so and remain VFR through the rest of today
and tonight. The front will lift back north slightly late tonight
into Thursday morning as an upper level disturbance moves across
the region. Showers and MVFR ceilings will spread back north as
well, reaching the I-72 corridor mid to late Thursday morning.

Deubelbeiss

&&

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

$$