929
FXUS63 KILX 150047
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
747 PM CDT Sun Jul 14 2024

.KEY MESSAGES...

- Intense heat continues tomorrow, with heat indices of 100-110
  degrees during the day. Not much relief is given overnight with
  lows in the mid to upper 70s.

- Some relief from the heat comes Wednesday as a cold front pushes
  through central and southeastern Illinois over night Tuesday.
  The CPC shows a below normal trend on temperatures for the next
  14 days.

- Multiple MCS passages are forecast for the coming days before a
  brief break starting Wednesday. Some of these storms have the
  potential to be severe with damaging winds as the main risk.

&&

.UPDATE...
Issued at 746 PM CDT Sun Jul 14 2024

This evening, a broken line of thunderstorms has developed from
near  Rockford SW across the Quad Cities. Strong instability in
excess of 3000 J/kg is in place ahead of this line of storms. 00Z
ILX sounding showed a "loaded gun" setup with around 3000 J/kg
MLCAPE and -68 J/kg MLCIN. Deep layer shear in the region is
marginally sufficient (around 25-30kt) to support organized
convection this evening and do anticipate storms to congeal into a
more organized line over the next few hours. Cloud bearing flow
and forward propagating corfidi vectors will generally steer these
storms west-to-east across northern Illinois with some potential
of clipping our far northern CWA where a severe thunderstorm watch
is currently in effect. Damaging wind gusts will be the primary
hazard with these storms. That said, veering LLJ this evening will
help the southwestern end of the line back-build with upshear
Corfidi vectors suggesting storms will propagate S/SW late this
evening into portions of the area. Where this occurs, a heavy rain
threat is possible due to the slow moving nature and training of
storms. Latest HRRR suggests a few pockets of around or just in
excess of 2 inches of rain is possible north of I-72.

Deubelbeiss

&&

.DISCUSSION...
Issued at 214 PM CDT Sun Jul 14 2024

The MCS this morning skirted by the northern periphery of the CWA
without incident. This won`t be the only round that threatens
central Illinois. Currently, we are keeping a close eye on the MCV
that is propagating through north-central Iowa. The HRRR and
NAMNest depict the MCV and it`s reignited convection taking a
southerly dip once it gets to Illinois, with the NAMNest being the
most dramatic in its southern pull. The environment will have had
time to recover from the morning convection, as surface heating
occurs with the mostly clear skies, the moisture is far from gone
(as we can feel the soupy airmass outside), and the MCV (and
rebounding CAPE values) provides the needed lifting mechanism. By
mid afternoon, SBCAPE values rise to ~3000 J/kg ahead of the CI,
with very little to no cap. The main hazard as the next round
moves through will be damaging, gusty winds.

Tomorrow, the severe threat continues, but this time bigger and
better than before. Another complex is expected to develop over Iowa
by late morning and move eastward. Its track has it entering the
northern CWA by late afternoon between 22-00z. As it does, the
environment is primed. The cap is very little (~-20 J/kg),
allowing the line to become surface based. SBCAPE values ahead of
the line as it enters are 4000-5000 J/kg. The 0-6km bulk shear
looks to be around 40-50 knots. SPC has areas along and north of
I-74 outlooked for an Enhanced Risk (level 3 out 5). There is a
30% damaging wind risk with a 10% chance of wind gusts greater
than 65 knots for areas along and north of I-72. Localized flash
flooding is also in play for tomorrow as the area is already quite
saturated and PWATs are 1.8-2 inches at the time of the passage.

The heat won`t be taking a break tomorrow neither. Today the heat
indices are expected to top out between 100 and 105 degrees. The dew
points today and tomorrow will be in the upper 70s, getting very
close to 80. The 12z.14 HREF shows a 60% chance of dewpoint
exceeding 78 degrees tomorrow afternoon, ahead of the storm complex.
Heat indices are forecast to top out near 110 degrees tomorrow
(Monday). A cool down is expected starting Tuesday as a cold front
is set to move through, wiping out the moisture. Beyond Tuesday,
temperatures become slightly below normal for this time of year,
giving us the well needed break from the soupy heat. Highs will be
around the upper 70s to mid 80s from Wednesday into the end of the
forecast period.

There are some additional rain chances through early Thursday
morning, then will be dry through Sunday. This break should give the
area a chance to breathe after the multiple rounds of heavy rain
recently.

Copple

&&

.AVIATION...  (For the 00z TAFs through 00z Monday Evening)
Issued at 631 PM CDT Sun Jul 14 2024

Scattered storms upstream over eastern Iowa will be the focus for
any activity spreading south into central Illinois later tonight.
Confidence remains low in timing and placement, but the better
chances for any storms will be at our northern 3 TAF sites (PIA,
BMI, CMI). PROB30 groups are noted at each of these airfields
between 04-10Z. South-southwest winds will become light overnight
then turn breezy tomorrow afternoon. Mostly VFR conditions will
be seen outside of storms, with another round of convection
possible Monday evening.

NMA

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM CDT Monday for ILZ027>031-036>038-
040>057-061>063-066>068-071>073.

&&

$$