934
FXUS63 KILX 161055
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
555 AM CDT Wed Jul 16 2025

.KEY MESSAGES...

- Strong thunderstorms will develop across parts of central
  Illinois today. The highest probability (15-30% chance) for
  severe weather will focus along and north of a Peoria to
  Bloomington line.

- Tonight, there is the potential for a training setup of storms
  in the middle part of the forecast area. A slight risk for
  excessive rainfall is in place for today/tonight.

- Heat and humidity will build next week...with early projections
  suggesting heat index values climbing well above 100 degrees by
  next Tuesday.

&&

.DISCUSSION...
Issued at 300 AM CDT Wed Jul 16 2025

Today brings hot/humid air, the risk of severe weather, and locally
heavy rainfall. Let`s get into the weeds a little to see what will
play out today. A cold front is set to pass through the Middle
Mississippi Valley this evening and overnight, bringing storms
along with it. An MCV looks to be developing as of this writing,
and it will trek near the IL/WI border.

We should start seeing the first round of storms developing in
early afternoon, with the severe threat focused from 2pm-8pm. This
round will become a linear mode in a north-south(ish) line,
trekking east. The second round of showers/storms comes overnight
tonight, ~midnight to around 8am. This round isn`t expected to
have a severe threat with it, but more of a hydro concern. This
round will develop an east-west line moving eastward. Training and
slow storm motions will be a concern, however the exact location
of this training may shift north or south of where we are
currently seeing in the models. As of now, it looks to be
somewhere around the I-72 corridor.

SPC has a slight risk for severe weather stretching from a Peoria to
Bloomington line and north, with a marginal risk everywhere else.
There is a 2% tornado risk and 5-15% chance of damaging winds. The
better shear will be found further up in northern IL and Wisconsin.
Our area could see around 20-30 knots of effective bulk shear.
The SBCAPE values today on model model soundings show around
2500-3500 J/kg, unless you look at the NAM or NAMNEST. Those two
show ridiculous values of >4500 J/kg. The best tornado chances
will be the more north you travel. The tornado risk will be
greater the closer to the MCV you get. In general, today, we are
most concerned with the damaging wind risk.

Heavy rain is a concern once again today with these storms. PWATs
are showing >2 inches once again. Some of the CAMs have the
overnight round losing steam as it moves into central IL, with
lesser rain rates than what could be expected in Missouri. We have
an inch or less in the forecast for QPF from 18z today to 12z
tomorrow, but would not be surprised if there was locally higher
amounts where higher rain rates and slow, training occurs. Nocturnal
flooding is slightly worse than daytime because you cannot see where
roads are flooded as easily. Try not to drive down any roads you are
familiar with if flooding does take place.

There is a marginal risk of severe weather (focused on damaging
winds) for tomorrow, south of I-70, as the front finishes exiting
the forecast area. Outside of that, daily chances for showers and
thunderstorms continue through the weekend.

Highs today will get up into the low to mid 90s, and with increasing
moisture ahead of the afternoon system, heat indices will be also
increasing. Heat indices today likely will get up around 100-105
degrees this afternoon. After the cold front passes through tonight,
we will see a brief cool down tomorrow, with highs only getting up
into the mid 70s to low 80s north of I-72 and mid 80s to low 90s
south of I-72. We quickly warm back up into the mid to upper 80s by
Friday. By early next week, humidity build, bringing heat indices
well into advisory criteria (>100-105 degrees).

Copple

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 555 AM CDT Wed Jul 16 2025

This morning some very patchy fog/low stratus has moved into the
sites. PIA and CMI have been the most affected thus far, but
wouldn`t be surprised if the other three sites saw a reduction in
visibility or lower ceilings, so threw in TEMPO for all sites. The
fog/low stratus should clear out fairly quickly, by 13z. MVFR (or
potentially lower) ceilings at PIA and CMI should clear out by
15z.

This afternoon some strong to severe storms are expected to move
through at least the northern sites. Uncertainty is high in if
SPI/DEC/CMI will get in on the action this afternoon, hence the
PROB30s. The location of the overnight showers and thunderstorms
will highly depend on where the cold front sets up today/this
evening. All sites have PROB30 for the 09-12z period. One or more
of them will see rain or storm overnight but none of the models
have been consistent on location.


Copple

&&

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

$$