Peoria, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

005
FXUS63 KILX 150851
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
351 AM CDT Sun Jun 15 2025

.KEY MESSAGES...

- Above-normal temperatures are favored this week. Daily highs of
  85 F and overnight lows of 63 F are considered normal for the
  middle of June in central Illinois, and we will average a solid
  3 to 5 degrees above these benchmarks, particularly at night.

- Heat stress will become prevalent at times this week, but
  especially by next weekend. Recent NBM guidance suggests we will
  make a run at triple-digit heat index values both Saturday and
  Sunday.

- Mid-range guidance continues to flash signals for flooding and
  severe weather between Tuesday night and Wednesday night, though
  predictability remains low at this time.

&&

.DISCUSSION...
Issued at 346 AM CDT Sun Jun 15 2025

This weeks 15-word weather summary:

An impactful week of weather lies ahead. Heat stress, flooding,
and severe storms. Oh my.

Lets start with the heat.

There is nothing out of the ordinary with temperatures and
humidity through Monday. The synoptic pattern between now and then
features a bit of a split-flow regime, with central Illinois
positioned in between a shortwave trough currently digging
southward across the Ozarks  forecast to become cut off from the
main belt of westerlies as it reaches the Gulf coast  and
additional shortwave energy that will mostly pass just to our
north. Temperatures are forecast to warm into the low-to-mid 80s
each day, per NBM guidance, with dewpoints in the mid-to-upper
60s. This fits mid-June climo to a T.

The pattern becomes notably hotter and more humid by Tuesday
afternoon as a western Gulf airmass surges up the Mississippi
Valley in between an expanding sub-tropical high across the
southeast US and a collapsing ridge over the western US. Current
NBM guidance supports late afternoon highs around 90 F, and this
seems reasonable given the pattern shift. It will be a heavy 90,
too, with dewpoints near 70. Not good for band camp.

Consensus is for temps to take a step down by Wednesday, likely
owing to the increasing signal for convective debris.
Deterministic NBM guidance suggests highs in the low-to-mid 80s
for Wednesday, and then again for Thursday behind a cold front.

The oppressive heat and humidity is likely to return Friday
onward. By then, a broad 588-mb ridge axis is modeled to push
across the Corn Belt, becoming amplified by Saturday and Sunday as
a deep western trough emerges. Daily temperatures are forecast to
warm into upper 80s by Friday, then lower 90s by Saturday and
Sunday amid low 70s dewpoints. This all adds up to triple-digit
heat index values by next weekend. Not good for anyone.

The signal for flooding and severe storms returns between Tuesday
night and Wednesday night, but it is not clear cut.
Predictability remains low, with mid-range global guidance all
offering a slightly different version of when and where.

The main theme is for a nocturnal MCS to develop Tuesday evening
somewhere over the Corn Belt, ahead of a robust shortwave trough
and on the nose of a strengthening LLJ. A quick glance at CAPE,
shear, lapse rates and the mean wind support healthy cold pool
maintenance deep into the overnight period as the MCS pushes east
of the Mississippi Valley. While the increasing kinematic fields
will support an attendant thunderstorm wind risk late Tuesday
night, heavy rainfall might steal the show. The NBM Mean QPF
continues to ratchet upwards with each subsequent run, now
averaging around 0.50 across the ILX CWA during the Tuesday night
period. The spread (10th to 90th percentile QPF) remains large;
generally 0-1.3. And then, there are a few outliers that support
3-4 of QPF with MCS activity Tuesday night.

To review, the possible outcomes at this juncture for Tuesday
night range anywhere between getting missed completely to getting
hit squarely by an MCS. The trend has been moving towards us not
getting missed, with the risks for flooding and damaging
thunderstorm winds increasing across central Illinois.

Wednesdays risk for flooding and severe storms will be highly
conditional on whatever happens Tuesday night. Either the boundary
layer will recover/destabilize Wednesday afternoon ahead of the
impending cold front, or it wont. If it does, the parameter space
is very favorable for deep/organized convection and somewhat
favorable for flooding. Any further analysis at this point is
empty, boastful talk.

Consensus is then for conditions to dry out Thursday onward. Rain
chances are not zero during the late week period, but with the
amplified ridge building over the southeast US, showers and storms
should have a tendency to get deflected to our north and west.

MJA

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1219 AM CDT Sun Jun 15 2025

A weak high pressure ridge extending southward from the upper
Midwest into western IL will promote light northeasterly winds and
mostly clear skies over west-central IL, while an area of low
clouds persists in east-central IL. As the night progresses, at
least MVFR vsby in thin fog should develop in the west, while MVFR
cigs in low clouds spread through east-central IL. Have started
MVFR conditions 09Z-10Z, but will need to monitor for later
development. VFR conditions should return by 13Z-18Z, with diurnal
cumulus producing sct-bkn sky cover around 4000 ft AGL. Winds NE
3-6 kts overnight, increasing to 6-10 kts by 13Z.

37

&&

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

$$