640
FXUS63 KILX 091040
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
540 AM CDT Mon Mar 9 2026

.KEY MESSAGES...

- Severe storms appear likely late Tuesday afternoon into Tuesday
  night. Storms will be capable of producing tornadoes, some of
  which could be strong, as well as large hail, damaging winds,
  and isolated flash flooding. There is an Enhanced Risk (Level 3
  of 5) of severe storms northwest of a Springfield to Hoopeston
  line, with a Slight Risk (level 2 of 5) to the south.

- A warming trend continues through Tuesday, with well-above
  normal temperatures in the 70s today, then near 80 degrees on
  Tuesday. Some locations could set record high temperatures.

- Total rainfall amounts from the mid-week system are favored to
  exceed an inch (60-70% chance), and localized amounts over 2"
  are possible (20-30% chance).

&&

.DISCUSSION...
Issued at 209 AM CDT Mon Mar 9 2026

*** THROUGH TONIGHT ***

Early Mon morning, a cut-off upper low remains positioned near
Baja California, with quasi-zonal flow across the CONUS and a few
shortwaves present over Canada. With a sfc low passing by to the
north, breezy SW flow persists today, advecting both moisture and
warmth northward. Highs are expected to push well above normal,
in the mid 70s, while dewpoints rise into the low 50s by this
afternoon (notably higher than the low 30s that occurred on
Sunday). Locations near the I-74 corridor could approach record
highs today. Refer to the Climate section of the AFD for a
specific listing of existing records.

High-res guidance depicts diurnal Cu developing first across
eastern IL by late morning, then expanding westward in time. This
general evolution is supported by fcst soundings as well, showing
deeper mixing required to reach LCLs across the western half of
the CWA.

The continued southerly flow into tonight will keep lows mild, in
the mid/upper 50s, which is well above the normal lows (near
freezing). Can`t rule out some advection fog development tonight,
but guidance does not appear overly bullish at this point.
Lingering cloud cover may help limit the fog potential. The latest
HREF (09.00z) has the probability of visibility below 2 miles
ranging anywhere from 10-40% across the region.

*** MID-WEEK SYSTEM ***

* Near-Record Warmth and Severe Storms Tuesday PM *

On Tues, the aforementioned cut-off low over the SW begins to
emerge, along with a northern stream disturbance. These will lead
to sfc pressure falls over the Plains, and latest high-res
guidance indicates that by Tues afternoon a weak sfc low will be
positioned over S IA with a warm front extending eastward. The
exact latitudinal position of this warm front may still shift in
subsequent model updates, but for now models place it somewhere
between the I-80 corridor and the northern fringes of the ILX CWA
(Galesburg to Pontiac). Across the warm sector, near-record highs
remain possible as temps surge into the upper 70s/near 80. Gulf
moisture also advects into the area, with dewpoints pushing at
least into the low 60s, potentially higher.

A volatile parameter space is expected to develop, with seasonably
high instability (approaching 2000 J/kg of SBCAPE), steep mid-
level lapse rates, and favorable wind profiles (45-50 kts of bulk
shear, exhibiting clear veering in the low levels). Scattered to
numerous severe storms are possible. The parameter space could be
further enhanced via backing of sfc winds in response to the sfc
low northwest of the area, as well as in the vicinity of the warm
front. 0-1 km storm-relative helicity (SRH) values are supportive
of tornadoes within the entire warm sector (over 150 J/kg), but
are especially so near the warm front (approaching or exceeding
300 J/kg). Deep layer shear vectors are close to parallel to the
warm front across IL, and the bunkers motion for right- moving
supercells is almost due easterly (also parallel to the front).
This raises concern that a supercell could maintain a prolonged
residence time near the warm front, which would carry a
substantial tornado risk. Large hail (over 2") is also a concern
given this parameter space and the initial discrete or semi-
discrete storm mode. The Day 2 Convective Outlook maintains an
Enhanced Risk (level 3 of 5) across the northern half of the ILX
CWA, and a Slight Risk (level 2 of 5) to the south. Tornadoes and
large hail are the top concerns, but all hazards are possible.

In terms of timing, the expectation remains that strong capping
will limit convective development through the morning and early
parts of the afternoon. CAMs tend to struggle at identifying when
the cap will break, but the best estimate right now based on
forecast soundings is that the potential for storm development
increases quickly around/after 5 PM. That`s not to say earlier
development can`t occur, but the chances certainly ramp up into
evening. Used 3- hour PoPs in the gridded forecast Tues afternoon
to highlight this evolution, with a 20-40% chance of storms north
of I-72 between 1-4 PM, increasing to 40-60% chance between 4-7
PM.

Into Tues night, that aforementioned sfc low over IA is progged
to slide east along the frontal zone towards Chicago, sending a
cold front pushing slowly south into the ILX CWA Tues night.
Combined with the onset of a robust LLJ, convective coverage is
likely to increase overnight, with high PoPs across our forecast
(80-90%). The orientation of the shear vectors relative to the
cold front favors upscale growth, and forecast soundings show
mid-level lapse rates becoming less steep during the night,
suggesting storms transition to more of a wind threat rather than
a hail threat. The diurnal timing is not favorable for tornadoes,
but if any surface based instability can persist into the night,
the robust LLJ will result in high 0-1 km storm-relative helicity.

Latest guidance still shows the front bisecting the ILX CWA Wed
morning, with widespread precip ongoing. The front progresses SE
in time and eventually exits by the afternoon. Can`t rule out
some strong to severe storms ahead of the front on Wed, as
moderate wind shear persists. However, the mid- level lapse rates
appear meager at best, resulting in substantially lower
instability than Tues. Deep layer shear vectors remain parallel to
the cold front, favoring continued upscale growth, so the main
concern would be isolated strong wind gusts. Hodographs appear
unidirectional in the low levels, and despite strong winds at 1 km
AGL there is only 30 kts of 0-3 km shear, all of which is
oriented parallel to the front. Typically, we seek 30 kts of 0-3
km line- normal (not line- parallel) shear for a QLCS tornado
threat, so this analysis suggests the tornado threat is low during
the day Wed. There is a Marginal Risk (level 1 of 5) of severe
storms in far southeastern Illinois (Lawrence County) on
Wednesday.

*** RAIN OUTLOOK ***

Precipitable water (PWAT) values are forecast to be between
1.2-1.5" across the warm sector, which is the near the maximum of
the ILX observed sounding climatology. We`re not quite to the
point that CAMs can capture the entirety of this event, but the
coarser ensemble guidance is still depicting a 60-70% chance of
total rainfall over 1" and a 20-30% chance for over 2". There are
some indications that back-building (or training) of storms is
possible Tues night, as fcst soundings show a period where the
cloud layer winds are similar (in both magnitude and orientation)
to the LLJ winds. It would not be a surprise if future CAM runs
depicted locally higher rainfall amounts approaching 3" in spots.
There is a Slight Risk (level 2 of 4) of Excessive Rainfall,
encompassing areas roughly from Sangamon to Vermilion Counties and
northward.

*** REST OF THE WEEK ***

Following the cold frontal passage on Wed, temps cool towards
seasonable values (near 50F) on Thurs, with high pressure sliding
east into the area. A compact low pressure tracks into the Great
Lakes by Fri AM, with the resultant pressure gradient producing
breezy southerly flow Thurs night keeping lows above normal, near
40F. Some light, WAA-induced rain is possible Thurs night into Fri
AM, but the precip associated with this system will largely be
focused north of our forecast area. Another system remains on
track to move across the Midwest during the latter half of the
weekend.

Erwin

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 532 AM CDT Mon Mar 9 2026

Minor LLWS may linger during the first few hours of the period for
KPIA/KBMI, with 2 kft winds around 45 kts from 240 degrees.
Otherwise, expect persistently southwesterly flow through the
period, with gusts around 20 kts from late morning through early
evening. Scattered diurnal cumulus could develop between 2-4 kft
today, with the greatest coverage being across eastern IL. Most
sites should stay scattered today, but some occasional MVFR
ceilings could occur. Cloud bases are expected to lower overnight,
with a 20-30% chance for bases below 1000 feet. The greatest cloud
cover is expected near KCMI (SCT to BKN coverage), while other
areas are favored to maintain FEW to SCT coverage.

Erwin

&&

.CLIMATE...
Issued at 1249 PM CDT Sun Mar 8 2026

Record high temperatures for Monday and Tuesday:

Location            Monday               Tuesday
========           =========            =========
Bloomington        73 (1974)            78 (1893)
Champaign          73 (1925)            73 (1990)
Charleston         79 (1925)            79 (1990)
Decatur            78 (1925)            79 (1990)
Lincoln            78 (2000)            78 (1955)
Olney              81 (1925)            80 (1990)
Peoria             71 (1918, 2021)      77 (1955)
Springfield        75 (1918, 1925)      80 (1955)

Geelhart


&&

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

$$