Severe Thunderstorm Warning 24, NWS Lincoln, IL

Area Forecast Discussion
National Weather Service Lincoln IL
149 PM CST Tue Mar 3 2026

.KEY MESSAGES...

- Beneficial rainfall chances continue this week. Through Thursday
  morning, the best chance for additional rainfall over 2" is near
  and south of a Shelbyville to Paris line (60-70% chance).
  Rainfall amounts are expected to be lighter (less than 0.5")
  near and north of the I-74 corridor.

- There is a Marginal Risk (level 1 of 5) for severe storms
  southwest of Jacksonville tonight and south of the I-70 corridor
  on Wednesday. The main concern is large hail, but isolated
  strong winds could also occur. There could be another chance for
  severe storms late Friday.

- A warming trend is expected this week, with temperatures
  reaching the mid 70s by Friday.

&&

.DISCUSSION...
Issued at 145 PM CST Tue Mar 3 2026

*** THROUGH EARLY WED ***

A warm front was draped over southeast IL (between the I-70 and US-
50 corridors) into portions of cntrl and SW MO as of 12pm/18z. As
expected, temps north of the front have struggled to warm above
the low 40s. With the exception of a few corridors across eastern
IL, shower activity has waned considerably compared to this
morning. MRMS rainfall estimates suggest a broad 0.50-0.75" of
rain fell south of I-72 this morning, with a narrow stripe of over
1" just south of I-70. However, comparing to sfc obs suggests
these estimates are overdone, with the measured values being more
like 2/3 of the MRMS amount.

Zooming out, the slowly approaching upper trough was positioned
over CO today, while an expansive sfc high over the Atlantic is
helping advect Gulf moisture northward towards our stalled frontal
boundary. Into this evening/tonight, continued WAA will lead to
an intensifying warm nose around 800mb, above which elevated
instability increases. The highest MUCAPE is expected across SW
portions of the ILX CWA, with up to 1000 J/kg. Effective shear for
parcels lifted from this level is around 30-40 kts, and these
conditions are conducive for hail with the strongest updrafts. A
marginal risk (level 1 of 5) was introduced for areas near and
southwest of Jacksonville, but some sub-severe hail wouldn't be a
surprise further northeast.

CAMs suggest showers and embedded storms will increase in coverage
after about 5-6pm/23-00z, with continued activity focused within
an east-west oriented corridor through the night. There is some
minor variation in the exact placement of this activity, but most
CAMs suggest it will be somewhere near or in between the I-72 and
I-70 corridors. Through midday Wednesday, localized rainfall
amounts within this corridor could approach 3 inches. Given the
ongoing drought and lack of a frost depth, it seems unlikely that
any hydrologic issues arise even with 3" of rain in a 24 hour
period. CAMs also depict a rather tight northern gradient, such
that areas north of a Macomb to Rantoul line may largely miss out
on this overnight activity. The probability of exceeding a half
inch of rain between 18z today and 18z Wed drops from 60% in
Lincoln to less than 20% north of that Macomb to Rantoul line. Fog
development remains possible tonight, especially near/south of
I-72, but there was not a strong signal for dense fog.

*** WED - THUR ***

The upper trough continues its approach, nearing the area by Wed
evening and resulting in a weak sfc low moving up the frontal zone
and tugging the frontal zone northward. After a relative lull in
precip Wed morning, rain chances ramp back up during the afternoon
and especially into the evening/overnight. There is once again a
low- end hail threat, with the best environment existing south of
I-70 during the evening/overnight (MUCAPEs approaching 1000-1500
J/kg). There is a marginal risk of severe storms in that area.
With low- level convergence near the front/sfc low, synoptic lift,
and saturated low-levels, fog is once again a concern, especially
given earlier rounds of rain. Some dense fog is possible Wed
night.

Precip chances may linger into Thurs morning across the eastern
half of the forecast area, but rain should come to an end as the
upper trough departs and height rises occur aloft. Highs are
expected to reach the 60s on Thurs.

*** FRI - SAT ***

The upper pattern remains highly amplified late in the week,
characterized by a deep trough emerging onto the western Plains
and a ridge axis over the eastern US. Lee cyclogenesis will result
in a warm front lifting north across the ILX CWA, with strong
southerly wind fields across the warm sector. These winds will
advect additional Gulf moisture northward, with PWATs over 1" and
sfc dewpoints approaching 60F. Some scattered storm development is
possible Fri AM in the vicinity of the warm front as it lifts
northward, otherwise, much of the open warm sector appears capped
during the day. High temps are forecast to reach the mid-70s,
which is generally below records but not far off in a few
locations.

Strong SW flow continues into the night, keeping anomalously warm
(potentially record warm) nocturnal temps in place beneath a
strengthening LLJ (850mb flow increasing over 50 kts). A cold
front and ongoing storms are expected to impinge upon this warm
moist airmass across IL Fri night. The Storm Prediction Center has
areas from St. Louis to Kankakee and westward in a Slight Risk
(15-29% chance) of severe storms Fri night, although the risk is
definitely greater further to the west where the diurnal timing is
more favorable. To what extent instability, particularly sfc-
based instability, persists across the ILX CWA will go a long way
towards determining the severe potential Fri night. One other
factor to note is the sfc low will be tracking across IA into
northern portions of WI, which is quite aways removed from the
local area. Thus, the sfc winds across IL are unlikely to back,
resulting in relatively unidirectional profiles in the low-levels.
Still, with sfc-1k shear in excess of 30 kts, a tornado threat
could develop if sfc-based instability persists.

Additional storm development is possible along/ahead of this front
on Sat, but whether or not that occurs across E/SE IL or if the
front has pushed south of our area remains to be determined.

Erwin

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1111 AM CST Tue Mar 3 2026

Ceilings and vis reductions persist through the period, with
waves of scattered SHRA and embedded TSRA. IFR or LIFR ceilings
will be prevalent, although PIA and BMI are the two sites that
may rise to MVFR this afternoon/evening before lowering again
overnight. Vis is generally expected to be between 2-5 miles, but
could be lower especially at the I-72 terminals towards 09-13z
Wed. Shower coverage is diminishing currently, with the next wave
anticipated to move in from the southwest around 23z. Some
embedded thunder is possible with that wave (best chance between
01-06z). Precip chances are highest at KSPI/KDEC, with rain
chances less certain to the north. Winds are expected to turn to
northeasterly this evening, generally around 10 kts.

Erwin

&&

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

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