textproduct: Central Illinois

KEY MESSAGES

- A developing storm on Saturday could bring heavy rain south of I-70. The current forecast supports a low (30-50%) chance of exceeding 1 inch of rain near and south of I-70. Further north, totals will be significantly lower.

- Unseasonably warm air (20-25 degrees above normal) arrives next week, peaking Wednesday and Thursday with mid-60s to lower 70s temperatures. Expect gusty southwest winds to accompany this warmup.

DISCUSSION

Issued at 144 PM CST Fri Feb 13 2026

An upstream ridge is forecast to weaken tonight as a vigorous shortwave trough moves across Baja California. The acceleration of this feature across the Lower-Mississippi Valley on Saturday will cause a surface low pressure system to deepen and broaden, drawing up moisture from the Gulf. Central Illinois will be situated on the northern edge of this developing low, resulting in uncertainty regarding the sharpness and northward extent of the low-level baroclinic zone, associated frontogenesis (FGEN), and subsequent precipitation. High-res guidance from the 12z model runs has shifted the expected precipitation much further south. Specifically, the HREF LPMM now keeps measurable rainfall south of a Rushville to Danville line. The RRFS model is even more aggressive, pushing the rain south of a Hannibal to Robinson line.

Probabilistically, the likelihood of heavier rain has also shifted south. The latest 12z HREF indicates a medium-to-high (50-70%) chance of rainfall exceeding 0.50 inches south of a Carlinville to Robinson line, with probabilities dropping sharply to the north. Furthermore, a low-to-medium (30-50%) chance of exceeding 1 inch of rain is forecast near and just south of I-70.

Drier weather will return on Sunday across the Plains and Midwest as surface high pressure settles in behind the departing storm system. An aggressive warm-up is then anticipated through the middle of next week. This pattern will be driven by a deep trough digging into the eastern Pacific, which will spread deep southwest flow across the intermountain west and the Plains states. As this trough moves eastward and a surface lee cyclone strengthens, the Midwest will experience gusty southwest winds. The net effect will be the warmest temperatures of the season so far. Current NBM median guidance supports 60s Monday through Thursday, with the upper tail of guidance pushing lower 70s for Wednesday and Thursday.

Top of the mind for the middle of next week is the potential for severe weather. Trends in global deterministic guidance have struggled to resolve a clear convective signal despite a favorable synoptic pattern. At least for now, models are either slow in moistening the low-levels, or conditions will truly be too dry to sustain organized convection Tuesday night into Wednesday. Perhaps the better signal will come Thursday night into Friday as another shortwave trough pivots somewhere in between the Upper- and Middle-Mississippi Valley, but once again, deterministic guidance is not very bullish on moisture/instability profiles ahead of this feature.

MJA

AVIATION

(For the 00z TAFs through 00z Saturday Evening) Issued at 500 PM CST Fri Feb 13 2026

High clouds will thicken and lower on Saturday, as a weather system approaches from the southwest. A few showers could reach as far north as KSPI-KDEC by late afternoon, and included a PROB30 group for this, though conditions should remain VFR. Winds will diminish early this evening, then remain under 10 kt for the remainder of the forecast.

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ILX WATCHES/WARNINGS/ADVISORIES

None.