textproduct: Central Illinois

KEY MESSAGES

- Temperatures trend warmer, in the 60s today but reaching near record levels by Tuesday when highs approach 80 degrees. Breezy southwest winds could gust to 30 mph today, then 35 mph on Monday.

- Severe storms could develop Tuesday afternoon into Tuesday night, with all severe hazards possible. There is an Enhanced Risk (level 3 of 5) of severe storms north of a Springfield to Rantoul line, with a Slight Risk (level 2 of 5) to the south.

- Beneficial rainfall is likely with the Tuesday-Wednesday system. There is a 60-80% chance of at least 1" of rain. Thunderstorms could lead to localized heavy amounts (10% chance of over 3" of rain).

DISCUSSION

Issued at 305 AM CDT Sun Mar 8 2026

*** TODAY INTO TUESDAY ***

Early Sun AM, the upper levels featured a cutoff low near Baja California and broad troughing over the eastern US with embedded disturbances tracking well to the north. A cold front extending from New England to Texas will slowly sag south today. Closer to home, a weak sfc ridge axis that extends from OK into IL is shifting south, which will swing winds around to southerly. As anticipated in previous forecasts, continued cloud cover across eastern IL is keeping temps warmer, with readings still in the 40s east of I-57 as of 12am CST/06z compared to mid-30s west of I-55.

Between a series of low pressure tracking across Canada/the northern Great Lakes and the sfc ridge axis shifting south, expect persistent southwest flow across IL into Tues. This will result in a warming trend through Tues, with highs in the 60s today, 70s on Mon, and then approaching 80F on Tues. The record highs for Mar 10th are 78F at Lincoln (50% chance of tying the record), 80F at Springfield (40% chance), and 77F at Peoria (65% chance). Record highs are certainly possible on Tuesday.

Minimal weather impacts are expected until the cutoff low ejects and brings storm chances into Tues night, although I continue to have minor concern that guidance is too high with the forecast dewpoints today which has implications for the fire wx conditions. The front draped to the south will limit moisture advection today. Forecast soundings suggest a well-mixed PBL, but depict a shallow near-sfc layer of higher dewpoints compared to the rest of the PBL. The expectation is that efficient mixing will drive sfc dewpoints lower than guidance suggests, and made adjustments to the model blend accordingly. Minimum RH values could drop towards 30%, which combined with peak gusts of 25-30 mph could lead to some minor risk of unwanted fire spread. Breezier winds are expected on Mon, with forecast soundings suggesting peak gusts around 35 mph. Moisture advection does start to increase, however, so RH values should be a bit higher than today.

*** TUESDAY STORM THREAT ***

Between near-record temps, continued moisture return (dewpoints into the 60s) , and increasing upper level lift in response to approaching troughs, the stage will be set for storms Tues PM into Wed, and these could be severe. The emerging cutoff low is joined by a northern stream wave to produce broad height falls aloft and pressure falls at the sfc, with most guidance depicting a warm front extending from south of Omaha, NE, to far northern IL Tues morning. A sfc low then lifts along this frontal zone, which combined with the increasing ascent aloft leads to convective development near the frontal zone (and perhaps within the warm sector).

Forecast soundings show a classic loaded gun look through the morning/early afternoon, that is, strong capping to limit convective development despite increasing instability. Area- averaged soundings from the GFS/NAM indicate seasonably high SBCAPE values (1000-1500 J/kg), and such values are also suggested by a majority of ensemble members. Convective inhibition (CIN) ranges from -25 to -100 J/kg through mid-afternoon, but starts to erode into the late afternoon/evening. Low-level wind profiles appear quite supportive of severe storms, veering with height (clockwise turning) and increasing in magnitude, at least in the lowest kilometer. This wind profile results in 0-1km SRH values over 150 J/kg. This environment is conditionally supportive of all severe hazards, pending cap erosion and the specific storm mode that develops.

Given the strong cap, storm development may be confined to the frontal zone rather than the open warm sector, although the strong synoptic-scale ascent adds uncertainty to the equation. Deep layer shear vectors oriented roughly parallel to the frontal zone suggest a trend towards upscale growth. We are still beyond the range of most CAMs, so don't yet have a chance to see how their modeled evolution compares to the expectations outlined above. There is also the diurnal timing factor. With the front positioned just to our northwest, it may not be until after sunset that robust storms move into the ILX CWA. Into Tues night, LLJ forcing increases, which could help increase convective coverage and would further strengthen the wind shear. The degree to which sfc instability will persist into the night is low confidence.

In summary, a parameter space supportive of severe storms will exist on Tuesday-Tuesday night. The expectation is that a strong cap will limit storm development until late afternoon or evening, with areas near the frontal zone having the best chance of storms forming during the afternoon/evening. There is an Enhanced Risk (level 3 of 5) of severe storms north of a Springfield to Rantoul line, with a Slight Risk (level 2 of 5) to the south.

*** WEDNESDAY AND BEYOND ***

The frontal zone pushes southeast on Wed as a cold front, keeping showers/storms in the forecast until it departs. Ensemble guidance continues to highlight beneficial rainfall from the Tues-Wed system, with a 60-80% chance of total rainfall of at least 1", and a 20-50% chance of 2" (highest south of I-72).

By Thursday, highs return to the upper 40s/low 50s, which is near seasonable values. A clipper-style system tracking across the Great Lakes region Thur night into Fri could offer a low chance (20%) of light rain (perhaps mixing with snow), mainly north of I-74. The precip chances associated with this system increase as you go northward (over 40% north of the I-88 corridor in N IL). The pattern remains progressive, with another disturbance keeping precip chances in the forecast for the latter half of the weekend (40-60% chance Sat night into Sun).

Erwin

AVIATION

(For the 06z TAFs through 06z Sunday Night) Issued at 1055 PM CST Sat Mar 7 2026

MVFR conditions will continue for a few more hours at all sites except SPI. Then VFR is expected the remainder of the night and through tomorrow. Winds will be westerly overnight and then become southwest again tomorrow and becoming gusty in the afternoon and evening hours.

Auten

ILX WATCHES/WARNINGS/ADVISORIES

None.