Area Forecast Discussion

KEY MESSAGES

- Cooler temperatures remain in place through the weekend. There is a 40-80% chance of lows falling below 40 degrees Sunday morning, mainly across northern and eastern areas, along with elevated areas in Southeast Missouri. Frost formation seems fairly unlikely at this time except for an area stretching from around Van Buren to Marble Hill in Southeast Missouri.

- Isolated to scattered showers and perhaps a thunderstorm are possible today (20-40% chance) east of the Mississippi River.

- While additional rain chances return Sunday night into Monday (mainly in the north), our best chance for rain looks to spread across the area Tuesday through Wednesday. Current guidance has increased rainfall potential, giving us a 50-75% chance at receiving at least 1" and about a 20-40% chance at 2".

UPDATE

Issued at 624 AM CDT Sat May 2 2026

Updated the aviation section for the 12Z TAF issuance.

DISCUSSION

Issued at 320 AM CDT Sat May 2 2026

Continued troughing over the Eastern U.S. will keep temperatures below normal for the weekend. A weak upper-level disturbance pivoting through the Quad State will bring a weak frontal passage and isolated-scattered showers today (a few sprinkles are possible before dawn) with a few lightning flashes possible in the afternoon. Rain chances will primarily be confined east of the Mississippi, with the highest chances in the Evansville Tri-State region. Surface high pressure follows, resulting in dry and clear/calm conditions tonight. Lows below 40 are favored for most of the Quad State (aside from the Missouri Bootheel), but frost is unlikely (<20%) except for a portion of SEMO from around Van Buren to Marble Hill with a 20-40% chance of lows below 36 for Sunday morning.

Height rises follow, with a shift to more zonal flow aloft for early next week. High pressure sets up shop in the southeast and low pressure pivots through Northern Ontario Monday-Tuesday. Marginal risk SPC outlooks cover a sliver of the northwestern/northern areas for D2/D3. On Sunday (D2), the focus is on a possible evening round of showers and thunderstorms developing in East-Central Missouri/Central Illinois which has mixed support in models. On Monday (D3), a more established frontal passage will approach but might not quite reach the Quad State Monday night. A few stronger storms are possible but severe weather support is limited.

The frontal boundary is projected to stall Tuesday-Wednesday in the Quad State. With vorticity being advected from a cutoff low in the Desert Southwest, moisture being pulled in from the Gulf, and the boundary providing forcing, rainy conditions are becoming more likely Tuesday-Wednesday with rainfall totals increasing compared to the prior forecast package. Chances of at least 1" of rain have risen from 40-50% 12hrs ago to 50-75% now, with a 20-40% chance of 2". Thunderstorms will be possible each day, with insufficient confidence for an SPC outlook at this time. The rainfall will help with drought conditions, at least in terms of avoiding further degradation of conditions.

Temperatures through the forecast period will generally be below normal with the exception of Monday's highs near 80 and early week lows in the mid to upper 50s. Following a record warm April, temperatures starting out May will generally better resemble a typical April. The 8-14 day outlook leans slightly towards below normal temperatures.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 624 AM CDT Sat May 2 2026

BKN clouds move through the Quad State region today, with cigs lowering to 4-6kft today. Winds shift to northerly. Light showers move through east of the Mississippi. Thunder is possible this afternoon, but with low enough probability to remain left out of the TAF. Winds calm tonight as skies clear.

PAH WATCHES / WARNINGS / ADVISORIES

IL...None. MO...None. IN...None. KY...None.