Area Forecast Discussion

KEY MESSAGES

- Elevated fire danger this afternoon thanks to good mixing leading to lower dewpoints and breezier winds, and in turn lower RH values.

- Lake Wind Advisory in effect this afternoon and evening for breezy and gusty conditions.

DISCUSSION

Issued at 237 AM CDT Tue Apr 21 2026

Ridging continues to build aloft over the Plains and will move over the area by Wednesday night. A tighter sfc pressure gradient today along with good mixing will lead to breezier conditions with winds of 15-20 mph and gusts to around 30 mph. EPS gusts are mainly greater than a 60% chance of gusts over 25 mph. Also lowered dewpoints to NBM 10th percentile due to the anticipated mixing. This coupled with the winds will make for lower RH values (25-35%) this afternoon and elevated fire danger. Have issued an SPS for elevated fire danger. Have also issued a Lake Wind Advisory for the breezy conditions.

NBM chances for 80+ degrees increase tomorrow and Thursday. NBM has generally a 40-60% chance for eastern portions of the area to reach 80 tomorrow. NBM has a greater than 70% chance of reaching at least 80 on Thursday across the board.

The upper ridge pushes east on Friday as a leading shortwave around a Canadian border low pushes into the Upper Midwest. This system brings a cold front and round of showers/storms to the area as early as Friday morning (60-80% chance). Showers last at least till Saturday morning. There are model discrepancies over whether or not showers/storms continue on Saturday (depending on frontal placement). NBM currently has a 20-30% chance roughly behind the front (just to our south Saturday). NBM also has generally a 30-60% chance of CAPE values greater than 1,000 J/kg in SEMO Friday afternoon and generally 30-50% in western portions of southern IL. So a few rogue strong to sever storms can't be ruled out Friday. Monday a shortwave aloft brings another sfc low through the Midwest and brings another round of showers/storms and another cold front through the area.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 544 PM CDT Mon Apr 20 2026

VFR conditions are expected across all terminals over the next 24 hours. High-level clouds begin to filter in Tuesday morning. Southwest winds midday increase to 12-18 kts, with gusts around 25 kts.

PAH WATCHES / WARNINGS / ADVISORIES

IL...Lake Wind Advisory from 11 AM this morning to 9 PM CDT this evening for ILZ075>078-080>094. MO...Lake Wind Advisory from 11 AM this morning to 9 PM CDT this evening for MOZ076-086-087-100-107>112-114. IN...Lake Wind Advisory from 11 AM CDT /noon EDT/ this morning to 9 PM CDT /10 PM EDT/ this evening for INZ081-082-085>088. KY...Lake Wind Advisory from 11 AM this morning to 9 PM CDT this evening for KYZ001>022.