Key messages
- A Frost Advisory is in effect Friday night across portions of northeastern Missouri and west-central Illinois where confidence is highest in widespread temperatures in the mid 30s.
Short Term /Through Saturday Night/
Issued at 215 AM CDT Fri Oct 16 2026
A highly amplified trough can be seen in water vapor imagery currently digging equatorward into the Midwest. The cold front associated with this trough and the one responsible for yesterday's rain has cleared the CWA to the southeast, with deepening northwesterly flow ushering in a fall-like air mass. This air mass will bring notably cooler temperatures compared to what we've been experiencing as of late, with a muted diurnal curve today leading to temperatures topping out in the low to mid 50s; some 20-30 degrees cooler than values on Thursday. Dry conditions are expected for most locations today, with the axis of the upper-level trough only producing a 20- 30% chance of light rain for areas east of the Mississippi River as it pivots overhead during the afternoon.
Tonight, high pressure at the surface will settle into the Central and Southern Plains; nosing into the Middle Mississippi Valley. As a result, the pressure gradient will slacken and winds become light to calm as skies gradually clear from north to south. This will make for ideal frost conditions across portions of northeastern Missouri and west-central Illinois, where radiational cooling will allow for widespread lows in the mid-30s - the temperature threshold generally needed for frost development. Where confidence is highest in these conditions occurring, a Frost Advisory is now in effect late Friday night through early Saturday morning.
Thanks to the upper-level trough moving further eastward of the region Saturday, low to mid-level temperatures will bounce back by a few degrees C compared to their Friday minimum. Between this and clear skies allowing for abundant insolation, afternoon temperatures will warm to around 60 degrees, which is still about 10 degrees below seasonal normals. There is a low threat (40%) for additional frost across portions of southeastern Missouri and southwestern Illinois Saturday night, and will be dependent on where the aforementioned surface high is relative to the CWA then.
Long Term /Sunday Through Thursday/
Issued at 215 AM CDT Fri Oct 16 2026
Thanks to consensus among ensemble clusters and deterministic guidance, confidence is high in a benign and uneventful pattern through the upcoming workweek. Continuous troughing over the West Coast and ridging to our east-southeast will keep upper-level flow weakly southwesterly through this portion of the period. This supports warm air advection, though subtly given the weakness of the flow. As a result, daily temperatures will only gradually warm through the workweek. Values closer to seasonal normals are at least expected through the first half of the workweek, but how much warmer we climb toward the end of the week is uncertain. The NBM pushes afternoon highs to around 80 degrees Thursday and Friday, though that is roughly 5 degrees warmer than the 75th percentile of ensemble guidance. This is due to the bias- corrected guidance composing the NBM, and this guidance is several degrees warmer than their non-biased counterparts. Given the bias factor applied here may be too warm given our seasonal cooling, confidence is low in the NBM's late-week temperature forecast.
Given the weakness of the flow aloft and lack of any notable disturbances in deterministic guidance, confidence is high in dry conditions prevailing through this portion of the period. This is supported by nearly all ensemble members showing this stretch being rain-free.
Aviation /00Z Tafs Through 06Z Saturday/
Issued at 1044 PM CDT Thu Oct 15 2026
The cold front has pushed through the terminals, with gusty northwest winds and ceilings around 1500 feet AGL in its wake. There is still expected to be a break in the MVFR ceilings later tonight into early Friday morning before more widespread stratus moves back in from the northwest. Ceilings with this round are expected to be near 2000 feet AGL, though sub 2000 foot ceilings are expected for a few hours at KUIN.
Lsx Watches/Warnings/Advisories
MO...Frost Advisory from 1 AM to 9 AM CDT Saturday for MOZ018-019- 026-027-034>036-042-052. IL...Frost Advisory from 1 AM to 9 AM CDT Saturday for ILZ058>060- 095>099.
SHORT TERM...Elmore LONG TERM...Elmore AVIATION...Gosselin