Area Forecast Discussion

KEY MESSAGES

- Breezy westerly winds gusting 15-25mph and intermittent patches of light drizzle and passing showers are expected today.

- This weekend, low-lying areas have greater than a 50% chance for sub-freezing morning lows, though lingering cloud cover has the potential to limit just how cool some locations get.

SHORT TERM /THROUGH THURSDAY/

Issued at 248 AM CST Wed Nov 4 2026

As of early this morning, around 09z, a vertically stacked mid- latitude cyclone is lifting northeastward into the Upper Midwest. There are two surface features that stretch to the south of this occluded system that are both currently marching eastward through the area. The first boundary is a pre-frontal trough associated with the leading edge of the system dry slot that has worked to push most showers east of the area with the main swath of showers now across eastern IL. The second boundary, a cold front, marks the western edge of the dry slot and is apparent on the most recent surface analysis nearing east-central and northeast MO. Along and behind this boundary, weak low-level CAA is leading to higher relative moisture content from the surface-850mb, which has resulted in areas of drizzle/mist upstream across western/central MO. As this post- frontal airmass filters into the region today, intermittent pockets of drizzle/mist are expected. Forecast model soundings for today reveal 0-1km lapse rates may be steep enough to get weak and shallow instability, favoring the potential for some quick hitting cumuliform type showers. In general, these pockets of mist and drizzle/showers are expected to be fairly isolated, but will be enough to make roadways wet where they move across. In addition, westerly surface winds around 15-25 mph combined with abundant cloud cover and temperatures mostly in the 50s will make for a chilly day across the region.

A gradual clearing trend from south to north is forecast to happen later this evening and into tonight. The reason for this being the vertically stacked cyclone lifts a bit further to the north and so does the best low-level moisture/synoptic lift. However, by Thursday morning the northward progression of the retreating cloud cover may come to a halt and move back south, as remnant lobes of mid-level vorticity swing southward into the area. As a result, confidence in clearing tonight is highest across southern MO/IL and decreases with northward extent. Clearing trends will play a key role in determining just how cool certain locations get tonight. Currently, the best setup for radiational cooling looks to be across southern MO/IL where light winds (<5kts) are expected along with a mostly clear sky for a majority of the night. This is where valley locations, particularly in the Ozarks in southeast MO, are expected to fall into the 30s. Some of the more sheltered low-lying locations that favor cold air drainage may approach the freezing mark by Thursday morning. Across the rest of the area, morning lows are forecast to reach the upper 30s with mid 40s favored where cloud cover is more prevalent.

By Thursday, another mid-level shortwave moves into the Great Plains, phasing with the current longwave trough that will still be lingering across the Upper Midwest. A combination of a weak feature aloft and limited moisture in the column results in a low chance 20% chance for light showers across the area Thursday evening into the night. The LREF indicates <10% chance of >0.1" of 24hr accumulated precipitation, highlighting the light nature that is expected with any associated showers. The most notable change will be increasing cloud cover from the northwest Thursday afternoon into the night as this feature traverses the region.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/

Issued at 248 AM CST Wed Nov 4 2026

More abundant cloud cover associated with this mid-level feature Thursday night will lead to warmer lows than tonight with low/mid 40s expected across the area. As the shortwave aloft traverses to the east, another surface cold front slides south across the region Friday morning. Better low-level CAA will accompany this post- frontal airmass, resulting in temperatures that are closer to seasonable normals (highs in the 50s to near 60), or about 5-10 degrees cooler than highs on Thursday. Behind this front, a surface high moves into the region from Canada, reinforcing northerly flow across the region into the weekend. With lower humidity in place and a nearby surface high leading to calmer winds at night, radiational cooling will play an important role in how cool locations get this weekend. Cloud cover is always a challenge to forecast, especially 3+ days in the future, leading to some variance in forecast lows. Regardless, probabilities for lows <32F creep back into the area beginning Friday night and stay around through early next week. Currently, there is a good portion of the area that has >50% chance for lows <32F sometime during this timeframe. The main takeaway is locations that see sufficient clearing any nights this weekend will fall into the 30s, potentially below the freezing mark. Like usual, low-lying sheltered locations would be the favored cold spots having the best chance of falling below freezing under mostly clear and calm conditions.

By early next week, a signal for slight warming returns as mid-level ridging works into the region. As a result, long range guidance indicates 850m temperatures warm back into double digit territory (near 10C) Monday into Tuesday. That would lead to highs back into the mid 60s/low 70s given complete atmospheric mixing, which would be seasonably warm once again. Recent LREF IQR spreads are <10 degrees early next week, indicating fairly good agreement among guidance. Analysis of the 25th percentile for high temperatures also highlights the potential for a warming trend with values that are slightly above seasonal averages.

AVIATION /00Z TAFS THROUGH 06Z THURSDAY/

Issued at 1059 PM CST Tue Nov 3 2026

A cold front is moving through MO with a line of showers ahead of it slowly making their way east through IL. As the front moves through and the showers continue to exit the region, winds will continue to die down and turn more westerly advecting lower ceilings back to the area making MVFR more common by the early morning hours on Wednesday. There is a small chance that some residual moisture behind the front will cause drizzle that would impact the terminals causing lower visibilities, but confidence is too low to include visibilities below 6 miles. By Wednesday afternoon, clouds are expected to begin lifting and scattering, returning terminals to VFR conditions thanks to high pressure moving into the region.

LSX WATCHES / WARNINGS / ADVISORIES

MO...None. IL...None.