textproduct: Kansas City/Pleasant Hill

KEY MESSAGES

- Areas of dense fog (visibility < 1/4 mile) along the MO/IA/NE borders potentially extending to the US-36 corridor.

- Small chance for showers across the NW corner of MO this morning. Additional small chances in NE MO early Friday morning. More substantial rainfall is expected late Friday through Monday.

- Warm into the weekend before cooler, more seasonable temperatures return next week.

DISCUSSION

Issued at 303 AM CDT Thu Sep 17 2026

Ridging and warm air pushed a little further north Wednesday afternoon which was a bit further than anticipated, but not surprising. This is part of a expansive high pressure across the SE CONUS building a bit northwestward. The two primary effects of this are warming temperatures and clearing skies through the overnight. This has also pushed the flow of upper level shortwaves NW keeping rain chance mostly across NE and IA, although there is a chance for a stray shower across far NW MO during the early morning hours. What is more likely though is some fog development as slowly departing rains on Wednesday have left much of far northern MO saturated and radiational cooling has fairly quickly shrunk dew point depressions creating a favorable environment for fog. The nighttime microphysics channel of GOES EAST shows low clouds and for extending from Holt County MO northeast through Schuyler County. Areas of dense fog (Visibility < 1/4) mile are possible yield a dense fog advisory for the NW corner with possible expansion SE depending on how fog advects from weather to the north. It is unlikely dense fog will extend much past the US-36 corridor.

Fog dissipates after sunrise with southerly flow once again dominating. The good news is that surface level southerly flow is rather meager which results in weaker warm air advection. This keeps the general pattern of more pleasant conditions across the north of the area and much hotter to the south; however, the gradient become much less stark. Highs north of I-70 range from the 80s to the low 90s with areas south of I-70 from the 90s to near 100F. Heat index values crest 100F along and south of the MO River peaking at 105-107 across central and SW MO.

This warming trend continues into Friday as the high ever so slowly build northward. However, on the opposite side of the country, a low digs from the Pacific NW which has a little more success showing its way south and eastward. This puts the exit region of this upper low over the Rockies creating a channel for lee trough development. This tries to piece together showers and storms Friday morning across NE and IA, but becomes more successful during the afternoon and evening as low level lee cyclogenesis develops across eastern CO and western KS. Model guidance remains somewhat uncertain as to the location of where this cyclogenesis will manifest itself, but consensus places it in the eastern CO foothills to the NE Sand Hills. As such, this looks to compress the pressure gradient across the central CONUS as the system begins intruding upon the high to the SE. As it does so, accelerated warm air and moisture advection lift temperatures. Strangely, this will be on display overnight Friday into Saturday as most areas will see lows in the low to mid 70s. The nocturnal LLJ will also crank up combined with multiple avenues for ascent resulting in showers and thunderstorms developing early Saturday morning. Ensemble guidance places the most likely chances for showers Saturday morning across far NW MO, but it is not implausible for rain chances to extend southward toward the I-70 corridor.

As the Sat AM lee trough moves, it runs into resistance from the high to the east. This deflects the system toward the northeast. However, additional waves are expected to travel this path thanks in part to a synoptic cold front that is expected to approach Saturday afternoon. This large scale front also runs into resistance from the high creating a channel across KS and NW MO for the waves and accompanying rain to follow. This set up sticks around through Sunday into early Monday looking fairly similar to what we saw Tuesday and Wednesday. This brings the potential for training showers and storms along a SW to NE oriented boundary. It remains fairly uncertain the exact hazards and impacts as resolution of convective variables remains rather course. The air mass behind this front is notably cooler than what we currently have, and such a transition is unlikely without at least a slim chance for isolated robust convection. PWAT values around 2 inches are on the higher side of normal creating an environment for heavy downpours. Uncertainties will narrow as higher resolution guidance comes into range.

The good news is that behind the cold front, temperatures dip back into the 70s and 80s. The upper level high is slowly beat into submission creating more zonal flow across the interior CONUS. This brings more transitive flow of system through the continent which looks to keep the extended pattern active with multiple chances for rain through the next week.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 649 AM CDT Thu Sep 17 2026

Fog at STJ is expected to lift through the morning hours rejoining the remaining terminal to VFR conditions. Winds start out of the west becoming light through the afternoon and evening as they shift to easterly during the overnight. High-res model guidance is suggesting a low MVFR to IFR cloud deck overnight; however, confidence is low for this current TAF issuance, so just indicated the possibility with a low SCT deck.

EAX WATCHES/WARNINGS/ADVISORIES

MO...Dense Fog Advisory until 10 AM CDT this morning for MOZ001>005- 011. KS...None.