textproduct: Kansas City/Pleasant Hill

KEY MESSAGES

- Severe storms are possible Tuesday afternoon into the evening/overnight hours. There is considerable uncertainty about the timing and location of this activity.

- Not as hot and less humid this week, with the exception of Tuesday.

DISCUSSION

Issued at 214 AM CDT Mon Aug 17 2026

Water vapor imagery with 500mb heights plotted shows that the upper ridge has been mostly suppressed to our south with quasi-zonal flow or subtle northwesterly flow over the region. At the surface, high pressure is building southward and the combination of the suppressed upper-level ridging and building surface high pressure will lead to more seasonal temperatures in the mid-80s and noticeably less humid conditions. Dewpoints today should be 5-10 degrees cooler than yesterday, topping out in the mid 60s vs the mid 70s we've seen the last few days. The cooler air may also lead to some river valley fog this morning, especially across northwestern MO/ northeastern KS where the high pressure center will be nearly overhead by 12Z this morning.

That surface high shifts to the east of the area tonight, shifting winds back to the south and leading some moisture streaming back north into the area. There is decent agreement amongst the models in developing a convective system Monday night to the northwest of the area, most likely in northwestern Nebraska into western South Dakota. This system tracks southeast early Tuesday morning and may begin to affect northwestern Missouri late morning or into the afternoon. This actually introduces a fair amount of uncertainty with the forecast because of its implications on convection later in the afternoon and into the evening/overnight hours. Several scenarios appear possible with this setup. One is that the MCS that develops Monday night is the main severe weather threat for us Tuesday afternoon and evening. This would require a later arrival into the forecast area, allowing for greater destabilization. This is closer to what the NAM shows. Another scenario is that the MCS weakens as it moves into NW/ northern MO but leaves a boundary that becomes the focus later in the day, most likely further to the south and possibly draped across the middle of forecast area. This scenario seems to be favored by the GFS and the Canadian. Regardless, based on the broader- scale pattern, with increasing flow aloft poleward, shear will be favorable for organized storms with potentially 40-50+ kts of deep-layer shear Tuesday afternoon and evening. This is coincident with steep mid- level lapse rates. At this time, all severe hazards appear possible, including a small potential for tornadoes. As is so often the case with these setups, we will need to see how the earlier activity evolves and where any resulting boundaries reside to better define a more probable risk area.

For the remainder of the forecast, temperatures look near to slightly below normal through late in the week, with a warming trend for the weekend and into next week. Northwest flow will become the predominate pattern again through the middle of the country, with the upper ridge building over the western third of the country. With this pattern, we'll need to watch for southeastward moving convective systems that often travel further southeast than forecast. So for now, the forecast is mainly dry but that could change if anything upstream of the area persists longer or is stronger than forecasts. Eventually that ridge shifts eastward with the axis moving from the Great Basin to the spine of the Rockies. The increasing heights and thicknesses should lead to warmer conditions late in the week and beyond this forecast. That should tend to shift rain chances north and northeast of the forecast area as well.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 607 AM CDT Mon Aug 17 2026

River valley fog is affecting the STJ terminal this morning. This will lift within a few hours of sunrise, leading to VFR conditions for the remainder of the forecast. With high pressure moving over the area, light winds are expected through the forecast.

EAX WATCHES/WARNINGS/ADVISORIES

MO...None. KS...None.