textproduct: Kansas City/Pleasant Hill

KEY MESSAGES

- Drier air behind today's slightly-ahead-of-schedule frontal passage will cap heat indices to around 100 degrees this afternoon in central Missouri, so the Heat Advisory has been cancelled early.

- Residual overnight showers and storms expected to dissipate by mid-morning today, giving way to mostly clear conditions this afternoon with the exception of some haze from wildfire smoke aloft.

- Cooler temperatures for the remainder of the work week with nightly rain chances in portions of the area Wednesday-Friday. Thursday and Friday both carry a Slight (Level 2 of 4) Risk of excessive rainfall leading to flooding.

DISCUSSION

Issued at 214 AM CDT Tue Jul 21 2026

Current Conditions & Synoptic Overview:

The cold front is approaching the Missouri/Iowa and Kansas/Nebraska state borders early this morning, with scattered convection ongoing ahead of the synoptic front. Multiple outflow boundaries are visible on early morning radar imagery well south of the showers and storms, with some notable lightning within the stronger cores. A secondary cold front has been analyzed by WPC along a kink in the surface isobars extending from the surface low near James Bay in Ontario southwest across Lake Superior into central South Dakota, with a plume of noticeably drier air visible on mid-level water vapor satellite imagery north of this front. This dry air is riding along the mid-level jet streak formed by the confluence of flow along the northern edge of ridging over the western US and the base of an upper-level trough pivoting across northern Ontario.

Showers/Storms This Morning:

The outflow should act as a stabilizing force on the environment, especially west of Highway 65, and should slowly erode the convection moving in from southwest Iowa as well as existing convection already across the area that is already struggling to sustain within an increasingly capped environment. Showers and storms will break apart and become increasingly scattered as we approach sunrise and they drift further south, with agreement from CAMs that the last showers should be dissipated from the area by 10AM. We have seen fairly efficient rainfall rates with some locations seeing 1-2" per hour with the strongest storms, but the progressive motion and overall weakening should prevent any flooding beyond temporary rate- driven ponding. Isolated gusty winds will be possible through 5AM with rain cores that get pushed down to the surface, but the window for severe weather has ended.

Temperatures/Wind/Heat Indices Today:

The outflow from storms will help to reduce the otherwise balmy temperatures early this morning, and lingering cloud cover will also help the cause, though the high cloud cover associated with the precip is expected to clear after the rain ends, bringing us to clear skies for this afternoon. The significantly cooler air will lag behind the surface front a bit, meaning that southern portions of the area won't see significant cold air advection until near/after peak heating, and high temperatures south of I-70 could be similarly hot to yesterday.

Where the cold front will really provide relief is on the moisture front (no pun intended). Not only will the front push the 70+ degree dew points south and out of the area, winds will gust up to 20-25 mph this afternoon behind the front, which will increase the efficiency of deep mixing and act to reduce dew points even further, into the low to mid-60s! Some may have noticed that the Heat Advisory has been cancelled early, and this is the reason why. The front has trended faster than previous guidance suggested, which means the drier air can progress further south before we reach peak heating. Even though central Missouri will likely see one more day of mid- to upper 90s temperatures this afternoon, the sub-70 dew points only produce heat index values up to 100 degrees.

Smoke:

The northwesterly flow aloft that moves into the area behind the front will act as a conduit for smoke from wildfires far to our northwest to move into the area this afternoon into this evening, creating some hazy conditions despite mostly clear skies. The RRFS indicates that air quality should remain yellow (AQI 50-100) until the overnight nocturnal inversion sets in tonight. Between 12AM and 10AM on Wednesday, the corridor that is collocated with the most dense plume of smoke aloft may have AQIs above 100, indicating air quality that may be unhealthy for sensitive groups and potentially that you'd be able to smell a faint smoky smell near the surface. The smoke plume should move out to the southwest overnight and into Wednesday, with haze clearing fully by Thursday.

Rainfall Later This Week:

Despite the shift to northwesterly flow, there are several rounds of rain chances before week's end. A series of shortwaves will send vort maxes riding across the northern edge of the anticyclonic circulation in the mid- and upper levels of the atmosphere, which is located across Nebraska on Wednesday and central Missouri on Thursday. These energy pulses will lead to repeated rounds of rainfall/mesoscale convective complexes Wednesday-Friday, with heavy rainfall looking increasingly plausible in association with this activity. Rain chances sit at 30-60% Wednesday night into Thursday morning in areas along and west of I-49, and 45-80% Thursday night into the day Friday areawide, lingering at 15-40% in southern portions of the area into Friday night.

We begin to see more moisture return aloft into our area Thursday and Friday, with a more favorable southwesterly wind for moisture advection arriving as the embedded 700mb ridge pushes across Missouri. PWATs increase above climatological average Thursday morning and are pushing 2-2.15" by Friday afternoon, which is above 80th percentile and as high as 97th percentile for PWAT this time of year. The 06Z NAM indicates a small embedded 700mb/500mb jet streak should develop across Kansas and Missouri Thursday and strengthen into Friday, which would help to initiate and sustain convection on Thursday night into Friday. This jet streak will increase shear, which may reduce the training potential a bit and keep systems progressive, but extremely efficient tropical warm rain processes could still prove problematic for flooding. Another concerning element relating to heavy rainfall is that the small embedded jet streak aloft sets up parallel to the expected 850mb temperature gradient, which points towards the classic Maddox synoptic flash flood conceptual model. For these reasons, WPC has maintained a Slight Risk (Level 2 of 4) for excessive rainfall leading to flash flooding for portions of the area on Thursday and Friday.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 625 AM CDT Tue Jul 21 2026

Outflow boundary from storms to the north has passed through all TAF sites and turned winds northerly ahead of a frontal passage expected later this morning. Winds gust 20-25kts with the frontal passage this afternoon, before becoming calm around 00Z this evening. Northwesterly winds aloft start to bring smoke from wildfires to the northwest in Canada, creating hazy conditions aloft but near-surface smoke should be minimal enough to avoid impacts to TAF sites.

STJ has a prob30 for showers that have formed to the north more near to the front that may persist long enough to briefly impact the site. Forecast suggests showers should dissipate within the next 2-4 hours, but cannot rule out an isolated cell persisting long enough to reach the STJ terminal.

EAX WATCHES/WARNINGS/ADVISORIES

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