textproduct: Kansas City/Pleasant Hill

KEY MESSAGES

- Strong to Severe Storms Late Tonight and Overnight

- Potential for Storm Redevelopment Wednesday Afternoon

- Seasonable Temperatures Over The Weekend

DISCUSSION

Issued at 341 PM CDT Tue Aug 18 2026

Shower and storm complex that dropped southeastward out of Nebraska today has a large role in how the mesoscale environment has evolved today. The expansive cloud cover associated with this limited the boundary layer's ability to destabilize through much of the afternoon, which stopped the conditional threat for stronger storms this afternoon. We currently have a series of H5 vort maxima that have been traversing the Central Plains and parts of the upper Midwest over the past several hours. This is downstream from a mid- level ridge present over the southwestern CONUS.

Differential cyclonic vorticity advection has remained present over the Central Plains, allowing the surface cyclone to deepen through the day and extend pressure falls eastward into the lower Missouri River Valley. The earlier outflow boundaries have washed out over the past couple of hours. The winds are now returning to a southerly direction after becoming northerly with the series of outflows from this morning's activity. This will attempt to restart theta-e advection through the afternoon, but, much of northwestern and north- central Missouri remains under overcast skies, which will limit instability and will play a role in the evolution of the late/overnight activity. However, recent satellite trends as of 20z is showing clearing in portions of eastern Kansas, perhaps an small area of subsidence that has developed with the enhanced mid-level flow over the past 24 hours. The next few hours late this afternoon and into the early evening should allow for an instability axis to develop over Central Kansas, perhaps as far east as the Flint Hills. Areas further east may struggle to destabilize, at least with respect to MLCAPE and surface-based CAPE parcels. As the cyclone deepens and slowly shifts eastward, low-level convergence should continue to increase through late evening, with the low-level jet set to ramp up as well. This will become the focus for storm initiation for the remainder of the night. With current instability trends, current expectation is for CI more in eastern KS, but should quickly expand eastward into the lower Missouri River Valley. Some cells may be able to go as early as 00z in central Kansas, but for our forecast area, may hold off until 03-04z for expansion. This timing and location of CI will have implications for storm mode, as well as the associated hazards. Given that there does not appear to be enough for sufficient surface CAPE to develop in our eastern Kansas counties over to Central Missouri, the opportunity for supercells will be more confined to Kansas, just west of the forecast area. However, supercells may be able to travel eastward, especially if they latch onto the cold front, potentially hitting our western zones, and may get close to the KC metro. If a supercell is able to develop, large hail (in excess of 2") is possible along with strong RFD winds. If the supercell remains surface based, it will present a tornado threat, though that threat seems to diminish the further east of the KS Flint Hills (given that 0-3km CAPE will be hard to come by and limited stretching potential). There will be plenty of kinematic support even into Central MO, but the thermodynamic environment remains in question. Low-level hodographs are expected to curve, especially close to the cold front where low- level SRH could easily exceed 150 m^2/s^2. The more likely scenario for our forecast area is upscale growth into an organized MCS. While new cell development may have elevated bases, mid-level lapse rates and MUCAPE profiles will allow for strong updrafts, with plenty of wind shear to help organize the activity. This would support the development of strong cold pools this evening, with strong negative buoyancy supporting damaging wind gusts, potentially with some near 70 MPH. New cores may briefly pose a hail threat before congealing with other cells or being ingested into an MCS. The kinematic environment could be favorable for attempting to support meso vortex generation if the mode should become more linear, but unsure if 0- 3km CAPE would be high enough to help with stretching that to the surface to present any QLCS tornado threat. The most robust activity is favored between 1a-5a overnight (06z-10z). Where a mature MCS tracks and propagates still remains uncertain, as this will largely depend on where the best CAPE axis can develop. Given the steering flow, this is likely to track toward the south-southeast, but at what point does it start to take on this motion remains the main the questions. The bulk of the activity should exit the forecast area after 12z.

Rainfall and hydrologically speaking, a widespread 1 to 2 inches of rainfall is expected overnight. 12z HREF PMM field does have a few pockets of 3 to 4 inches. But, the 12z HREF members did not handle this morning's activity well, and therefore, having a hard time putting confidence into its output. With the stronger mid-level steering flow available, would expect that any MCS that develops would be fairly progressive. Therefore, have continued to hold back from issuing a Flood Watch. If there is more back building though that occurs along the front, or individual cells take on a training pattern, would increase the QPF that could create flooding issues. This will need to be monitored over the next few hours. The initial storm development location will also play a role in how the hydro situation evolves overnight.

Wednesday afternoon, there is the potential for afternoon redevelopment in north-central MO between 18z-21z, associated with another mid-level vort maxima that moves over the region. However, unsure what kind of instability we will see, especially if the boundary is well south of the area. The 18z HRRR though, does show enough boundary layer mixing to get surface based parcels, and enough shear to try and organize convection. Plenty of speed shear will be available, but is unidirectional, which may result in more multi-cell activity, capable of some hail and wind gusts. However, uncertainty remains very high for how redevelopment occurs. Elsewhere, lingering shower activity may be possible into Central Missouri on the backside of the exiting front, with mid-level lift from the next H5 short-wave that moves through.

For the remainder of the forecast period, the area will be in northwesterly mid-level flow as ridge amplifies over the southwestern CONUS. Several disturbances though may ride through the flow, which will provide opportunities for more showers and storms through the weekend.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1225 PM CDT Tue Aug 18 2026

Decaying showers are still present over eastern Kansas and western MO. We are expecting these to continue to produce showers at STJ and the KC Metro terminals through at least 19z. Ceilings are expected to remain VFR through most of this activity. The cold front moves through later tonight and through the overnight hours, and is expected to development showers and thunderstorms across much of the region. The timing for this seems favorable between 03-04z, then continues into early Wednesday morning. During heaviest precipitation activity, periods of IFR conditions are possible. Activity should push out of the area after 12z Wednesday morning.

EAX WATCHES/WARNINGS/ADVISORIES

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