textproduct: Topeka

KEY MESSAGES

- The extreme heat warning has been downgraded to an advisory through Saturday with heat indices expected to stay around 100 degrees.

- There is a chance for thunderstorms after midnight. If storms develop there is a risk for damaging winds.

- Thunderstorms could redevelop during the late afternoon and early evening of the Fourth of July. Have a plan to move outdoor activities inside should thunderstorms move into your area.

DISCUSSION

Issued at 228 PM CDT Fri Jul 3 2026

19Z water vapor imagery showed the mean westerlies across the northern tier of the country with a relatively weak southwest to westerly upper level flow over the central plains. Surface obs placed a low over southeast CO with high pressure across the southern MS river valley. Overall this would support southerly flow with hot and humid air across the area. But thunderstorms that started out across northwest KS this morning managed to move all the way across the state and are now moving into MO.

For tonight through Saturday night, there is not much confidence in the CAMs radar simulations as they have shown a poor handle on current convection and inconsistent forecasts recently. However think there is some potential for an MCS to develop overnight tonight. Think eastern NEB is the favored area for storms overnight. This is where a weak inverted trough axis is set up with models showing the low level jet converging into this feature. The question is will the MCS move into parts of northeast KS. It is possible, but there are a couple signs from the models that point towards this being less likely. First the Corfidi vectors from the NAM/RAP for a forward propagating MCS are nearly dew east along the state line. Second is the isentropic surfaces tend to keep the better saturation/lift combo just north of the state line through the night. There is still the chance for some propagation south into the low level jet and have some 20 to 50 percent chance POPs to account for this with the higher chances along the state line. If storms do move into the area, steep mid level lapse rates and a moderately unstable airmass could support the MCS in producing severe wind gusts. Interestingly the last couple of HRRR runs highlight this potential. Again the probability for this looks to be less than 50 percent, but it is something to keep an eye on in any case.

For the Fourth of July, the forecast has chance POPs in the afternoon with increasing chances during the evening. The expectation is for a conditionally unstable airmass to remain in place waiting for something to trigger thunderstorm development. This could be convergence along an old outflow boundary or a shortwave propagating across the forecast area. Think the location of any boundary will have a big effect on where storms form, and this is the main uncertainty in the forecast. Otherwise everything is pointing to showers and storms developing late in the afternoon and early evening. For now the forecast favors likely POPs across the southern half of the forecast area expecting the overnight outflow to push into central KS. A very unstable airmass is progged by the models with some modest bulk shear. So initial storms may show some supercell characteristics. But overall mean flow being around 10KT or less suggests storm mergers and evolution into clusters are likely to occur. There could be damaging winds and large hail initially as storms develop that is expected to transition to more of a wind and heavy rain risk as we get into the overnight hours.

With this morning's storms knocking temps and dewpoints down, it is a little more marginal that we will see heat indices of 105 or better. And the chance for showers and clouds Saturday make it a little marginal again that we would reach advisory levels. So a heat warning seems like the wrong message at this point. We should still see highs in the 90s with heat indices around 100, but at this point that seems not so extreme. With this in mind, have gone ahead and downgraded the heat warning to an advisory through 8pm Saturday.

For Sunday the nocturnal convection is progged to be moving southeast of the area early in the day. The blend held onto some chance POPs through the afternoon which looks to be a result of the 00Z ECMWF. For collaboration I left the low end POPs in, but with much of the 12Z operational solutions showing things pushing out of the area through the morning the POP forecast may be a little overdone. Cluster analysis of the 00Z ensembles show little difference in the synoptic pattern across the central plains leading to some confidence in the NBM initialization. The mid range solutions tend to keep mid level high pressure over the forecast area early next week. This should favor dry weather and seasonal temps. By the back half of next week models show the pattern becoming a little more zonal with perturbations impacting the area. So precip chances return to the forecast as temps gradually trend warmer.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 538 PM CDT Fri Jul 3 2026

VFR at all TAF sites through the TAF period. There is a chance storms may move in tonight around 05z, but confidence isn't high enough for more than a PROB30 mention at this time, but should trends change and confidence increase, thunderstorms may be added.

TOP WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM CDT Saturday for KSZ012-KSZ024-KSZ026- KSZ038-KSZ039-KSZ040-KSZ054-KSZ055-KSZ056-KSZ058-KSZ059.