textproduct: Topeka

KEY MESSAGES

- Scattered non-severe storms linger this morning, otherwise relatively cooler today with highs in the low 70s north to mid 80s south.

- Multiple rounds of rainfall are possible this week, with the greatest focus being Monday night through Wednesday morning. A few storms could be severe with damaging wind and hail threats, and locally heavy rainfall is also a concern.

- Confidence decreases with time, but rain chances remain in the forecast through the end of the week. This could increase flooding concerns if heavy rain falls repeatedly in the same locations.

DISCUSSION

Issued at 421 AM CDT Sun Sep 13 2026

We are in zonal flow aloft as upper ridging has been pushed to the southern tier of the CONUS, while a cutoff low spins over the Pacific Northwest and broader cyclonic flow encompasses the rest of the northern CONUS thanks to another low near the Hudson Bay. A surface low sits in the eastern NM and west TX vicinity with its frontal boundary remaining stationary in southern KS early this morning. WAA north of the front has sustained scattered storms across much of the CWA despite the LLJ not being overly strong at around 25-30 kts. Storms may decrease in coverage through the morning as the jet weakens, but with the WAA regime staying in place through the day, am hesitant to buy into the CAM solutions that dry us out completely earlier in the day. It would seem reasonable to at least keep some isolated or widely scattered showery activity into the afternoon, so held onto low chance PoPs to account for that possibility. Outside of rain, the sfc boundary may lift north some today with clearing skies more likely to occur south of the front. However far north it manages to make it will determine how warm temperatures will get. For that reason, highs in the 80s are mostly confined to areas south of I-70 with locations north remaining in the 70s today. Later tonight, CAMs redevelop elevated convection along the instability gradient within the WAA regime, but vary in its eastward/westward placement. Some solutions keep all of this east into MO, while others include part of northeast KS. Most of this activity shouldn't be severe, but with effective shear around 30 kts, that will be something to monitor.

On Monday, there is good agreement on the warm air surging north with breezy southerly winds. This brings a quick warm-up with highs in the 90s and heat indices near 100 degrees. Dry weather is expected in the warm sector, so the main focus for storms will be with the approach of the cold front in north central KS during the late afternoon and evening. Shear is modest around 25-30 kts, but inverted-V soundings indicate a potential wind threat if an updraft grows strong enough. The severe threat should diminish later in the evening and overnight as instability decreases.

As we get into Tuesday, this is where this system could become more impactful but there is still a fair amount of uncertainty. The cold front looks to slowly sag south through the day, and its location in the afternoon and evening will ultimately determine where the severe and hydro threats will be greatest. With clearer skies south of the front comes greater instability, and with slightly better shear and more instability compared to Monday, think Tuesday presents a slightly better severe weather setup with damaging wind and perhaps hail up to 1 inch as potential threats. The bigger concern with time is that storms may train over the same locations with storm motions being parallel to the front. This along with ensemble guidance showing Pwat near the 99th percentile indicates some concern for locally heavy rainfall amounts. NBM currently has a 40-80% probability of totals exceeding 2" by 12z Wednesday (mainly along and north of I-70), though it should be noted that this is only incorporating the coarser model guidance for now. Of the high-res models, only the 00z and 06z RRFS go out far enough, and for now they show a couple swaths of 2-4" indicating a more localized heavy rain threat. Once we get within range of more CAM guidance, we should get a better idea of the potential for any higher-end amounts that could be more concerning, and where the heavy rain axis might be.

The front may move around a little bit later in the week, but looks to stall somewhere in the region. Given the uncertainty in exactly where it will be each day Wednesday onward, temperature spreads remain large in the ensemble guidance and PoPs continue through the end of the week. In any case, warmer temperatures in the 80s (possibly around 90) can be expected south of the front with cooler temperatures in the 70s north, especially if clouds and rain linger. The placement of the front will also be key in determining where flooding concerns could grow, as multiple rounds of rain over the same locations would become a problem, but if later rounds go through areas less impacted earlier in the week, that would limit the risk. By next weekend, we finally get a strong enough shortwave in the area to push the front south with better agreement on cooler temperatures.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1153 AM CDT Sun Sep 13 2026

Scattered showers and thunderstorms will continue to push through the Topeka area through mid-afternoon. Additional thunderstorms overnight look to stay mostly north of the main TAF sites. Otherwise, some scattered MVFR ceilings can't be ruled out through tonight but VFR conditions should generally prevail. Clouds clear out by tomorrow morning as winds begin to increase to around 10-15 kts and turn from the east to more southerly. Before this shift to south winds occurs, some LLWS will be possible overnight, mainly towards KMHK where the LLJ will be stronger.

TOP WATCHES/WARNINGS/ADVISORIES

None.