textproduct: Topeka

KEY MESSAGES

- Multiple rounds of rain are likely this afternoon through Thursday evening. Heavy rain at times could lead to flooding, and a Flood Watch remains in effect primarily for areas north of I-70 through Thursday afternoon.

- As confidence in heavy rainfall increases, total rainfall amounts have increased to a widespread 2-4" with locally higher amounts around 6".

- A few strong or severe storms are possible Wednesday late afternoon into early evening towards central KS, mainly for damaging wind.

DISCUSSION

Issued at 302 PM CDT Tue Sep 29 2026

Deep upper low is circulating over southern CA and western AZ, and Hurricane Polo is seen merging into that system via water vapor imagery early this afternoon. The main westerlies aloft are along the US-Canada border. The sfc trough axis extends from north TX up through the Central and Northern Plains with a long fetch of mid- level moisture streaming from the upper low through the central part of the country. As a result of all this, deeper moisture has gradually moved from western KS into our forecast area throughout the day. Isentropic ascent coupled with that moisture has brought the first batch of rain into eastern KS this afternoon with weak instability leading to isolated thunderstorms. This rain will continue through the afternoon and most of the evening, bringing moderate to heavy rain in spotty locations at times. CAMs indicate there may be a short time period later this evening when the rain lets up and becomes more scattered in coverage for a bit, but then should pick up again during the overnight hours as the LLJ strengthens. The high end of guidance shows a few isolated pockets of 3+ inches could be possible by daybreak, though 1-2" appears more likely for most.

There should be a bit more of a lull mid to late morning Wednesday before the next round of rain moves in for the afternoon and evening. The sfc low deepens and matures through the day with the warm front pushing north during this time frame, although there remain some differences in the position of the low, which will impact where exactly the dryline and triple point set up. Forecast soundings and hodographs show veering in the low levels through the afternoon with CAPE increasing to 1000-1500 J/kg. The instability is uncertain and could be lower if clouds and rain linger longer through the morning without adequate clearing. However, low-level shear could still be enough to provide a high-shear low-CAPE setup which leads to some concern for low-topped supercells. Damaging wind would be the main hazard for any storm that can grow strong enough, and given the shear, it would be a short time window but cannot entirely rule out the possibility of a quick tornado spinning up or hail within any rotating updrafts. However, it should be noted that continued heavy rain remains the primary concern. There is higher confidence in the heavy rain and flooding threat regardless of the instability, but a more convective nature would add to the potential for intense rainfall rates in an environment that will already have Pwat between 1.75-2".

As our forecast area ends up firmly within the warm sector later Wednesday night into early Thursday morning, this should allow for another break in the heavier rain especially south of I-70. However, areas near the KS/NE border may still see showers and storms at times through the night, which could exacerbate any flooding that may be ongoing. Getting into daybreak Thursday, another batch of rain looks to move from south to north from OK into east central KS. The cold front gradually moves across the area through the day, making for a wet day until it eventually moves out towards the evening, and the upper low fills and merges into the westerlies to the north. By the time all is said and done, most areas should see a total of 2-4" with localized amounts around 6" spread over three days. Felt the current Flood Watch well covered the areas where those high- end amounts look most favorable based on 12z guidance, so have made no changes to headlines at this time.

Drier and cooler weather is favored through the weekend into early next week as zonal flow aloft transitions to northwest flow with a strengthening ridge over the Four Corners region. High temperatures drop to the 60s Friday, then warm up slightly to the lower 70s by next Monday.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1247 PM CDT Tue Sep 29 2026

The main challenge this period will be the timing for multiple rounds of rain. Opted to go with VCSH for time periods when coverage looks more scattered with prevailing showers during periods of higher confidence with greater coverage. There should be some dry time, but it looks like a potentially short window for that and confidence on timing those windows is low. Cannot rule out a few thunderstorms this afternoon and early evening impacting terminals, as well as some MVFR cigs. However, lower cigs look more probable later in the period from MHK westward.

TOP WATCHES/WARNINGS/ADVISORIES

Flood Watch from 7 PM CDT this evening through Thursday afternoon for KSZ008-KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023- KSZ024-KSZ034.