textproduct: Topeka

KEY MESSAGES

- Thunderstorm chances increase this evening, then become likely overnight into Sunday morning (60-90%). Heavy rainfall with flooding and severe storms with damaging winds are the primary concerns, although hail to quarter size and a brief tornado cannot be ruled out.

- Storms may linger in east central KS Sunday late morning and afternoon (20-50% chance).

- Temperatures stay a bit cooler than average through next week alongside periodic storm chances.

DISCUSSION

Issued at 248 PM CDT Sat Jun 20 2026

Surface low pressure has been deepening in eastern CO in response to an upper trough traversing out of the Great Basin and Intermountain West region. The surface warm front has started to slowly lift north through the CWA this morning, likely placed along or just south of the I-70 corridor based on 19z observations and visible satellite. Meanwhile, a subtle perturbation rounding the low-amplitude ridge overhead has helped to trigger elevated supercells in central Nebraska, which have been following the MUCAPE gradient this morning into the early afternoon. This trajectory would favor these storms staying just north of the KS/NE border through the afternoon, which is what more recent HRRR runs have shown as well.

Our main focus remains on this evening and overnight, and we should stay quiet until then assuming the above scenario pans out. Shortwave energy from the aforementioned upper trough looks to eject across the High Plains this evening and eventually across the MO River Valley by Sunday morning. This feature will lead to the development of storms in western KS this evening that will eventually evolve into an MCS. There is still a bit of uncertainty in whether any discrete storms can develop along the warm front earlier this evening (around 02-03z) ahead of the MCS, which looks to move into our area closer to midnight. If these discrete cells can develop, this would present more of a threat for hail or tornadoes than anything later on, as sfc winds are more backed at this time. They become more veered with the approach of the MCS. All the while, the strengthening LLJ this evening will continue to pump in more moisture and provide the lift needed to maintain a severe weather risk as storms enter north central KS. Damaging winds are the main severe hazard with a lower risk for hail or a brief spin-up tornado. Flooding is the other primary concern with storms overnight. In addition to the MCS coming from western KS, CAMs have shown more rounds of rainfall with clusters and lines of storms coming southeastward out of Nebraska. This setup could lead to some locations getting hit by repeated rounds of heavy rainfall if they go over the same places again and again. While it is uncertain exactly where this might happen and where the highest amounts could be as a result, several CAM solutions show pockets of 3-6" through Sunday morning. The HREF has a subtle signal for intense rainfall rates, and more specifically, the HRRR has been indicating 2-3"/hr rainfall rates may be possible in localized areas. Overall, most locations can expect to see 1-3", but some will probably see those locally higher amounts mentioned, which presents a concern for flash flooding and river flooding. Have made no changes to the going Flood Watch.

Some of the storms and heavy rain may linger into mid/late morning in east central KS before it eventually moves out and subsidence takes over behind the upper wave. From there, the chance of any redeveloping storms in the afternoon and evening will be highly dependent on the location of any outflow boundary the morning convection lays out. That or the synoptic cold front could be the focus for afternoon storms by that point. Current CAMs have this activity mainly along and south of I-35 before it pushes south later in the evening. If storms develop before the boundary moves south, they could have large hail or damaging winds with them.

Getting into the next work week, our area finds itself in a northwest flow pattern aloft with ridging parked over the southwestern US. Embedded perturbations rounding the ridge bring more chances for storms at times through the next week, but predictability of the timing and placement of these waves tends to be lower at this range, so PoPs are generally below 50% at any particular time period. Temperatures look to hold slightly cooler than average through the week with highs in the upper 70s to low 80s and lows in the upper 50s to low 60s.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1224 PM CDT Sat Jun 20 2026

Main concern will be the evolution of thunderstorms as they move out of western/central KS as well as additional rounds that come out of southeastern NE overnight. Have gone with a best first guess for impacts at terminals, but timing may need to be adjusted with future issuances and/or amendments. Most guidance is consistent on bringing MVFR to borderline IFR cigs late in the period as well, which should lift to VFR just beyond this forecast period.

TOP WATCHES/WARNINGS/ADVISORIES

Flood Watch from 7 PM CDT this evening through Sunday afternoon for KSZ008-KSZ009-KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023- KSZ024-KSZ026-KSZ034-KSZ035-KSZ036-KSZ037-KSZ038-KSZ039-KSZ040. Flood Watch from 7 PM CDT this evening through Sunday evening for KSZ054-KSZ055-KSZ056-KSZ058-KSZ059.