textproduct: Topeka

KEY MESSAGES

- Severe storm potential this evening, particularly along/south of a frontal boundary near I-70. Large hail, damaging winds, and heavy rain the main threats, with Flood Watch in effect through Wed AM.

- Another round of rain Wednesday night into Thursday, though uncertainty persists in where the heaviest rain will set up (east- central KS or farther south).

- Much cooler and drier for Friday and the weekend. By far the coldest airmass yet this autumn. Some frost possible Saturday morning.

DISCUSSION

Issued at 146 PM CDT Tue Oct 13 2026

Water vapor imagery this afternoon highlights the deep upper low over the western CONUS, with broad ridging in place across most of the eastern CONUS. There are hints at a weak vorticity maximum moving out onto the Central Plains ahead of the main upper low. This will be a player our likely thunderstorm development this evening. At the surface, high pressure over the Northern Plains has helped to push a frontal boundary southward overnight into the area. This front has stalled along a roughly McPherson to Topeka line, and has even pushed a bit back north here in Topeka over the past couple hours. Along and south of the boundary we remain very warm and humid, with dewpoints in the low 70s and temperatures approaching 90 in spots. This is allowing ML CAPE to climb above 2000 J/kg. Coupled with strong effective shear of around 45 kts, and the ingredients are in place for severe storms. Convergence along the front will gradually increase over the afternoon, supporting storm development initially to our west in central KS by mid/late afternoon and towards Topeka by 5-6 PM. The strong effective shear and steep mid- level lapse rates will be favorable for initial supercells capable of producing hail up to around golf ball size. However boundary parallel shear vectors should favor upscale growth with time, trending the main hazards more towards damaging winds and heavy rain. Still can't completely rule out a brief tornado, especially towards sunset with any supercell riding the boundary. However the overall threat looks rather limited, given a very short window between a more discrete storm mode earlier in the evening and better low-level shear later in the evening. The severe threat should gradually taper off mid to late evening as instability weakens, but a heavy rain and flash flooding threat may linger overnight given near record PWAT for mid October and potential for localized training of thunderstorms.

Indications are still that we'll see a bit of a break in rain coverage Wednesday before the main upper low approaches Wednesday night and Thursday. A few scattered showers may linger during the day, but for the most part it looks cool and cloudy on the north side of the front. As the upper low does approach Wednesday night, guidance is generally split into two camps for the potential second round of rain. On one end, some guidance (including the AI versions of both the GFS and ECMWF) keeps the surface low weaker and farther south across southeast Kansas. This would keep the better isentropic ascent to our south, along with the heaviest rain. Most of northeast Kansas would still see some rain, but lighter amounts and rates. Alternatively some guidance, particularly the global models, lift a stronger surface low farther north through northeast Kansas. This would allow stronger WAA and isentropic ascent across east-central KS, supporting another swath of heavy rain, potentially 1-3" in spots. May still need to extend the Flood Watch through Thursday morning, but given the uncertainty have decided to hold off for now. Leaning towards the lighter scenario anyway, given how convectively influenced boundaries like this often behave.

Once the surface low does pull off to the east Thursday evening, much cooler and drier air will be ushered in behind the trailing cold front. Strong CAA should bring temperatures into the low/mid 40s by Friday morning, and keep Friday highs in the 50s despite plenty of sun. By Saturday morning, strong high pressure will be located nearly overhead. Clear skies and light winds will promote near-ideal radiational cooling, which may allow for some of our first frost of the season as temperatures fall into the low/mid 30s. Return flow sets up for the latter part of the weekend as the high departs to our east. This will result in a gradual warming trend for the end of the forecast period, with highs climbing back into the 70s for early next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1208 PM CDT Tue Oct 13 2026

Frontal boundary is currently south of KMHK and somewhere right around KTOP. Expecting KMHK to remain north of the front through the period, with north/northeast winds persisting. KTOP and KFOE should have a few hours of more southerly winds as the front inches north this afternoon, before pushing back south this evening as thunderstorms (a few strong) develop along the front. Overnight, scattered showers and thunderstorms will persist behind the front, with MVFR to IFR ceilings likely arriving at some point late evening to early morning.

TOP WATCHES/WARNINGS/ADVISORIES

Flood Watch from 5 PM CDT this afternoon through Wednesday morning for KSZ026-KSZ037-KSZ038-KSZ039-KSZ040-KSZ054-KSZ055-KSZ056-KSZ058- KSZ059.