textproduct: Topeka

KEY MESSAGES

- Slight risk for severe weather this evening brings primarily a wind threat with isolated large hail and heavy rainfall. Plenty of uncertainty remains regarding storm location, timing, and coverage of severe storms.

- Warmer today where skies are able to clear out, but otherwise near to slightly below average temperatures continue through early next week.

- Some additional opportunities for rain Wednesday night and later this week, but low predictability in timing and location leads to low confidence at this time.

DISCUSSION

Issued at 440 AM CDT Tue Aug 18 2026

The MCS that tracked across southern Nebraska earlier in the night has weakened considerably since 3am, with its remnants going through the MO River Valley as of 840z. Additional non-severe storms have developed within the WAA regime upstream in western Nebraska and eastern SD. These are the storms that are progged to move across Nebraska and eventually enter northern KS during the mid to late morning hours. There are varying ideas among CAMs on how far south this activity will make it into the area, and some solutions hang onto light showery activity in northeast KS even into the afternoon. This leads to questions on where any outflow boundary will set up, as well as how much the atmosphere will be able to destabilize, especially if clouds and rain hang around longer. Consensus appears to place a boundary near the I-70 corridor, perhaps due to differential heating creating an effective warm front. Soundings continue to show a lot of inhibition, whether that's because of better mixing south of the boundary leading to warmer temperatures and lower dew points, or because of capping north of the boundary. Either way, it appears as though there needs to be a stronger source of lift to overcome the inhibition and develop stronger storms, and the cold front seems to be that necessary forcing. Generally speaking, models struggle to develop stronger convection until the cold front moves through later in the evening. Location of initiation is still up in the air, as models still haven't shown much consistency on where storms will develop. Recent runs are now trying to initiate closer to Hwy 36, which would theoretically be within the rain-cooled air, and the timing would suggest it's related to the 850mb boundary. The environment for these elevated storms would still be favorable for mainly damaging wind with DCAPE over 1000 J/kg with perhaps some large hail. Skinny CAPE profiles and Pwat near 90th percentile also point to efficient rainfall producers, so heavy rain would be a potential concern as well. While it's uncertain how much coverage there will be (particularly severe coverage), storms should generally weaken through the night. Some rain may linger into Wednesday morning before finally moving out by midday.

As for later in the day Wednesday, the wave within the northwest flow aloft has shifted east in the latest model runs, favoring storm chances to the south and east of the area. Some low PoPs remain in east central KS with higher chances outside of the forecast area. Temperatures are cooler Wednesday behind the front with highs in the 80s, perhaps some upper 70s in northern KS. A gradual warming trend occurs the rest of the week with temperatures increasing a couple degrees each day. We remain in a northwest flow pattern aloft with an amplifying ridge to our west and a deep trough to our east. Timing and placement of embedded waves within this pattern are typically hard to predict several days out, so low chance PoPs appear periodically towards the end of the week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1237 AM CDT Tue Aug 18 2026

VFR conditions are forecast, but will need to monitor for showers and thunderstorms mainly towards the end of the period. The convection currently moving southeastward through Nebraska looks favored to stay north of terminals as it weakens into northern KS this morning. The more favorable time frame for storms to impact TAF sites is in the evening following the passage of a cold front. Timing and location of these storms is still up in the air though, so have limited mention to a PROB30 group at all sites for now. Outside of TS, expect light southerly winds most of the day before they turn to the ENE behind the front.

TOP WATCHES/WARNINGS/ADVISORIES

None.