textproduct: Topeka

KEY MESSAGES

- Dense Fog Advisory issued for northern KS with some patchy fog expected further south in low-lying areas especially.

- Isolated to widely scattered showers and storms may develop late tonight into Friday morning, although better chances (30-50%) come late Friday night into Saturday morning.

- There are additional chances for showers and storms early next week, but low predictability of timing and location leads to low confidence.

- Temperatures stay near or slightly below average through the middle of next week.

DISCUSSION

Issued at 428 AM CDT Thu Aug 20 2026

Upper pattern is becoming more amplified with a ridge over the Desert Southwest and a strengthening trough to our east, putting us in northwest flow aloft which will persist for the next several days. At the surface, the ridge axis is placed to our north over eastern Nebraska, although high pressure will continue to have an influence on our weather for today. Have been monitoring satellite, observations, and especially webcams for fog development and expansion southwest into more of our CWA. Dense Fog Advisory has been issued across the Hwy 36 corridor where it is more prevalent based on the aforementioned sources. Further south and further away from the ridge axis, fog should be patchier in nature, but still can't rule out some quick drops in visibility in low-lying spots and areas near water. Forecast soundings show the moisture is shallow and should mix out around 14-15z.

After fog lifts, the late morning and afternoon look to be mostly sunny with temperatures similar to yesterday -- low 80s for northeastern areas, upper 80s approaching 90 further south. The surface high slowly slides east throughout the day, leading to light winds gradually turning southerly toward the evening. There is low confidence in a subtle perturbation aloft leading to some convection late tonight and overnight. Short-term models have not been consistent in developing this activity in central NE/KS during this time period, and the LLJ isn't overly strong. Even so, its position would tend to favor more of southern Nebraska. More recent guidance has delayed the development of any isolated or scattered storms until Friday morning, and exactly how soon has also varied from run to run. That said, if anything were to develop and clip parts of north central KS overnight tonight, soundings show these to be high- based and the environment would support a conditional severe threat with isolated damaging winds or large hail. If the later trend holds and clouds/rain hang on longer Friday, then temperatures may not be as warm as currently forecast.

The more discernible shortwave aloft is progged to develop thunderstorms in southwestern Nebraska Friday evening. If these track far enough east closer to midnight, then once again soundings show enough elevated instability and shear to support a wind and hail threat.

Following any lingering rain Saturday morning, skies should clear out for a dry afternoon and evening. While temperatures the next several days will be dependent on clouds and precipitation, medium- range guidance seems to be coming into better agreement on a back door cold front entering the area Saturday night into Sunday, leading to cooler highs on Sunday. The pattern remains rather nebulous through the first half of next week as we remain on the northeast periphery of the upper ridge, which keeps us close enough to any embedded perturbations that are difficult to predict the timing and location of this far out. At this time, Sunday and Tuesday bring the next best chances for rain, but PoPs are limited to 40% or less for any given time frame given the low predictability of these features.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 608 AM CDT Thu Aug 20 2026

Fog has set in at TOP/FOE and should be on its way to the MHK terminal based on satellite. Will keep LIFR conditions until it mixes out, which soundings show happening around 14-15z when it lifts to stratus briefly. Once that scatters out, clear skies with light winds are expected the rest of the period.

TOP WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 10 AM CDT this morning for KSZ008-KSZ009- KSZ010-KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-KSZ026- KSZ038-KSZ039-KSZ040.