textproduct: Topeka

KEY MESSAGES

- Slight risk for severe weather this evening and Tonight. The primarily hazard will be damaging wind gusts, 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 average temperatures continue through early next week.

- There will be another chance for strong to severe thunderstorms across north central and northeast KS Wednesday afternoon and evening.

- There will be chances for showers and thunderstorms early next week.

DISCUSSION

Issued at 139 PM CDT Tue Aug 18 2026

Early this afternoon, water vapor satellite imagery along with upper air analysis showed a broad upper trough centered across east central Canada, with a trough axis extending southwestward across the the upper Midwest into eastern NE/western IA. A broad upper ridge was located across the the southwestern US.

The 17Z surface map showed a cold front extending southwest from a surface low across Ontario, Canada, then southwest across northwest WI, then southwest across western NE and central WY. An outflow boundary that was produced by thunderstorms across southern NE and north central KS earlier this morning has moved southeast of I-35. Temperatures behind the outflow boundary were in the lower to mid 70s. Ahead of the outflow boundary temperatures were in the mid 80s. There may be a few showers or sprinkles through 1 PM behind this boundary across east central KS.

Today through Tonight:

The outflow boundary will push south of the CWA early this afternoon and become stationary. The boundary will washout across central KS during the mid and late afternoon hours. Most CAMs show southerly flow developing across central KS, that will transport richer moisture northwest. Eastern KS will gradually see the OFB reform around I-70 late this afternoon into the evening hours. Most CAMs do not show isolated thunderstorms developing along the outflow boundary within the TOP CWA. It will also be difficult to determine where this boundary will be located late this afternoon and early evening. If a surface based storm manages to develop it may become severe with damaging winds being the primary hazard due to the deeper mixing and inverted V soundings. If the updraft manages to ride along the OFB There may be enhanced low-level vertical windshear for an updraft to develop mid-level rotation to produce hail larger than quarters.

Later this evening, a southwesterly LLJ will increase to 30 to 35 KTS. The resulting isentropic lift will will cause thunderstorms to develop north of the boundary across south central NE and northeast KS. Forecast soundings show that these storms north of the boundary will be elevated. Though the inversion does not look too strong, so any complex of storms that develop may produce strong outflow and resulting damaging wind gusts. There may also be some quarter size hail as the effective shear increases to 35 to 40 KTS. Areas where storms train later Tonight and through the early morning hours may see some localized flooding. Forecast sounding PWs are nearly 2 inches. Most CAMs show the possible training of thunderstorms north of I-70 across the northeast counties of the CWA. The complex of storms should push southeast of the CWA after 9Z WED.

Wednesday through Thursday:

The H5 ridge across the southwest US will amplify northward across the Great Basin. This will cause the mid-level flow to become northwesterly. Minor perturbation embedded within the northwest flow may provide enough ascent for thunderstorms to develop across NE along a secondary cold front. There remains uncertainty where thunderstorms will develop across NE. The 12Z HRRR forecast thunderstorms to develop across southeast NE, which may just clip our northeast counties. Other CAMs, such as the RRFS show storms developing farther west across southern NE and moving southeast into the northern counties of the CWA. The environment across northern KS Wednesday afternoon will have MLCAPE values of 1500-2200 J/KG and effective shear of 45 KTS. Some of these storms may have mid-level mesocyclones which will bring a risk of larger hail. But there remains uncertainty on where these storms will develop and if they will weaken by the time they reach the northern counties of the CWA by the early evening hours.

Thursday, we may see a break in the showers and thunderstorms as the first perturbations shifts southeast across MO. So expect dry conditions.

Highs Wednesday and Thursday will be in the lower 80s north to upper 80s south.

Thursday night through Friday night:

The upper ridge will shift east into the central Rockies. The extended range models are in good agreement with an H5 trough digging southeast from the northern high Plains into the upper Midwest and MS River Valley. The stronger ascent ahead of the H5 trough will cause scattered showers and thunderstorms to develop across the CWA Friday afternoon into Friday night.

Saturday through Tuesday:

The H5 ridge will shift east into the southern and central high Plains on Saturday and Sunday. The H5 ridge will flatten a bit and mid level perturbations will round the ridge axis Sunday through Tuesday. There will be chances for for showers and thunderstorms Sunday through Monday. A back door cold front will push southwest across the CWA Monday afternoon as an H5 trough amplifies across the east central conus. The better chances for showers and thunderstorms will shift south and west of the CWA on Tuesday. There will not be much of a cool down as high temperatures remain in the upper 80s to lower 90s.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1230 PM CDT Tue Aug 18 2026

The isolated showers and thunderstorms will move east of KTOP and KFOE in by 1830Z. Skies will clear this afternoon. There may be a few isolated storms south of the terminals late this afternoon and into the early evening. A cluster of storms will form across north northern KS then shift southeast through the late evening and early morning hours. Still some uncertainty remains in the timing and the probability of storms at the terminals. I placed a 30 PROB in the TAFs for thunderstorms between 4Z-10Z.

TOP WATCHES/WARNINGS/ADVISORIES

None.