textproduct: Topeka

KEY MESSAGES

- Thunderstorm chances increase Saturday afternoon, with the most widespread storms and heavy rain potential Saturday night into Sunday. Strong to severe storms and flooding remain possible.

- Confidence is higher in a Saturday night into Sunday morning MCS bringing heavy rain and strong/severe storms than in any isolated Saturday afternoon development, which remains more conditional on cap erosion.

- Storm and heavy rain chances gradually diminish Sunday night into Monday as the front pushes east. An active weather pattern remains into next week.

DISCUSSION

Issued at 238 AM CDT Sat Jun 20 2026

Early this morning a broad upper level trough extended from the western Great Lakes, southwest across the mid MS River valley. An upper trough was located across eastern CA and western NV.

The 6Z surface map showed a cold font extending from eastern WI, southwest across northern MO, southwest into southeast KS. The front then extended west north of ICT, then west-northwest into northwest KS and northeast CO. Showers and a few elevated storms continue across east central KS early this morning.

Today through Sunday night:

The CA/NV H5 trough will move east across the central Rockies Today and then across the central Plains Saturday night into Sunday. The surface warm front will lift northward across the CWA to the be located along the NE border and extend northwest into far western NE by the late afternoon hours. At the surface a lee cyclone will deepen across eastern CO. Strong southerly flow, east of the lee surface low, will transport rich moisture northward across KS. Scattered supercell thunderstorms will develop across western KS ahead of a dryline/pacific front. Supercell thunderstorms will also develop along the warm front across central and eastern NE. The HRRR model shows that a few discrete supercell thunderstorms may move southeast into the north central counties of the CWA during the early evening hours. The environment across the northern counties of the CWA late this afternoon will see instability increase, with MLCAPES across the northern counties of 1500-2500 J/KG. The effective shear is forecasted to be 40 to 45 KTS, along with backed surface winds and curved low-level hodographs. Thus, any discrete supercell that does move southeast into the north central counties of the CWA will be capable of large hail, damaging wind gusts, and a few tornadoes. During the mid evening hours the scattered supercell across the north central counties will congeal into a complex of storms and move east-southeast across the northeast counties of the CWA. Severe wind gusts of 60 to 75 MPH will be possible, along with large hail in any embedded rotating updrafts.

The scattered supercells across west central KS will congeal into a line and move into the western counties of the CWA during the late evening hours. If a QLCS becomes well organized there may be some wind gusts of 75+ MPH and possible mesovortex tornadoes along the QLCS. HRRR model does show the potential for an outflow boundary to outrun the line, which may weaken the line across the southern and east central KS counties. However, other CAMS such as the ARW forecast the line remaining intense as it moves east across the CWA. The CAMs shows another area of thunderstorms developing along a cold front across north central KS and moving southeast along the outflow boundary from the first line of storms across the southern counties of the CWA during the morning and early afternoon hours of Sunday.

Expect widespread heavy rainfall with QPF amounts of 1.5 to 2.75 across the CWA. The northeast counties may see locally more rainfall, may be 3 to 4 inches as they will be affected by two storm complexes, the first in the evening and the second during the early morning hours of Sunday. I have placed the entire CWA under a flood watch through 18Z SUN, with the southeast counties extending through 7 PM SUN

The last of the thunderstorms will move out of the southeast counties overnight, as the front pushes southeast of the CWA.

Monday Through Saturday:

The extended models are in good agreement with the a west-northwest upper flow pattern through the end of the week. The surface front will stall out across central OK but there will be enough residual moisture across the CWA for slight chances of showers and thunderstorms through the period, as minor perturbations move east- southeast across the Plains.

A more amplified upper trough will move into the western US by Friday and the surface warm front will move northward into NE by Saturday. The ECMWF model shows minor perturbations in the southern stream of the jet moving across KS/OK. This could provide the CWA with a better chance for showers and thunderstorms late Friday into Saturday morning. Eventually a downstream H5 ridge will amplify across the Plains by Sunday, providing drier and warmer conditions.

Highs Monday will only reach the mid to upper 70s behind the cold front. The remainder of the week will see highs in the lower to mid 80s.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1223 AM CDT Sat Jun 20 2026

Showers around the terminals to begin the period but these should diminish with time and drift southeast of the terminals. Expect a relatively quiet period with mainly VFR conditions through the day. Cloud coverage may scatter for a period of time this afternoon but generally expect cloud decks above FL030. Storm chances increase into the afternoon but remain too low to mention in the forecast right now and will be conditional of the cap or inversion aloft eroding. If clouds hold strong then this may not occur and the risk for storms is delayed into the overnight period generally after the forecast period with the exception of KMHK which may see storms beginning to enter the area around the end of the period. The expectation into the beginning of the next forecast period is that a line of storms will advance into the area from the northwest and push southeast across the area likely slowing as they do so.

TOP WATCHES/WARNINGS/ADVISORIES

Flood Watch from 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 this evening through Sunday evening for KSZ054- KSZ055-KSZ056-KSZ058-KSZ059.