textproduct: Topeka

KEY MESSAGES

- There is a 40-60% chance of storms for north central KS tonight. An isolated severe storm with damaging winds cannot be ruled out.

- Storm chances are expected to increase to around 90% by Tuesday night. Rounds of heavy rain may cause flooding and a Flood Watch is posted for northeast and parts of north central KS. - Warm and dry conditions are forecast to end the week before another front moves in this weekend with rain chances and cooler temps.

DISCUSSION

Issued at 220 PM CDT Mon Sep 14 2026

A closed upper low was noted on the 19Z water vapor imagery over MT moving towards the northern plains while high pressure remained over the southern MS river valley. Surface obs showed a trough of low pressure stretching from the central high plains into the northern plains with a warm front lifting across the forecast area into southern NEB.

For this afternoon and tonight, CAMs still indicate some isolated convection developing across north central KS and there have been some weak showers pestering through the early afternoon. But forecast soundings have the boundary layer mixing out fairly deeply east of the surface trough. As a result the instability is progged to diminish as the boundary layer moisture scours out. So chances for severe storms through the evening across north central KS appear to be pretty conditional on there being enough instability for a robust updraft to develop. If this happens, there could be some damaging wind potential with an inverted V soundings and weak effective shear to sustain updrafts. Overall the chances for severe thunderstorms appear to be low.

For Tuesday afternoon through Wednesday morning, chances for showers and thunderstorms will increase as a weak boundary slides south into southern KS. Short term models show a similar setup of a stalled boundary across southern KS while moisture continues to lift north of the boundary. The RAP and NAM show sustained isentropic lift into northeast KS as precipital water vales increase over two inches, or well above the ninetieth percentile for PWs and near a record. This setup could favor the redevelopment of thunderstorms Tuesday evening and into Wednesday morning with torrential rainfall. The 13Z NBM has probabilities of 2.5 inches or more between 50 and 75 percent across northeast KS and the 12Z HREF, while a little more isolated, supports this idea. If storms move across the same location multiple times, it is not inconceivable to see locations get 3 or more inches of rain by midday Wednesday. So have posted a flood watch for the areas with the better probability of receiving heavy rainfall. There is also a risk for severe weather Tuesday afternoon ahead of the front over parts of east central KS. The forecast has temps warming into the middle 90s before the boundary moves through. This could yield MUCAPE values around 3000 J/kg depending on how boundary layer moisture holds up along the boundary. Bulk shear around 30KT could support some severe potential through the afternoon hours.

Models show the mid level ridging re-amplifiing over the central plains to end the week. This should push precip chances back north of the area with highs still hanging on to the lower 90s. By this weekend and early next week the ECMWF and GFS show a better wave coming out into the plains. Ensembles show increasing spread in the forecast due to differences in the amplitude and timing of the wave. But the larger trend of precip chances this weekend with more fall like temps for the start of next week is consistent in the ensembles. Have not made any changes from the WPC/NBM forecast but I would expect there to be some refinement of the forecast as the differences narrow.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1223 PM CDT Mon Sep 14 2026

A VFR forecast should continue into this evening as a well mixed boundary layer allows for some gusty south winds to reach the surface. There continues to be a signal for some LLWS overnight as the boundary layer decouples. Then as a surface front moves through the terminals by mid morning, some showers and storms could develop. Have a PROB30 group for now since it is the last several hours of the forecast. Think the chances for MVFR CIGS will increase through the day Tuesday as the front moves south of the terminals.

TOP WATCHES/WARNINGS/ADVISORIES

Flood Watch from Tuesday afternoon through Wednesday afternoon for KSZ009-KSZ010-KSZ011-KSZ012-KSZ021-KSZ022-KSZ023-KSZ024-KSZ026.