939
FXUS63 KTOP 150600
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
100 AM CDT Tue Sep 15 2026

.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 /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1253 AM CDT Tue Sep 15 2026

VFR to start this period, but conditions will deteriorate throughout,
particularly from late afternoon onward. Maintained LLWS for the
first 5-6 hours overnight, as gusts at the surface may help to
mitigate it some, but the 50kt jet overhead warrants a mention for
marginal speed shear. There remains some uncertainty in coverage of
storms just ahead of an approaching frontal boundary this morning,
but felt the possibility was enough to keep the prob30 group. If the
front slows, the timing could still be adjusted and tried to trend
that direction with a few hours of variable wind direction before
fropa occurs. Storm coverage increases late this afternoon and
especially tonight, which should bring a drop to MVFR and eventually
IFR cigs as well as vsby within heavier downpours. The front hanging
around the area unfortunately keeps a prolonged period with TS
impacting terminals.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Flood Watch from this afternoon through Wednesday afternoon for
KSZ009-KSZ010-KSZ011-KSZ012-KSZ021-KSZ022-KSZ023-KSZ024-KSZ026.

&&

$$

DISCUSSION...Wolters
AVIATION...Picha