113
FXUS63 KTOP 312329
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
629 PM CDT Sun Aug 31 2025

.KEY MESSAGES...

- Scattered showers and storms are expected to persist through the
  day Monday.

- A cold front is forecast to move through the area Wednesday with a
  chance for thunderstorms.

- Seasonably cool weather is forecast to continue into next weekend.

&&

.DISCUSSION...
Issued at 237 PM CDT Sun Aug 31 2025

A weak area of cyclonic shear was seen on the 19Z water vapor
imagery over the middle MO river valley within a weak northwesterly
flow. Surface obs showed a weak pattern with high pressure over the
Upper Midwest and low pressure along the southern high plains.

Not a lot of change to the forecast for tonight through Monday
night. As long as the upper disturbance remains near the forecast
area, there should be some forcing with little or no inhibition for
scattered showers to develop off an on. Lapse rates are still
progged to be rather modest at 5.5 to 6 C/km. So thunderstorm
activity is likely to remain isolated. Forecast soundings continue
to show a deep warm cloud layer up to about 12 KFT. This is expected
to allow showers to be efficient rain producers with warm rain
processes promoting periods of heavy rain. But the heavy rain risk
should remain isolated enough to preclude any organized flooding
risk with the main concern likely ponding of water on roads or water
collecting in poor drainage area. Cloud cover should hold lows in
the lower 60s and limit highs tomorrow into the lower and middle
70s.

The upper disturbance finally shears out and passes to the southeast
by Tuesday. This should bring dry weather to the region. Weak high
pressure and lower dewpoints on Tuesday should make for a nice day
with highs in the middle 70s.

Models continue to show a pattern change with a long wave trough
developing over the Great Lakes by mid-week. However the operational
solutions have trended towards a weaker surface ridge building into
the plains as an upper closed low develops north of the Great Lakes.
Ensembles have been showing quite a bit of spread with the shortwave
activity within the upper trough and the 00Z ensembles are just
about evenly split between a sharp shortwave and a less amplified
shortwave. In either case, the majority of ensembles bring a cold
front through the area late Wednesday. The NAM and GFS have trended
with a little more instability (as much as 2000 to 3000 J/kg CAPE)
and reasonable bulk shear (around 40KT) along and ahead of the front
for there to be some concern for severe thunderstorms.  Will keep an
eye on later model runs as the forecast has chance POPs for
convection Wednesday afternoon and evening.

Models show a second shortwave swinging through the northern plains
Thursday night with a reinforcing cold front moving into the forecast
area Friday morning. The blend doesn`t have any POPs with this
second front, but there is some signal from the 12Z ECMWF for precip
chances Friday. Cluster analysis of the 00Z ensembles shows the
little difference in the overall pattern but large spreads in the
details like temps and POPs. This is directly related to the
strength of the shortwave energy moving through the longwave
trough. So will stick with the NBM for now and see how later runs
trend. The first front being a little weaker than earlier forecast
means temps Thursday are now forecast to be a little more moderate,
and the second front Friday means the cooler weather should last
into the weekend. But I would expect some adjustments to the actual
numbers as models try to resolve the pattern change.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 629 PM CDT Sun Aug 31 2025

Confidence is on the low side in trends through this forecast.
Cloud heights continue to be higher then anticipated and showers
somewhat more limited. Considered holding off VCSH for a few
hours but recent IR satellite trends suggest more development
may not be far away. Guidance continues to show falling flight
conditions forming after 06Z and linger through the end of the
forecast in low stratus and some BR. This appears to be from
moisture convergence along a weak inverted surface trough just
upstream of the terminals. Have kept MVFR at TOP and FOE and
IFR and MHK though delayed them a few hours based on recent
trends. TS chances remain quite low.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Wolters
AVIATION...Poage