725
FXUS63 KTOP 181134
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
634 AM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Slight risk for severe weather this evening brings primarily a
wind threat 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
to slightly below average temperatures continue through early next
week.

- Some additional opportunities for rain Wednesday night and later
this week, but low predictability in timing and location leads to
low confidence at this time.

&&

.DISCUSSION...
Issued at 440 AM CDT Tue Aug 18 2026

The MCS that tracked across southern Nebraska earlier in the night
has weakened considerably since 3am, with its remnants going through
the MO River Valley as of 840z. Additional non-severe storms have
developed within the WAA regime upstream in western Nebraska and
eastern SD. These are the storms that are progged to move across
Nebraska and eventually enter northern KS during the mid to late
morning hours. There are varying ideas among CAMs on how far south
this activity will make it into the area, and some solutions hang
onto light showery activity in northeast KS even into the afternoon.
This leads to questions on where any outflow boundary will set up,
as well as how much the atmosphere will be able to destabilize,
especially if clouds and rain hang around longer. Consensus appears
to place a boundary near the I-70 corridor, perhaps due to
differential heating creating an effective warm front. Soundings
continue to show a lot of inhibition, whether that`s because of
better mixing south of the boundary leading to warmer temperatures
and lower dew points, or because of capping north of the boundary.
Either way, it appears as though there needs to be a stronger source
of lift to overcome the inhibition and develop stronger storms, and
the cold front seems to be that necessary forcing. Generally
speaking, models struggle to develop stronger convection until the
cold front moves through later in the evening. Location of
initiation is still up in the air, as models still haven`t shown
much consistency on where storms will develop. Recent runs are now
trying to initiate closer to Hwy 36, which would theoretically be
within the rain-cooled air, and the timing would suggest it`s
related to the 850mb boundary. The environment for these elevated
storms would still be favorable for mainly damaging wind with DCAPE
over 1000 J/kg with perhaps some large hail. Skinny CAPE profiles
and Pwat near 90th percentile also point to efficient rainfall
producers, so heavy rain would be a potential concern as well. While
it`s uncertain how much coverage there will be (particularly severe
coverage), storms should generally weaken through the night. Some
rain may linger into Wednesday morning before finally moving out by
midday.

As for later in the day Wednesday, the wave within the northwest
flow aloft has shifted east in the latest model runs, favoring storm
chances to the south and east of the area. Some low PoPs remain in
east central KS with higher chances outside of the forecast area.
Temperatures are cooler Wednesday behind the front with highs in the
80s, perhaps some upper 70s in northern KS. A gradual warming trend
occurs the rest of the week with temperatures increasing a couple
degrees each day. We remain in a northwest flow pattern aloft with
an amplifying ridge to our west and a deep trough to our east.
Timing and placement of embedded waves within this pattern are
typically hard to predict several days out, so low chance PoPs
appear periodically towards the end of the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 628 AM CDT Tue Aug 18 2026

Timing and development of thunderstorms this evening is the main
challenge of this forecast period. Will hold off on mentioning any
showers or storms related to the activity coming out of southeastern
NE this morning, as most guidance still keeps this north of
terminals, but there is a non-zero chance it reaches TAF sites. From
there, will need to watch where a boundary sets up to determine
location of storm development this evening, which will determine
timing to some extent. Have moved the PROB30 group based on the
latest guidance, but this could still change.

&&

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

&&

$$

DISCUSSION...Picha
AVIATION...Picha