434
FXUS63 KTOP 182342
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
642 PM CDT Tue Aug 18 2026

.KEY MESSAGES...

- Slight risk for severe weather this evening and Tonight. The
  primarily hazard will be damaging wind gusts, 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 average
  temperatures continue through early next week.

- There will be another chance for strong to severe thunderstorms
  across north central and northeast KS Wednesday afternoon and
  evening.

- There will be chances for showers and thunderstorms early next
  week.

&&

.DISCUSSION...
Issued at 139 PM CDT Tue Aug 18 2026


Early this afternoon, water vapor satellite imagery along with upper
air analysis showed a broad upper trough centered across east
central Canada, with a trough axis extending southwestward across
the the upper Midwest into eastern NE/western IA. A broad upper ridge
was located across the the southwestern US.

The 17Z surface map showed a cold front extending southwest from a
surface low across Ontario, Canada, then southwest across northwest
WI, then southwest across western NE and central WY. An outflow
boundary that was produced by thunderstorms across southern NE and
north central KS earlier this morning has moved southeast of I-35.
Temperatures behind the outflow boundary were in the lower to mid
70s. Ahead of the outflow boundary temperatures were in the mid 80s.
There may be a few showers or sprinkles through 1 PM behind this
boundary across east central KS.

Today through Tonight:

The outflow boundary will push south of the CWA early this afternoon
and become stationary. The boundary will washout across central KS
during the mid and late afternoon hours. Most CAMs show southerly
flow developing across central KS, that will transport richer
moisture northwest. Eastern KS will gradually see the OFB reform
around I-70 late this afternoon into the evening hours. Most CAMs do
not show isolated thunderstorms developing along the outflow
boundary within the TOP CWA. It will also be difficult to determine
where this boundary will be located late this afternoon and early
evening. If a surface based storm manages to develop it may become
severe with damaging winds being the primary hazard due to the deeper
mixing and inverted V soundings. If the updraft manages to ride
along the OFB There may be enhanced low-level vertical windshear for
an updraft to develop mid-level rotation to produce hail larger than
quarters.

Later this evening, a southwesterly LLJ will increase to 30 to 35
KTS. The resulting isentropic lift will will cause thunderstorms to
develop north of the boundary across south central NE and northeast
KS. Forecast soundings show that these storms north of the boundary
will be elevated. Though the inversion does not look too strong, so
any complex of storms that develop may produce strong outflow and
resulting damaging wind gusts. There may also be some quarter size
hail as the effective shear increases to 35 to 40 KTS. Areas where
storms train later Tonight and through the early morning hours may
see some localized flooding. Forecast sounding PWs are nearly 2
inches. Most CAMs show the possible training of thunderstorms north
of I-70 across the northeast counties of the CWA. The complex of
storms should push southeast of the CWA after 9Z WED.


Wednesday through Thursday:

The H5 ridge across the southwest US will amplify northward across
the Great Basin. This will cause the mid-level flow to become
northwesterly. Minor perturbation embedded within the northwest flow
may provide enough ascent for thunderstorms to develop across NE
along a secondary cold front. There remains uncertainty where
thunderstorms will develop across NE. The 12Z HRRR forecast
thunderstorms to develop across southeast NE, which may just clip
our northeast counties. Other CAMs, such as the RRFS show storms
developing farther west across southern NE and moving southeast into
the northern counties of the CWA. The environment across northern KS
Wednesday afternoon will have MLCAPE values of  1500-2200 J/KG and
effective shear of 45 KTS. Some of these storms may have mid-level
mesocyclones which will bring a risk of larger hail. But there
remains uncertainty on where these storms will develop and if they
will weaken by the time they reach the northern counties of the CWA
by the early evening hours.

Thursday, we may see a break in the showers and thunderstorms as the
first perturbations shifts southeast across MO. So expect dry
conditions.

Highs Wednesday and Thursday will be in the lower 80s north to upper
80s south.

Thursday night through Friday night:

The upper ridge will shift east into the central Rockies. The
extended range models are in good agreement with an H5 trough
digging southeast from the northern high Plains into the upper
Midwest and MS River Valley. The stronger ascent ahead of the H5
trough will cause scattered showers and thunderstorms to develop
across the CWA Friday afternoon into Friday night.

Saturday through Tuesday:

The H5 ridge will shift east into the southern and central high
Plains on Saturday and Sunday. The H5 ridge will flatten a bit and
mid level perturbations will round the ridge axis Sunday through
Tuesday. There will be chances for for showers and thunderstorms
Sunday through Monday. A back door cold front will push southwest
across the CWA Monday afternoon as an H5 trough amplifies across the
east central conus. The better chances for showers and thunderstorms
will shift south and west of the CWA on Tuesday. There will not be
much of a cool down as high temperatures remain in the upper 80s to
lower 90s.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 640 PM CDT Tue Aug 18 2026

VFR at all TAF sites through the TAF period. Showers and
thunderstorms are likely tonight, but coverage and timing are still a
bit ambiguous at this point. A few different rounds of storms may be
possible. The first could start as early as 02z, with the more likely
round/time closer to 06z. There may be a break from around 08z to 14z
before another line of showers and storms moves in from Nebraska.

&&

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

&&

$$

DISCUSSION...Gargan
AVIATION...Jones