979
FXUS63 KTOP 030804
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
304 AM CDT Wed Sep 3 2025

.KEY MESSAGES...

- Potential for a few severe thunderstorms this afternoon and
  evening as a cold front moves through the area. Large hail
  with isolated damaging wind gusts will be the primary hazards.

- Cool temperatures with occasional rain showers Thursday night
  through Friday.

- The weekend looks dry with highs in the lower to mid 70s.

&&

.DISCUSSION...
Issued at 247 AM CDT Wed Sep 3 2025

An amplified upper level trough was located over south central
Canada on the west side of a broad upper trough located across the
eastern US. An upper level low remained stationary across the
eastern Pacific off the WA/OR coast.

The 6z surface map showed a cold front pushing south across south
central SD and southern MN. surface winds were light and variable
across the CWA with patchy ground fog around MHK.

Today through Tonight:

The surface front across the northern Plains will move southward
across NE during the remainder of the morning hours and then into
the CWA by the early afternoon hours. The amplified H5 trough across
south central Canada will dig southeast into the northern Great
Lakes. An H5 trough axis on the west side of the H5 low will move
southeast across NE/ eastern KS/MO through the late afternoon and
evening hours. The combination of surface convergence along the
front and DCVA ahead of the H5 trough will cause isolated to
scattered thunderstorms to develop after 20Z along the I-70
corridor, which most CAMs are in agreement with this solution.
The environment ahead of the front will consist of MLCAPE of
1200-2000 J/kG and 40 to 50 KTS of effective shear. Thus, some
of the initial updrafts may develop rotation which could produce
both large hail 1 to 2 inches and damaging wind gusts. The low-
level vertical wind shear looks weaker then previous forecasts, and
forecast hodographs have straight line profiles in the 0-3KM
column, thus the horizontal vorticity will be more
perpendicular to the shear vector. therefore the chances for any weak
tornadoes will be extremely low. As the front pushes south of
I-70, like most CAMs show by the late afternoon hours, the
scattered storms will congeal into line segments. DCAPE will be
around 1000 J/KG, thus any line segments or a developing squall
line across the southern counties may have isolated damaging
wind gusts. If there are no rotating updrafts, the larger hail
size threat will diminish. The HRRR and 3KM NAM actually show
the storms weakening as they reach the far southern counties
early this evening. This may be due to the front/outflow
boundary undercutting the updrafts. The front should push
southeast of the CWA by the early evening hours ending any
severe thunderstorm threat. There could be scattered showers and
elevated non-severe storms north of the front through the mid
evening hours across east central KS, until the H5 trough axis
shifts southeast into MO.

Highs Today within the warm sector should reach the lower to mid
80s, with some upper 80s across the southwest counties. west-
southwest winds will shift to the north behind the front and may be
gusty through the late afternoon and early evening hours.

Thursday through Friday:

We will see a break in the weather on Thursday as the first
front pushes southward across OK. A second H5 trough will dig
southeast across the Plains late Thursday night into Friday, on
the west side of the upper low across the northern Great Lakes.
AS the H5 trough digs southeast across NE into northern MO
there will be enough ascent for showers and a few thunderstorms
to develop along a second cold front that will move southward
across the CWA late Thursday night into Friday. Most of the
showers will be post frontal and the moisture return ahead of
this next front will probably consist of residual moisture,
since the richer moisture will be across OK and north TX. There
may be enough instability for a few elevated thunderstorms late
Thursday night into Friday. As the front shifts south into far
southern KS late Friday afternoon the rain should shift
southeast of the CWA.

Highs Thursday ahead of the second front will recover into the mid to
upper 70s. Expect much cooler temperatures on Friday with cloudy
skies, northeast winds, and periods of showers through the
morning into the early afternoon hours. Highs Friday will only
reach the mid to upper 60s.

Friday night through Monday:

The weekend looks dry as a surface ridge builds southeast across
eastern KS and MO. The upper low over the northern Great Lakes will
dampen and shift east across New England and eastern Canada.
The upper low in the eastern Pacific will phase with another H5
trough moving east across the eastern Pacific and amplify as it
moves onshore across the west coast. High temperatures will
reach the lower to mid 70s.

Monday night through Wednesday:

An upper through will dig southward across the west coast of Canada
and the Pacific northwest and amplify the western US Trough. This
will amplify a downstream H5 trough across the Plains by mid
week. There may be a few isolated showers and storms as a lee
trough deepens across the high Plains and richer moisture
advects northward, but if these showers develop, they should
remain isolated under the H5 ridge axis. Highs will slowly warm
into the lower 80s by Wednesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1233 AM CDT Wed Sep 3 2025

All the terminal sites will have lows dropping below the
crossover temperature, so there may be patchy dense fog.
However, a northwest wind of 10 to 15 KTS at 500 FT above the
surface may create enough PBL turbulent mixing to prevent dense
fog but there may be ism - ism visibility with patchy ground
fog at times through 13Z. Isolated storms may form around the
terminals betweeen 20-22Z WED as a cold front moves south across
the terminals, but most CAMs show the convection developing
south of the terminals this afternoon and early evening.

&&

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

&&

$$

DISCUSSION...Gargan
AVIATION...Gargan