910
FXUS63 KTOP 202226
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
526 PM CDT Fri Sep 20 2024

.KEY MESSAGES...

- Chances for thunderstorms this evening, some of which could be
  strong to severe.

- Rainfall becomes more widespread Saturday night through Sunday
  with most places looking to see at least an inch by Sunday
  night. Can`t rule out a few severe storms, but confidence
  remains low.

- A much cooler and more fall-like pattern is in place for next
  week with dry conditions.

&&

.MESOSCALE...
Issued at 526 PM CDT Fri Sep 20 2024

A cluster of storms has developed across southwest Kansas in
response to a subtle shortwave rotating around the Southern Plains
ridge. 50-60MPH wind gusts have been reported with these storms
given a favorable parameter space featuring 2500-3000 J/kg of
surface-based CAPE, effective shear of 25-35 kts, and DCAPE values
of 1000-1200 J/kg. This convection is favored to continue northeast
before turning more eastward with time, following the trajectory of
the aforementioned shortwave. Extrapolation of the current radar
brings these storms into Ottawa and Dickinson Counties around 7PM
before convection pushes east, mainly along and south of Interstate
70. Initial clusters of storms could be strong to severe with
damaging wind gusts (60-65mph) being the main hazard, but hail
around 1" in diameter is also possible. Convection is likely to
weaken as it pushes east and eventually diminishes and/or moves
out of the area by midnight.

&&

.DISCUSSION...
Issued at 251 PM CDT Fri Sep 20 2024

Water vapor imagery at 19Z depicts the main upper trough slowly
swinging through southern CA with moisture streaming ahead of it
into the Central Plains. The surface front that moved through the
area yesterday has remained stalled (and diffuse) in southern KS
today. This boundary will move north as a warm front this evening
and overnight with shortwave energy ahead of the main trough looking
to help spark some convection during this time frame. Confidence in
storms and their location is not very high given that CAM guidance
hasn`t shown much consistency between the different models or from
run to run. They have at least been consistent in developing a
cluster of storms in southwest or south central KS late this
afternoon before moving northeast. An instability axis is progged to
move across the area late this evening into the overnight hours with
MUCAPE of 1000-2000 J/kg supporting some elevated storms with just
enough shear to support a few stronger updrafts. For this reason, a
couple of severe storms with wind and/or hail can`t be ruled out,
but confidence is on the low side.

After any remaining convection moves out tomorrow morning, there
should be a lull in the activity in the afternoon, particularly
along and south of I-70. As the northern stream upper trough passes
through the Northern Plains, a cold front approaches the area by mid
to late afternoon, which could help to trigger a few thunderstorms
near the KS/NE border during the late afternoon to early evening.
Instability and shear parameters may again be just enough to support
severe weather if a strong enough updraft can get going, but
confidence is still low. The best chances for rain overall come
Saturday night through Sunday as the southern stream trough moves
through the area and increases DCVA as a result. This is also the
time frame with the best moisture quality with Pwats looking to be
between 1.5 and 2" across the area, highest in eastern KS. QPF has
overall trended down area-wide and some ensemble solutions are
keeping amounts under an inch in some locations. That said, amounts
of at least 1 inch are still favored area-wide with locations north
of I-70 seeing the highest amounts, which could exceed 1.5".

Between the clouds and rain and CAA behind the cold front, Sunday
brings the start to cooler conditions next week. Parts of northern
KS may struggle to get above 60, while parts of east central KS
could still see highs in the mid 70s before the 850mb front makes it
through the area. There may be some lingering rain in far eastern KS
Monday morning, though all areas see cooler highs in the 60s in the
wake of the front. The pattern favors moderating temperatures and
dry weather the rest of the week with highs in the 70s and lows in
the 50s, much closer to seasonal norms.

&&


.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1153 AM CDT Fri Sep 20 2024

VFR conditions are forecast through the period. Main challenge
is monitoring TS development in southwestern KS this evening and
the evolution of any activity that may move into northeastern
KS late tonight into early Saturday. Right now, probabilities
for storms are too low at any one location to include in TAFs so
have opted to leave out mention at this time. Still expecting
mid to high clouds to increase at least.

&&

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

&&

$$

MESOSCALE...Flanagan
DISCUSSION...Picha
AVIATION...Picha