419
FXUS63 KTOP 211925
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
225 PM CDT Sat Sep 21 2024

.KEY MESSAGES...

- Widespread rain and T-storms tonight with some severe risk
  this evening and heavy rains overnight.

- Much cooler weather arrives on Sunday and lasts into next
  week.


&&

.DISCUSSION...
Issued at 157 PM CDT Sat Sep 21 2024

A large scale upper low was located across northeast AZ this
afternoon while another upper wave was located across the ND/MN
region. The northern stream upper wave has pushed a cold front
into northwest KS this afternoon. At 19Z the sfc map showed low
pressure around CNK with a sfc trough extending southwest
toward Medicine Lodge and the cold front approaching Hays.
Dewpoints were in the upper 60s to around 70 in the warm sector
while PWATs were approaching 2" which would be near record
values for the date across northeast KS.

Latest mesoanalysis shows MLCAPE of 1500-2500j/kg with around
100 CINH remaining along with effective shear of 25-35kts.
Forcing ahead of the upper system is already supporting t-storm
development across the OK Panhandle and that area of
lift/convection is expected to move ENE toward the area later
this afternoon/evening. Another area to watch is along the
actual front across north central KS into southern NE where
additional storms should develop later this afternoon into this
evening. This area of storms could impact parts of the area as
well with some risk for hail/wind at least for several hours
this evening.

The overall scenario should see increasing storm development
from the southwest ahead of the upper low in the mixed unstable
but perhaps still capped atmosphere from the southwest along
with additional storm development along the front this evening.
Both areas of convection should eventually yield a larger area
of rain and t-storms as the upper low approaches and the LLJ
increases this evening. Heavy rains will occur and areas of 1-2"
should be common tonight with some receiving 2-3" or more
depending on how the convective area evolves especially this
evening through midnight. Cannot rule out some flash flood risk
in urban areas if training sets up however given how
exceptionally dry it has been the creek/river flood risk remains
low.

After midnight the models suggest that the LLJ/winds in the
925-850 mb layer should veer and focus the better low level
convergence to our east and MUCAPE values are forecast to drop
to below 1000j/kg. This should result in more rain and embedded
thunder after midnight into Sunday morning as the upper low
gradually emerges and weakens. Expect a much cooler Sunday with
remnant showers and the cooler weather will stick around into at
least early next week with below avg highs in the 60s and 70s
expected.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1144 AM CDT Sat Sep 21 2024

VFR conditions will persist until after 00Z when thunderstorms
will develop along a cold front mainly to the northwest of the
TAF sites and move across the area through 6Z. Exact coverage
and location of the storms remains somewhat in question so have
inserted VCTS in that time frame. As the night wears on rainfall
coverage should increase with occasional rain and sct tsra
expected overnight through at least 12z. As winds shift to the
north and the cold front passes expect CIGS to drop into the IFR
category toward 12z Sunday.

&&

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

&&

$$

DISCUSSION...Omitt
AVIATION...Omitt