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515
FXUS63 KTOP 171038
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
538 AM CDT Tue Sep 17 2024

.KEY MESSAGES...

- Strong thunderstorms are possible Wednesday and Thursday.

- Temperatures remain above normal through Friday.

- The best chance for rain is expected Saturday and Saturday
  night. Parts of the forecast area could see around a half to
  one inch of rain.

&&

.DISCUSSION...
Issued at 244 AM CDT Tue Sep 17 2024

07Z water vapor imagery showed a closed upper low over the
Sierra Nevadas with a low amplitude upper ridge over the
southern plains. The surface pattern, with troughing in the lee
of the Rockies and ridging east of the Mississippi River,
favored continued low level southerly flow and mild temps
currently across the Great Plains.

The 06Z RAP continues to show isentropic lift persisting across
north central Kansas through the morning. With some signal from the
CAMs and the HREF of lingering showers and storms, have kept some
scattered wording in the forecast through the morning for areas west
and north of Manhattan. The lingering clouds could also hold highs a
few degrees lower that otherwise would occur similar to yesterday.
So have highs in the mid 80s where clouds and morning rain are most
likely with highs near 90 elsewhere.

There continues to be s signal for additional thunderstorms late
tonight and Wednesday morning as shortwave energy lifts into the
northern plains. Initially elevated instability around 1000 J/kg
could cause some storms to be strong. But 0-6km bulk shear generally
less than 30KT is expected to limit severe potential. Morning storms
should fall apart and models want to recover the boundary layer in
their wake with surface CAPE of 2500 J/kg possible. Bulk shear
remains marginal for supercell storm structure, but there could be
enough instability for pulse severe storms. It is noteworthy that
there isn`t a great deal of forcing or lift progged so the risk for
severe storms Wednesday afternoon and evening appears to be
conditional on storm development.

Shortwave ridging is progged for Thursday, but a weak boundary may
slide into the forecast area by peak heating. Forecast soundings
show potentially MLCAPE values of 2000 to 3000 J/kg ahead of this
boundary. Again bulk shear looks to be 30KT or less. However a hot
and deeply mixed boundary layer could favor damaging wind gusts if
storms develop along the boundary. Forecast soundings suggest
downdraft CAPE could approach 2000 J/kg. Aside from the convective
potential, strong southwesterly winds are expected to advect hot air
into northeast KS and highs are forecast to be in the lower to
middle 90s.

Operational models continue to show the best precip potential to
impact the area Saturday and Saturday night as another upper wave
lifts through the central plains. The slightly slower progression
has caused POPs to trend lower for Friday. The NBM keeps some likely
POPs (around 60%) in the forecast for Saturday and Saturday night.
Think small differences in the timing and location of surface
boundaries is the reason the blend isn`t giving higher POPs. Will
see if later runs trend higher.

Confidence in the forecast diminishes for Sunday night and Monday as
models diverge on the synoptic scale. The lower predictability as
models appear to be struggling with a change in pattern, makes it
difficult to deviate from the NBM. So have kept some low end POPs
but this may change in the coming days. Temps should be cooler for
the weekend and into next week with models bringing a cold front
through the area on Sunday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
-- Changed Discussion --
Issued at 538 AM CDT Tue Sep 17 2024

Not much change to the forecast from 6hrs ago. Isentropic lift
is progged to persist across north central KS through midday.
Will keep a VCSH at MHK for a stray shower. This activity should
remain west and north of TOP and FOE. Otherwise models just show
some mid and high clouds. Precip Wednesday morning looks to
remain west of the terminals through 12Z.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Wolters