-- Discussion containing changed information from previous version are highlighted. --
598
FXUS63 KTOP 211735
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1235 PM CDT Fri Jun 21 2024

.KEY MESSAGES...

- Isolated showers and storms may develop by mid-day. Severe
  storms are unlikely (less than 10 percent).

- A better chance for thunderstorms is forecast for Saturday
  evening. The stronger storms could be capable of damaging wind
  gusts.

- Excessive heat could develop for Monday and Tuesday of next
  week.

&&

.DISCUSSION...
Issued at 237 AM CDT Fri Jun 21 2024

07Z water vapor showed the upper ridge nosing into central TX
while an upper trough propagated east over NV. This placed the
stronger westerlies across the northern plains. Surface obs had
high pressure centered over the MS river valley with low
pressure along the lee of the central Rockies. The pattern
favored southerly low level flow and dewpoints holding around 70
degrees F.

Models prog little in the way of synoptic forcing with the stronger
mid and upper level flow remaining northeast of the forecast area.
But the warm moist boundary layer is expected to become
conditionally unstable by mid day with little inhibition and CAPE
values up to 2000 J/kg. Because of this and a couple of the CAMs
showing isolated showers developing by mid-day, have kept some
slight chance POPs in the forecast for today. Since there isn`t a
lot of forcing or a focus for lift, think the shower activity should
remain isolated with most areas missing the precip. And deep layer
shear should remain weak so organized severe weather appears
unlikely (less than 10 percent).

A frontal boundary is expected to move into the forecast area
Saturday afternoon as a shortwave trough passes to the north of the
forecast area. Again a warm moist airmass ahead of the boundary is
progged to have little CIN. And with some convergence along the
boundary, most guidance is developing precip by the early evening
Saturday. Again deep layer shear is forecast to be on the modest
side, but MUCAPE could be between 3000 and 4000 J/kg could support
some damaging wind gusts with any of the stronger updrafts. NAM
forecast soundings over northeast KS suggest downdraft CAPE could be
as high as 1200 J/kg.

The GFS and ECMWF show the potential for another frontal system to
move into the region late Tuesday and Tuesday night as a shortwave
moves across the northern plains. Again an unstable airmass with
little inhibition is progged ahead of this boundary. So the forecast
keeps some chance POPs in the 30 to 50 percent range mainly for
Tuesday evening.

Summer time temperatures are forecast to stay with us for several
days and the NBM shows there is not a lot of spread among the
various solutions for highs and lows through the weekend. The
forecast standard deviations increase for Tuesday and think this may
be a result of timing differences with the boundary. But the
operational solutions still support the overall forecast from the
NBM. The concern with highs in the upper 90s and around 100 for
Monday and Tuesday with low level moisture remaining in place is for
excessive heat to develop. The forecast has heat indices between 100
and 110 each afternoon and an experimental heat risk product from
NCEP shows all of the area in the major risk (level 3 of 4)
category. So a heat advisory may become necessary in the coming
days. Fortunately the excessive heat looks to break by Wednesday as
weak surface ridging moves in Wednesday and the upper ridge
redevelops over the southwest.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
-- Changed Discussion --
Issued at 1234 PM CDT Fri Jun 21 2024

Main aviation hazard over the period will be isolated showers
and a few rumbles of thunder this afternoon within the developed
cu field. Added mention of VCTS to account for the scattered
storms across the area today. There will be some marginal LLWS
overnight at all terminals, but kept out of the TAF since the BL
should remain mixed with low-level winds fairly unidirectional.
Later in the TAF, south/southwest winds will increase mid
morning tomorrow ahead of a frontal boundary with gusts upwards
of 30 mph.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Griesemer