608
FXUS63 KTOP 161048
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
548 AM CDT Mon Sep 16 2024

.KEY MESSAGES...

- Above normal temperatures are forecast to persist through the
  workweek.

- There is a 30 to 60 percent chance of showers and
  thunderstorms Wednesday morning.

- Better chances (around 60 percent) for widespread rain and
  storms are forecast Friday night through Saturday night.

&&

.DISCUSSION...
Issued at 234 AM CDT Mon Sep 16 2024

07Z water vapor imagery showed a weak upper low over the lower
MS river valley with a closed low over northern CA. This left
weak ridging from the southern Rockies into the middle MO river
valley and a generally confluent pattern over northeast KS.
Surface obs showed low pressure along the lee of the Rockies
with high pressure east of the MS river. This has allowed
southerly low level flow to persist.

There are not a lot of changes to the forecast. Models show a weakly
forced pattern remaining over the forecast area through Tuesday with
POPs mainly driven by some mid level warm air advection and
isentropic lift. This lift is progged to be strongest during the
morning hours today and Tuesday. But elevated instability remains
modest and bulk shear looks to be weak, around 20KT. Overall CAMs
have backed off on developing elevated showers and storms this
morning and especially Tuesday when the HREF has probabilities
around 10 to 20 percent. Have kept some small POPs through the late
morning today with some convection already occurring to the west.
But followed the NBM and lowered POPs for Tuesday morning. With the
forcing remaining rather subtle the next few days, confidence in
the POP forecast will remain on the low side.

The overall ideas from the deterministic solutions are pretty much
unchanged through the end of the week and into the weekend. A
shortwave trough lifting into the northern plains Tuesday night
could clip north central KS with showers and storms Wednesday
morning. The better dynamics look to lift north but most guidance is
developing some QPF over north central KS. Because of this POPs from
the NBM have trended higher with likely chances across north central
KS. Don`t think 60 percent chances are unreasonable, but the lack of
synoptic scale forcing and lift brings into question the coverage of
precip Wednesday.

Models show a better organized upper wave lifting through northwest
KS over the weekend. While the trend has been to slow the
progression of the upper wave, there is not a lot of disagreement
from the operational solutions. And ensemble data from the ECMWF and
GFS continue to show high probabilities, 80 percent or greater, of
measurable precip on Saturday. The NBM appears to be catching up
with this idea and now has 50 to 70 percent chance POPs for late
Friday through Saturday night. So there is increasing confidence in
precipitation chances this weekend, and I wouldn`t be surprised if
POPs trend higher in the coming days.

The pattern through the workweek supports southerly low level winds
and continued warm air advection. This should keep temperatures
above normal with highs in the middle 80s to around 90. The warmest
day looks to be Thursday as models strengthen southwesterly flow in
the wake of the initial shortwave. Highs could end up in the lower
to middle 90s on Thursday. Rain chances and increased cloud cover
are expected to keep temperatures cooler for the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 548 AM CDT Mon Sep 16 2024

The latest RAP and NAM solutions keep the best isentropic lift
to the west of MHK and the CAMs want to keep convection west of
MHK too. Will be watching TS closely but for now will keep TS
out of the MHK terminal this morning. Otherwise storms are
expected to fall apart around mid-day with weakening lift and
VFR conditions are expected to prevail.

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Wolters