587
FXUS63 KTOP 232310
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
510 PM CST Sat Nov 23 2024

.KEY MESSAGES...

- Cooler weather is expected for the start of next week.

- There is a 20 to 30 percent chance for rain and snow Wednesday
  night into Thursday morning. Any snow looks to be light.

- Below normal temperatures set to stick around into next
  weekend.

&&

.DISCUSSION...
Issued at 218 PM CST Sat Nov 23 2024

19Z water vapor imagery showed an upper trough over the Pacific
Northwest with a low amplitude ridge over the central and
northern plains. Surface obs had a trough of low pressure along
the lee of the Rockies with high pressure along the lower MS
river valley. This has allowed a southerly low level flow to
develop today.

The forecast for tonight is for dry weather to continue due to a
lack of synoptic scale forcing and just some high clouds moving in
from the west. Models show enough of a pressure gradient overnight
for southerly winds to hold in the 5 to 15 mph range. This is
expected to keep lows tonight in the lower and middle 40s. The NAM
wants to cool the boundary layer into the upper 30s and as a result
of continued moisture advection, saturates the boundary layer and
spits out some very light QPF in the form of drizzle. The NBM and
ensemble do not support the NAM, which has a bias of being to
aggressive in saturating the boundary layer, keeping lows in the
lower 40s. So have shied away from the NAM solution in the short
term. A relatively warm start to the day Sunday and continued
southerly winds are expected to help highs warm into the middle 60s
across east central KS. Meanwhile a slow moving front is forecast to
move into north central KS by mid-day. Increasing clouds behind a
front and neutral advection may hold highs in the upper 50s for
north central KS.

The front is expected to push southeast of the area Sunday evening
with cold dry air advecting in from the northwest. With zonal flow
developing Monday and Tuesday, dry and cool weather is forecast
which is in line with previous forecasts.

There still remains some spread in ensemble data for the
Thanksgiving Holiday travel window Wednesday and Thursday morning.
This is evident by the last couple runs of the ECMWF showing a
variable track to the shortwave progged to move through the central
US. Meanwhile the latest run of the NBM has trended lower with POPs
and QPF. Think this may be a result of the 00Z operational runs
showing less QPF. But even the 12Z ensemble members are showing
lower probabilities for snow which is around 40 percent for northern
KS, down from about 50 percent. I expect this variability to persist
while the operational runs continue to swing back and forth. But
based on the ensemble runs, which continue to suggest the most
likely solution is a progressive and open wave, think a 20 to 30
percent chance for rain and snow is the best forecast. Most ensemble
members show less than an inch of snow or no snow with only about a
10 percent chance for an inch or more of snow. So impacts from this
system continue to appear minor, especially with the K-State mesonet
indicating ground temps are still in the 40s.

Below normal temps are forecast to persist into next weekend. And
the models are hinting at some possible frontogenetical bands of
precip clipping the area late Friday night or Saturday. Continuity
in these solutions have not been great, so there is little
confidence in adding a POP at this time. But if the bands do form,
temp profiles suggests the precip would be mainly light snow. Will
keep an eye on this in the coming days.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 510 PM CST Sat Nov 23 2024

VFR conditions are expected. South to southeast winds will
persist with a moderate nocturnal low-level jet developing by
03Z. Winds should steadily veer as they increase with height to
result in turbulence more than wind shear. The vast majority of
guidance keeps any limiting ceilings in check and will continue
to forecast this occurrence. A cold front may pass through MHK
late in this forecast.

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Poage