973
FXUS63 KTOP 281919
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
219 PM CDT Sun Apr 28 2024

.KEY MESSAGES...

- Storms exit to the east this afternoon.

- Could be some patchy ground fog Monday morning.

- Active pattern with some potential for severe thunderstorms
  persists for Tuesday through Thursday.

&&

.DISCUSSION...
Issued at 218 PM CDT Sun Apr 28 2024

19Z water vapor imagery showed a closed upper low over western
NEB. The associated surface low was noted in the obs over east
central NEB with a stretching south through northeast and south
central KS. Showers and storms along the boundary have been sub-
severe thanks to cloud cover preventing much in the way of
destabilization ahead of the front. This activity along with the
surface front is forecast to be east of the forecast area by
00Z. Clearing skies and diminishing surface winds may allow from
some ground fog to develop Monday morning. Forecast soundings
from the RAP and NAM have not been that bullish on fog in part
to some wind at the top of the boundary layer and drier
dewpoints moving in from the northwest. But given recent rains
and not much mixing of the boundary layer this afternoon, think
the models may be under doing the fog potential. Have only added
some patchy fog in the favorable low lying areas for now, but
later shifts may need to reevaluate the potential for fog.

Monday brings a break from the thunderstorm activity with subsidence
behind the exiting wave providing mostly sunny skies. With good
insolation have bumped up highs a few degrees with middle 70s
expected for most locations. There are signs from the operational
models for some weak warm air advection developing Monday evening.
Moisture return looks muted so don`t think it will amount to much,
but it is something to keep an eye on nonetheless.

Better moisture return develops Tuesday and through mid-week. Models
are in good agreement with a shortwave passing mainly north of the
forecast area into Tuesday evening. While the better dynamics look
to stay north of the area, the wave is progged to push a frontal
boundary into the area with a narrow axis of CAPE between 2000 and
3000 J/kg developing ahead of the front. Bulk shear of 40KT to 50KT
maybe enough for some organized updrafts. So will need to keep an
eye on convection late in the afternoon Tuesday and Tuesday night.

A moist and unstable boundary layer is progged to remain in place
for Wednesday, but forcing for vertical motion is not obvious.
Shower and thunderstorm activity could be higher Wednesday night as
the low level jet increases and provides some lift for convection to
form on. Another frontal system is forecast to move through the
central plains Thursday as a more amplified shortwave trough
propagates east. There is good agreement in the models with the
timing of the front so the NBM has some high POPs with this feature.
GFS forecast of 0-6km bulk shear is less than stellar for severe
weather, probably due to a relatively weak wind field forecast. But
given the time of year we`ll need to monitor this for the severe
potential in the coming days.

Operational solutions show the deeper moisture getting displaces to
the east and south for Friday through Sunday. But the model blend
holds onto some small POPs through the weekend indicative of greater
spread from the ensembles. Looking at the 500MB cluster analysis
from the 00Z runs shows that negative height anomalies could end up
anywhere from northern MN to CO. Given the uncertainty, have stuck
with the model blend in what is a low confidence POP forecast. This
increase forecast spread also tends to smooth out temperature
anomalies. But even the operational runs don`t show persistent warm
air advection. So temps generally remain mild with readings near or
a little above normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1202 PM CDT Sun Apr 28 2024

Scattered showers and possibly a thunderstorm will move west to
east through the afternoon and should pass to the east of TOP
and FOE around 22Z. CIGS should also improve above 3KFT once the
SHRA move east. Think there could be some ground fog develop
around dawn Monday. Will keep visibilities MVFR for now since
RAP and NAM forecast soundings don`t completely saturate the
boundary layer.

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Wolters