231
FXUS63 KTOP 181644
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1144 AM CDT Sun Aug 18 2024

.KEY MESSAGES...

- Showers and thunderstorms are possible today (30-50%) and
  tonight (30-55% chance). A few severe storms are not out of
  the question.

- Below normal temperatures to start the workweek before
  temperatures gradually warm into next weekend.

&&

.UPDATE...
Issued at 942 AM CDT Sun Aug 18 2024

Convective cluster across central NEB continues to make steady
progress south in spite of most earlier runs of the CAMs showing
it falling apart. There remains quite a bit of inhibition for
surface or mixed layer parcels (100+ J/kg on the 13Z RAP
forecast soundings) over the forecast area. But the latest RAP
shows the warm air advection with good isentropic assent holding
together into the afternoon. This makes me think we will see the
showers and storms make it into the forecast area but I suspect
the storms will become increasingly elevated. Bulk shear remains
favorable for organized updrafts so there could be some hail
with the storms. But the main concern will be damaging wind
gusts with downdraft CAPE on the order of 1000 J/kg. Have
increased POPs across the area this afternoon for scattered
coverage and will continue to monitor trends.

&&

.DISCUSSION...
Issued at 319 AM CDT Sun Aug 18 2024

Upper ridging persists across the Southern Plains and Desert
Southwest this morning with a couple of perturbations rounding the
ridge. Surface high pressure is in control of the middle of the
CONUS, keeping conditions across the forecast area benign overnight.
Lift associated with the aforementioned waves along with isentropic
ascent have generated showers and storms across South Dakota and
Nebraska. As these features continue around the ridge, sufficient
lift and saturation in the mid-levels will support the development
of showers and storms later this morning into the afternoon.
Uncertainty remains in coverage and intensity of storms with CAMs
showing a wide variety of solutions. Several CAMs show a complex of
storms moving along the instability gradient into northeast Kansas.
Others suggest a more scattered natured to convection with recent
runs of the HRRR being an outlier solution, showing little to no
precipitation across the area through the day. The passing waves are
fairly weak and isentropic ascent becomes better focused across
eastern Kansas this afternoon and evening. This supports
isolated to scattered storms through the afternoon and evening
as the most probable solution. Elevated instability of 500-1000
J/kg coupled with 45-50kts of effective shear would support a
low-end severe threat and the strongest storms could produce
hail up to quarter size and damaging wind gusts. If an organized
MCS moves into the area, the potential for severe storms
increases with damaging wind gusts being the main hazard.

CAMs are in good agreement with additional storms developing this
evening and overnight as a slightly stronger wave progresses
southeast and isentropic ascent increases. Instability is progged to
be weak (<500 J/kg) which should preclude any severe weather
potential.

A surface high builds south on Monday and Tuesday bringing in drier
air and keeping temperatures in the 80s. Another wave rounds the
ridge Monday night into Tuesday, bringing a small chance of
precipitation across central Kansas. Upper ridging builds overhead
Wednesday with gradually warming temperatures and dry conditions
into next weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1144 AM CDT Sun Aug 18 2024

CAMs still want to weaken the convection as it moves southeast
and have generally be a little to far northeast with the track
of the stronger cells. Forecast soundings still show a fair
amount of inhibition but think elevated showers and
thunderstorms will be able to ride the instability gradient
southeast. Have adjusted the track of the CAMs southwest which
would put the terminals in line for some TS. They have shown a
tendency to weaken over the last hour or so and think the
most likely impact at the terminals will be some temporary
gusty winds of 20KT to 25KT. Have kept CIGS VFR but visibility
will probably drop with the rain for a brief period of time.
Once the afternoon convection moves off, additional TS are
expected to redevelop overnight with the low level jet. There
has been some variability in the location of the narrow axis of
TS so confidence in impacts at the terminals are only medium
for now.


&&

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

&&

$$

UPDATE...Wolters
DISCUSSION...Flanagan
AVIATION...Wolters