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000
FXUS63 KTOP 251949
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
249 PM CDT Thu Apr 25 2024

.KEY MESSAGES...

- Several rounds of thunderstorms are expected to move across
 the area through Sunday.

- There is a risk for severe weather each day, with the
  greatest risk including tornadoes on Saturday.

- Multiple rounds of heavy rain could lead to isolated flooding.

&&

.DISCUSSION...
Issued at 249 PM CDT Thu Apr 25 2024

19Z water vapor imagery showed an upper trough over the Great
Basin with a shortwave lifting through the four corners region.
At the surface, low pressure was noted in southeast CO with a
warm/stationary front extending through southwest KS and north
central OK. Persistent moisture advection over this boundary has
maintained the elevated showers and thunderstorms across the
forecast area today.

The main focus of the forecast is on the potential for severe
weather in the coming days. 12Z model consistency is good with an
upper low lifting into central NEB Friday morning with a second
upper low coming out into the western plains Saturday night and
Sunday morning. The warm sector with dewpoints in the lower and
middle 60s is expected to lift into northeast KS by Friday afternoon
as the initial upper low lifts to the northwest of the forecast area
with a dry line developing by the afternoon. This warm moist airmass
remains over the area through Saturday night and becomes somewhat
modified by Sunday afternoon. Though there is still expected to be
some moisture lingering across northeast and east central KS Sunday
afternoon. Good environmental shear is progged with a strong wind
field forecast through the weekend and the setup for severe storms
just doesn`t move out of the area until Sunday evening.

The MCS this afternoon is expected to continue to propagate
southeast along the axis of MUCAPE that extends northeast of the
surface warm front. With this having worked over the environment a
little, think there may be a break from the deep moist convection
into the evening, but the CAMs hint at the redevelopment of showers
through the evening. The main point of uncertainty through the
evening is where new convection develops. The HRRR has been
consistent in thunderstorms developing more over northwest KS within
the low level convergence area northeast of the surface low. This
would tend to keep storms mainly north of the forecast area through
the late evening. However by the early morning hours, PVA with the
shortwave should cause development to become more widespread and
move east through the morning. These storms look to be mainly
elevated with a hail and damaging wind risk, but there does appear
to be a narrow axis of surface based instability advecting north
through the morning. If storms develop in this axis of surface based
instability, the risk for a tornado or two will be higher.

By Friday afternoon, forecast soundings from the NAM and RAP show
MUCAPE around 3500 J/kg just ahead of the dryline. Good turning in
the low level winds are progged to create SRH around 200 m2/s2. More
of the models are starting to show a signal for convective
initiation along the dryline in northeast KS though there remains
some uncertainty given the lack of convection from the HRRR this far
south. Supercell thunderstorms would be favored with the potential
for very large hail and perhaps a strong tornado into the evening
across northeast KS thanks to increasing SRH with the strengthening
low level jet. This risk may move east and north of the forecast
area by mid evening with shortwave ridging overspreading the area.

This should lead to a break in the thunderstorm activity heading
into Saturday with the dryline retreating west. The setup for
Saturday looks ominous with forecast soundings showing a capped
boundary layer with large amounts of CAPE (3000 to 4000 J/kg) within
the warm sector east of the dryline. Again good environmental shear
would support supercell thunderstorms and as the low level jet
increases in the early evening, SRH also increases to around 300
m2/s2. So the concern for Saturday afternoon and evening is for
tornadoes, some potentially strong. Shortwave energy is progged to
be lifting over the dryline through peak heating and could be the
trigger for thunderstorm development.

By Sunday, the upper low should be to the north of the forecast area
but a diffuse boundary may still be over eastern KS acting as a focus
for renewed convection. Models are not as strong with the instability
and deep layer shear looks to be a little weaker too. So severe
risks may be a little more marginal. Repeated rounds of heavy
rainfall could cause some flooding problems before the weekend is
over. But confidence in the location of the thunderstorms and where
heavy rain develops is a little to low to pinpoint with a watch at
this time. Right now the heaviest rainfall is forecast for parts of
east central KS, but this could change depending on the short term
evolution of the storms.

For next week, the pattern becomes a little more zonal with
shortwave energy passing through the plains mid-week. With a frontal
boundary in the area, there looks to be another chance for showers
and thunderstorms Tuesday through Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1149 AM CDT Thu Apr 25 2024

There is good agreement among the models for continues southerly
return flow advecting moisture into the area. So confidence in
IFR CIGS moving in is good. CAMs show this initial cluster of
storms moving through the terminals early this afternoon with
activity becoming more isolated by early evening. A shortwave
lifting through NE KS is expected to cause additional TS
development by the early morning hours of Friday. CIGS may
improve Friday as a surface low lifts north, but this looks to
be after 18Z.

&&

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

&&

$$

DISCUSSION...Wolters
AVIATION...Wolters