195
FXUS63 KTOP 060933
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
433 AM CDT Mon May 6 2024

.KEY MESSAGES...

- Dense fog early this morning, generally south of I-70.

- Severe storms are likely this afternoon/evening. Hail up to
  three inches in diameter, winds to 80 mph, a few strong
  tornadoes and isolated flash flooding are all possible.

- Mild and mainly dry the rest of the week.

&&

.DISCUSSION...
Issued at 335 AM CDT Mon May 6 2024

The ingredients are coming together for a higher-end severe
weather event this afternoon and evening. There are two main
scenarios that could play out, one that is more likely and one
that is more impactful:

Scenario One: A line of storms quickly develops across central
Kansas and marches eastward through late afternoon and evening.

This is the most-likely scenario. All model guidance depicts a
robust line of storms developing and moving into Republic, Cloud
and Ottawa Counties in the 4-6 pm timeframe. This is plausible
as shear vectors are generally more parallel off the front which
favors upscale growth and congealing of cold pools quickly
after convective development. Despite cloud cover for most of
the day, ample instability is expected given strong warm/moist
advection ahead of the front and an EML bringing steep mid-level
lapse rates over the area. With effective shear of 50-60 knots,
ML CAPE of 1500-2500 J/Kg, lapse rates of 7-8 C/Km and a
strongly veered wind profile with effective SRH of 200+ M^2/S^2,
all severe hazards are possible, including hail up to three
inches in diameter, wind gusts to 80 mph and tornadoes. As the
line of storms pushes eastward into the evening the hail threat
should subside slightly, but the low-level jet will likely
increase in strength and shear vectors could become more
favorably oriented for QLCS tornado development. The line of
storms is expected to be out of the area by midnight.

Scenario Two: A line of storms quickly develops across central
Kansas, but isolated supercells also develop ahead of the line.

This is the less likely, but more impactful scenario. Everything
that was described in the first scenario would remain true in
this scenario, but isolated supercells would develop out ahead
of the front. As they would not be driven by frontal forcing or
likely have to compete in an environment with other storm
interactions, they would be more free to develop deviant motion.
This would greatly enhance their ability to utilize
environmental vorticity, leading to a higher-end strong tornado
threat and giant hail possibility. Several CAMs depict such a
scenario playing out, but there are a few limiting factors that
make this scenario less likely. First, we may remain capped all
day under a layer of stratus. Second, ascent is mostly co-
located with the front, so without a lifting mechanism, even
without the presence of a cap, initiation would be challenging
at best.

Regardless of what scenario plays out, this has the potential to
be a very impactful severe weather day.

Another potential impact from today`s storms is that of flash
flooding. While very high rain rates are expected given the
impressive thermodynamics and kinematics likely today, storm
motions of 40-50 mph should keep the flash flood threat minimal.
The exception would be if training storms develop or isolated
cells develop ahead of the main front.

After the front moves through today, quiet and mild weather is
favored for the rest of the week. A few low chances for some
showers appear here and there, but no major storm systems look
likely in the near future.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1242 AM CDT Mon May 6 2024

IFR conditions tonight, becoming MVFR by late morning. Low
stratus, fog and drizzle are all likely tonight as warm, moist
advection from the south overspreads the area. There is some
uncertainty as to how low and thick cloud cover will remain
through the day tomorrow, but MVFR conditions are currently
favored. A line of thunderstorms is still favored to move
through after 00z Tuesday.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CDT this morning for KSZ040-
KSZ054-KSZ055-KSZ056-KSZ058-KSZ059.

&&

$$

DISCUSSION...Jones
AVIATION...Jones