297
ACUS01 KWNS 280104
SWODY1
SPC AC 280102

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0802 PM CDT Sat Apr 27 2024

Valid 280100Z - 281200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTH TEXAS...OKLAHOMA...FAR SOUTHEAST KANSAS AND FAR SOUTHWEST
MISSOURI...

...SUMMARY...
Severe thunderstorms are expected this evening into tonight across
much of the southern Plains and lower Missouri Valley. The greatest
severe threat will be from north Texas northeastward through
Oklahoma into far southeast Kansas and southwest Missouri. All
hazards will be possible including tornadoes, with some strong,
damaging wind gusts above 70 mph, and very large hail exceeding 2
inches in diameter. Scattered severe storms will also be possible
later this evening in parts of west-central and southwest Texas.
Isolated severe storms are also expected to occur this evening in
parts of the mid to upper Mississippi Valley northeastward into the
Great Lakes.

...Southern Plains/Lower Missouri Valley...
An upper-level trough, evident on water vapor imagery, is
approaching the southern High Plains. An associated 60 to 80 knot
mid-level jet streak is currently ejecting northeastward into the
southern Plains. This feature has been slower than forecast, and
convective coverage across much of the southern Plains has been slow
to increase. The lack of convection across much of Oklahoma has
likely been a result of a capping inversion, that is evident on the
00Z Norman sounding just below 700 mb. As the mid-level jet streak
moves over the southern Plains this evening, this cap is expected to
weaken and the low-level jet will continue to strengthen. This
should result in a ramp up in convective coverage over the next 2 to
3 hours, with a line of strong to severe storms developing along the
western edge of the low-level jet from north Texas through central
and northeast Oklahoma into southwest Missouri.

The overall environment from north Texas into Oklahoma and southwest
Missouri is characterized by moderate instability (MLCAPE around
2500 J/kg), 0-6 km shear near 60 knots, and 700 to 500 mb lapse
rates from 8 to 8.5 C/km. This should continue to support the
development of supercells with large hail this evening. The more
intense supercells could produce hailstones greater than 2 inches in
diameter. In addition, the 00Z sounding from Norman has 0-3 km
storm-relative helicity around 400 m2/s2. This will also be
favorable for tornadoes. The tornado threat is expected to be
greatest with either supercells embedded in the line, or with
discrete cells ahead of the line. Strong tornadoes will be possible.
As the QLCS organizes this evening, tornadoes may also develop with
rotating elements within the line itself. This linear MCS is
expected to produce widespread wind damage and large hail from north
Texas into central and eastern Oklahoma, and west-central/southwest
Missouri. The severe threat will likely continue well into the
overnight period.

...Mid to Upper Mississippi Valley/Great Lakes...
The latest surface analysis shows a front from eastern Iowa
northeastward into the western Great Lakes. A moist airmass is
located to the southeast of the front, where surface dewpoints are
mostly from near 60 into the mid 60s F. The RAP is analyzing MLCAPE
in the 1000 to 2000 J/kg range, and moderate deep-layer shear across
much of this airmass near the front. The latest WSR-88D VWP from
Chicago has 0-6 km shear near 40 knots, and strong speed shear in
the low-levels. RAP forecast soundings this evening in the vicinity
also have steep lapse rates. This environment should support
supercell development with large hail. Wind damage will also be
possible with supercells and short bowing line segments.

..Broyles.. 04/28/2024

$$