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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



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