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ACUS01 KWNS 260527

SWODY1

SPC AC 260525



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

1225 AM CDT Fri Apr 26 2024



Valid 261200Z - 271200Z



...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF

THE LOWER TO MID MISSOURI VALLEY...AND CENTRAL PLAINS...



...SUMMARY...

Severe thunderstorms will be likely today from parts of eastern

Nebraska into western and central Iowa, southward into eastern

Kansas and Northwest Missouri. All hazards will be possible,

including tornadoes with some potentially strong, very large hail

over two inches in diameter, and wind damage. A more isolated severe

threat will extend south-southwestward into parts of the southern

Plains, Ozarks and Ark-La-Tex from late afternoon into the evening.



...Significant Severe Weather Event Expected Today Across Parts of

The Lower To Mid Missouri Valley and Central Plains...



...Lower to Mid Missouri Valley/Central Plains...

A negatively tilted upper-level trough will move northeastward

across the mid Missouri Valley today, as an associated 50 to 60 knot

mid-level jet translates northeastward through the base of the

system. At the surface, a low will deepen and move northeastward

across Nebraska. A north-to-south corridor of maximized low-level

moisture, with surface dewpoints in the mid 60s F, will be in place

by midday across eastern Kansas and southeast Nebraska. Moderate

instability will develop across most of the moist sector by

afternoon, with thunderstorms first developing in east-central

Nebraska around midday. These storms are expected to move eastward

across eastern Nebraska during the afternoon, as convective coverage

gradually expands south-southeastward into eastern Kansas. The

environment will be favorable for severe storms, with several

clusters moving eastward from Nebraska into Iowa, and from Kansas

into Missouri during the late afternoon and early evening.



Several factors appear to be supportive of a significant tornado

event today across eastern part of the central Plains into the lower

to mid Missouri Valley. The first is that a 60 to 70 knot mid-level

jet, associated with a negatively tilted trough, will become coupled

with a 50 to 60 knot low-level jet over a moist and unstable warm

sector. A second factor is that a band of large-scale ascent will

move over the warm sector this afternoon, as the capping inversion

diminishes. Steep low to mid-level lapse rates are forecast to

spread over the warm sector, which combined with moderate deep-layer

shear, will be favorable supercells with strong updrafts at

relatively low-levels within the storms. In addition, 0-3 km

storm-relative helicity is forecast to increase into the 300 to 400

m2/s2 range along the western edge of the low-level jet, which will

be favorable for strong tornadoes. A few tornadic supercells are

expected, with the greatest potential from near Omaha eastward to

near Des Moines and southward to south of the Kansas City Metro.

Along this corridor, the more dominant supercell storms will also

have a potential to produce hailstones greater than 2 inches in

diameter and wind damage. The severe threat is expected to shift

eastward across Iowa and Missouri during the mid to late evening,

with an isolated severe threat continuing after midnight.



...Southern Plains/Ozarks/Ark-La-Tex...

Southwesterly mid-level flow will be in place today across the

south-central U.S., with a broad moist warm sector located from the

southern Plains eastward into the Ark-La-Tex and Ozarks. An MCS is

expected to move across central and eastern Oklahoma during the

morning, which will stabilize the airmass. However, instability is

forecast to redevelop across Oklahoma by afternoon. Further south,

strong instability is expected to develop across much of central and

east Texas by afternoon, where MLCAPE should peak in the 2500 to

3500 J/kg range. Although large-scale ascent will be weak across

most of the southern Plains, the cap is expected to diminish and

isolated thunderstorms appear likely to develop by late afternoon. A

severe threat is expected to persist along and near the instability

axis during the early to mid evening.



RAP forecast soundings at 00Z/Saturday along and near the

instability axis from southeast/south-central Oklahoma into

north-central Texas have 0-6 km shear between 40 and 50 knots. Low

to mid-level lapse rates will become steepest in areas that heat up

the most. The environment will likely be favorable for isolated

supercells with large hail. By late afternoon, forecast soundings

also have 0-3 Km storm-relative helicity reaching 200 m2/s2

suggesting that an isolated tornado threat will be possible. The

tornado threat is expected to be the greatest across eastern

Oklahoma, northeast Texas and western Arkansas, as the low-level jet

ramps up in the early evening. Wind damage will also be possible

with storms that develop.



..Broyles/Thornton.. 04/26/2024



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