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ACUS02 KWNS 061728

SWODY2

SPC AC 061726



Day 2 Convective Outlook  

NWS Storm Prediction Center Norman OK

1226 PM CDT Sat Apr 06 2024



Valid 071200Z - 081200Z



...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF

FAR EAST TEXAS INTO THE LOWER/MID MISSISSIPPI VALLEY...



...SUMMARY...

Isolated strong to severe thunderstorms appear possible during the

late afternoon to mid-evening Sunday from parts of far east Texas

into the lower/mid Mississippi Valley.



...Synopsis...

A deep, closed upper cyclone centered over NE/SD Sunday morning

should gradually weaken as it moves slowly east-northeastward across

the northern Plains and Upper Midwest. Similarly, a sub-990 mb

surface low is forecast to occlude as it develops towards IA/MN

through the period. A composite front/dryline will advance eastward

across parts of the lower/mid MS Valley through Sunday evening.

Appreciable low-level moisture, characterized by generally 60s

surface dewpoints, will attempt to advance northward ahead of this

boundary, perhaps reaching the western KY/TN vicinity by late Sunday

afternoon.



...Far East Texas into the Lower/Mid Mississippi Valley...

The environment ahead of the front/dryline should become at least

weakly unstable through the day as diurnal heating acts on the

gradually moistening low-level airmass. Still, modest mid-level

lapse rates should temper the degree of instability that can develop

through peak heating, with most guidance suggesting MLCAPE will

reach 500-1000 J/kg. Strong deep-layer shear around 45-55 kt will

support thunderstorm organization with any convection that can form,

with some potential for a supercell or two. Isolated large hail and

strong/damaging winds should be the main threats with the more

robust thunderstorms that can develop and persist from parts of far

east TX into the lower/mid MS Valley along/ahead of the front. The

best time frame for this severe potential should focus from late

Sunday afternoon through evening (about 21Z to 03Z). Given

sufficient low-level shear, a tornado or two also appears possible,

primarily if a supercell can be maintained.



The severe potential is expected to wane through the evening hours

as thunderstorms spread eastward into a less favorable thermodynamic

environment. The overall coverage of severe thunderstorms will

probably remain fairly isolated, with neutral mid-level height

tendencies and weak large-scale ascent present south of the

occluding cyclone. Confidence in a more concentrated corridor of

severe hail and/or tornado risk, associated mainly with supercell

potential, remains too low to include greater severe probabilities

with this update.



...Iowa into Northeastern Missouri and Western Illinois...

An occluded front should extend eastward from the deep surface low

across parts of IA into northeastern MO and western IL through

Sunday afternoon. While low-level moisture will remain limited

across these areas, some steepening of low-level lapse rates is

anticipated along/south of the boundary with daytime heating.

Enhanced near-surface vorticity along the occluded front could

support the potential for a landspout/non-supercell tornado,

assuming sufficient boundary-layer instability is present to support

low-topped convection. At this point, confidence in this scenario

occurring is not high enough to include low tornado probabilities.



..Gleason.. 04/06/2024



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