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ACUS01 KWNS 252000

SWODY1

SPC AC 251958



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0258 PM CDT Thu Apr 25 2024



Valid 252000Z - 261200Z



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

THE CENTRAL AND SOUTHERN PLAINS...



...SUMMARY...

Very large hail up to 3 inches in diameter and a strong tornado or

two will be possible this evening across western Kansas and

vicinity. Large hail, damaging winds to 70 mph, and a few tornadoes

will be possible this evening and tonight from northwest Texas into

central Oklahoma.



...20Z Update...

The Enhanced Risk across western KS has been expanded to include

more of northwest KS, far northeast CO, and far southwest NE. Based

on recent visible satellite trends, convective initiation appears

imminent across east-central CO along/near a surface dryline.

Additional robust thunderstorm development will likely occur this

afternoon across northeast CO into northwest KS and vicinity as an

upper trough continues ejecting eastward over the central High

Plains. Given moderate buoyancy and strong deep-layer shear, very

large hail (possibly up to around 3 inches) should be the main

threat with initial supercells. By early this evening, strengthening

low-level shear should encourage a greater tornado threat with any

supercells that can persist, especially as this activity interacts

with a warm front across northwest KS. A strong tornado or two

remains a possibility across this area. See Mesoscale Discussion 513

and recently issued Tornado Watch 133 for more details on the severe

threat for this region.



No changes have been made to the separate Enhanced Risk across parts

of northwest TX into southern/central OK. It still appears likely

that convection will develop by 06Z across this region, and quickly

spread east-northeastward through early Friday morning. All severe

hazards still appear possible with this activity, including the

potential for a few nocturnal tornadoes given the forecast strength

of the low-level shear.



In between the two Enhanced Risks (OK/TX Panhandles), there is still

a fair amount of uncertainty regarding how many supercells may

develop along/east of the dryline. Some cu has recently formed over

the northwest TX Panhandle. But, a 19Z special sounding from DDC

still shows substantial capping in place. Regardless, a conditional

threat for supercells posing an isolated threat for very large hail

and perhaps a couple of tornadoes will exist through this evening

across this area.



..Gleason.. 04/25/2024



.PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Apr 25 2024/



...Synopsis...

Morning water vapor imagery shows a negatively-tilted shortwave

trough rotating across UT/AZ, with an associated 70kt mid-level jet

max moving into NM.  This system will eject into the

central/southern Plains this evening/tonight, resulting in multiple

clusters of severe thunderstorm activity.



...Western KS...

A quasi-stationary surface boundary extends from northwest CO into

northwest KS.  Visible imagery shows broken cloud cover across

western KS this morning, with dewpoints in the low 60s to the south

of the front.  Strong heating will likely ensue through the

afternoon, resulting in deepening mixing to the east of the dryline

and eventual isolated thunderstorm development.  CAM solutions

differ significantly on coverage of convection, but it appears

likely that at least isolated supercells will form along the

dryline, capable of very large hail, damaging winds, and a few

tornadoes (possibly strong).  



The confidence of initiation is much higher along the warm front

from northeast CO into northwest KS, and forecast soundings along

this corridor show strong low-level vertical shear supporting

supercell structures.  It is uncertain how far north these storms

can remain surface-based, but there is an apparent tornado risk

(possibly strong) along the immediate boundary and a large hail risk

for some distance northward.  This activity will likely spread into

south-central NE after dark.



...TX Panhandle/Western OK...

As the primary upper trough ejects this evening, large-scale height

falls and forcing will overspread the dryline across the OK/TX

Panhandles.  Forecast soundings show a persistent capping inversion

along the dryline, and CAM guidance generally shows very isolated

convective initiation.  Any storm that forms will pose a risk of all

severe hazards, including very large hail.



Overnight, a strengthening low-level jet over west TX will likely

lead to a large cluster of thunderstorm.  These storms will track

northeastward across northwest TX and into western/central OK in the

pre-dawn hours.  Large hail will be likely with these storms, but

damaging winds and isolated tornadoes will also be a risk if a more

organized linear MCS can evolve.



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