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ACUS01 KWNS 271257

SWODY1

SPC AC 271256



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0756 AM CDT Sat Apr 27 2024



Valid 271300Z - 281200Z



...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT

FOR OK...NORTH TX...SOUTHEAST KS AND EXTREME SOUTHWEST MO...



...SUMMARY...

Severe thunderstorms are likely today and tonight across the

southern and central Plains into the lower to mid Missouri Valley.

The most numerous/intense storms are expected from north Texas into

Oklahoma and southeast Kansas, where strong tornadoes, very large

hail of 2-3 inches in diameter and damaging winds of 60-70 mph are

all possible.



...A regional severe-weather outbreak is expected from north TX

across OK into KS with strong tornadoes, very large hail and

damaging winds all part of a long-duration threat...



...OK/KS/north TX through tonight...

A pronounced midlevel trough over the Four Corners will move

eastward today and then begin to eject northeastward tonight over

the central/southern High Plains.  This synoptic pattern will

maintain a lee cyclone in southeast CO and a dryline arcing

southeastward and then southward close to the western OK border. 

Farther north, a stalling baroclinic zone will move slowly northward

into northern KS today and central IA by this evening.

A broad, unstable warm sector with boundary-layer dewpoints of 65-70

F will support multiple rounds of severe/tornadic storms through the

period, both along the synoptic boundaries and in parts of the open

warm sector for OK/KS.



The initial severe/tornado threat has already begun near Caprock

from Lubbock to Childress as an embedded jet streak (evident as the

fast-moving cloud streak over west TX) begins to interact with the

northwest edge of the richer low-level moisture.  Despite the

unusually early start, there will be the potential for embedded

supercells capable of all hazards as the storms overspread

western/northern OK into southern KS through midday.  An outflow

boundary and/or differential heating corridor is likely in the

immediate wake of these morning storms from southern KS into north

central and southwest OK.  Additional thunderstorm development is

likely by early-mid afternoon along this zone and the dryline to the

south into TX, and storms will spread generally northeastward toward

southern/central OK and southeast KS.  A moist boundary layer,

MLCAPE of 2500-3500 J/kg and lengthening/enlarging hodographs with

time (as a mass response to the approaching shortwave trough) will

become more favorable for tornadic supercells, including the

potential for long-track EF2-EF3+ tornadoes.  The significant

tornado threat will be greatest if semi-discrete supercells can be

maintained well into the afternoon/evening.  Very large hail up to 3

inches in diameter can also be expected with the more intense

supercells.



The storm evolution has the potential to be a bit messy with

multiple training/conjoined supercells, posing a relatively

long-duration and repeat threat to areas within the training storm

corridors across the central third of OK.  Damaging winds will

become more probable with storm clustering, and there will likely be

upscale growth into a larger QLCS this evening into tonight as the

primary shortwave trough approaches from the west.  The potential

for tornadoes with embedded circulation will continue into the

overnight hours, along with damaging winds.



...East central CO/far western KS this afternoon/evening...

Near the lee cyclone and a stalled front, thunderstorm development

is expected by early afternoon in a small cluster/arc across east

central CO.  Despite boundary-layer dewpoints only in the 40s, cold

midlevel temperatures and steep lapse rates will contribute to

surface-based CAPE up to 1000 J/kg.  Relatively large, curved

hodographs will favor supercells capable of producing a few

tornadoes and large hail, as well as damaging gusts once any upscale

growth into a line segment occurs.



...Northern IL/southeast WI/Lower MI this afternoon/evening...

A midlevel trough and associated surface cyclone will move

northeastward today from the upper MS Valley to the upper Great

Lakes.  The stronger forcing for ascent has already moved northeast

of the surface warm sector, so storm development in this corridor

will likely be later this afternoon/evening in association with

low-level ascent along the stalling front across WI/lower MI.  A

band of storms is expected along the front, and other convection

could eventually spread into northern IL from eastern IA.  Forecast

profiles along and south of the front show sufficient hodograph

length/deep-layer shear for organized line segments and some

embedded supercells capable of producing damaging gusts and possibly

a tornado or two.  Isolated large hail will also be possible, given

some potential for embedded supercells within the northeast extent

of the 7-8 C/km midlevel lapse rates.



..Thompson/Hart.. 04/27/2024



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