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ACUS01 KWNS 151246

SWODY1

SPC AC 151245



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0745 AM CDT Mon Apr 15 2024



Valid 151300Z - 161200Z



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

THE CENTRAL PLAINS...



...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF

THE SOUTHERN MID-ATLANTIC...



...SUMMARY...

Scattered severe thunderstorms are likely across parts of the Great

Plains, beginning mainly this evening and continuing overnight.

Several tornadoes, large to very large hail, and damaging wind gusts

all appear possible. Strong tornadoes may occur this evening across

parts of Kansas and Nebraska.



...Synopsis...

A large, closed upper cyclone is present over the Great Basin this

morning. This feature will track eastward across the central

Rockies, eventually ejecting over the southern/central Plains

tonight. A strong mid/upper-level jet attendant to this upper

cyclone will overspread much of the southern/central Plains through

this evening. Pronounced large-scale ascent preceding the

upper-level trough/low will encourage additional deepening of a

surface low over the central High Plains though the day. Moisture

will continue streaming northward through the period in tandem with

a warm front and persistent low-level warm/moist advection. This

warm front should be located across NE and perhaps into far southern

SD by late this evening, as the primary surface low consolidates

over the NE Panhandle. A dryline is forecast to mix eastward across

the southern/central High Plains through peak afternoon heating,

before retreating westward this evening across parts of the TX/OK

Panhandles and western KS.



...Northern/Central Plains (Kansas/Nebraska/South Dakota)...

A cap and the late timing of large-scale ascent associated with the

ejecting upper cyclone will likely inhibit convective development

across the northern/central Plains through at least late afternoon.

Still, low-level moisture will gradually increase through the day,

with surface dewpoints of at least upper 50s to low 60s becoming

common by early this evening across the warm sector. Steep mid-level

lapse rates and cooling thermal profiles aloft are expected to

contribute to substantial MLCAPE by the peak of the diurnal heating

cycle, with values likely ranging around 2000-3000 J/kg. With

gradually strengthening mid/upper-level flow anticipated, deep-layer

shear should also become sufficiently strong to support a mix of

supercells and multicells across this region.



Convective initiation should be delayed across much of KS/NE/SD

until around 00Z as a southerly low-level jet rapidly strengthens to

50-60 kt. Very large hail (around 2-3 inches in diameter) will be a

threat with any supercells that can form along/near the warm front,

or southward along the length of the dryline into western KS.

Low-level hodographs are forecast to become enlarged/curved in the

00-06Z time frame tonight, and the threat for tornadoes is likewise

expected to increase with any supercells that can persist and remain

at least semi-discrete. Confidence has increased in a more

concentrated corridor of tornado potential across parts of

western/central KS into central NE, where supercells appear most

likely in very favorable thermodynamic and kinematic parameter

space. Given the forecast strength of the low-level shear, strong

tornadoes appear possible this evening/tonight across this area.

Severe/damaging winds will also be possible as convection attempts

to grow upscale into one or more clusters overnight. Even with

nocturnal cooling, these severe/damaging winds may persist given the

ample reservoir of buoyancy available.



...Southern Plains (Oklahoma/Texas)...

The overall coverage and severity of convection across the southern

Plains is somewhat more uncertain compared to locations farther

north across the central Plains. This uncertainty is largely tied to

the influence of a sub-tropical mid/upper-level jet that will move

over the southern Plains through the period, along with associated

mid/upper-level cloudiness. These clouds may tend to limit daytime

heating to some extent along the length of the dryline. Even so,

attempts at robust convective development will probably occur across

parts of northwest TX by late this afternoon. If this activity can

be sustained, then supercells appear likely given ample (50-60 kt)

deep-layer shear. Isolated large to very large hail will probably be

the main threat with this convection as it moves towards

north-central TX. But, occasional severe/damaging winds and perhaps

a couple of tornadoes may also occur through the early evening. Most

guidance indicates any supercells which develop will weaken with

eastward extent as they encounter increasing MLCIN, and become

increasingly displaced from the better large-scale ascent with the

upper trough/low ejecting over the central Plains. A highly

conditional severe threat remains apparent across OK late this

afternoon and evening, with a favorable parameter space to support

supercells capable of producing all severe hazards. But, much of OK

may have a relative minimum in convective activity until late

tonight as a Pacific cold front overtakes the dryline.



...Mid-Atlantic to the Mid Mississippi Valley...

The glancing influence and modest ascent with an upper trough across

the Northeast and eastern Canada will overspread parts of the

Mid-Atlantic by early afternoon. Weak low-level convergence along a

sagging cold front should be sufficient to support isolated to

scattered thunderstorm development through the afternoon and evening

from parts of the mid MS Valley into the OH Valley, central

Appalachians, and southern Mid-Atlantic. Ahead of the front across

the Mid-Atlantic, generally low 50s surface dewpoints and steepened

mid-level lapse rates will foster around 1000-1500 J/kg of MLCAPE

with moderately enhanced westerly mid/upper-level flow. Deep-layer

shear across this region appears strong enough to support supercells

with an associated threat for large hail. Damaging wind gusts may

also occur with multicell clusters that attempt to form as they

track generally east-southeastward through the evening hours. With

weaker deep-layer shear across the mid MS and OH Valleys, convection

should be somewhat less organized while still posing an isolated

threat for hail/wind. The overall severe threat should gradually

diminish through late evening with the loss of diurnal heating.



..Gleason/Grams.. 04/15/2024



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