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ACUS01 KWNS 150558

SWODY1

SPC AC 150557



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

1257 AM CDT Mon Apr 15 2024



Valid 151200Z - 161200Z



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

OF SOUTH DAKOTA...NEBRASKA...AND KANSAS...



...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE

MID ATLANTIC...



...SUMMARY...

Scattered severe thunderstorms are likely across the southern to

central Great Plains, mainly this evening and into tonight. Large to

very large hail, damaging wind gusts, and a few tornadoes are

possible. More isolated severe storms are also possible over parts

of the Ohio Valley and Mid Atlantic with a risk for mainly damaging

winds and hail.



...Synopsis...

An upper low over the western Great Basin is forecast to amplify

considerably as it begins to phase with an increasingly strong

mid-level subtropical jet located over the Southwestern US. Early

morning WV imagery and RAOBS show this jet is currently moving out

of northern MEX into southern AZ and NM. As the upper low and jet

amplify, they will move eastward and spread broad-scale ascent over

much of the southern and central High Plains late in the diurnal

cycle. At the same time, a subtle mid-level perturbation east of the

building central US ridge will move south overspreading a modestly

warm air mass near a slowly sagging cold front in the Mid Atlantic.

An initially diffuse lee trough/weak cyclone is forecast to quickly

consolidate and deepen below 1000 mb over eastern CO and western NE

by late afternoon. Large-scale mass response from the approaching

trough and deepening low will aid in advecting a fairly broad and

increasingly moist (mid 60s F surface dewpoints) modified Gulf air

mass northward, east of a sharp dryline. While some uncertainty

exists regarding convective initiation owing to the late arrival of

large-scale ascent, mid and high-level cloud cover and capping,

scattered severe thunderstorms capable of all hazards are possible

over much of the Plains. Isolated storms are also possible over

parts of the OH Valley and Mid Atlantic with a risk for damaging

gusts.



...Central Plains Triple Point/Warm Front...

A well defined warm front is expected to mark the northern edge of

the ongoing moisture return near the KS/NE border at 12z. As the

surface cyclone to the west begins to deepen, the warm front should

lift northward into central NE and southern SD by mid afternoon.

Strong low-level moisture advection and sheltering by mid and

high-level clouds should allow for upper 50s to low 60s F dewpoints

to pool near the front ahead of a subtle shortwave trough on the

eastern periphery of the approaching upper low. Diurnal heating and

forcing for ascent from the approaching shortwave should allow for

removal of remaining inhibition by mid to late afternoon near and

along the warm front and closer to the triple point. Mid-level lapse

rates near 8-8.5 C/km and cool mid-level temps will support moderate

buoyancy with large clockwise curved hodographs. Initial supercells

are likely with the potential for large to very large hail. A few

tornadoes are also possible given large low-level buoyancy and

enhanced low-level SRH along the warm front.



...Central and southern Plains Dryline...

Considerable uncertainty exists regarding diurnal convective

development east of the dryline. Mid and high-level cloud cover from

the active subtropical jet may stunt daytime heating/mixing while

the later arrival of the main upper-low will limit large-scale

ascent. With a stout EML in place, it is unclear if subtle ascent

from embedded perturbations within the subtropical jet and the

dryline circulation will support convective development from western

KS and OK into the TX Panhandle during the day. CAM guidance

suggests a few storms may develop farther south in west/western

North TX within the deeply mixed air mass. With increasingly strong

wind fields in place these storms would likely be supercellular with

large to very large hail and the potential for a couple tornadoes.



Additional development appears likely later in the evening and into

the overnight hours as a Pacific front moves east and intersects

with the retreating dryline. Uncertainty remains high with various

model solutions, but higher probabilities of convective development

appear likely across western and central KS with mid-level height

falls and strong tropospheric flow fields increasing overnight.

Large hail and damaging winds would be possible with this second

round of storms, along with potential for a couple of tornadoes.



...Ohio Valley into VA and NC...

Weak height falls from the subtle trough are expected to move over

Mid Atlantic by early to mid afternoon timed with peak heating and

modest boundary-layer moisture return. Weak surface convergence

along a sagging cold front and surrounding terrain should be

sufficient to support isolated to scattered thunderstorm development

through the afternoon across the central OH Valley into eastern WV

and northern VA. Ahead of the front, potentially low 50s F surface

dewpoints and mid-level lapse rates of 7-8 C/km will support

1000-1500 J/kg of MLCAPE with moderately strong mid and upper-level

flow. Several bands or clusters of storms are expected to develop

and may pose a risk for isolated severe hail and damaging wind gusts

as they track east/southeast into the evening hours. The threat

should gradually diminish after sunset with the loss of diurnal

heating.



..Lyons/Kerr.. 04/15/2024



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