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ACUS01 KWNS 171253

SWODY1

SPC AC 171252



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0752 AM CDT Wed Apr 17 2024



Valid 171300Z - 181200Z



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

SOUTHERN LOWER MICHIGAN INTO THE OHIO VALLEY...



...SUMMARY...

Scattered thunderstorms capable of producing damaging winds, large

hail, and a few tornadoes should develop across parts of the Ohio

Valley and Lower Great Lakes this afternoon. Thunderstorms with

mainly a large hail threat may occur tonight over parts of the

central Plains.



...Synopsis...

An upper trough/low over the Upper Midwest this morning will

continue to move east-northeastward across the Great Lakes and OH

Valley today while gradually de-amplifying/weakening. An associated

40-60 kt mid-level jet will accompany this trough and overspread

much of the OH/TN Valleys. At the surface, a low over southeastern

MN/western WI should continue to gradually occlude through the day

in tandem with the weakening upper cyclone. An attendant cold front

will sweep eastward over the Lower Great Lakes/OH Valley through

this evening, while a warm front advances as far north as parts of

Lower MI and perhaps far western NY.



...Lower Michigan into the Ohio/Tennessee Valleys and

Mid-Atlantic...

Upper 50s to low 60s surface dewpoints are expected to be in place

ahead of the cold front late this morning/early afternoon. A

pronounced mid-level dry slot evident on water vapor satellite

imagery should aid in diurnal destabilization via a general lack of

mid/upper-level cloud cover across parts of the OH Valley. As the

boundary layer gradually warms/moistens, around 1000-1500 J/kg of

MLCAPE should develop across southern Lower MI, eastern IN, and OH.

Sufficiently strong low/mid-level winds will support 40-50 kt of

deep-layer shear and updraft organization. Current expectations are

for convection to develop along or just ahead of the cold front by

early afternoon, and subsequently spread quickly east-northeastward

across Lower MI, OH, and western PA through this evening. Tendency

may be for thunderstorms to quickly organize into a line, especially

across Lower MI which will be in closer proximity to the large-scale

ascent attendant to the upper trough/low. If this evolution occurs,

then severe/damaging winds would be the main threat with this

activity. Have expanded the Marginal and Slight Risks northward

across Lower MI to account for this potential.



Farther south across eastern IN and OH, forcing will gradually

become more limited, which may allow for somewhat lower thunderstorm

coverage initially. Even so, deep-layer shear will be strong enough

to support supercells, with large hail, damaging wind, and a few

tornadoes all possible. The best tornado potential may be focused

across parts of southeastern Lower MI and northern OH, in closer

proximity to the warm front and greater low-level shear. Some

upscale growth may also occur with this activity as it moves into

eastern OH and western PA, with a potentially greater threat for

damaging winds through the early evening before convection

eventually weakens.



Overall convective coverage should be lower across the TN Valley

into the Southeast, with weaker large-scale ascent present over

these regions. Still, isolated strong thunderstorms may occur this

afternoon and early evening in a weakly unstable but strong

deep-layer shear environment. Occasional hail and gusty winds appear

possible with the more robust cores. Based on latest guidance

trends, have trimmed the western extent of the Marginal Risk over

western KY/TN and northern MS.



Across the eastern Mid-Atlantic (northern VA/MD/DC/DE/south-central

PA), a well-mixed boundary layer and steep low-level lapse rates

forecast by some guidance may support occasional strong to damaging

winds with convection spreading eastward off the higher terrain of

the Appalachians and Blue Ridge Mountains. With limited instability,

the overall severe wind threat will likely remain isolated.



...Nebraska/Kansas into Iowa/Missouri...

An upper-level trough will move eastward across the north-central

CONUS tonight. A 40-45 kt southerly low-level jet will develop this

evening across parts of the southern/central Plains in response.

Thunderstorms should eventually initiate near the northern edge of

the low-level jet late this evening from central KS into far

southeast NE. Ample MUCAPE, steep mid-level lapse rates, and strong

shear in the cloud-bearing layer should support some threat for

large hail with this mainly elevated convection. The large hail

threat should to be greatest in the 04Z to 08Z time window with

initial development, but it may persist through the end of the

period. If convection can grow upscale into a small bowing cluster,

then isolated damaging winds may also occur.



A conditional threat for a supercell or two will exist farther south

across south-central/southeastern KS into far northeastern OK. Here,

modest low-level convergence along the intersection of a developing

warm front and dryline may be sufficient to initiate isolated

convection early this evening as the low-level jet strengthens. If

this occurs, then all severe hazards appear possible.



...Texas...

Very isolated thunderstorms may develop late this afternoon and

early evening across parts of south-central into central TX along a

surface dryline. If any convection can be sustained, it could

produce severe winds and hail. But, this threat currently appears

too conditional and uncertain to add low severe probabilities.



..Gleason/Bentley.. 04/17/2024



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