SPC Apr 27, 2017 0100 UTC Day 1 Convective Outlook

SPC 0100Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0759 PM CDT Wed Apr 26 2017

Valid 270100Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE LOWER MS VALLEY AND VICINITY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHERN IN AND NORTHWEST OH...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
THE SOUTHERN GREAT LAKES REGION TO THE NORTH-CENTRAL GULF COAST...

...SUMMARY...
Severe thunderstorms will remain possible from portions of the
north-central Gulf Coast region northward to the southern Great
Lakes region into tonight. Widely scattered damaging wind gusts and
perhaps a couple of tornadoes may accompany storms moving across
parts of the lower Mississippi Valley and vicinity into the
overnight hours, while a cluster of storms moving across portions of
northern Indiana and northwest Ohio may produce widely scattered
damaging winds into the evening hours.

...Portions of the north-central Gulf Coast region northward to the
southern Great Lakes region...
A corridor of convective bands extends from the lower OH Valley to
the north-central Gulf Coast vicinity. The northern portion of this
activity is pinching off the northernmost extent of more appreciable
moisture return, which 00Z observed soundings suggest resides closer
to the coast. While poleward return of more substantially modified
maritime air will occur ahead of the convection, the richer moisture
and related substantive buoyancy (MLCAPE around 500-1500 J/kg)
should remain generally near and south of western/middle TN. This is
where sufficient deep shear (45-65 kt of effective bulk shear) will
also exist in favor of continued quasi-linear convective modes
capable of widely scattered damaging winds. This activity will
spread into western AL through the overnight hours, and sufficient
low-level shear may exist for occasional line-embedded and
line-preceding supercell structures to support a couple of
tornadoes. Some isolated severe risk could extend even farther east
later in the night.

Farther north, a sustained cluster of storms continues advancing
northeastward across northern IN, and may eventually affect parts of
northwest OH before weakening in southern Lower MI this evening.
Moderately steep midlevel lapse rates around 7.3 C/km, based on the
Detroit 00Z sounding, will support sufficient buoyancy amid modest
moisture return for some severe risk persisting in the short-term.

Relatively weaker low-level lapse rates and limited moisture return
between the Slight Risk areas suggest that the severe risk should
remain more isolated across parts of the lower/middle Ohio Valley
region and vicinity. However, locally damaging wind gusts may
accompany the most pronounced bowing convective line segments.

..Cohen.. 04/27/2017

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