SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1229 AM CDT Fri Oct 23 2020

Valid 231200Z - 241200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
THE LOWER GREAT LAKES INTO THE OHIO VALLEY...

...SUMMARY...
Threat for a few severe storms capable of damaging wind, hail and
perhaps a tornado or two will exist this afternoon into the early
evening over a portion of the lower Great Lakes and Ohio Valley.

...Lower Great Lakes and Ohio Valley region...

A mid-upper speed max situated within the base of a synoptic trough
will move through the Great Lakes today. Accompanying weak surface
low will develop northeastward through the Great Lakes this morning
with a moist warm sector (low to mid 60s F dewpoints) advecting into
the southern portion of lower MI. Cold front trailing from the low
will reach Lake Erie southwestward into the lower MS Valley by early
evening. Diabatic warming of the surface layer and modest mid level
lapse rates will promote moderate instability in pre-frontal warm
sector with 1500-2000 J/kg MLCAPE possible. Vertical shear will
strengthen as the upper jet advances through the Great Lakes with
40-45 kt effective bulk shear along with 200-300 m2/s2 0-1 km storm
relative helicity, especially from northern IN into southern lower
MI. Elevated storms should be ongoing in post-frontal region during
the morning. However, surface-based storms are expected to develop
along the cold front from southern lower MI into IN as it encounters
an increasingly unstable boundary layer this afternoon. Vertical
wind profiles will be sufficient for organized structures,
especially with storms that can be sustained for a while along the
advancing cold front before potentially being undercut. Damaging
wind and hail are the primary threats, but a tornado or two will
also be possible.

..Dial/Cook.. 10/23/2020

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