SPC 1200Z Day 1 Outlook
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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