National Weather Service Detroit/Pontiac MI
230 PM EDT Fri Jul 14 2023
.DISCUSSION...
Moderate instability has built up, with 18z SPC mesoscale analysis
indicating 1500 J/kg of MLcape and 2500+ J/kg. Jet streak/40+ knots
of 0-6 KM bulk shear aligned over/around I-94 corridor, presenting
the elevated concern for severe storms, as the Lake Michigan shadow
push has begun and some activity is attempting to go up. Will need to
be leery of the backed flow near Lake Erie to increase low level
shear and lead to potential rotation. Some enhanced low level
convergence and enough 0-1 km bulk shear (up to 15 knots) over the
Thumb region to allow for rotation and more organized activity as
well, with possible tornadoes indicated.
Once the scattered strong-severe storms/surface based activity
dwindles early this evening, still a muddled forecast for tonight
into Saturday, as 12z hires solutions are all over the place with
convection, or lack there of if you believe certain solutions.
Unfortunately, with the amount of upper level shortwaves seen on the
water vapory imagery tracking through northern Plains/Midwest, it is
not surprising and difficult to latch on to the main/dominant player
as we work through the diurnal cycle. Ultimately, with moderate
southwest low level winds and solid negative showalter index values
persisting, will lean toward the redevelopment of convection tonight
within the backdrop of upper level ridge building into between the
Central/Eastern Great Lakes region toward Saturday morning, as
shortwave energy/lead PV advection tracks in from the western Ohio
Valley. With 700 MB dew pts rising into the low-mid single numbers,
excessive/heavy rainfall becomes an increasing concern as we head
into Saturday as well. 12z Regional GEM seems to have the general
flavor of the forecast for tonight and tomorrow. With the morning
shower/thunderstorm activity slow to exit, anticipating afternoon
instability to be low, with mlcapes generally under 1000 J/kg, which
is a good thing as wind shear appears to be moderate, with 35+ knots
of 0-6 km bulk shear to work with. Day 2 out of SPC has dropped the
marginal risk of severe storms for bulk of southeast Michigan, which
is fine as long as that morning activity verifies.