Update from Grand Rapids.....
Area Forecast Discussion
National Weather Service Grand Rapids MI
Issued at 1225 PM EDT Wed Jul 28 2021
Latest 12Z guidance is continuing the farther north trend of the
most severe convection later tonight, even hinting at the
possibility of a derecho impacting much or parts of wrn Lwr MI.
Since this is a potentially high impact severe weather event
while many folks will be sleeping, communication/messaging the
possibility of high/destructive winds this afternoon/evening will
Timing looks to be similar, with potential for a large bow echo
sweeping across Lk MI toward or after midnight. Also some
potential for the warm advection wing ahead of the main line
becoming active a couple hours beforehand. If that does occur, we
could have some tornado potential with discrete cells since the
warm front will be draped over the area. HRRR has 0-1km SRH of
150-200 m2/s2 with LCLs below 1km. A QLCS-type tornado threat may
also develop/exist within the main line.
Also of note, in terms of the straight line wind potential, HRRR
shows 70 kts at 3 km, of potential descending rear inflow into
the back of that line. So some isolated pockets of destructive
80+ mph winds seem plausible later tonight.
As far as heavy rainfall/flooding concerns, some intense rainfall
rates are likely as the strong/svr convection is coming through
tonight, although the progressive nature of the MCS may limit
the overall flooding risk. That said, some urban flooding -
possibly worthy of areal flood advisories/warnings - may also be