Update; Severe Weather Outbreak 8/2/15 - Strong Cold Front to Usher in Strong to Severe Storms This Evening into Overnight and Refreshingly Cooler Weather for the Week

8/3/15 - Update
Widespread severe weather was reported across all of Lower Michigan on Sunday. It was definitely one of the more impressive outbreaks across the northern half of the state. The largest hail was enormous for Michigan standards up to 4.25" inches, the size of softballs. Southeast Lower Michigan received scattered damaging winds, hail up to 1.75" /golf ball/ and one confirmed tornado was pegged over Owendale in the Thumb.

For a complete listing of severe weather in Northern Lower Michigan, click here

For a complete listing of severe weather in Southeast Lower Michigan, click here

Original Post 8/12/15

Only one other time this summer, I felt to write up a blog and comment on a potential severe weather outbreak and that was back on June 21-22nd, which turned out to be the really only notable, widespread event of the summer. Yes, it's been a slow summer severe weather-wise with just the occasional severe thunderstorm. The more notable aspect of the summer has been the heavy rains earlier this summer and cool temperatures; that have given way to overall drier and warmer weather.

The system expected through Southeast Lower Michigan is worth noting due to the strong winds aloft, the robust instability into the evening and overnight night hours and the shear. The overall low pressure and cold front are already somewhat impressive for August standards, a month that is usually more benign when it comes to clashing air masses and low pressure systems. The strong low pressure over southern Canada is the second low to move across that region recently of note; the previous one a stronger low with central pressure down to I believe about 992 MB. After frontal passage overnight, look for a overall comfortable week for August standards.

Anyway; an area of strong to severe storms is expected to push east southeast tonight ahead of the front as it enters Southeast Lower Michigan. Already, strong to severe storms are or have occurred this early afternoon across Northern Lower Michigan and as far south as the Saginaw Valley and Thumb Region. Even at this late time, data coming in is mixed on the actual atmosphere to be over the region. While instability and helecity do wane somewhat toward the midnight hour, the stronger winds aloft (bulk shear) to the west begin to enter the system at about the same time (on the GFS). The best instability remains west of the region while the dynamics for progressive storm development move into the region. Therefore, any area -or squall line- of storms that does get going later today north of the region; should hold together in favorable conditions as it enters the region through the over night hours. This is strongly displayed on the NAM composite radar during the overnight hours. Of course this is an estimate of the radar echoes during the times displayed. One can also see even though the atmosphere is more unstable to the west over the upper Midwest (in successive instability maps), the atmosphere remains more capped and thus, less storm activity can bust through the cap.

Radar Composite /NAM/


Instability Maps

8 PM


Note; the potent helecity to our west on the NAM at 11PM tonight this gives credence to possible tornadic signatures with the squall.

Stay current on any warnings from the National Weather Service /DTX/ or several available media outlets.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

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