Alert archive / Michigan / Mesoscale Discussions in 2021
Mesoscale Discussion 1639
The Storm Prediction Center issued this mesoscale discussion at Aug 29, 2021, 1:05 PM EDT for 26 counties in Michigan. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- Aug 29, 2021, 1:05 PM EDT (17:05 UTC)
- Expired
- Aug 29, 2021, 3:00 PM EDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 26 counties
Alcona County, MI, Alpena County, MI, Antrim County, MI, Arenac County, MI, Bay County, MI, Cheboygan County, MI, Clare County, MI, Crawford County, MI, Emmet County, MI, Gladwin County, MI, Grand Traverse County, MI, Iosco County, MI, Isabella County, MI, Kalkaska County, MI, Lake County, MI, Mecosta County, MI, Midland County, MI, Missaukee County, MI, Montmorency County, MI, Ogemaw County, MI, Osceola County, MI, Oscoda County, MI, Otsego County, MI, Presque Isle County, MI, Roscommon County, MI, Wexford County, MI
The radar
The NCL Michigan radar (KAPX), 45 km from the middle of the area, began a volume at 17:07 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Alpena, MI (KAPX), launched 12:00Z, 5.1 hours before the alert went out and 167 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 221 J/kg
- Mixed-layer CIN
- -108 J/kg
- Mixed-layer LCL
- 1035 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 113 m²/s²
- 0-3 km storm-relative helicity
- 149 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.6
The text
As transmitted.
884
ACUS11 KWNS 291706
SWOMCD
SPC MCD 291705
MIZ000-291900-
Mesoscale Discussion 1639
NWS Storm Prediction Center Norman OK
1205 PM CDT Sun Aug 29 2021
Areas affected...much of northern Lower Michigan
Concerning...Severe potential...Watch possible
Valid 291705Z - 291900Z
Probability of Watch Issuance...60 percent
SUMMARY...Scattered storms, some producing damaging wind gusts and
marginally severe hail, are expected to develop around 19Z over
northern Lower Michigan.
DISCUSSION...Strong heating continues across Lower MI well ahead of
a cold front approaching Lake MI from the west. Scattered convection
is already developing along the front from southeast WI into the
eastern Upper MI.
The greatest threat of severe storms appears to be over the northern
half of Lower MI. Here, deep-layer shear will average near 40 kt,
aiding storm longevity. A line, or broken line of cells is expected
form ahead of the front, with both damaging wind and marginal hail
risk. Although shear decreases rapidly farther south into central
and southern MI, favorable instability as well as sufficient mean
wind speeds suggest at least isolated strong wind gusts are
possible.
..Jewell/Grams.. 08/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...APX...GRR...
LAT...LON 45338330 44718319 44348323 43668370 43378415 43348469
43378535 43718586 44468589 45088554 45758508 45908454
45688383 45338330SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 29, 1:46 PM EDT | Severe Thunderstorm Watch | SPC | Alcona, Alpena, Antrim, Arenac, Bay, Benzie and 42 more | 6 hr |
| Aug 29, 4:08 PM EDT | Mesoscale Discussion | SPC | Allegan, Barry, Berrien, Branch, Calhoun, Cass and 10 more | 97 min |
| Aug 29, 4:27 PM EDT | Mesoscale Discussion | SPC | Alcona, Alpena, Arenac, Barry, Bay, Clinton and 16 more | 93 min |
Nearby
Mesoscale Discussions in Michigan, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.