Alert archive / Michigan / Mesoscale Discussions in 2021
Mesoscale Discussion 1729
The Storm Prediction Center issued this mesoscale discussion at Sep 12, 2021, 2:43 PM EDT for 26 counties in Michigan. It was in force for 92 min.
The area
The outline as issued.
The facts
- Issued
- Sep 12, 2021, 2:43 PM EDT (18:43 UTC)
- Expired
- Sep 12, 2021, 4:15 PM EDT
- In force
- 92 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 26 counties
Arenac County, MI, Bay County, MI, Clare County, MI, Genesee County, MI, Gladwin County, MI, Gratiot County, MI, Huron County, MI, Isabella County, MI, Lake County, MI, Lapeer County, MI, Manistee County, MI, Mason County, MI, Mecosta County, MI, Midland County, MI, Missaukee County, MI, Montcalm County, MI, Muskegon County, MI, Newaygo County, MI, Oceana County, MI, Ogemaw County, MI, Osceola County, MI, Roscommon County, MI, Saginaw County, MI, Shiawassee County, MI, Tuscola County, MI, Wexford County, MI
The radar
The Grand Rapids radar (KGRR), 87 km from the middle of the area, began a volume at 18:45 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
Detroit, MI (KDTX), launched 12:00Z, 6.7 hours before the alert went out and 178 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
- 677 J/kg
- Mixed-layer CIN
- -369 J/kg
- Mixed-layer LCL
- 734 m above ground
- 0-6 km bulk shear
- 53 kt
- 0-1 km storm-relative helicity
- 157 m²/s²
- 0-3 km storm-relative helicity
- 299 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.5
The text
As transmitted.
887
ACUS11 KWNS 121844
SWOMCD
SPC MCD 121843
MIZ000-122015-
Mesoscale Discussion 1729
NWS Storm Prediction Center Norman OK
0143 PM CDT Sun Sep 12 2021
Areas affected...Central Lower Michigan
Concerning...Severe potential...Watch possible
Valid 121843Z - 122015Z
Probability of Watch Issuance...40 percent
SUMMARY...Elevated storms over Lake Michigan will pose a very
limited severe risk in the short-term. However, this activity could
become near surface based this afternoon. A watch will be considered
as convective trends warrant.
DISCUSSION...Elevated thunderstorms have initiated well ahead of an
MCV currently moving across northeastern Iowa into western
Wisconsin. In the short-term, it would appear that the severe threat
with these storms will be low on account of stout MLCIN. Morning
observed regional soundings indicated a layer of mid-level
subsidence. Greater boundary-layer destabilization and/or lift from
the MCV will likely be needed for storms to become near surface
based. However, given how early these storms have developed, there
is some possibility that they pose a severe threat (primarily
damaging wind gusts) before exiting central Lower Michigan later in
the afternoon. Trends will need to be monitored for a possible
watch.
..Wendt/Thompson.. 09/12/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...APX...GRR...
LAT...LON 43418709 43778748 44388731 44438485 44228324 43738260
43048280 42918416 43118571 43418709SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 12, 4:44 PM EDT | Mesoscale Discussion | SPC | Kent, Muskegon, Ottawa | 91 min |
| Sep 12, 5:15 PM EDT | Severe Thunderstorm Watch | SPC | Allegan, Barry, Clinton, Eaton, Gratiot, Ingham and 5 more | 3 hr |
| Sep 12, 5:22 PM EDT | Severe Thunderstorm Watch | SPC | Genesee, Lapeer, Livingston, Macomb, Oakland, Saginaw and 4 more | 4 hr |
| Sep 12, 6:52 PM EDT | Mesoscale Discussion | SPC | Clinton, Genesee, Gratiot, Ionia, Kent, Lapeer and 7 more | 113 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.