Alert archive / Michigan / Mesoscale Discussions in 2020
Mesoscale Discussion 1621
The Storm Prediction Center issued this mesoscale discussion at Aug 28, 2020, 9:15 PM EDT for 25 counties in Michigan. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 28, 2020, 9:15 PM EDT (01:15 UTC)
- Expired
- Aug 28, 2020, 11:45 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 25 counties
Barry County, MI, Branch County, MI, Calhoun County, MI, Clinton County, MI, Eaton County, MI, Genesee County, MI, Gratiot County, MI, Hillsdale County, MI, Ingham County, MI, Ionia County, MI, Jackson County, MI, Kalamazoo County, MI, Kent County, MI, Lenawee County, MI, Livingston County, MI, Mecosta County, MI, Montcalm County, MI, Newaygo County, MI, Oakland County, MI, Ottawa County, MI, Saginaw County, MI, Saint Joseph County, MI, Shiawassee County, MI, Washtenaw County, MI, Wayne County, MI
The radar
The Grand Rapids radar (KGRR), 41 km from the middle of the area, began a volume at 01:15 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 00:00Z, 1.3 hours before the alert went out and 137 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
- 961 J/kg
- Mixed-layer CIN
- -33 J/kg
- Mixed-layer LCL
- 671 m above ground
- 0-6 km bulk shear
- 45 kt
- 0-1 km storm-relative helicity
- 143 m²/s²
- 0-3 km storm-relative helicity
- 196 m²/s²
- Significant tornado parameter
- 1.0
- Supercell composite
- 5.9
The text
As transmitted.
615
ACUS11 KWNS 290116
SWOMCD
SPC MCD 290115
MIZ000-290345-
Mesoscale Discussion 1621
NWS Storm Prediction Center Norman OK
0815 PM CDT Fri Aug 28 2020
Areas affected...Southern Lower Michigan
Concerning...Severe potential...Watch possible
Valid 290115Z - 290345Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorms have increased in coverage and intensity
over Lake Michigan and are expected to pose a severe weather threat
as they move into southern Lower Michigan. Convective trends will
be monitored for the possibility of a watch.
DISCUSSION...An upper-level impulse moving across southern Wisconsin
has aided the initiation of storms across Lake Michigan (including a
long-lived supercell). These storms have increased in coverage and
intensity with time and are expected to persist as they move
eastward across Lower Michigan tonight. Given a relatively
favorable kinematic and thermodynamic environment downstream, these
storms should remain organized (including transient supercell
structures), posing a severe weather threat. Some surface-based CIN
is present (per current mesoanalysis) over southern Lower Michigan
given the stabilizing nocturnal boundary layer, but RAP forecast
soundings suggest effective layer inflow parcels are likely to
originate from the surface. Thus, damaging winds are possible along
with hail, and a tornado cannot be ruled out. Convective trends
will be monitored for the possibility of a watch.
..Jirak/Guyer.. 08/29/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...IWX...GRR...
LAT...LON 43198630 43588628 43698546 43628475 43298384 42728317
42358295 42068326 41878390 41818474 41958594 42158616
42228628 42608619 42998619 43198630SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 28, 9:57 PM EDT | Severe Thunderstorm Watch | SPC | Allegan, Barry, Calhoun, Clinton, Eaton, Genesee and 12 more | 4 hr |
| Aug 28, 11:41 PM EDT | Mesoscale Discussion | SPC | Berrien, Branch, Calhoun, Cass, Eaton, Hillsdale and 7 more | 94 min |
Nearby
Mesoscale Discussions in Michigan, 2020Every mesoscale discussion in 2020
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.