Mesoscale Discussion 1954
The Storm Prediction Center issued this mesoscale discussion at Dec 4, 2021, 10:39 AM CST. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Dec 4, 2021, 10:39 AM CST (16:39 UTC)
- Expired
- Dec 4, 2021, 1:45 PM CST
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Heavy snow
The radar
The Marquette radar (KMQT), 100 km from the middle of the area, began a volume at 16:41 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 nearest sounding before it
Green Bay/Straub, WI (KGRB), launched 12:00Z, 4.7 hours before the alert went out and 262 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1317 m above ground
- 0-6 km bulk shear
- 104 kt
- 0-1 km storm-relative helicity
- -93 m²/s²
- 0-3 km storm-relative helicity
- 47 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
093
ACUS11 KWNS 041640
SWOMCD
SPC MCD 041639
MIZ000-041945-
Mesoscale Discussion 1954
NWS Storm Prediction Center Norman OK
1039 AM CST Sat Dec 04 2021
Areas affected...Southwest Alger and northern School Craft Counties
in the Upper Peninsula of Michigan
Concerning...Heavy snow
Valid 041639Z - 041945Z
SUMMARY...Heavy lake effect snow is expected to continue in
southwest Alger and northern School Craft Counties into the
afternoon.
DISCUSSION...A lake effect snow band has developed from near the
Keweenaw Peninsula to near Grand Island and it dissipates near the
border of Schoolcraft, Luce, and Mackinac counties. There are no
observations within this band to observe current snowfall rates, but
based on radar and satellite presentation, 2+ inch per hour snowfall
rates are likely with 3+ possible. Over the past 2 hours,
convergence has increased between KCMX and P59 near the origination
point of this lake effect band. Therefore, expect it to maintain
intensity (or possibly even strengthen) over the next hour or two
and continue into the afternoon. Current observations and forecast
conditions would suggest very little shifting of this band through
the afternoon with the same locations possibly being impacted
continuously. Inversion heights eventually lower through the
afternoon which may start to weaken this band by evening. In
addition to the heavy snow, winds of 15 to 20 mph with gusts 30 to
35 mph are present in the entire region. This is causing significant
blowing and drifting which will further lower visibility.
..Bentley/Hart.. 12/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MQT...
LAT...LON 46638632 46458593 46298588 46258609 46378656 46498661
46638632Nearby
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.