Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 476
The Storm Prediction Center issued this mesoscale discussion at May 2, 2021, 4:20 PM CDT for 24 counties in Iowa; 9 counties in Minnesota; 9 counties in Wisconsin. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- May 2, 2021, 4:20 PM CDT (21:20 UTC)
- Expired
- May 2, 2021, 6:15 PM CDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
All 42 counties
Allamakee County, IA, Bremer County, IA, Butler County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Clay County, IA, Clayton County, IA, Dickinson County, IA, Emmet County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Hancock County, IA, Howard County, IA, Humboldt County, IA, Kossuth County, IA, Mitchell County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Winnebago County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Houston County, MN, Martin County, MN, Mower County, MN, Olmsted County, MN, Winona County, MN, Crawford County, WI, Grant County, WI, Iowa County, WI, Juneau County, WI, La Crosse County, WI, Monroe County, WI, Richland County, WI, Sauk County, WI, Vernon County, WI
The radar
The La Crosse radar (KARX), 136 km from the middle of the area, began a volume at 21:19 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
Minneapolis, MN (KMPX), launched 12:00Z, 9.3 hours before the alert went out and 180 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
- 3075 m above ground
- 0-6 km bulk shear
- 38 kt
- 0-1 km storm-relative helicity
- -80 m²/s²
- 0-3 km storm-relative helicity
- -13 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
642
ACUS11 KWNS 022121
SWOMCD
SPC MCD 022120
WIZ000-IAZ000-MNZ000-022315-
Mesoscale Discussion 0476
NWS Storm Prediction Center Norman OK
0420 PM CDT Sun May 02 2021
Areas affected...Southeast Minnesota...Northeast Iowa...and
Southwest Wisconsin
Concerning...Severe potential...Watch unlikely
Valid 022120Z - 022315Z
Probability of Watch Issuance...20 percent
SUMMARY...Scattered strong, to perhaps severe, thunderstorms will
continue to develop across the MN/IA/WI region over the next few
hours. A watch is not expected
DISCUSSION...Thunderstorm development is underway along and just
south of a warm frontal boundary across southeast MN into northeast
IA and far southwest WI. Partly cloudy to mostly clear skies along
and south of the boundary have allowed temperatures to warm into the
low 80s, which has helped erode lingering MLCIN. Dewpoints in the
mid to upper 50s across the region is supporting MLCAPE values up to
around 1000 J/kg. Although sufficient instability is in place,
stronger flow aloft associated with a departing jet streak is
displaced to the north of the better instability across eastern MN.
The lack of more robust deep-layer shear over the bulk of the warm
sector should limit the overall severe threat. However, a few strong
to severe storms are possible along the boundary where a narrow
region of favorable instability and 30-40 knots of effective bulk
shear exists. Given the limited nature of this threat, a watch is
not expected.
..Moore/Thompson.. 05/02/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MKX...ARX...MPX...DMX...FSD...
LAT...LON 43329583 43769439 44039286 44209177 44169039 43868964
43308955 42989003 42729082 42739245 42729374 42839528
43029593 43329583Nearby
Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Minnesota, 2021Mesoscale Discussions in Wisconsin, 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.