Alert archive / Iowa / Mesoscale Discussions in 2021
Mesoscale Discussion 694
The Storm Prediction Center issued this mesoscale discussion at May 20, 2021, 9:05 PM CDT for 33 counties in Iowa; 4 counties in Minnesota. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- May 20, 2021, 9:05 PM CDT (02:05 UTC)
- Expired
- May 20, 2021, 11:00 PM CDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 37 counties
Adair County, IA, Allamakee County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Butler County, IA, Cerro Gordo County, IA, Chickasaw County, IA, Dallas County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Howard County, IA, Jasper County, IA, Madison County, IA, Marion County, IA, Marshall County, IA, Mitchell County, IA, Polk County, IA, Story County, IA, Tama County, IA, Warren County, IA, Webster County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Fillmore County, MN, Freeborn County, MN, Houston County, MN, Mower County, MN
The radar
The Des Moines radar (KDMX), 91 km from the middle of the area, began a volume at 02:07 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 nearest sounding before it
Davenport, (KDVN), launched 00:00Z, 2.1 hours before the alert went out and 238 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
- 91 J/kg
- Mixed-layer CIN
- -4 J/kg
- Mixed-layer LCL
- 1385 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 47 m²/s²
- 0-3 km storm-relative helicity
- 117 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
246
ACUS11 KWNS 210205
SWOMCD
SPC MCD 210205
WIZ000-IAZ000-MNZ000-210400-
Mesoscale Discussion 0694
NWS Storm Prediction Center Norman OK
0905 PM CDT Thu May 20 2021
Areas affected...Central Iowa into Southeast Minnesota
Concerning...Severe potential...Watch unlikely
Valid 210205Z - 210400Z
Probability of Watch Issuance...5 percent
SUMMARY...A low-end threat for a brief tornado exists in association
with strong low-level shear and MCV moving through central Iowa. The
threat will be limited by a very poor thermodynamic environment. No
WW is expected.
DISCUSSION...The KDMX VAD has shown an increase in low-level winds
over the past few hours. 0-1 km shear is now near 40 kts as the core
of the low-level jet has intensified within the region. With an MCV
moving through the area, a storm or two will be possible into the
overnight. Given the wind profiles depicted by the VAD, low-level
rotation and a brief tornado could occur if a storm were to
intensify. Thermodynamics in this very moist, tropical-like
environment are quite poor, however, and will limit the overall
threat. No WW is expected.
..Wendt/Dial.. 05/21/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DVN...ARX...MPX...DMX...
LAT...LON 41819451 42889417 43799330 44029194 43779135 43299118
42029219 41099319 41019403 41339449 41819451Nearby
Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Minnesota, 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.