Alert archive / Iowa / Mesoscale Discussions in 2021

Mesoscale Discussion 1615

August 26, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Aug 26, 2021, 10:45 PM CDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 26, 2021, 10:45 PM CDT (03:45 UTC)
Expired
Aug 27, 2021, 12:45 AM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch possible
Chance of a watch
40%
All 49 counties

Bremer County, IA, Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Cerro Gordo County, IA, Cherokee County, IA, Chickasaw County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Floyd County, IA, Franklin County, IA, Hancock County, IA, Howard County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Lyon County, IA, Mitchell County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Plymouth County, IA, Pocahontas County, IA, Sac County, IA, Sioux County, IA, Webster County, IA, Winnebago County, IA, Woodbury County, IA, Worth County, IA, Wright County, IA, Blue Earth County, MN, Cottonwood County, MN, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Jackson County, MN, Martin County, MN, Mower County, MN, Murray County, MN, Nobles County, MN, Pipestone County, MN, Rock County, MN, Steele County, MN, Waseca County, MN, Watonwan County, MN, Dakota County, NE, Union County, SD

The radar

The Minneapolis radar (KMPX), 184 km from the middle of the area, began a volume at 03:48 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 00:00Z, 3.8 hours before the alert went out and 183 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.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 2021-08-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Minneapolis, MN at 00:00Z on 2021-08-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 393 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
792 m above ground
0-6 km bulk shear
49 kt
0-1 km storm-relative helicity
393 m²/s²
0-3 km storm-relative helicity
392 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted.

022 
ACUS11 KWNS 270346
SWOMCD
SPC MCD 270345 
IAZ000-MNZ000-NEZ000-SDZ000-270545-

Mesoscale Discussion 1615
NWS Storm Prediction Center Norman OK
1045 PM CDT Thu Aug 26 2021

Areas affected...portions of southern MN and northern IA

Concerning...Severe potential...Watch possible 

Valid 270345Z - 270545Z

Probability of Watch Issuance...40 percent

SUMMARY...Strong to isolated severe thunderstorms producing locally
strong gusts and hail are possible into the early overnight period
across parts of southern MN into northern IA.

DISCUSSION...Isolated to scattered convection has developed across
far southern MN into far northern IA late this evening. This
activity is to the north of a west-to-east oriented stationary
surface boundary extending across northern IA. This activity has
intensified recently as warm advection increases across the region
as a southerly low level jet has strengthened over the mid-MO valley
vicinity. Strong inhibition exists, especially north of the
boundary, but moderate instability amid steep midlevel lapse rates
and effective shear greater than 35 kt is aiding in organized
clusters. Hail and locally strong gusts could accompany this
activity into the early overnight period. However, the elevated
nature of convection may temper the overall severe threat as
convection shifts northeast into a somewhat less favorable
environment. While a severe thunderstorm watch does not appear
imminent at this time, convective trends are being monitored, both
with activity across northern IA as well as further west across
northeast NE/southeast SD. If better organized clusters develop, a
watch could become necessary.

..Leitman/Bunting.. 08/27/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...ARX...MPX...DMX...FSD...OAX...

LAT...LON   44159610 44259541 44179345 44029257 43759202 43259193
            42779202 42539265 42339426 42219599 42169667 42689678
            44069644 44159610

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 26, 8:03 PM CDTSevere Thunderstorm WatchSPCBuena Vista, Cherokee, Clay, Dickinson, Ida, Lyon and 5 more7 hr
Aug 27, 1:53 PM CDTMesoscale DiscussionSPCBlack Hawk, Bremer, Butler, Calhoun, Cerro Gordo, Chickasaw and 18 more97 min
Aug 27, 4:01 PM CDTMesoscale DiscussionSPCAllamakee, Black Hawk, Bremer, Butler, Calhoun, Cerro Gordo and 20 more59 min
Aug 27, 5:15 PM CDTTornado WatchSPCAllamakee, Bremer, Butler, Cerro Gordo, Chickasaw, Clayton and 12 more6 hr
Aug 27, 5:30 PM CDTMesoscale DiscussionSPCAllamakee, Cerro Gordo, Chickasaw, Floyd, Howard, Winneshiek60 min
Aug 27, 6:28 PM CDTMesoscale DiscussionSPCAudubon, Calhoun, Carroll, Crawford, Greene, Guthrie and 6 more92 min
Aug 26, 7:25 PM CDTMesoscale DiscussionSPCBoyd, Brown, Cherry, Holt, Keya Paha, Rock2 hr
Aug 27, 3:55 PM CDTMesoscale DiscussionSPCButte, Harding, Perkins2 hr
Aug 27, 6:33 PM CDTMesoscale DiscussionSPCButte, Perkins, Ziebach117 min

Nearby

Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Minnesota, 2021Mesoscale Discussions in Nebraska, 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.