Mesoscale Discussion 1429

Issued

Aug 7, 2021, 2:10 AM CDT (07:10 UTC)

Expired

Aug 7, 2021, 4:15 AM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

Counties Lyon County, IA, Osceola County, IA, Jackson County, MN, Lac qui Parle County, MN, Lincoln County, MN, Lyon County, MN, Murray County, MN, Nobles County, MN, Pipestone County, MN, Rock County, MN, Yellow Medicine County, MN, Brookings County, SD, Clark County, SD, Codington County, SD, Day County, SD, Deuel County, SD, Grant County, SD, Hamlin County, SD, Moody County, SD, Spink County, SD

The Sioux Falls radar (KFSD), 121 km from the middle of the area, began a volume at 07:13 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.

601 
ACUS11 KWNS 070711
SWOMCD
SPC MCD 070710 
MNZ000-IAZ000-SDZ000-070915-

Mesoscale Discussion 1429
NWS Storm Prediction Center Norman OK
0210 AM CDT Sat Aug 07 2021

Areas affected...Northeast/East-Central SD...Far Southwest
MN...Extreme Northwest IA

Concerning...Severe potential...Watch unlikely 

Valid 070710Z - 070915Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated large hail is possible across
northeast/east-central SD, far southwest MN, and extreme northwest
IA during the next few hours.

DISCUSSION...Regional radar imagery shows a well-defined mesoscale
convective vortex about 20 miles west of HON. This MCV is associated
with the organized convective line that moved through central SD
earlier this evening. Forward-propagating character to the storms
moving across Spink and Clark Counties suggests cold pool from the
earlier convective line continues to promote elevated thunderstorm
development as it moves northeastward. Overall updraft strength
within this line of storms has stayed relatively constant over the
past hour, but the instability weakens with northern extent and a
gradual weakening is eventually expected.

Additionally, warm-air advection showers and thunderstorms have
increase in coverage over the region during the past hour or so,
supported by a low-level jet stretching from western KS through
eastern NE into southeast SD. These storms are likely rooted within
the 850-700 mb layer. Mid-level lapse rates and vertical shear are
strong enough to support a few more robust updrafts capable of a
large hail. Intersection of this arc of warm-air advection storms
with the ongoing convective line discussed above may also lead to
brief updraft intensification and a few instance of large hail.

..Mosier/Guyer.. 08/07/2021

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

ATTN...WFO...MPX...FSD...ABR...

LAT...LON   45159895 45749761 45069561 43539508 43219617 44289717
            44799831 45159895

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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.