644
ACUS11 KWNS 212158
SWOMCD
SPC MCD 212158
IAZ000-MNZ000-212330-

Mesoscale Discussion 1364
NWS Storm Prediction Center Norman OK
0458 PM CDT Fri Jun 21 2024

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

Concerning...Severe Thunderstorm Watch 445...

Valid 212158Z - 212330Z

The severe weather threat for Severe Thunderstorm Watch 445
continues.

SUMMARY...Trends are being monitored for possible downstream watch
issuance in northern Iowa and perhaps far southern Minnesota. At
least isolated severe hail/damaging winds and a couple tornadoes all
appear possible.

DISCUSSION...A supercell which has recently exhibited some low-level
rotation is ongoing across northwest IA, generally along/near a
surface front. Other strong to severe convection is ongoing farther
east across northern IA along this boundary. This activity is likely
being aided by modest warm advection associated with a weak
southwesterly low-level jet over the central Plains and mid MO
Valley. Although mid-level flow is not overly strong per recent
mesoanalysis estimates, sufficient veering/strengthening of the
winds through mid levels (in recent VWPs from KFSD) is supporting
around 30-45 kt of deep-layer shear. A mix of multicells and
supercells will remain possible as convection spreads slowly
eastward along/near the front across northern IA over the next
several hours. At least isolated severe hail around 1-2 inches in
diameter and damaging winds generally 55-70 mph should be the main
threats with this activity in the short term. The threat for severe
winds may increase this evening if a small bowing cluster can
consolidate along the front. Low-level shear/winds remain somewhat
weak at the moment, but a couple of tornadoes may still occur with
any sustained, surface-based supercell. Observational trends will be
closely monitored for possible downstream watch issuance into
northern IA and vicinity.

..Gleason/Edwards.. 06/21/2024

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

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

LAT...LON   43319573 43669546 43869466 43889257 43869166 43539129
            43009136 42869244 42569401 42389497 42579543 43319573