Mesoscale Discussion 521

Issued

May 25, 2018, 5:20 PM CDT (22:20 UTC)

Expired

May 25, 2018, 7:15 PM CDT

In force

115 min

Issued by

the Storm Prediction Center

The Minneapolis radar (KMPX), 62 km from the middle of the area, began a volume at 22:22 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.

455 
ACUS11 KWNS 252221
SWOMCD
SPC MCD 252220 
WIZ000-IAZ000-MNZ000-SDZ000-260015-

Mesoscale Discussion 0521
NWS Storm Prediction Center Norman OK
0520 PM CDT Fri May 25 2018

Areas affected...far eastern South Dakota...southern and central
Minnesota...western and central Wisconsin...and far northern Iowa

Concerning...Severe Thunderstorm Watch 120...

Valid 252220Z - 260015Z

The severe weather threat for Severe Thunderstorm Watch 120
continues.

SUMMARY...Thunderstorms continue within a moist, unstable
environment. Isolated hail and gusty thunderstorm winds will be
possible for another few hours before thunderstorms weaken after
sunset.

DISCUSSION...Thunderstorms continue throughout the region within a
moist, weakly-capped environment. GOES-EAST 1-minute visible imagery
suggest that occasionally strong updraft pulses are occurring, but
are not being sustained for any significant duration. These strong
updraft pulses are likely stemming from most-unstable CAPE values
ranging from a 1200 J/kg across southwest Minnesota up to around
2500 J/kg across portions of western Wisconsin (in and near Severe
Thunderstorm Watch #120). However, deep-layer shear is generally
less than 30 knots across much of the region, which is likely
contributing to the inability of any sustained intense updrafts.
Although large hail and gusty thunderstorm winds will be possible
with the stronger updraft pulses (especially in and near WW 120),
the overall lack of sufficient deep-layer shear will act to broadly
limit thunderstorm organization/maturation and preclude a more
robust, widespread severe threat.

..Marsh.. 05/25/2018

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

ATTN...WFO...GRB...MKX...DVN...DLH...ARX...MPX...DMX...FSD...
ABR...

LAT...LON   44589717 45609388 46289221 45988891 43088946 42479088
            42699520 43449837 44589717

Mesoscale Discussions in Minnesota, 2018Mesoscale Discussions in Wisconsin, 2018Mesoscale Discussions in Iowa, 2018Every mesoscale discussion in 2018

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.