Mesoscale Discussion 1819

Issued

Oct 10, 2021, 12:57 PM CDT (17:57 UTC)

Expired

Oct 10, 2021, 3:00 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

60%

Counties Itasca County, MN, Koochiching County, MN, Lake County, MN, Lake of the Woods County, MN, Saint Louis County, MN

The Duluth radar (KDLH), 122 km from the middle of the area, began a volume at 17:57 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 516Oct 10, 1:40 PM CDT

936 
ACUS11 KWNS 101758
SWOMCD
SPC MCD 101757 
MNZ000-102000-

Mesoscale Discussion 1819
NWS Storm Prediction Center Norman OK
1257 PM CDT Sun Oct 10 2021

Areas affected...northern Minnesota

Concerning...Severe potential...Watch possible 

Valid 101757Z - 102000Z

Probability of Watch Issuance...60 percent

SUMMARY...Isolated to scattered strong storms, including a few
supercells, may pose a risk for isolated hail, a brief tornado, and
or strong wind gusts this afternoon. A weather watch is being
considered.

DISCUSSION...As of 1730 UTC, WV satellite imagery showed a
pronounced upper low moving northeastward across the northern Plains
and upper Midwest. Strong mid-level height falls have been observed
near and to the east of the low where a 995 mb surface cyclone was
analyzed across eastern North Dakota. Near the surface low, visible
imagery showed towering cumulus and shallow convection developing
early this afternoon. Breaks in the clouds were allowing surface
heating and destabilization of a relatively moist boundary layer
with dewpoints near 60 F. As strong lift from the upper low and
convergence along the bent back cold/occluded front continue to move
northward, additional thunderstorm development appears likely across
northern Minnesota by mid afternoon. Steep mid-level lapse rates
near 7 C/km exist beneath the cold pocket aloft supporting around
1000 J/kg of MLCAPE. Strong southwesterly mid-level flow is also
aiding in strong wind profiles with effective shear upwards of 50
kts. While buoyancy may limit the threat somewhat, the strong shear
suggests that organized storms including supercells are likely. The
steep lapse rates and favorable deep-layer shear will likely support
a hail risk with the stronger cores that develop. Backed surface
flow east of the low may also support a brief tornado with the
stronger supercells. 

The severe risk is expected to gradually evolve with initial storms
developing within cloud breaks close to the surface low early this
afternoon. Despite cooler surface temperatures, dynamic lift should
continue to support a severe risk as storms move northward toward
the Canadian border. Farther east across the Arrowhead, dense cloud
cover and cooler temperatures have remained in place through much of
the morning. Model soundings show inhibition remains strong enough
to limit deep convection, casting doubt on the eastward extent of
the severe threat. Better clearing and rapid warm advection across
northwestern Wisconsin behind a warm front is evident on visible
imagery, hinting that storms may develop farther south later this
afternoon. Exact convective evolution of these storms is unclear
given the less favorable environment northward. Nonetheless, a
severe risk appears likely to evolve this afternoon with a risk for
hail and tornadoes/damaging wind gusts. A weather watch is possible.

..Lyons/Hart.. 10/10/2021

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

ATTN...WFO...DLH...FGF...

LAT...LON   47329092 47099127 46919182 46859266 47209373 48299478
            48989508 48849408 48729346 48649258 48539199 48399146
            48279124 48059088 47889081 47629080 47329092

Mesoscale Discussions in Minnesota, 2021Every mesoscale discussion in 2021

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.