Mesoscale Discussion 1374
NWS Storm Prediction Center Norman OK
1259 PM CDT Wed Jul 28 2021
Areas affected...North-Central/Northeast MN...MN Arrowhead
Concerning...Severe potential...Watch possible=20
Valid 281759Z - 282000Z
Probability of Watch Issuance...40 percent
SUMMARY...Large hail is possible this afternoon from north-central
MN through the MN Arrowhead.
DISCUSSION...Recent surface analysis places a cold front from far
southeast Saskatchewan southwestward across far northwest MN and
through southeast ND. A surface low resides along this boundary
about 15 miles east of GFK. A warm front extends arcs southeastward
from this low across north-central MN and then back more southward
across east-central MN. A secondary low exists over far southeast
ND, with another warm front extending southeastward across southwest
MN. This second warm front is demarcated well by the 75 deg F
Moderate low-level southwesterly flow is in place within the warm
sector of MN, and the attendant warm-air advection across the
northern warm front is contributing to thunderstorm development.
Much of this activity is north of the International Border. However,
some more southerly development has occurred, including one fairly
strong storm moving across Koochiching County. Persistent warm-air
advection could result in additional development across this region.
The overall environment is characterized by steep mid-level lapse
rates and strong flow aloft. Recent mesoanalysis estimates bulk
effective shear over the region exceeds 50 kt. As a result, any
updrafts that can persist should be able to organize/rotate, with an
attendant threat for large hail.
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