Mesoscale Discussion 1384
NWS Storm Prediction Center Norman OK
0625 PM CDT Fri Jul 21 2017
Areas affected...Central MN...Southeast ND...Northeast SD
Concerning...Severe Thunderstorm Watch 428...
Valid 212325Z - 220100Z
The severe weather threat for Severe Thunderstorm Watch 428
SUMMARY...The threat continues across WW 428, with an increasing
damaging wind risk associated with the developing bow echo over
north-central MN. Downstream watch issuance is likely.
DISCUSSION...At 2315Z, a developing bow echo was located over
north-central MN, with more discrete activity further southwest into
far southeast ND. Downstream of the bow echo, MLCAPE has increased
to the 1500-2500 J/kg range, with effective shear of 45-55 kt per
recent mesoanalyses. This environment will allow continue maturation
of this system and a continuation of the damaging wind risk for the
next 1-2 hours at least, before it encounters a more stable and
capped environment across northeast MN/northern WI. East of the
watch, a weaker cluster may also pose some isolated damaging wind
risk into the Duluth area over the next hour or so.
Further southwest, weaker convection continues along the trailing
outflow into west-central MN, while a strong discrete cell is
located over extreme southeast ND. Strong buoyancy and sufficient
effective shear will support a continued severe wind and hail risk
across this area. With time, some upscale growth of convection is
possible along the outflow boundary and/or evolving out of the
aforementioned discrete cells, resulting in an increasing severe
risk across portions of central MN as storms move southeastward,
though weak low-level flow may temper this threat to some extent.
Downstream watch issuance will likely be required into portions of
central MN to cover this threat.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 46109761 46759634 47369481 47499192 46809213 46069281
45489403 45249481 45079580 45079680 45449725 45619757