|Mesoscale Discussion 1677|
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Mesoscale Discussion 1677
NWS Storm Prediction Center Norman OK
0106 AM CDT Sun Sep 06 2020
Areas affected...Southern MN...Northern/Northeastern IA
Concerning...Severe Thunderstorm Watch 486...
Valid 060606Z - 060730Z
The severe weather threat for Severe Thunderstorm Watch 486
SUMMARY...Threat for large hail continues across southern MN and
northern/northeast IA. Potential for damaging wind gusts has also
increased across the region.
DISCUSSION...Recent surface analysis places a warm front from BKX
(in far east-central SD) southwestward across southwest MN and
north-central IA to near CID in southeast IA. A strong low-level jet
(i.e. 40 to 50 kt) continues across this tight frontal zone,
contributing to strong warm-air advection and widespread elevated
Recent RAP soundings reveal a mid-level dry layer, roughly between
850 and 700 mb, from a remnant elevated mixed layer. This EML is
contributing to both strong buoyancy as well as the potential for
strong downbursts. Regional radar imagery shows that a few of these
storms have begun to accelerate more southward/southeastward,
indicative of strong outflow and a tendency toward more forward
propagation. A 54 kt was measured at RWF at 0516Z and other strong
gusts of 42 kt and 38 kt were measured at MKT and AUM, respectively.
This is evidence that despite the elevated character of the storms,
the downbursts are strong enough to penetrate through the low-level
stability and reach the surface. Consequently, the threat for
damaging wind gusts has increased. The threat for large hail also
remains over the region.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 44729636 45059549 44899454 44199263 43329128 42029120
41589159 41779270 43539594 44729636
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