SPC MD 1678

MD 1678 CONCERNING SEVERE THUNDERSTORM WATCH 486... FOR SOUTHERN MN...NORTHERN/NORTHEAST/EASTERN IA...FAR SOUTHWEST WI...NORTHWEST IL

Mesoscale Discussion 1678
NWS Storm Prediction Center Norman OK
0232 AM CDT Sun Sep 06 2020

Areas affected...Southern MN...Northern/Northeast/Eastern IA...Far
Southwest WI...Northwest IL

Concerning...Severe Thunderstorm Watch 486...

Valid 060732Z - 060900Z

The severe weather threat for Severe Thunderstorm Watch 486
continues.

SUMMARY...Threat for severe hail and damaging wind gusts will
continue for the next few hours. Given that Severe Thunderstorm
Watch #486 is set to expire at 08Z, a watch extension and/or new
watch will be needed to address the continuing severe threat.

DISCUSSION...Recent surface observations reveal the position of the
warm front has been modified slightly by storm outflow. Currently
the warm front lies from FSD (in far southwest SD)
east-southeastward to AXA (in north-central IA) and then more
southeastward across IA to near MUT on the southern IL/IA border.
Intense updrafts persist within several of the thunderstorms north
of this front across south-central MN/north-central IA into
northeast/east-central IA. 

Recent radar imagery has shown a trend toward more storm clustering
and forward propagation, potential signalling a transition to more
cold pool dominant storm structures. Even with the elevated nature
of the ongoing storms, cold pool amalgamation is still possible,
with the resulting clusters then progressing quickly southeastward.

A strong low-level jet will continue to support warm-air advection
across the frontal zone, helping to provide warm, moist inflow to
the ongoing storms. Expectation is for the threat for large hail and
damaging wind gusts to persist for at least the next few hours,
particularly from south-central MN/north-central IA downstream into
southwest WI and northwest IL. Severe Thunderstorm    Watch #486 is
set to expire at 08Z and a watch extension and/or new watch will
likely be needed to address the continuing severe threat.

..Mosier/Guyer.. 09/06/2020

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

ATTN...WFO...LOT...ILX...MKX...DVN...ARX...MPX...DMX...FSD...

LAT...LON   44479532 44639379 43609117 41848918 40589060 42059401
            43199544 44479532 

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from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1678.html