Mesoscale Discussion 0687
NWS Storm Prediction Center Norman OK
0630 PM CDT Sat Jun 09 2018
Areas affected...eastern Iowa...southwestern Wisconsin...and into
Concerning...Tornado Watch 165...
Valid 092330Z - 100130Z
The severe weather threat for Tornado Watch 165 continues.
SUMMARY...Severe/isolated tornado risk continues across parts of
northeast Iowa, with severe potential to expand southeastward with
time. A downstream Severe Thunderstorm Watch may be needed.
DISCUSSION...Latest radar loop shows storms over northeast Iowa now
appearing to be in the beginning stages of upscale/linear growth,
which should continue over the next few hours. With a warm front --
and associated axis of instability -- lying west-northwest to
east-southeast into northern Illinois, and a southwesterly low-level
jet forecast to increase over the next several hours, a compact,
southeastward-moving MCS is expected to evolve with time.
With a small zone of moderately strong westerly flow in the 700 to
500 mb layer forecast to spread across Iowa and eventually into
northern Illinois, fast-moving convection is expected. As such, the
severe risk is likely to trend gradually toward primarily damaging
winds, with this risk possibly requiring downstream Severe
Thunderstorm Watch issuance in the next 1-2 hours.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 42479356 42989324 43459196 43269087 42679002 41918862
40758862 40789034 41389186 42479356