|Mesoscale Discussion 1250|
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Mesoscale Discussion 1250
NWS Storm Prediction Center Norman OK
0943 PM CDT Thu Jul 06 2017
Areas affected...Wisconsin...portions of the southern Michigan Upper
Peninsula and northwest lower Michigan
Concerning...Severe Thunderstorm Watch 400...
Valid 070243Z - 070415Z
The severe weather threat for Severe Thunderstorm Watch 400
SUMMARY...The risk for large hail and damaging winds continues
across the remaining valid portions of Severe Thunderstorm Watch
400. A bowing line of severe storms across Door County WI may enter
northwest lower Michigan around 0330Z with at least a localized risk
for damaging winds. Trends in thunderstorm coverage across central
Wisconsin are being monitored however the need for a downstream
watch is not immediately evident.
DISCUSSION...A bowing line of severe storms was moving southeast at
40 kts across the northern Door Peninsula in northeast Wisconsin at
0230Z with a history of marginally severe wind gusts and small hail.
As this complex continues southeast in the vicinity of a diffuse
northwest-southeast oriented outflow boundary from storms earlier
today, some risk for damaging gusts may continue across northwest
lower Michigan into the late evening hours. With the onset of
nocturnal cooling, some uncertainty remains regarding the potential
longevity of this convective line as it moves across northwest lower
Michigan within a gradient in MUCAPE, however radar/near-storm
environmental trends will continue to be monitored.
To the west of the bowing segment, a broken line of
strong/occasionally severe thunderstorms extends west to vicinity of
Rusk County Wisconsin. In the presence of moderate elevated
instability and 35-40 kts of deep-layer shear, the risk for isolated
severe storms is expected to continue for at least a couple more
hours, aided by ascent with a mid-level impulse moving southeast
across the watch area.
A third area of severe storms exhibiting supercell characteristics
was located over central Wisconsin at 0230Z with a history of
large/isolated significant hail. Left split-associated storm
mergers have recently resulted in an increase in coverage as the
storms move southeast within a moderate-strongly unstable
environment and 30-35 kts of deep shear. Latest high-resolution
guidance suggests that the severe threat may remain somewhat
focused/localized for the next couple of hours, casting some
uncertainty on the need for a downstream watch. Radar trends will
be monitored for increasing organization of the thunderstorms across
southern portions of Wisconsin this evening.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 44809030 45159032 45319126 45539141 45679056 45698946
45828880 45918815 45968751 45888684 45198572 44768541
44308550 44038589 43928653 43728708 43178782 42908876
42948973 43089047 43379114 43849126 44239090 44709036
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