SPC MD 1458



MD 1458 CONCERNING SEVERE THUNDERSTORM WATCH 426…429… FOR PORTIONS OF NORTHERN/CENTRAL IL…FAR SOUTHEASTERN WI…NORTHWESTERN IN…AND FAR SOUTHWESTERN LOWER MI

MD 1458 Image


Mesoscale Discussion 1458
NWS Storm Prediction Center Norman OK
0336 PM CDT Mon Aug 10 2020

Areas affected...Portions of northern/central IL...far southeastern
WI...northwestern IN...and far southwestern Lower MI

Concerning...Severe Thunderstorm Watch 426...429...

Valid 102036Z - 102200Z

The severe weather threat for Severe Thunderstorm Watch 426, 429
continues.

SUMMARY...A widespread severe/damaging wind threat continues with a
line of storms moving quickly eastward. A tornado also remains
possible. The greatest threat for 70-80+ mph wind gusts will likely
focus over the Chicago metro area over the next hour.

DISCUSSION...Latest velocity data from KLOT shows somewhat less
extreme inbound velocities (generally 50-80 kt) compared to earlier.
Even so, the overall bow echo remains well organized, and it is
moving through a very strongly unstable airmass (3500-4000+ J/kg
MLCAPE). A severe wind gust to 54 kt was observed in Aurora IL at
2016Z. The northern portion of the bow will have the best potential
to continue producing widespread damaging wind gusts as it moves
across the Chicago metro area over the next hour, with some possibly
still significant (75-80+ mph). A tornado or two embedded within the
line also remains possible across this area, but the primary risk is
still widespread damaging straight-line winds. This substantial
severe wind threat will likely continue across southern Lake
Michigan and into southwestern Lower MI and northwestern IN late
this afternoon and into the early evening given a favorable
combination of moderate to strong instability present across these
areas.

The southern portion of the line into central IL has shown less
intensity recently, with outflow beginning to surge southeastward
ahead of the updrafts. This is likely due to weaker mid-level flow
with southward extent across central IL (see recent VWPs from KILX).
Still, isolated damaging winds will remain possible across this area
in the short term.

..Gleason.. 08/10/2020

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

ATTN...WFO...IWX...GRR...LOT...ILX...MKX...

LAT...LON   40378880 40548971 41108914 42008878 42528895 43048858
            43088611 42778558 41128626 40808664 40548725 40378880 

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