SPC MD 962


MD 0962 Image

Mesoscale Discussion 0962
NWS Storm Prediction Center Norman OK
0909 PM CDT Sun Jun 21 2020

Areas affected...Portions of southeast Minnesota...northeast
Iowa...western Wisconsin

Concerning...Severe potential...Watch unlikely 

Valid 220209Z - 220415Z

Probability of Watch Issuance...20 percent

SUMMARY...A couple damaging gusts, with perhaps a severe gust or
two, remain possible with the ongoing squall line. However, diurnal
cooling and waning instability should limit the ongoing threat. The
isolated nature of the severe threat suggests that a new WW issuance
is not necessary.

DISCUSSION...An organized MCS/squall line is ongoing across
northeast IA into western WI. A few severe gusts have been reported
over the past two hours across northeast IA. A narrow corridor of
adequate instability (around 1000 J/kg MLCAPE per latest
Mesoanalysis) resides immediately ahead of the line, suggesting that
a few damaging gusts, perhaps one or two approaching severe levels,
remains possible over the next couple of hours. While the 00Z DVN
sounding had indicated up to 1300 J/kg MLCAPE, modifying this
sounding based on current surface temperatures (roughly in the mid
70s F) shows MLCAPE within the 500-1000 J/kg range. Further
nocturnal cooling should contribute to boundary-layer decoupling and
associated gradual decline in severe potential, even if squall-line
structure persists. 

The ongoing squall outrunning the instability axis, along with
boundary-layer stabilization suggest that the severe threat should
be relatively sparse and brief in nature. As such, a future WW
issuance is not anticipated.

..Squitieri/Thompson.. 06/22/2020

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


LAT...LON   42669386 44179182 45269056 45668954 45638909 45028918
            43998911 43108953 42709029 42469068 42159112 42369332

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