SPC MD 1440


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Mesoscale Discussion 1440
NWS Storm Prediction Center Norman OK
0725 PM CDT Thu Jul 11 2019

Areas affected...Portions of ND and northwestern MN

Concerning...Severe potential...Watch possible 

Valid 120025Z - 120230Z

Probability of Watch Issuance...40 percent

SUMMARY...Large hail, damaging winds, and perhaps a tornado will be
possible with any storms that develop this evening. Watch issuance
is possible, but is conditional on storm development.

DISCUSSION...A 40-55 kt westerly mid-level jet will continue to
overspread ND and northwestern MN this evening as a surface cold
front likewise develops eastward across this region. Although
low-level convergence along the front does not appear very strong,
it may be sufficient in tandem with ascent attendant to the
mid-level jet to initiate isolated storms by 02Z near the
international border and into parts of northern ND. An elevated
mixed layer characterized by 7-8 C/km lapse rates is present over
this region, and is supporting generally 1500-2500 J/kg of MLCAPE
per 00Z mesoanalysis estimates. South-southwesterly low-level winds
quickly veer and strengthen into mid levels, with 45-50 kt of
effective bulk shear.

Supercells would likely be the dominant storm mode initially given
the strong shear, with both large hail and damaging winds possible.
Isolated very large hail (2+ inches in diameter) may occur where
instability is forecast to be strongest in a narrow corridor ahead
of the front in northeastern ND and far northwestern MN. A tornado
or two may also occur with these supercells as a southwesterly
low-level jet strengthens to around 25-35 kt through 03Z, modestly
enhancing low-level shear.

Primary uncertainty remains overall convective coverage, which may
be quite isolated. An attempt at initiation in Mercer/McLean
counties in central ND appears to have failed, likely related to an
inversion in the 850-830 mb layer noted on the 00Z sounding from
Bismarck ND. A more probable zone of initiation may be across
north-central into northeastern ND where ACCAS has recently formed
and the strongest surface pressure falls exist. Regardless, this
severe threat remains conditional on storms forming and/or moving
southeastward into ND and northwestern MN this evening.

..Gleason/Hart.. 07/12/2019

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


LAT...LON   47460125 47680113 49039942 49049524 49469522 49419476
            48879471 48179520 47709588 47489701 47129845 46859994
            47140097 47460125 

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