SPC MD 1440



MD 1440 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR PORTIONS OF ND AND NORTHWESTERN MN

MD 1440 Image

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...

ATTN...WFO...FGF...BIS...

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

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