Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 230143
SWOMCD
SPC MCD 230143
MNZ000-230345-

Mesoscale Discussion 1668
NWS Storm Prediction Center Norman OK
0843 PM CDT Fri Sep 22 2017

Areas affected...Northern MN

Concerning...Severe potential...Watch unlikely

Valid 230143Z - 230345Z

Probability of Watch Issuance...20 percent

SUMMARY...Strong to locally severe thunderstorms are expected to
increase in areal coverage across northern Minnesota this evening.
Hail and damaging winds are the primary severe threats.

DISCUSSION...Strong inhibition appears to be mostly responsible for
slow evolution of deep convection across the eastern Dakotas into
northern MN this evening. 00z soundings across this region exhibit
steep mid-level lapse rates but notable capping between 750-800mb.
However, sustained low-level warm advection appears to be weakening
this stable layer and elevated thunderstorms are gradually
increasing north of the warm front over northern MN. Latest radar
data suggests a few of the most robust updrafts are beginning to
show supercell characteristics, especially over Beltami County MN
and this is to be expected given the more favorable shear along the
cool side of the warm front. This activity should spread toward the
international border over the next few hours then become
concentrated over northwest ON as the front advances north.
Additionally, of some concern is the weak convection trying to
mature just ahead of the surface low over the warm sector in western
Becker County MN. It`s not entirely clear whether this convection
will grow upscale, as capping appears to remain an issue south of
the front where less forcing is noted. At this time a watch is not
anticipated as primary severe threat should cover a limited area and
shift north of the border into southern Canada within a few hours.

..Darrow/Edwards.. 09/23/2017

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

ATTN...WFO...DLH...FGF...

LAT...LON   47449669 48929578 48929311 47839255 47119476 46509613
            47449669




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