Severe Storm Outlook Narrative (AC)
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586
ACUS02 KWNS 191702
SWODY2
SPC AC 191701

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1201 PM CDT Tue Sep 19 2017

Valid 201200Z - 211200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE U.P. OF
MI TO NORTHEAST KS...

...SUMMARY...
A few severe storms are possible from northeastern Kansas
northeastward to the Upper Peninsula of Michigan Wednesday afternoon
and evening.

...Discussion...

Strong short-wave trough is expected to eject across the upper Red
River Valley as a 500mb speed max translates across eastern ND
toward the international border region of northern MN. Height falls
will focus across this region early in the period before shifting
into northwest ON where large-scale forcing for ascent should
encourage convection along/ahead of cold front.

In the wake of the short-wave, surface pressures will rise across
the plains which will drive a surface front to a position from
western WI, southwest into central KS by early afternoon. Strong
capping along this boundary should inhibit thunderstorm development
until later in the day when boundary-layer heating should weaken CIN
such that parcels, assisted by frontal ascent, are capable of
reaching their LFC. While large-scale ascent will focus across
Canada, it appears strong, potentially severe, thunderstorms will
develop along the wind shift within a sheared environment supportive
of sustaining organized updrafts. Large hail and damaging winds are
the primary threats with line segments/clusters that should mature
during the late afternoon/early evening. This activity should linger
into the overnight hours across this Mid-Mississippi Valley as the
front stalls and convection is aided by a veered LLJ into northern
MO.

A few strong storms could evolve along the dry line across the
southern Plains but overall the severe threat appears too limited to
warrant 5% severe probs at this time.

..Darrow.. 09/19/2017

$$



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