Severe Storm Outlook Narrative (AC)
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491
ACUS48 KWNS 200842
SWOD48
SPC AC 200840

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0340 AM CDT Fri Oct 20 2017

Valid 231200Z - 281200Z

...DISCUSSION...
Models suggest that an amplification within the mid-latitude
westerlies, across the eastern Pacific into western North America by
late this weekend, will translate eastward during the early to
middle portion of next week.  This may occur in the form of a
significant digging upper trough to the lee of ridging centered near
the Pacific coast, from the upper Mississippi Valley into much of
the eastern U.S. by late next Wednesday.  When and just how this
feature consolidates with another perturbation initially over the
lower Mississippi Valley remains unclear, but strong surface
cyclogenesis appears at least a possibility across parts of upper
Ohio Valley/lower Great Lakes region.  If this is realized, it is
possible that any associated convective development embedded within
potentially strong deep layer mean wind fields could aid downward
transfer of this momentum to the surface, with a risk for
potentially damaging wind gusts.  At the present time, any such
activity seems most probable Tuesday, east of the lower Great Lakes
region into portions of New England, and/or across parts of the Mid
Atlantic Coast region.  It is unclear if thermodynamic profiles will
be supportive of lightning with this convection, which may be mostly
low-topped in nature.

..Kerr.. 10/20/2017



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