Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 190959
SWOD48
SPC AC 190958

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CST Mon Feb 19 2018

Valid 221200Z - 271200Z

...DISCUSSION...
Better agreement/consistency is evident at this time with respect to
various medium-range model runs through a majority of the day 4-8
period, as compared to 24 hours prior.  Models in general depict
that a major short-wave trough -- digging across California and the
Great Basin day 4 (Thursday) will eject east across the Desert
Southwest/southern Rockies day 5, and then the central and southern
Plains day 6 (Saturday).  While this feature is progged to
weaken/deamplify with time due to persistence of southeastern U.S.
ridging, surface lee cyclogenesis is expected over the southern High
Plains early in the day which will deepen/shift quickly
east-northeast into the Ohio Valley/Midwest overnight.  Ahead of
this system, low-level moisture return from the Gulf of Mexico
should prove sufficient for at least some warm-sector CAPE
development which -- combined with what should be a favorable
background lower- and middle-tropospheric wind field -- suggests
that some severe weather risk may evolve Saturday.  While degree of
instability may limit risk to some degree, ample evidence exists to
suggest initial introduction of 15% severe weather probability from
the Arklatex vicinity east across parts of the lower Mississippi and
into the Tennessee Valleys.

As the weakening upper system shifts quickly east-northeast across
the lower Great Lakes region day 7 (Sunday), expect the trailing
surface front to weaken and become oriented increasingly
west-to-east across the Gulf Coast region, suggestive of diminished
severe potential.  In addition, model differences increasing through
the end of the period result in reduced confidence with respect to
the convective forecast through early next week.

..Goss.. 02/19/2018



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