Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 140959
SWOD48
SPC AC 140958

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0358 AM CST Thu Dec 14 2017

Valid 171200Z - 221200Z

...DISCUSSION...
Medium-range models are in general agreement indicating the Day 3
Rockies trough will become more positively tilted on Day 4 (Sunday)
as it shifts east, extending from northwest Mexico and the southwest
states to the upper MS Valley.  And, consensus exists with an
amplified upper-air flow pattern across the northern half of the
United States for Day 5 & 6 (Monday & Tuesday), before the next
large-scale Pacific trough advances inland in the western U.S. late
Day 6 and Day 7 (Wednesday).  Meanwhile, model differences exist
with a midlevel cyclone evolving across the Baja/northwest Mexico
(per ECMWF) and the southwest states (per GFS), and its
amplification and eastward movement through the southern Plains and
Gulf coast states through Day 7 (Wednesday).

...Day 4 (Sunday)...
There will be a potential for thunderstorms across the Gulf coast
region on Sunday.  However, given the Day 3 TX shortwave trough
should be weakening and moving northeast away from the Gulf coast,
the lack of stronger forcing for ascent and weak instability suggest
any severe-weather potential will be less than 15%.

...Beyond Day 4...
Given model differences with the southern-stream shortwave trough
and stronger instability remaining across the Gulf Basin, the
potential for severe-weather will remain less than 15%.

..Peters.. 12/14/2017



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