Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 120958
SWOD48
SPC AC 120956

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0356 AM CST Tue Dec 12 2017

Valid 151200Z - 201200Z

...DISCUSSION...
Although there are differences between the GFS/ECMWF with the
timing, amplification and trough orientations across the contiguous
U.S. for much of the medium range, an overall agreement exists with
a change in the upper air pattern.  The current ridge in the west
and trough east of the Rockies is expected to evolve into a broad
cyclonic flow regime by Day 5 /Saturday/ to zonal flow on Day 8
/Tuesday/.

...Day 6 (Sunday)...
Models suggest a potential for thunderstorms across portions of the
northwest Gulf coast into the lower MS Valley on Sunday.  Despite
aforementioned model differences, even the more amplified ECMWF
indicated surface-based storms would be confined to the coastal
areas.  Poor lapse rates and weak instability should prove
detrimental for robust/sustained updrafts, especially inland away
from the coast.  These factors suggest the potential for severe
storms is too low for a 15% probability.

..Peters.. 12/12/2017



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