Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 180658
SWOD48
SPC AC 180656

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0156 AM CDT Wed Oct 18 2017

Valid 211200Z - 261200Z

...DISCUSSION...
Medium-range models are in general agreement regarding the evolution
of a short-wave trough as it migrates across the western US late
this week before affecting the Plains/MS Valley during the day4/5
time period. While there remain timing differences among the models,
with the ECMWF being the fastest, most agree that significant height
falls will spread into the central Plains Saturday with lesser
certainty across lower latitudes into the day5 period. Higher-PW air
mass will advance northward across OK/KS prior to a strong frontal
passage and adequate instability should be in place for robust
convection along the surging boundary, including the possibility for
severe. For these reasons have introduced 15% severe probs from
eastern KS into north-central TX where greatest confidence in
buoyancy overlaps expected thunderstorm development. Predictability
decreases Sunday as models begin to diverge in their solutions.
However, some threat for strong storms may evolve across the upper
TX Coast into LA and this region will be monitored for possible
inclusion of severe probs in later outlooks.

..Darrow.. 10/18/2017



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