Severe Storm Outlook Narrative (AC)
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092
ACUS48 KWNS 160944
SWOD48
SPC AC 160943

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CST Tue Jan 16 2018

Valid 191200Z - 241200Z

...DISCUSSION...
Relatively zonal mid-level flow will be positioned over much of the
US by the end of this week, prior to a trough digging across the
southwestern US this weekend. Subsequently, increasing flow across
the Rockies will induce lee troughing/cyclogenesis during this time
frame. In response, southerly low-level flow across the southern
Plains and lower Mississippi Valley will aid in modifying the
remnant continental air mass from the prior week. As the mid-level
trough ejects east across the Plains, showers and thunderstorms will
become more likely, primarily on D6/Sunday. Some potential for
severe weather may exist, augmented by potent mid/upper wind fields
overspreading the south-central US. However, considerable
uncertainty remains regarding the quality of boundary-layer moisture
return (and related surface-based buoyancy) in the wake of a
shortwave trough crossing the Gulf this weekend. Indeed, ensemble
ECMWF data suggest quite low probabilities for MUCAPE greater than
250 J/kg over Texas and Louisiana. Therefore, while some severe
threat may evolve by D6/Sunday, predictability remains too low for a
15% area at this time.

Thereafter, more notable low-level moisture return may materialize
ahead of a deepening western-US trough early next week (primarily
D8/Tuesday and beyond). More substantial buoyancy could yield a
greater severe potential, but the progressive/uncertain nature of
the pattern (combined with inherent uncertainty at this forecast
range) casts too much doubt for probabilities at this time.

..Picca.. 01/16/2018



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