Severe Storm Outlook Narrative (AC)
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000
ACUS48 KWNS 230902
SWOD48
SPC AC 230900

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0400 AM CDT Tue May 23 2017

Valid 261200Z - 311200Z

...DISCUSSION...
A low-amplitude mid-level flow pattern will develop at the beginning
of the Day 4-8 time frame across much of the central/eastern U.S.,
gradually evolving into a broadly cyclonic regime around an upper
low between the Great Lakes and Hudson Bay by Tue/May 30th.

...Day 4/Friday...
Rich gulf moisture returns to the central/southern Plains and
western gulf coast in advance of a cold front from the upper Midwest
into the southern High Plains, and east of a dryline over
Oklahoma/north Texas. A plume of steep mid-level lapse rates and
attendant capping inversion will also likely be in place, casting
uncertainty on the potential for thunderstorm development along the
southern High Plains dryline and in advance of the cold front.
Somewhat higher confidence exists for strong/severe storms to
develop in the easterly surface flow north of the front across the
central High Plains late in the day, moving east Friday night with a
developing/veering low-level jet. Severe probabilities will likely
be warranted in future outlooks as confidence on specific risk areas
increases.

...Day 5/Saturday and Day 6/Sunday...
Severe potential may accompany the southern Plains dryline, and cold
front as it moves south/eastward across the Great Lakes/Appalachians
into the southern Plains during the weekend. Unstable/favorably
sheared conditions will exist over a broad area from the
central/southern Plains eastward into portions of the mid-Atlantic
states. Uncertainty regarding timing of upper-level impulses and
effects of prior convection preclude severe risk areas with this
outlook.

...Day 7/Monday and beyond...
Thunderstorms will be possible along a weakening frontal boundary
extending from the northeast U.S. south/west into Texas, with
substantial uncertainty regarding daily risk areas.

..Bunting.. 05/23/2017



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