Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 190945
SPC AC 190943

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0343 AM CST Sun Feb 19 2017

Valid 221200Z - 271200Z

The potential for severe thunderstorms will focus late in the work
week as a very strong mid-level speed max moves from the Four
Corners into the Great Plains on Thursday (Day 5) and later into the
OH Valley/Great Lakes on Friday (Day 6).  Despite the development of
a deep surface cyclone over the central Great Plains on Thursday,
limited moisture because of an early-mid week mid-level low over the
Gulf of Mexico will likely prove detrimental in the return of rich
low-level moisture into the central and southern Great Plains.  The
greatest risk for severe thunderstorms appears to occur on Friday
across the far southern Great Lakes and OH Valley.  Both
deterministic ECMWF and GFS models have exhibited consistency in
longitudinally placing the aforementioned closed low/trough in the
vicinity of IA.  Models and their ensembles indicate that an
elevated mixed layer originating from the Great Plains will be
advected into the highlighted area along with a strong consensus for
marginal low-level moisture (50s degrees F boundary-layer
dewpoints).  Given the expected setup, sufficient confidence is
attained for some severe risk to be highlighted graphically, with
the expected severe hazard to be mainly damaging winds.  Additional
adjustments in the area are likely with subsequent outlooks as
confidence increases with spatial placement of the severe risk.

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