Severe Storm Outlook Narrative (AC)
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ACUS48 KWNS 190847
SPC AC 190846

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Sat Aug 19 2017

Valid 221200Z - 271200Z

The mid-latitude westerlies may undergo further amplification
through the middle of the coming work week, including the evolution
of large-scale troughing across much of the Great Lakes, Ohio Valley
and Northeast.  Within this regime, models suggest that one
significant short wave impulse could support significant
cyclogenesis across Quebec, accompanied by a trailing cold front
which may advance through much of the eastern U.S. before weakening.
There remains a signal within model output that pre-frontal forcing
for ascent may be favorably timed with peak diurnal destabilization
across parts of the lower Great Lakes region and upper Ohio Valley
on Tuesday to support considerable vigorous thunderstorm activity.
In the presence of 30-50 kt deep layer mean flow and shear,
organized severe storm development appears possible, with
potentially damaging wind gusts the primary hazard.  Continuation of
this threat across southern New England and the northern Mid
Atlantic on Wednesday remains more unclear, with possible early day
progression of the front off the coast.

Thereafter, late next week into early next weekend, upper
troughiness may linger across parts of the Upper Midwest/Great Lakes
and Atlantic Seaboard, as subtropical ridging becomes increasingly
prominent across the Intermountain West and Rockies.  Although short
wave developments within this regime remain more uncertain, there
appears little obvious at the present time to suggest anything more
than perhaps generally low severe weather potential.

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