Day 1 Severe Weather Outlook

Valid 151300Z – 161200Z


Organized severe thunderstorms are not expected across the U.S.

On the larger scale, a trough will amplify near the Pacific
Northwest coast through tonight, while downstream heights will rise
across the northern Plains and upper MS Valley. Isolated lightning
strikes may occur along the coasts of WA/OR as the midlevel thermal
trough and steeper lapse rates spread inland tonight. Farther east,
a low-amplitude shortwave trough will continue eastward over the
upper Great Lakes today. Clusters of mostly elevated thunderstorms
are ongoing across northern IL within a zone of low-level warm
advection associated with the upper Great Lakes trough. There is a
low chance for hail with the strongest storms this morning, though
the warm advection will weaken and shift eastward later today, with
an associated decrease in storm coverage/intensity expected.

South of the main belt of westerlies, a midlevel low is moving
slowly westward over the northwest Gulf of Mexico, and will continue
to support a threat for additional storms near the coast along the
north edge of the richer tropical moisture. A separate midlevel low
will continue to move slowly northeastward from southeast AZ toward
the Four Corners through tonight. Scattered thunderstorms are
expected with diurnal heating in cloud breaks over the high terrain
and in the zone of ascent north through east of the low. Vertical
shear and buoyancy may become sufficient for a strong storm or two
in the vicinity of extreme southwest NM this afternoon, though the
threat for damaging winds appears too low to warrant an outlook

..Thompson/Gleason.. 09/15/2019


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