SPC May 2, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0230 AM CDT Tue May 02 2017

Valid 041200Z - 051200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE PACIFIC NORTHWEST...

...SUMMARY...
A few strong/severe thunderstorms will be possible across parts of
the Southweast, as well as the Pacific Northwest, Thursday into
Thursday night.

...Synopsis...
An amplified mid-level trough and embedded closed low will gradually
advance towards the Appalachians Thursday, as several weak impulses
rotate around its periphery. Meanwhile, upstream ridging will build
towards the Rockies, with a trough and increasing southerly
mid-level flow approaching the Pacific Northwest.

...Portions of the Southeast US...
Related to the mid-level trough, a surface cold front will continue
to sweep east/southeast across the central/eastern Gulf Coast region
Thursday into Thursday night. Most likely, a weakening band of
convection from Wednesday night will be ongoing ahead of this front.
With considerable precipitation/cloud cover spreading ahead of the
main band of ascent, significant downstream destabilization seems
quite uncertain during the day, especially with upstream mid-level
lapse rates becoming less steep due to convective overturning.
Nonetheless, within the remnant band of convection spreading east,
or within re-development along the front itself, modest
surface-based buoyancy and sufficient low-level/deep-layer shear
will likely encourage a few strong/severe storms, primarily capable
of damaging wind gusts. Additionally, low-level veering with height
and fairly rich boundary-layer moisture near the coast may be
sufficient for a tornado or two, as storms advance east towards the
southeast Atlantic Coast.

...Portions of the Pacific Northwest...
On the backside of the departing mid-level ridge, mid-level
southerly flow is forecast to increase considerably through Thursday
afternoon and evening. Guidance is in relatively good agreement that
a small layer of modestly steep mid-level lapse rates, in
combination with increasing boundary-layer moisture and diurnal
heating, will yield moderate buoyancy near the Willamette Valley and
along the western foothills of the Cascades. As such, thunderstorms
that develop during the afternoon/evening may be capable of a few
instances of severe hail and/or strong wind gusts.

..Picca.. 05/02/2017

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