SPC AC 230555
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1155 PM CST Mon Jan 22 2018
Valid 241200Z - 251200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
A few thunderstorms will be possible across coastal areas of the
Pacific Northwest from Wednesday afternoon into Wednesday night.
A progressive and amplified mid-upper level flow pattern is expected
across the contiguous U.S. during this forecast period, as two
shortwave troughs reinforce an eastern states longwave trough.
Meanwhile, an upper ridge will shift east of the Rockies as a large
Pacific trough moves into the western states. Aside from a low
probability of thunderstorms across coastal areas of southwest WA,
OR, and northern CA beginning Wednesday afternoon into the evening,
a stable boundary layer across the rest of the CONUS will preclude
the potential for thunderstorms.
...Coastal areas of southwest WA, OR, and northern CA...
A cold front attendant to the inland-moving large-scale Pacific
trough should spread into the western third of WA, OR, and far
northwest CA during Wednesday afternoon, and proceed farther inland
through the rest of WA/OR into northwest NV and northern CA. Cold
500-mb temperatures (-30 to -34 C) with the trough will further
steepen lapse rates in the post-cold front environment, with weak
buoyancy supporting lightning production. In addition to strong
height falls, the timing of an embedded shortwave trough reaching
western OR/WA Wednesday afternoon suggests sufficient upward
vertical motion could enhance the potential for thunderstorms.
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z