Day 1 Severe Weather Outlook

Valid 311300Z – 011200Z


Severe thunderstorms are not expected today nor tonight.

…Synopsis and Discussion…
In mid/upper levels, a split-flow pattern will continue across the
western CONUS, related to a well-defined, closed cyclone currently
west of northern Baja. This vortex is forecast to pivot slowly/
erratically southeastward across central Baja through the end of the
period, anchoring a positively tilted trough. By 12Z, the trough
should extend from northeastern NM across northwestern MX, through
the 500-mb low, to an area of the Pacific well west of Los Cabos.
Meanwhile, a broad, occluded, deep-layer cyclone — now covering the
upper Great Lakes and much of surrounding states and ON — will
pivot northeastward across southern/central QC, while gradually
filling. In low levels, the cold front and subsequent continental/
polar air mass related to this feature has spread across the
central/eastern CONUS, and will preclude thunder potential over

In the midlatitude westerlies, isolated/brief thunder cannot be
ruled out over parts of western WA today into this evening, based on
forecast soundings showing elevated buoyancy straddling the -20 C
isotherm, with MUCAPE around 100-300 J/kg. Somewhat greater but
still isolated thunder potential is expected after 06Z, as a
shortwave trough and related speed max now over the north-central
Pacific races eastward, reaching the Pacific Northwest coast around
12Z. Associated large-scale DCVA/ascent and cooling aloft will
further steepen low/middle-level lapse rates atop the moist marine

..Edwards.. 12/31/2019


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