Day 1 Severe Weather Outlook

Valid 211630Z – 221200Z


The risk for thunderstorms appears negligible across much of the
nation today into tonight, but a couple of thunderstorms could
develop near southern California coastal areas late tonight.

Large-scale mid-level troughing will continue to progress across and
east of the Atlantic Seaboard today through tonight. As this
occurs, an associated significant cold front will advance
southeastward through the western Atlantic and the remainder of the
southern Florida Peninsula, while likely stalling and weakening over
the southern Gulf of Mexico.

In the wake of the front, generally dry and/or stable conditions
prevail across much of the nation. Little substantive change is
expected through early Saturday, but models do indicate that a
significant closed low emerging from the southern mid-latitude
eastern Pacific probably will begin progressing inland across
southern California coastal areas by 12Z Saturday.

…Southern Florida Peninsula…
Although the pre-frontal boundary layer is moist and potentially
unstable across southeast coastal areas and the Keys, inhibition
associated with relatively warm and dry air in the lower/mid
troposphere, coupled with weak forcing for ascent, still appears
likely to preclude thunderstorm development before the front
advances offshore.

…Southern California coastal areas…
Model output appears generally similar with the cold core (-24 to
-26 C at 500 mb) of the mid-level closed low spreading into southern
California coastal areas, from around Santa Barbara County into the
Los Angeles Basin, by 09-12Z. Based on latest forecast soundings,
steepening of lower/mid tropospheric lapse rates will result in
increasingly favorable thermodynamic profiles to support potential
for isolated to widely scattered weak thunderstorm development by
the end of the period.

..Kerr.. 02/21/2020


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