Graphic for MPD #0019

Mesoscale Precipitation Discussion 0019
NWS Weather Prediction Center College Park MD
440 AM EST Mon Jan 22 2024

Areas affected...central and southern California

Concerning...Heavy rainfall

Valid 220939Z - 222139Z

Summary...Moderate to heavy rainfall will gradually spread
southward across the discussion area.  Widespread 1-2 inch
rainfall amounts are expected, which could cause localized
flood/flash flood issues through late Monday.

Discussion...A broad axis of moderate to heavy rainfall was
located from the windward slopes of the Sierra south-southwestward
through the central California coastline near Santa Cruz. 
Additional areas of heavy rainfall were located just west of Santa
Monica and should reach that part of the coast within the next
hour or two.  Rain rates of 0.25-0.5 inch/hr have been noted with
the heaviest rainfall - and the highest rates have been observed
along terrain-favored areas where orographic ascent has been
maximized.  The rainfall is being driven by ascent from a
mid-level wave approaching the state from the west, moisture (~1
inch PW values along the coast and offshore), and modest
instability (500+ J/kg also along the coast).

With time, the approaching mid-level wave will result a modest
strengthening of westerly low-level flow (into the 10-20 kt range
at 850mb) is expected to occur from central into southern
California - especially near coastal ranges.  As this occurs, an
increase in rain rates will spread southeastward from the Santa
Barbara area (beginning around 10Z) through the Los Angeles and
San Diego areas (and adjacent coastal ranges) beginning in the
14-15Z timeframe.  Several hours of rainfall will likely lead to
widespread 1-2 inch rainfall amounts through Monday afternoon,
with locally higher totals possible along windward slopes of
higher terrain.  The rainfall is expected to cause occasional,
isolated flood and flash flood issues especially in low-lying and
sensitive areas.

Cook

ATTN...WFO...HNX...LOX...MTR...SGX...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON   37222105 36512058 35802010 35261927 34931787
            34301698 33451639 32621620 32411669 32471724
            33041771 33591839 33931928 34282029 34722082
            35672168 36362205 36782189 37182151
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Last Updated: 440 AM EST Mon Jan 22 2024