Mesoscale Precipitation Discussion 0039
NWS Weather Prediction Center College Park MD
537 PM EST Wed Jan 11 2023

Areas affected...northwestern, central California

Concerning...Heavy rainfall

Valid 112237Z - 120300Z

Summary...Spots of 0.25-0.5 inch/hr rainfall rates should continue
across the discussion area through 03Z or so.  A lessening of
rainfall rates is expected thereafter.  An additional 1-2 inches
of rainfall are possible.

Discussion...As anticipated, a broad fetch of Pacific moisture/IVT
resulted in areas of moderate to locally heavy rainfall across the
discussion area, with rain rates ramping up locally to around 0.5
inch/hr especially after around 18Z or so.  This axis of
lift/moisture will continue to persist across the area for at
least another 4-5 hours or so, with 1-1.2 inch PW values and
onshore mid-level providing lift/ascent for continued convective
development.  These rainfall rates are also continuing atop areas
that have received 10-20+ inches of rainfall in the past 2-2.5
weeks along with widespread flood/flash flood impacts (some of
which are continuing).  The locally heavier rainfall rates could
exacerbate ongoing impacts especially in/near sensitive or already
flooded areas.

Models (CAMs particularly) indicate that the ongoing regime should
continue to produce locally heavy rainfall (and 1-2 inch totals)
through 03Z or so.  Thereafter, backing mid-level flow (in tandem
with a deepening cyclone over northeastern Pacific Waters) will
result in a northward shift of the heaviest of rainfall rates into
far northwestern California and perhaps southern Oregon.

Cook

ATTN...WFO...EKA...HNX...MFR...MTR...STO...

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

LAT...LON   41462399 40552209 38412159 37092123 36472144
            36472237 37542327 39082414 40012461 41072472