Graphic for MPD #0049
Mesoscale Precipitation Discussion 0049
NWS Weather Prediction Center College Park MD
342 AM EST Mon Feb 05 2024

Areas affected...Southern California...

Concerning...Heavy rainfall...Flash flooding likely

Valid 050900Z - 051800Z

SUMMARY...Core of Atmospheric River stalling over Southern
California. While intensity of moisture flux, rainfall rates will
be reducing through the early morning; prolonged moderate rainfall
will support an additional 1-4" through 18z and likely to continue
considerable flash flooding,  mud & landslide conditions.

DISCUSSION...GOES-W WV depicts the main upper low continuing to
swirl along the NW CA/SW ORE coastline with 985mb surface low
starting to show signs of filling.  As both lift north, broadening
mid-level dry slot is expanding over the Central California coast
and broadening the sfc to 850 pressure/height gradient reducing
the strength of the winds across the California Bight.  CIRA LPW
also denotes the sfc-850mb moisture stream is narrowing and
pinching a bit through the Channel Islands toward Orange county;
though 850-700mb moisture stream remains fairly broad and within
confluent flow of 40-55kts through the region.

As such, limited height-falls and perhaps weak shortwave
height-rises have been noted and forward propagation of the warm
conveyor belt has begun to stall.  A few more hours of 25-30kts of
south-southeasterly flow along/ahead of the cold front will
continue to support maximized moisture convergence with embedded
vertical development along the leading edge. Narrow bands of
.25-.5"/hr rates can be seen through the Bight into Southern LA
county, Orange county and starting to enter NW San Diego county. 
These cells will become more wavy and diffuse with time and reduce
to below .25"/hr by morning.  This diffusion should allow for
broadening of the plume bringing back lighter but still up to
.25"/hr into Ventura/western LA county after 12z, resulting in an
additional 1-3" by 18z. 

However, southwesterly flow through depth will continue to ascend
favorably through the Santa Ana, eastern San Gabriel and into the
San Bernadino Ranges and perhaps the northern portions of the San
Jacinto Range.  Rates of .5" to .75"/hr will reduce to .33-.5"/hr
after 12-15z but still support 2-5" of additional rain.  This will
continue/maintain the risk of flash flooding and mud slides across
the Hollywood Hills across into the San Gabriel Range, likely to
expand into the Santa Ana and San Bernardino Range...though given
reduced rates, the rise may be a tad slower than experienced
further west, still this flooding will be dangerous and
life-threatening through Monday morning.

Gallina

ATTN...WFO...LOX...SGX...

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

LAT...LON   34771897 34701812 34521742 34291683 33851661
            33461665 32931697 32621758 32711839 33011884
            33511905 34011916 34301933 34601933
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Last Updated: 342 AM EST Mon Feb 05 2024