Flash Flood Watch 2, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
225 PM PST Tue Jan 15 2019

.SYNOPSIS...
A series of storms will bring periods of rain and mountain snow
through Thursday. Heavy rain is likely at times on the slopes of
the San Bernardino County mountains. Dry and warmer Friday through
Sunday with moderate offshore winds.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Rain over the coastal waters this afternoon will race eastward and
overspread the area tonight. The rain extends from Santa Barbara
southward to the San Diego County coastal waters, which is a little
farther south than projected. The heaviest rain was over LA and
Ventura Counties at 2 PM and was moving east.

The rain is associated with a Pacific shortwave near Pt Conception
which is providing enough instability for thunderstorms over the
ocean. Moisture is plentiful with this first "mini" atmospheric
river (PW's of 0.90"), and the warm air advection will also
contribute to the rainfall totals. Highest amounts will be over the
south facing slopes of the San Bernardino Mountains where 1-3" are
likely, with highest amounts at the focal points for orographic
rains like Lytle Creek. Snow levels will remain fairly high in the
warm air advection, from 5,500-6,000 feet, with significant snow
accumulations above 8,000 feet.

On Thursday, a more impressive Atmospheric River will bring even
more substantial rain. The PW increases to around 1.25", which will
rank in the Top 20 of January PW's. The highest was 1.56" in January
of 1997. This system is also trending a little farther north with
greatest rain amounts in Orange, Riverside and San Bernardino
Counties, but San Diego County will see rain too. Rain amounts with
this third and final storm Thursday will range from 0.10"-0.50" in
the deserts and southern San Diego County to 2-5" on the south
facing slopes of San Bernardino County. Orange County coast and
inland areas and the Inland Empire, could receive 1-2" of rain. This
system may have the greatest risk of flash flooding and urban
flooding, and a Flash Flood Watch may be needed. Snow levels will
increase to 7500 ft Thursday, with large accumulations confined to
areas above 8000 ft, an only an inch or two between 6500-7500 ft.
Southwesterly wind gusts of 55-65 mph are possible Thursday as the
system moves across the region.

Upper-level ridging then builds in for the weekend, along with
surface high pressure over the Great Basin. This will help
generate gusty east to northeast winds across inland areas, and
increase high temperatures to above seasonal normals. Another
round of gusty offshore winds may develop next Tuesday.

&&

.AVIATION...
152130Z...Coasts/Valleys...SCT-BKN clouds with bases 1500-6000 ft
MSL will continue through this afternoon. Cigs lowering to blo 2000
ft MSL this evening through early Wednesday morning, with widespread
VIS 2-4SM in -RA developing by 03Z Wed.

Deserts...SCT-BKN with cloud bases 2500-5000 ft MSL. Cigs could
lower to blo 1500 ft at times through tonight.

Mountains...Obscured in clouds/fog/pcpn through tonight.

&&

.MARINE...
Showers, possibly with embedded thunderstorms are expected to move
eastward across the coastal waters this afternoon through tonight.
Winds increasing this afternoon and evening. A Small Craft Advisory
goes into effect 3PM PST today to 4AM PST Wednesday for wind gusts
up to 30 kt. Conditions improve on Wed before another storm arrives
Thursday evening into Friday, again generating rough seas.

&&

.BEACHES...
A west-northwest swell of 4-6 ft at 18 sec will gradually subside
through Wednesday. Another northwest swell arrives late Wednesday
and builds Thursday into Friday. Periods of high surf are likely
with this swell also. A Beach Hazards Statement continues through
Friday afternoon.

&&

.FIRE WEATHER...
Gusty east to northeast winds are expected at times for inland
areas this weekend and again next Tuesday. Afternoon relative
humidity will lower to near 20 percent away from the coast through
the period. Given the amount of wetting rains received across the
region this week, fire weather conditions are only expected to be
elevated, but not critical for the period.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Winter Storm Warning until 3 AM PST Wednesday for Riverside
     County Mountains-San Bernardino County Mountains.

     Beach Hazards Statement through Friday afternoon for Orange
     County Coastal Areas-San Diego County Coastal Areas.

PZ...Small Craft Advisory for winds until 4 AM PST Wednesday for
     Coastal Waters from San Mateo Point to the Mexican Border
     and out to 30 nm-Waters from San Mateo point to the Mexican
     Border Extending 30 to 60 nm out including San Clemente
     Island.

&&

PUBLIC...Moede
FIRE WEATHER...JJT
AVIATION/MARINE/BEACHES...PG

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN DIEGO CA
708 PM PST TUE JAN 15 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0658 PM     HAIL             6 E MISSION VIEJO       33.64N 117.56W
01/15/2019  E0.25 INCH       ORANGE             CA   TRAINED SPOTTER

            ESTIMATED PEA SIZED HAIL REPORTED. SEVERAL
            CLOUD TO GROUND LIGHTNING STRIKES IN SANTA
            ANA MOUNTAINS IMMEDIATELY SOUTH OF TRABUCO
            CANYON (BELL CANYON AREA.).

&&

CO