FXUS66 KSGX 160526

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

A series of storms will bring periods of rain and mountain snow
through Thursday. Heavy rain is likely at times, especially in
Orange County and the south and southwest mountain slopes in San
Bernardino and Riverside County. Flash flooding and debris flows
will be possible where heavy rains occur. Some snow will fall in the
higher mountains, mainly tonight. Strong gusty west winds will occur
in the mountains and deserts Thursday. Fair but cool weather will
return Friday, then dry warmer weather will return Saturday through
early next week with moderate northeast winds at times.



Heavy rains were occurring over parts of the forecast area,
especially Orange County. Seal Beach had a report of 2.05" between 6
PM and 9 PM, and several other locations from northwestern to
central Orange County had over one inch. A thunderstorm occurred
along the south edge of the Holy Fire burn scar earlier this evening
as well, with a few lightning strikes detected near there. More
heavy rain will occur at times through about 2 or 3 AM in Orange
County and into parts of SW San Bernardino and far W Riverside
County, with focus on convective banding. Lighter rains will occur
elsewhere. Some snow will occur in the mountains, though amounts
will be variable due to the convective banding. After 2-3 AM, the
trough axis will have shifted east of coastal SoCal, and activity
will taper off, including snow in the mountains, and Wednesday
should mostly just have scattered showers due to the moist
atmosphere at/below 700 MB before the next wave comes in from the
west Wednesday night. The flash flood watch was issued for Orange,
SW San Bernardino and W Riverside Counties through Thursday to cover
both the activity tonight and with the Wednesday night/Thursday

From previous discussion...

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.


160430Z...Coasts/Valleys...BKN cloud deck with bases 1000-2000 ft
MSL will continue through late morning Wednesday. Widespread -RA
expected through 15Z Wednesday. From late morning to afternoon
Wednesday rain is expected to mostly come to an end over San Diego
County. Ceilings at KCRQ/KSAN should improve to over 3000 ft MSL by
the afternoon and persist into the evening. Scattered -SHRA will
linger near KSNA/KONT/KSBD through Wednesday afternoon/evening with
ceilings of 1800-2500 ft MSL.

Deserts...SCT-BKN with cloud bases 2500-5000 ft MSL tonight along
with patchy -RA. Expect ceilings above 3000 ft MSL on
Wednesday/Wednesday night with scattered -SHRA. Minimal impact on
visibilities expected.

Mountains...Obscured in clouds/fog/pcpn through Wednesday night.


Showers and a few embedded thunderstorms are expected to move
eastward across the coastal waters through tonight. A Small Craft
Advisory is in effect until 4AM PST Wednesday for wind gusts up to
30 kt. Conditions improve on Wednesday before another storm arrives
Thursday and Friday, again generating rough seas.


Another northwest swell arrives late Wednesday and builds Thursday
into Friday. A period of high surf is expected from Thursday night
through Saturday especially from Encinitas south with surf height of
6 to 8 feet with sets to 10 feet expected this period. A Beach
Hazards Statement continues through Friday afternoon.


.FIRE WEATHER... From previous discussion...
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 activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


CA...Flash Flood Watch through Thursday afternoon for Orange County
     Coastal Areas-Orange County Inland Areas-Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-Santa Ana
     Mountains and Foothills.

     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




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