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Area forecast discussion 
National Weather Service San Diego California
200 PM PDT Wednesday may 6 2015

a deep marine layer will continue the areas of low clouds tonight
west of the mountains. Patchy fog will continue in the mountains
through Friday. Gusty west winds will occur in the mountains and
deserts through Friday. A cold low pressure system will bring
periods of showers Thursday through Friday night along with
widespread cloudiness. There will also be a slight chance of
thunderstorms Thursday night through Friday...and there could be
some snow in the higher mountains...mainly in San Bernardino County.
Dry and warmer weather will return over the weekend as high pressure
aloft moves through...but then some cooling will occur by next
Tuesday as another low approaches.


Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino

Widespread stratus was continuing west of the mountains due to a
5000-5500 foot deep marine layer and an unstable layer below the
inversion. The strong thermal and pressure gradients between the
cool valleys and the somewhat warm deserts will continue strong
gusty winds in the mountains and deserts...with local gusts over 55
miles per hour at times especially tonight and Thursday night. A Wind Advisory
will go into effect for the deserts at 4 PM this afternoon.

The upper low is currently over Washington/Oregon and will dive down
into central California Thursday and inland Southern California
Thursday night. Models have mostly been consistent on tracking and
timing...and this low should give enough instability...onshore low-
level trajectory and moisture...mostly below 700 give
precipitation. Most model runs are showing average precipitation around one-
quarter inch west of the mountains with up to an inch in the
mountains...mainly the orographic west/SW slopes. There could be a few
thunderstorms Thursday night/Fri...and this would bring locally higher
amounts...and I would not be surprised to see a local 1.5 to 2 inch
amount over higher terrain in San Bernardino County close to the
cold core...mainly coastal slopes. Mostly light precipitation from moist
onshore flow will occur late tonight/Thu...then the more variable
and briefly heavy precipitation will occur Thursday night into Friday. Another
wave on the back side of the closed low could prolong precipitation into
Friday night...mainly based on the 12z NAM solution. Some island
banding is possible in San Diego County even late Friday night or
even very early Saturday morning. With the colder air in place...and
850 mb temperatures down as low as 2-3 degree c...we could get snow levels
down to about 5500 feet in San Bernardino County...and a few inches
of snow could fall there.

After the low moves east Saturday...fair warmer conditions will
occur...though with some night and morning low clouds in coastal
areas. Temperatures should peak near or just a bit above normal sun/Monday
before another trough brings cooling and probably a deeper marine
layer Tuesday.


062030z...low clouds in the coastal basin will continue with only
partial brief clearing through the evening. Bases will be around
3500 feet mean sea level with tops to 5500 feet mean sea level. Low clouds will fill the
coastal basin this evening with similar bases and tops...spreading
inland to touch the coastal slopes overnight. Local mountain
obscuration through 17z Thursday within that layer. Strong and gusty
westerly winds will continue in the mountains and deserts mainly
during afternoons and evenings. Strong updrafts and low level wind shear possible
over and east of the mountains at times.


200 PM...there is a chance of thunderstorms and isolated cloud-to-
water lightning strikes over the coastal waters Thursday night into
early Friday. hazardous marine weather is expected
through Monday.


200 will continue rather high through the evening...along
with strong rip currents...especially in Orange County. Southerly
swell and surf will fade slowly through Thursday. For surf details
see the beach hazards statement (laxcfwsgx) and the surf zone
forecast (laxsrfsgx).


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


Sgx watches/warnings/advisories...
California...Wind Advisory from 4 PM this afternoon to 3 am PDT Friday for
apple and Lucerne valleys-San Diego County deserts-San
Gorgonio Pass near Banning.

Beach hazards statement through this evening for Orange County
coastal areas.





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