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FXUS66 KSGX 251610

Area Forecast Discussion
National Weather Service San Diego CA
810 AM PST Sun Feb 25 2018

Today will be dry and warmer with locally gusty northeast winds near 
the coastal foothills and below passes and canyons. A cold low 
pressure system from the north will bring periods of rain and snow 
showers with low snow levels for Monday night and Tuesday. Dry and 
little warmer on Wednesday, then cool and breezy with more showers 
possible late Thursday through Saturday. 



Skies were clear over SoCal this morning. Some marine clouds were 
visible in satellite imagery, but were well offshore. Surface 
pressure gradients were running around 5 MBS offshore SW NV to KSAN 
and weaker from the east, supporting some NE winds of 20-25 MPH with 
gusts 35 to 40 MPH in the wind prone areas near the foothills and 
through passes. The 12Z Miramar sounding had a sfc-based inversion 
with modest warming below 3500 FT MSL and greater warming above. No 
easterly wind layer was present.  

After a chilly start...temperatures were warming rapidly under sunny 
skies so the Frost Advisory has been cancelled, otherwise no 
forecast changes this morning.

From previous discussion...

.SHORT TERM (Today through Tuesday)...
High pressure aloft and weak offshore flow will bring warming for
the lower elevations today with gusty northeast winds to 35 mph
near the coastal foothills and below passes for this morning.
Patchy stratus may return to coastal areas for late tonight into
Monday morning.

Onshore flow will strengthen on Monday bringing cooling as a cold
low pressure system moves southward along the West Coast. The
center is expected for move from near the Bay Area late Monday near Point Conception early Tuesday morning...then
inland across far southern California and northern Baja late
Tuesday afternoon. A few showers may develop Monday
afternoon...with more widespread showers late Monday night into
early Tuesday with scattered showers continuing Tuesday into
Tuesday evening. A few showers could linger into early Wednesday.
There is also a slight chance of thunderstorms Tuesday as the core
of the coldest air aloft moves across southwest California. Given
the low freezing would not be surprising for some of
the stronger rain showers at lower elevations on Tuesday into 
Tuesday evening to have some graupel.

Given the showery nature of the precipitations...amounts will be
somewhat variable...but general amounts are expected to range 
from around one tenth to one third inch near the one 
half to three quarters of an inch in the mountains with local 
amounts to around one inch. Mostly less than one tenth is possible
in the lower deserts with one tenth to locally one quarter inch 
in the upper deserts. 

Snow levels near 4500 to 5000 feet late Monday...will lower to
2500 to 3000 feet early Tuesday...then fluctuate between 3000 and
3500 feet for late Tuesday morning into Tuesday evening. In the
mountains...3 to 6 inches of snowfall is possible above 4000 feet
with locally greater amounts above 6000 feet. Snow showers are
also possible across the upper deserts Tuesday morning with any
accumulating snowfall more likely near higher terrain. With the 
low snow levels...snowfall could also impact the Tuesday morning 
commute through the Cajon Pass and possibly also the PM commute.


.LONG TERM (Wednesday through Saturday)...
A few showers could linger into early Wednesday morning... 
otherwise Wednesday will be dry and a little warmer but with high 
temperatures still 5 to 10 degrees below average. For Thursday
into Friday...another low pressure system will develop near the
west coast with the center of a closed low pressure system off the
Pacific Northwest coast. This is expected to spread additional
showers into Southern California for late Thursday into Friday.
Additional showers could linger into Saturday with the GFS faster
to move this low pressure system inland and the ECMWF a little
slower. For Sunday and Monday...dry and a little warmer weather is
expected as high pressure aloft develops near or a little off the
California coast.


251600Z...Mostly clear skies and unrestricted VIS will prevail 
through 15Z Mon, with SCT-BKN clouds developing after 15Z Monday 
from the coast to the coastal mountain slopes with variable bases 
1500-3000 ft MSL possible. Local gusty northeast/east winds 15-25 kt 
gusts 30-40 kt will produce LLWS and moderate up/downdrafts below 
Cajon and San Gorgonio Passes and along some coastal mountain slopes 
through 20Z. LLWS may impact KONT and KSNA during this period.


No hazardous marine weather is expected through Monday morning. 
Winds and seas will increase over the SoCal Bight late Monday 
through Tuesday as a storm system moves through the region. Combined 
seas of 6-9 ft and northwest winds 20-25 kt will be likely. Isolated 
thunderstorms are possible Tuesday.


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





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