000 
fxus66 ksgx 192036 
afdsgx 


Area forecast discussion 
National Weather Service San Diego California 
136 PM PDT Fri Oct 19 2018 


Synopsis... 
offshore flow will continue into Saturday with periods of gusty 
east to northeast winds, strongest today. Onshore flow will 
return Saturday night into Sunday along with night and morning 
coastal low clouds and fog. Some mid level moisture moving in from 
the southeast could bring clouds for the mountains and deserts 
Sunday into Monday. The marine layer will slowly deepen for 
Tuesday, with coastal low clouds spreading into portions of the 
valleys. This will be followed by warming during the middle to 
latter part of next week as high pressure to the southwest expands 
across Southern California, making the marine layer shallower. 


&& 


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


Sfc pressure gradients remain offshore this afternoon with -9.3 mb 
san-tph and -1.1 mb san-trm. Highest wind gusts in the last hour 
are 45-50 mph. The highest gusts so far today have been in the 
wind- prone locations in the San Diego County mountains for easterly 
flow situations, with a gust of 63 mph at Sill Hill. Sill Hill is 
about Half Way between alpine and Julian at an elevation of about 
3550 ft. Wind speeds peaked this morning and have begun to 
decrease. This trend will continue through tonight before 
increasing again on Saturday morning. 


Through Sunday...weak upper level low pressure off the northern 
Baja Coast will move slowly northward to near the Bay area on 
Sunday. This weak upper low combined with surface high pressure 
over the Great Basin will maintain offshore flow into Saturday, 
with periods of gusty east to northeast winds in the mountains, 
valleys, and inland Orange County. The strongest gusts will be 
mostly near the Mountain Ridge tops in San Diego County and in the 
inland Empire below the Banning pass. Weaker offshore winds are 
expected for Saturday morning as the upper low begins to move 
northward. 


As that weak upper low moves northward, the lower level flow 
across Southern California will become onshore for Saturday night 
and Sunday. This low will also draw some mid level moisture northward 
into California. This is expected to bring more clouds over the 
mountains for Saturday into Sunday with any precipitation more 
likely across the eastern deserts of Southern California northward 
into Nevada. 


The offshore flow will bring some additional warming for coastal 
and western valley areas today with cooling spreading inland into 
the valleys for the weekend. The development of a coastal eddy and 
the return of onshore flow will bring a return of marine layer low 
clouds near the coast for late Saturday night into Sunday. 


Monday through Thursday...the upper low will weaken and move 
inland over Nevada as high pressure aloft from the southwest 
expands across Southern California for the middle and latter part 
of next week. 


The marine layer is expected to slowly deepen into Tuesday in 
response to the upper low, with night and morning coastal low 
clouds and fog returning to portions of the western valleys. Slow 
cooling will continue for coastal and valley areas into Tuesday. 
The marine layer will become shallower during the latter half of 
the week with warming for valley and coastal areas. 


&& 


Aviation... 
192015z...NE/E winds will continue this afternoon with sfc gusts 25- 
35 kt below the passes and canyons and on the coastal mountain 
slopes and foothills. Winds will gradually diminish late this 
afternoon through Saturday morning. Moderate-strong uddfs through this 
afternoon, and pockets of low level wind shear possible S/SW of the mountains 10-15z 
Saturday as winds diminish. Otherwise, clear with unrestricted vis 
through Saturday. 


&& 


Marine... 
no hazardous marine weather is expected through Wednesday. 


&& 


Fire weather... 
upper level low pressure centered off the northern Baja Coast and 
surface high pressure over the Great Basin will maintain offshore 
flow into Saturday, with periods of gusty east to northeast winds 
and low humidity. Winds will be strongest and humidity lowest 
today. The winds have peaked and will gradually diminish later 
this afternoon and evening. Gusts will mostly be 40 mph or less, 
but will locally gust to around 50-55 mph in the inland Empire 
below the Banning pass and near the coastal slopes of the San 
Diego County mountains with isolated gusts to around 60 mph. 
Lowest humidity in the inland Empire and inland Orange County will 
fall to around 10 percent today and to around 15 percent in 
portions of the San Diego County valleys. Good humidity recovery 
is expected for tonight. There will be another round of weaker 
east to northeast winds Saturday morning with lowest humidity on 
Saturday afternoon of around 20 percent. Onshore flow and the 
marine layer will return for Saturday night and Sunday, bringing 
greater humidity recovery. 


&& 


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




&& 


Sgx watches/warnings/advisories... 
California...red flag warning until 10 PM PDT this evening for Orange County 
coastal areas-Orange County inland areas-Riverside County 
mountains-including the San Jacinto Ranger district of the 
San Bernardino National Forest-San Bernardino County 
mountains-including the mountain top and front country 
Ranger districts of the San Bernardino National Forest-San 
Bernardino and Riverside County valleys -the inland Empire- 
San Diego County inland valleys-San Diego County mountains- 
including the Palomar and Descanso Ranger districts of the 
Cleveland National Forest-San Gorgonio Pass near Banning- 
Santa Ana Mountains-including the Trabuco Ranger district 
of the Cleveland National Forest. 


Pz...none. 
&& 






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