Area Forecast Discussion
Issued by NWS San Diego, CA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS66 KSGX 190507

Area Forecast Discussion
National Weather Service San Diego CA
907 PM PST Fri Jan 18 2019

Some low clouds will persist tonight west of the mountains before
clearing out on Saturday morning. Dry and much warmer this weekend
under a passing ridge aloft, with weak offshore flow at the surface.
A deepening trough will bring cooler weather on Monday as the marine
layer surges back inland on strong westerly winds. Clouds, and even
a few light showers are possible along and west of the mountains.
Dry and warmer again Tuesday through Friday with gusty p northeast
winds in the mountains and on the coastal foothills. The offshore
winds may be quite strong on Tuesday.



Some patchy low clouds were visible through a veil of thin, high
clouds this evening. Surface dewpoints were still in the 50s F well
inland at 8 PM PST, even as the sfc gradient was turning offshore at
about 3 MBS (SW NV to KSAN). The 00Z Miramar sounding was drying out
but still had a PW value of 0.84", and a 3C inversion based near
3500 FT. The offshore trend and cool air drainage is expected to
keep any ground fog development to a minimum overnight.

No forecast changes tonight.

From previous discussion...

Saturday and Sunday will be sunny, dry and much warmer under a
ridge of high pressure with weak offshore flow as a sfc high moves
into the Great Basin. Saturday will be the warmer of the 2 days
with daytime temperatures in the 70s to low 80s west of the mtns.
The offshore flow could produce local wind gusts to 45 mph in the
mtn passes and coastal foothills, most likely on Saturday.

A little cooler on Monday with increasing clouds as the flow
turns onshore in response to a low pressure trough moving inland
to the north. Increasing low clouds west of the mtns could produce
patchy drizzle in those areas on Monday morning.

For Tue through Fri...The low pressure trough moves east into the
Great Basin and deepens over the southern Rockies as a ridge of
high pressure builds over the East Pac/West coast. This will bring
a warming trend with dry offshore flow. The offshore flow will
likely bring strong and gusty northeast to east winds in the mtns
and areas west of the mtns. Current indications are that the winds
will be strongest and most widespread on Tuesday with wind gusts
of 50-60 mph possible in wind-prone areas. Daytime temps will be
in the upper 60s to low 70s west of the mtns on Tue but by
Thu/Fri, temps could be in the upper 70s to low 80s. This warm and
dry pattern could extend into next weekend.


190500Z...Coast/Valleys...Local vis below 3 miles will occur in fog
in the valleys, including VCNTY KRNM and KL18, through 14Z Sat.
Otherwise, mostly SCT high clouds above 20000 ft MSL will prevail
through Sat.

Mountains...Areas of northeasterly winds will develop overnight with
surface speeds generally 15-25 knots with gusts to 30-40 knots,
mainly on the coastal slopes and will be accompanied by LLWS and
moderate up/downdrafts. Winds will decrease somewhat late Saturday.
Otherwise, unrestricted vis with SCT high clouds above 20000 ft MSL
will prevail through Sat.

Deserts...Unrestricted vis with SCT high clouds above 20000 ft MSL
will prevail through Sat.


The west-northwest swell will very slowly decline overnight and
should be less than 10 feet in the outer coastal waters by early
Saturday morning. Due to large breaking waves, entrances to harbors
and bays will be difficult for small craft. A Small Craft Advisory
is effect until 4 AM Saturday. Another west-northwest swell could
bring seas around 10 feet in the outer coastal waters Monday and
Monday night.


Surf will gradually lower overnight and should mostly be below 7
feet by Saturday morning. A High Surf Advisory is in effect until 4
AM Saturday. Another elevated west-northwest swell will arrive
Monday, but the direction will be from 290-295 degrees, and the
period will only be 10-11 seconds, so fewer impacts are expected
along the beaches than with the surf that occurred today.
Regardless, some surf heights could reach 8 feet in southern San
Diego County, so a High Surf Advisory may be needed Monday.



AVIATION/MARINE/BEACHES...Maxwell is the U.S. government's official web portal to all federal, state and local government web resources and services.