Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 241549

Area Forecast Discussion
National Weather Service San Diego CA
849 AM PDT Sat Mar 24 2018

A low pressure trough along the West Coast will maintain onshore
flow and cool weather this weekend under a deep marine layer with
areas of night and morning low clouds and patchy fog extending onto
the coastal slopes. A few light showers or sprinkles are possible
again tonight into early Sunday as well. A warming trend begins on
Monday as offshore flow shrinks the marine layer and high pressure
builds along the West Coast for the balance of the week.



High clouds were drifting across SoCal this morning, obscuring the
lower clouds reported from numerous sites west of the mts. Based on
the 12Z Miramar sounding...the cloud layer is thin with a weak
inversion near 3400 FT MSL. The base of the higher moist layer was
near 27K FT and the PW in the column had dropped below one-half inch.
some scattered, very light precip amounts were logged earlier this
morning but appear to have ended by 7 AM PDT. The sfc pressure
gradients were respectable at 6-7 MBS KSAN to the deserts and a
handful of sites were reporting westerly wind gusts of 25 to 35 MPH
in the mts/deserts.

No forecast updates this morning.

From previous discussion...

A low pressure system is centered off the Pacific Northwest coast
early this morning. It will move slowly inland with high pressure
aloft developing off the California coast early next week.

This will maintain stronger onshore flow through the weekend with
below average high temperatures...a deeper marine layer with
coastal low clouds and patchy fog extending onto the lower
coastal slopes. There will be periods of stronger and gusty
southwest to west winds in the mountains and deserts at times into
Sunday evening. Strongest gusts to 50 mph are expected near the
mountain ridge tops onto the desert slopes of the mountains from
the San Bernardino Mountains southward. There will also be a
slight chance of light showers for the mountains and inland
valleys for tonight through early Sunday.

For Monday and Tuesday...weak to moderate strength offshore flow
will bring dry and warmer weather with gusty north to northeast
winds near the coastal foothills.

For Wednesday through Friday...high pressure aloft off the
California coast will move slowly across California. This will
maintain dry weather with weaker winds and additional warming for
inland areas.


241530Z...Coasts/Valleys...Multiple low cloud decks, with bases from
2000-4500 ft MSL, will continue through the morning, and become more
scattered this afternoon. Stratus will then refill the coastal basin
this evening and overnight, with slightly higher bases. -DZ is
possible at times tonight, mainly in the foothills, as the marine
layer deepens.

Mountains/Deserts...SCT high clouds and P6SM VIS through Sunday
morning. Westerly surface wind gusts of 30-45 kt will develop over
and east of the mountains this afternoon and continue through Sunday
morning. Areas of LLWS and strong UDDFS likely east of the
mountains, including near KPSP and KTRM.


Northwest winds increasing this morning and continuing through
Sunday, strongest over the Outer Waters with gusts 25 to 30 kt. The
winds, along with combined seas of 7-10 ft at times and steep waves,
will produce hazardous boating conditions. A Small Craft Advisory
remains in effect for the Outer Waters through Sunday evening. Gusty
northwest winds may continue into Monday.


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


PZ...Small Craft Advisory until 8 PM PDT Sunday for Waters from San
     Mateo point to the Mexican Border Extending 30 to 60 nm out
     including San Clemente Island.



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