Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 162128

Area Forecast Discussion
National Weather Service San Diego CA
127 PM PST Mon Jan 16 2017

High pressure aloft will continue dry weather through Wednesday
with weak offshore flow today and Tuesday, becoming onshore
Wednesday. For Thursday into early early next week...a series of
Pacific storm systems are expected to bring periods of strong
onshore winds...rain...and mountain snow which could be heavy at



Satellite imagery early this afternoon shows that the clouds
over the region have thinned nicely, leaving mostly sunny skies. At 1
PM PST...Surface pressure gradients were around 6 MBS offshore from
SW NV to KSAN, supporting NE winds over the mts and wind-prone areas
where local gusts were reaching 25-30 MPH.

Some marine clouds may reform overnight along the San Diego County
coast, otherwise mostly clear and cool. sunny and warmer on Tuesday
as a high pressure ridge builds aloft. Offshore gradients will
support locally gusty winds below the passes and canyons at times,
but onshore flow should return to the coast each afternoon and may
result in some marine clouds each night and morning. The onshore
flow will increase on Wednesday for a slightly cooler afternoon
west of the mts.

For Thursday through early next week...westerly winds aloft over the
Pacific, will be suppressed farther to the south, steering a series
of disturbances onto the coast of CA. Unlike the last week, SoCal
should share more fully in the precip generated by these systems.

The Thu system could produce a period of moderate rainfall, but the
potential for heavier rain and snowfall rates, and total
accumulations, comes Fri through early next week as PW increases and
there is better support aloft. Timing and intensity differences
between model/model runs still exist, but in general, expect to see
large amounts of precipitation accumulate across the region through
next Tuesday.

In addition to the precipitation, there will be periods of strong and
gusty onshore winds from the south and southwest. Some of these
episodes may affect coastal and valley areas, as well as the mts/
deserts. This stormy, unsettled period is expected to abate after
next Tue as the westerly winds aloft over the EastPac lift back to
higher latitudes.


162107Z...Primarily SCT-BKN clouds AOA 12000 ft msl and P6SM vis
through 17/0000 UTC. 17/0000-1500 UTC...patchy BKN stratus may
develop within 10 SM of the central and southern San Diego county
coast, possibly impacting KSAN and KCRQ, but confidence is low.
Bases and tops would be around 1000 ft msl and 1500 ft msl
respectively. Otherwise, FEW clouds AOA 20000 ft msl and vis P6SM.


A Pacific storm will bring rain, strong southwest to west winds
gusting to 25 kt and large seas of 7-10 feet on Thursday, mainly in
the outer waters. These conditions would be hazardous to small
craft. The storm system that follows mid Friday into Saturday has
the potential for winds reaching gale force at times in the inner
and outer waters, in addition to combined seas of around 11 to 18
feet (highest seas south of San Clemente island). Winds and seas
diminish a little early Sunday but then pick up again late Sunday as
another storm system moves through the region.


A moderate sized long-period west-northwest swell from around 285
degrees will peak today and lower Tuesday. The swell will create
surf of around 3-6 ft with local 7 ft sets and strong rip currents.
However, widespread high surf is not expected.

From Thursday through next weekend, a couple short to moderate
period large west-northwest swells (from 285 degrees) will impact
the coast. The highest surf will occur over the weekend when a very
large short-period WNW swell combines with a moderate sized WNW long-
period swell. During the peak of the swell event, surf could be
large enough (sets possibly reaching 15 ft) to cause coastal damage,
minor coastal flooding and moderate beach erosion.

A Hydrologic Outlook has been issued to discuss precipitation
potential, flooding issues, and runoff, including potential river
flooding issues. Please see LAXESFSGX, or the link on our home page





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