Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 151609
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
910 AM PDT Sun Oct 15 2017

.SYNOPSIS...
High pressure aloft and weak offshore flow will continue hot and
very dry weather west of the mountains through Tuesday with high
temperatures in the valleys and inland coastal areas in the 90s to
around 100. Cooling will begin to spread inland with onshore flow
Tuesday afternoon and Wednesday with greater cooling on Thursday and
Friday as a trough of low pressure moves inland along the West
Coast. This will bring more cloud cover...gusty west winds in the
mountains and deserts...and a slight chance of showers for Thursday
night and Friday. Dry with a warming trend for next weekend with
strengthening high pressure aloft and moderate offshore flow.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

No changes were made to the forecast this morning. Very dry air
continues through Tuesday. Gusty Santa Ana winds will continue this
morning and gradually weaken throughout the day. The red flag
warning will expire at noon today due to the loss of strong winds in
the forecast.

...early morning discussion below...

Early this morning...satellite imagery shows patchy stratus mostly
over the coastal waters...extending locally inland along portions
of the northern Orange County coast. Aircraft soundings late
Saturday evening showed the base of the marine inversion around
700 feet. Los Alamitos has briefly had visibility less than one
mile with low clouds and fog. Much of the stratus will remain off
the coast...but will briefly impinge on the coast at times in a
few locations. Satellite imagery also shows a few subtropical high
clouds spreading eastward across northern Baja and far southern
California.

Weak offshore flow continues with gusty northeast to
east winds near coastal foothills and below passes and canyons
with strongest gusts to around 40 mph. These winds will continue
into the morning...then diminish through the afternoon. Weaker and
more localized northeast winds will return for late tonight into
early Monday morning.

High pressure aloft combined with the offshore flow will bring
well above average high temperatures west of the mountains
through Monday with high temperatures in the valleys and inland
coastal areas in the 90s to around 100. Cooling will begin to
spread inland on Tuesday and Wednesday as weak onshore flow
returns. Mid level subtropical moisture could bring some clouds to
the mountains Tuesday and Wednesday afternoons in addition to some
high clouds.

A trough of low pressure moving inland along the West Coast on
Thursday and Friday will bring stronger onshore flow with stronger
and gusty west winds for the mountains and deserts. As the trough
of low pressure moves inland to the north...it may draw some
subtropical moisture northward into Southern California with more
clouds and a slight chance of showers for Thursday night and
Friday.

For next weekend...the GFS and ECMWF are in better agreement in
showing subtropical high pressure extending into Southern
California with the high pressure across Southern California
stronger than the high pressure this weekend. Surface high
pressure over the Great Basin could bring moderate strength
offshore flow for Sunday and Monday.

&&

.AVIATION...
151600Z...Clear skies, unrestricted visibility and light winds will
continue through Monday morning at the TAF sites. Areas of 20-25 kt
LLWS will remain possible below the Cajon Pass and the Canyons of
the Santa Ana Mountains through 20Z Today. Patchy fog is possible
over the coastal waters between 03Z and 16Z Monday.

&&

.MARINE...
No hazardous marine weather is expected through Thursday.

&&

.BEACHES...A long period south swell will arrive in the Bight late
Monday evening and continue through Thursday. This will bring 3-6 ft
surf to the beaches with occasional sets to 7 ft north of Oceanside
along southwest facing beaches. Strong rip and longshore currents
will accompany the elevated surf.

&&

.FIRE WEATHER...
High pressure aloft combined with weak offshore flow will continue
well above average high temperatures through Monday west of the
mountains with high temperatures into the 90s to around 100 for
valley and inland coastal areas. Lowest inland humidities will
fall to around 5 percent today and Monday with poor overnight
recovery near the coastal foothills. Gusty northeast to east winds
will continue near the coastal foothills and below passes and
canyons into this morning with strongest gusts to around 40 mph.
Winds will diminish this afternoon with another round of weaker
and more localized northeast winds near the coastal foothills late
tonight into early Monday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning until noon PDT today for Orange County Inland
     Areas-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-Santa Ana Mountains-
     Including The Trabuco Ranger District of the Cleveland
     National Forest.

PZ...NONE.
&&

$$

PUBLIC/FIRE WEATHER...17/JMB
AVIATION/MARINE/BEACHES...BA



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