National Weather Service Forecast Discussion

Dicussion provided by the National Weather Service Forecast Office located in San Diego, California

000
FXUS66 KSGX 150411 AAA
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
910 PM PDT Sun Oct 14 2018

.SYNOPSIS...
Some patchy stratus may occur late this evening along the coast.
From late tonight through Tuesday, a Santa Ana weather pattern will
bring strong gusty northeast winds to the mountains, valleys and
even some coastal areas, along with low humidity and higher
temperatures. The offshore flow will be much weaker Wednesday
through Friday, but dry warm weather will continue. Upper low
pressure could bring a few clouds this weekend.

&&

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

Evening update: Made an update this evening to add a wind advisory
for Monday for the Coachella Valley, San Diego County Deserts, San
Gorgonio Pass, and Coastal San Diego County. The winds in the desert
will be strongest below the south facing slopes and could even
approach wind advisory level (45 mph) in the Coachella Valley. The
winds in Coastal San Diego County will be strongest (35-40 mph)
north of Encinitas towards Camp Pendleton where Santa Ana wind will
surface out of the northeast. Winds will likely remain below
advisory level in the City of San Diego although still gusty at
times throughout the day Monday.

Have also added blowing dust in areas of strong winds especially for
the Northern Inland Empire where blowing dust could create impacts
to travel during the strongest winds. There could also be some
blowing dust/sand concerns in the lower deserts immediately below
the south facing slopes.

Other than the above changes the forecast remains on track with a
strong offshore gradient developing late tonight, continuing through
Tuesday. The strongest winds will be likely late tonight through
Monday, although periods of strong winds will be likely through
Tuesday although not quite as strong. The strongest winds will be
likely below the Cajon Pass and in the Santa Ana Mountains where
gusts as high as 80 mph will be possible in the more remote
locations, and gusts of 60 mph are forecast for populated areas,
which could cause damage to trees and property.

The remainder of the previous forecaster discussion issued at 200 pm
Sunday afternoon remains valid below:

The big change will occur late tonight and early Monday as a Santa
Ana wind event develops. Winds will gradually increase from the
northern mountain crests a little after midnight tonight south and
southwest through the coastal foothills and valleys, including
through and below passes and canyons. Winds likely will not arrive
in the San Diego County Valleys until after sunrise Monday.
Strongest support aloft will be late tonight and Monday morning,
with high-resolution models, including the local WRF and Cansac WRF,
indicating gust potential between 70 and 80 MPH in the strongest
locations, mainly below Cajon Pass and in the Santa Ana Mountains in
the 4 AM-noon PDT time range Monday. San Diego County should have
somewhat weaker winds than farther north, with peak gust potential
around 50-55 MPH in strongest locations. There will be much less
support for strong winds Monday night and Tuesday, but local gusts
over 50 MPH will still be possible Tuesday morning. Humidity will be
low due to the offshore flow, below 10 percent at times.
Temperatures will be higher once the offshore flow arrives with
mostly 80s west of the mountains starting Monday.

The upper low which will move through the region from north to south
Monday will remain over the SW US the rest of the week, with the
interior SW being the most likely location of the low. This will
keep us on the back side of the low with NE flow aloft and mostly
weak offshore flow at the surface. Some model runs have the upper
low moving west towards So-Cal or northern Baja next weekend which
could enhance the offshore flow again, though that is dependent on
the track of the low. Some moisture wraps around the low, based on
the 12Z GFS solution, and that could even bring some precipitation.
12Z ECMWF has some precip just to the north and east of our area.
Have not added any precip for next weekend, but if models continue
to show some precip in or near our forecast area, then I will add
that to the forecast package Monday. MOS guidance shows it could be
quite warm next weekend with 90s possible west of the mountains
based on GFS MOS.

&&

.AVIATION...
150200Z....Coastal low clouds will develop after 05Z tonight with
bases near 2500 ft MSL and spreading 15-20 miles inland, then a slow
clearing around 10-11Z once offshore winds develop. N-NE winds will
strengthen tonight with sfc gusts 35-45 kt on the coastal mountain
slopes and through and below the passes after 06Z, then increasing
to 45-55 kt by Monday morning and spreading into the valleys and
Orange County coastal plain. LLWS likely at SBD, KONT, and KSNA
Monday morning prior to winds surfacing. STG-SVR UDDFS likely over
and S/SW of the mountains. Gusty sfc winds will continue into
Tuesday and begin to diminish Tuesday evening.

&&

.MARINE...
Northeast wind gusts to around 20 kt possible near and northeast of
San Clemente Island Monday morning through Monday evening. No
hazardous marine weather is expected Tuesday through Thursday.

&&

.FIRE WEATHER...
Critical fire weather conditions will occur at least Monday and
Tuesday due to the Santa Ana Winds. Fuels which will be initially
wet from the recent rains should dry out Monday as humidity will be
10 percent or less in most low elevation locations, combined with
winds 20-40 MPH with local gusts 55-75 MPH (Santa Ana Mtns and
Inland Empire). Strongest winds will be Monday morning with winds
somewhat weaker Tuesday. Mostly lighter winds are expected Wednesday
through Friday, though humidity will stay low.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning from 3 AM Monday to 8 PM PDT Tuesday 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-Santa Ana Mountains-Including The
     Trabuco Ranger District of the Cleveland National Forest.

     Wind Advisory until 8 PM PDT Monday for Coachella Valley-San
     Diego County Deserts-San Gorgonio Pass Near Banning.

     High Wind Warning until 3 PM PDT Monday for Orange County Inland
     Areas-San Bernardino County Mountains-San Bernardino and
     Riverside County Valleys-The Inland Empire-Santa Ana
     Mountains and Foothills.

     Beach Hazards Statement until 10 PM PDT this evening for Orange
     County Coastal Areas-San Diego County Coastal Areas.

     Wind Advisory from 6 AM to 6 PM PDT Monday for San Diego County
     Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...Maxwell/JMB
AVIATION/MARINE/BEACHES...Connolly

NWS SGX Office Area Forecast Discussion