Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 242009
AREA FORECAST DISCUSSION
National Weather Service San Diego CA
108 PM PDT SAT SEP 24 2016
Strong high pressure aloft off the California coast and surface
high pressure over the Great Basin will bring dry and warmer
weather through Monday with periods of gusty northeast winds near
the coastal foothills. Hottest days and strongest winds are expected
on Sunday and Monday. Upper level low pressure over the Sea of Cortes
will bring increasing moisture and slow cooling for Tuesday into
Wednesday. Onshore flow and seasonal temperatures return for the
latter half of the week as a developing trough moves inland over the
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Skies were clear and winds mostly light at Noon PDT, except in some
offshore wind-prone mountain locations where gusts were picking up to
25-30 MPH. The surface pressure gradients were holding around 6-7 MBS
offshore KSAN-SW NV, but were weakly onshore to the lower deserts.
A strong 596 DM ridge over the far EastPac will force a trough to
dig south over the southern Rockies, then retrograde westward over
NW Mexico through Tue. This will result in general Santa Ana
conditions over far SW CA, with gusty northeast winds along the
foothills, very low humidity, and hot days west of the mts through
The easterly flow generated by the low to the south will eventually
pick up some moisture and drive it west across the region, raising
the humidity and possibly generating a few clouds. This will also
result in a slow cooling trend which will be further enhanced by a
developing trough along the west coast late in the week.
Numerous products are in effect including a Heat Advisory West of
the mts...Wind Advisories for the mts/valleys...a Red Flag
Warning...and a Beach Hazard Statement. Please see LAXNPWSGX...the
fire weather discussion below...and LAXCFWSGX for details.
There is a small chance that the moisture associated with the cut-
off low to the south could generate a few showers Tue into Wed, but
the chance looks too slim at this point to include in the forecast.
Temperatures should be back to average by midweek and fall below
average next weekend.
242030Z...Wind is the story for the next 48 hours or so across
the local area. Most areas for the next 20 hours won`t be a problem,
but Local N to NE winds gusting 20 to 25 kt on the coastal mountain
slopes, below the passes and canyons is possible through 242100Z.
Moderate low level wind shear and up and downdrafts are possible
over and S and SW of the mountains. Winds will weaken after 242100Z.
However starting around 250800Z winds will be on the increase from
northeast through Sunday and peaking Monday for KSAN. Winds won`t be
continuous in direction or intensity especially at the surface, but
above the surface will become more consistently northeast with time
a risk of impacts on KSAN and KSNA with LLWS and up/drafts.
As for sky conditions, a few high clouds and unrestricted vis through
Monday evening across the forecast area. Overall forecast confidence
is moderate to high.
No hazardous marine weather is expected through Wednesday.
Forecast confidence high.
Beach Hazard statement is in effect...with A long period south swell
from 200-220 degrees creating elevated surf of 4 to 6 along
southwest-facing beaches today in Orange County. Surf of 3 to 5 ft
is possible along select, mostly southwest facing San Diego County
beaches north of Carlsbad. Strong and dangerous rip currents are
expected with the elevated surf. Swell and surf will subside Sunday
Weather conditions will deteriorate through Sunday as offshore flow
increases and drives RH values down along and west of the mountains.
The combination of wind and low RH has prompted a Red Flag Warning
from late tonight into Monday afternoon for all areas except the
coastal strip. Northeast to east winds will be strongest through and
below the wind-prone passes, and areas of the coastal slopes and
adjacent foothills where local gusts of 45 to 55 MPH are possible.
For the remainder of the valley areas and inland Orange County,
expect northeast to east winds of 15-25 MPH with higher gusts at
times. RH will be around 8 to 12 percent on Sunday, increasing to 12
to 20 percent on Monday. Only modest overnight recovery is
anticipated with the least near the wind prone foothills.
The winds are expected to decrease a bit north of Riverside County
on Monday, but remain quite strong over San Diego County. Also, on
Monday, RH will be increasing from the east. Most areas should be
above the 15 percent threshold late in the day as the winds begin to
Weaker offshore flow will continue into Tuesday and Wednesday as
humidity and heat moderate.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Red Flag Warning from midnight tonight to 3 PM PDT Monday for
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-San Gorgonio Pass Near Banning-
Santa Ana Mountains-Including The Trabuco Ranger District
of the Cleveland National Forest.
Wind Advisory from midnight tonight to 5 PM PDT Monday for San
Diego County Mountains-San Diego County Valleys.
Wind Advisory from midnight tonight to 4 PM PDT Sunday for
Orange County Inland Areas-Riverside County Mountains-San
Bernardino County Mountains-San Bernardino and Riverside
County Valleys-The Inland Empire-Santa Ana Mountains and
Heat Advisory from 11 AM Sunday to 8 PM PDT Monday for Orange
County Coastal Areas-Orange County Inland Areas-San
Bernardino and Riverside County Valleys-The Inland Empire-
San Diego County Coastal Areas-San Diego County Valleys-
Santa Ana Mountains and Foothills.
Beach Hazards Statement through Sunday evening for Orange County
Coastal Areas-San Diego County Coastal Areas.