Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 201652
Area Forecast Discussion
National Weather Service San Diego CA
952 AM PDT Thu Oct 20 2016
Hot and dry weather continues through Friday with gusty northeast
winds for wind prone areas in the coastal foothills and inland
valleys. Onshore flow brings a cooling trend this weekend
especially on Sunday. Even cooler, with increasing clouds and a
chance of precipitation Sunday afternoon through Monday, due to a
surge of subtropical moisture ahead of a large upper trough moving
onto the West Coast. Dry and a little warmer for Tuesday and
Wednesday as a weak high pressure ridge builds over the Southwest.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Lows this morning were dependent on wind/mixing with areas closer
to the foothills much warmer than near the coast. Most areas near
the coast dropped into the 50s this morning while inland locales
were in the 60s and 70s.
Santa Ana winds will result in a dry and hot day with temps
soaring into the 90s and even topping 100F degrees across portions
of inland Orange County and the Inland Empire. Localized wind
gusts this morning were 48 mph at Highland Springs in Riverside
County, 45 mph at Pleasants Peak in the Santa Ana Mountains, and
45 mph at Sill Hill in the San Diego County mountains. No
significant changes were made to the forecast this morning. Please
see previous discussion below for further forecast details.
...PREVIOUS DISCUSSION (Issued 2:48 AM PDT Thu Oct 20 2016)...
Strong offshore pattern will continue today and temperatures will
likely be the hottest today west of the mountains. Temperatures
will reach the 90s just away from the immediate coast and into the
mid 90s to around 100 in the valleys and inland Orange County. As
funny as it may sound, relief from the heat today could be found
in the desert where temps will only be in the lower 80s in the
high desert such as Victorville and Apple Valley. Even the
Coachella Valley will be relatively moderate in the lower to mid
90s. Gusty winds will continue to be a concern today with a wind
advisory remaining in effect west of the mountains, especially in
the favorable offshore areas through and below the canyons and
Although gradients will relax on Friday, and temperatures will
start a slight downward trend, it will still be nearly as warm as
today due to continued but lighter offshore flow and residual
warm air. On Saturday onshore flow will develop locally and mid
level SE flow will bring a narrow plume of moisture into the
region, bringing a chance for rain to the mountains by Sunday
afternoon, and across much of the region by Sunday night. Chances
for rain continue into Monday as a strong low over the Pac NW
drags a trough as far south as Southern California across our
Temperatures will rebound a bit by mid next week as ridging
redevelops across SoCal.
201520Z...Mostly SKC and unrestricted vis through Friday morning. NE
to E winds 15-25 kt wind gusts of 30-35 kt will continue through and
below mountain passes/canyons, and along coastal mountain slopes and
foothills through 1800 UTC, resulting in mod-stg uddfs/LLWS over and
W or SW of the mountains. LLWS is possible when/where winds do not
quite surface, such as around KONT, KSBD and KSNA, through 1800 UTC.
After 1800 UTC, weaker NE to E winds and associated uddfs/LLWS will
continue into Friday morning.
No hazardous marine weather is expected through Monday.
A Red Flag Warning remains in effect through 8 PM this evening.
Areas of gusty north-northeast winds will continue through late this
afternoon, with strongest winds in the Cajon Pass, the Inland
Empire, and the Santa Ana Mountains and Foothills gusting 25-40 mph
Gusty winds will slacken some this evening, but remain a bit breezy
tonight. Minimum humidities will still be very low this afternoon,
around 6 to 10 percent, with continued poor recovery again tonight.
Low humidity will continue Friday, but with less offshore wind.
Onshore flow will return Saturday, bringing cooling and higher
humidity west of the mountains, with a chance for rain by Sunday
afternoon or evening.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Red Flag Warning until 8 PM PDT this evening 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
Wind Advisory until 2 PM PDT this afternoon for Orange County
Inland Areas-San Bernardino and Riverside County Valleys-
The Inland Empire-Santa Ana Mountains and Foothills.