Strong Wind in California, April 14 to 18, 2021

Area Forecast Discussion
National Weather Service San Diego CA
858 AM PDT Wed Apr 14 2021

.SYNOPSIS...
A low pressure system over the Great Basin will continue to lead
to stronger onshore winds across southern California along with a
fairly deep marine layer. Strong and gusty west winds will impact
the mountains and deserts late this afternoon through early
Thursday morning. An upper ridge will gradually build into the
area from the northwest through the weekend. This will lead to
significant warming and more sunshine heading into the weekend and
into early next week.

&&

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

Update:

West winds will again strengthen late this afternoon and evening
along the desert mountain slopes and across the lower deserts.
Expanded the Wind Advisory and extended the advisory in time,
through 2 AM Thursday. The advisory now covers more of the
Coachella Valley. Wind gusts of 40-50 mph is forecast, especially
from north Palm Springs to Thousand Palms. No other changes were
made to the forecast this morning.

Previous Discussion (Issued at 315 AM PDT Wed Apr 14 2021):

.SHORT TERM (Today through Friday)...
Upper level low pressure is centered over the Great Basin with
stronger onshore flow across southern California. The marine layer
has deepened to around 5000 feet with coastal low clouds extending
inland onto the coastal mountain slopes. Stronger and gusty winds
continue along the desert slopes of the mountains into the
deserts. The strongest gusts have been 64 mph at Whitewater near
the San Gorgonio Pass and 67 mph at Mountain Springs Grade near
Interstate 8 near the border between San Diego and Imperial
Counties. The winds are expected to subside some during the
morning with another round of similar strength winds for this
afternoon into the evening.

There have continued to be some light measurable amounts of
precipitation overnight from the deep marine layer and that is
expected to continue into early this morning. The marine layer
will then become gradually shallower for Thursday into the
weekend. High temperatures will continue to cool for the mountain
and deserts today with not much change for the coast and valleys.
High temperatures will generally be 5 to 10 degrees below average
near the coast and in the deserts and as much as 15 to 20 degrees
below average for portions of the valleys onto the coastal slopes
of the mountains. A warming trend will following for Thursday and
Friday with Friday high temperatures still a few degrees below
average.

&&

.LONG TERM (Saturday through Tuesday)...
High pressure aloft will be centered near the West Coast for the
weekend, then weaken some for the early to middle part of next
week. High temperatures will continue to warm for the weekend with
the warming possibly continuing into Monday for some inland areas.

The lower level flow may go offshore on Sunday with gusty north to
northeast winds. Ensemble members of the ECMWF show weak to
moderate strength winds at Ontario on Sunday. With offshore flow,
Sunday would most likely be the warmest day for coastal areas.

The greater spread in guidance for Tuesday and Wednesday near the
West Coast continues. Those solutions with greater troughing over
California have the greatest support from ensemble members of the
ECMWF while those with stronger high pressure off the West Coast
and weaker troughing over the western states are most strongly
supported by ensemble members of the Canadian model. Cooling for
Tuesday and Wednesday could range from slight to somewhat greater.
But even the coolest solutions are warmer than for high
temperatures for the middle of this week.

&&

.AVIATION...
141530Z...Coast/Valleys...Areas of BKN-OVC clouds will continue
through 19Z, with bases 2000-4000 ft MSL. Most areas will become SCT-
locally BKN with mid-level cloud bases 4000-5500 ft MSL and high
clouds AOA 15000 ft MSL after 19Z. Stratus redeveloping after 02Z
Thu with bases 2500-3500 ft MSL and tops 4000-4500 ft MSL.

Mountains/Deserts...Through 20Z, stratus/fog on the coastal slopes
of the mountains will result in terrain obscurations below 5500 ft
MSL. West winds 15-30 kt with local gusts 35-50 kt will continue at
times through this evening from the mountain crests east into the
deserts and below the San Gorgonio Pass. MOD-STG up/downdrafts and
LLWS are likely over/east of the mountains through this evening. PSP
and TRM will occasionally encounter gusts around 30 knots from the
NW this afternoon/evening.

&&

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

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 2 AM PDT Thursday for Coachella Valley-
     Riverside County Mountains-San Diego County Deserts-San
     Diego County Mountains-San Gorgonio Pass Near Banning.

PZ...NONE.
&&

PUBLIC...Gregoria
AVIATION/MARINE...CO