669 
FXUS66 KSGX 041116 AAA
AFDSGX

Area Forecast Discussion...Updated
National Weather Service San Diego CA
415 AM PDT Sun Apr 4 2021

.SYNOPSIS... 
A ridge aloft will remain over California today, continuing the 
streak of very warm weather away from the coast, where a shallow 
marine layer will keep the weather cooler, along with areas of night 
and morning low clouds and fog. A passing disturbance to the north 
will create strong westerly winds over the mountains and some desert 
areas late tonight and Monday. This will bring some cooling inland, 
but temperatures will remain above average all week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Updated...
...Marine clouds covered the San Diego County Coast at 4 AM PDT and 
visibility was falling just inland along the mesas and on higher 
coastal terrain where 1/4 mile or less visibility was reported in 
fog. With little change expected in the next few hours, a Dense Fog 
Advisory has been issued through 8 AM PDT...

Elsewhere over SoCal skies were clear. The onshore sfc pressure 
gradient from the SoCal coast to the high desert areas remained 
weak, but the gradient to the lower deserts was stronger and 
supporting winds of 20-30 MPH and Gusts 35-45 MPH through and 
below the San Gorgonio Pass area. Late this afternoon those winds 
will increase and become quite strong over the mountains late 
tonight through Monday night. A High Wind Watch has been posted for 
possible wind gusts of 65-75 MPH in the mountains, with Wind 
Advisories possible for the deserts on Monday. 

That strong ridge, centered west of the southern Baja Peninsula 
remains firmly in control of our weather today and will again result 
in some hot weather over the deserts, where daytime maximums will 
again be around the century mark. These levels will be knocked down 
a bit on Monday as a shortwave flattens the ridge as it traverses 
the Great Basin. This will sharpen the height/pressure gradient 
across SoCal, resulting in some strong gradient winds, especially at 
higher elevations. Some of this will mix to the sfc over the deserts 
and provide some cooling as marine air is forced through the passes. 

The ridge will rebound once the trough passes but 500 MB heights and 
associated thickness will not be as high, so it should be a bit 
cooler inland and over the deserts. A few more weak shortwaves will 
pass by later in the week, maintaining onshore flow and additional 
cooling by next weekend. Beyond that, there appears to still be a 
chance at some precipitation (around mid month) as several ensemble 
members of all the major hemispheric models turn wet. In the 
meantime, look for the dry Spring pattern to persist with warm days 
inland and periods of coastal clouds and fog. 

&&

.AVIATION... 
040900Z...Coast/Valleys...Areas of low clouds with bases 600-900 ft 
MSL and tops to 1200 ft MSL will continue along the coast and up to 
10 mi inland this morning, mainly in San Diego County. Low 
confidence in any CIGS at KSNA. Areas of vis 2-4 miles will occur, 
locally below 1 mile, mainly over higher coastal terrain and on the 
coastal mesas. Clouds and vis restrictions clearing 16-18Z. Areas of 
low clouds with bases 500-1000 ft MSL redeveloping after 05/06Z and 
spreading around 10 mi inland again overnight.

Mountains/Deserts...FEW-SCT high clouds AOA 20,000 ft MSL and 
unrestricted vis through Monday morning. West winds with sfc gusts 
30-45 kt developing over the mountain ridges, upper desert slopes, 
and locally into the deserts after 05/00Z and continuing into Monday 
morning. Strong up/downdrafts, LLWS, and rotors possible over/east 
of the mountains.

&& 

.MARINE...
Occasional west-northwest winds with local gusts over 20 knots will 
occur over the outer coastal waters (30-60 NM from the coast) each 
afternoon through Thursday, with strongest winds likely 
Monday through Wednesday.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...High Wind Watch from late tonight through late Monday night for 
     Riverside County Mountains-San Bernardino County Mountains-
     San Diego County Mountains-San Gorgonio Pass Near Banning.

     Dense Fog Advisory until 8 AM PDT this morning for San Diego 
     County Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC...10
AVIATION/MARINE...SS