Small Craft Advisory 18, NWS San Diego, CA

Area Forecast Discussion
National Weather Service San Diego CA
950 AM PST Thu Nov 5 2020

.SYNOPSIS...
High pressure and weak offshore flow will continue to bring warm
weather today, with high clouds continuing to move in from the
south. A big weather change is in store for Friday through the
weekend as a pair of low pressure systems move over California.
Significant cooling, gusty southwest to west winds, and periods of
precipitation will occur Friday evening through the weekend. A
very gradual warming trend and drying will occur through much of
next week.

&&

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

At 9 AM, satellite imagery showed high clouds streaming from the
south into Southern California from Tropical Storm Odalys. High
clouds will continue to increase in coverage today, decreasing
some on Friday.

Today will be the warmest day of the next week, thanks to high
pressure aloft and weak offshore flow. Temperatures will be
slightly warmer than yesterday, although high clouds could limit
how hot it gets today. Generally, temperatures in the valleys and
lower deserts will be in the low to mid 90s, inland coastal areas
will be in the 80s, and beaches will be in the upper 70s to low
80s.

A big pattern change is in store Friday through the weekend as a
pair of low pressure systems from the north impacts California. These
low pressure systems will bring much cooler weather, gusty
southwest to west winds, and periods of showers Friday evening
through Sunday night across Southern California.

Significant cooling will spread inland Friday through the weekend,
with the coolest days on Saturday and Sunday. Temperatures will
be 15 to 25 degrees below normal in the valleys, mountains, and
deserts. Along the coast, temperatures will be 10 to 15 degrees
below normal.

Gusty southwest to west winds will increase Friday afternoon and
continue through Sunday night in the mountains and deserts. Peak
wind gusts will range from 40 to 50 mph, but higher gusts are
possible in wind prone locations. It will also be breezy in the
valleys and along the coast, with peak gusts of 20 to 25 mph.

Precipitation will begin to move into the region Friday evening
and Friday night. This round of initial showers will be fairly light,
but will increase in coverage after sunrise on Saturday. More
widespread precipitation is expected Saturday morning through
Saturday afternoon, decreasing in coverage for Saturday evening
through Saturday night. Another round of more widespread
precipitation is expected Sunday morning through Sunday afternoon
as the second low pressure system moves through California.

The greatest precipitation totals are looking to occur in San
Diego County with less to the north. The greatest totals will occur
in the coastal slopes of the San Diego mountains where upslope
enhancement will occur, with precipitation totals ranging from 1
inch in the southern San Diego mountains, to 1.5 to 2 inches in
the northern San Diego mountains. The San Diego valleys will see
precipitation totals of 1 to 1.5 inches. Coastal areas in San
Diego County will see a bit less, with totals of a half inch to 1
inch. Upslope enhancement will also occur in the San Bernardino
and Riverside mountains, with total precipitation amounts around 1
to 1.5 inches. Inland Orange County and the Inland Empire will
see far less precipitation, with totals around a half inch to 1
inch. The deserts may see a few sprinkles, but total precipitation
should remain below two tenths of an inch.

Snow levels will drop to around 5,000 feet by Saturday morning in
the mountains and continue through the weekend. In the San
Bernardino and Riverside mountains, snow totals between 5000 and
6000 feet will range from 1 to 3 inches. Above 6000 feet, totals
will range from 4 to 8 inches. On the highest peaks, totals could
be around one foot.

The low pressure systems will weaken and push east early next
week. A very gradual warming trend will occur for much of next
week, although temperatures will continue to be below seasonal
normals.

&&

.AVIATION...
051630Z...BKN clouds AOA 10,000 ft today and tonight. Easterly winds
of 20-25 kts with localized higher gusts into the early afternoon
across the mountains and foothills, leading to localized
up/downdrafts and LLWS through 21z. Low clouds and local areas of
fog to develop after 10z Fri across coastal areas with bases 800-
1000 ft MSL and reduced VIS where clouds interact with terrain. Low
clouds and fog to push inland through Fri morning.

&&

.MARINE...
No hazardous marine conditions are expected through Fri morning.
Strong northwest winds of 20-30 kts will arrive Fri afternoon along
with hazardous combined seas of 10-12 ft. These will peak Sat and
Sun before subsiding Monday.

&&

.BEACHES...
Surf will build Fri and peak during the weekend. Surf of 4 to 6 feet
with local sets to 7 feet is expected, highest in southern San Diego
County, producing a high rip current risk.

&&

.FIRE WEATHER...
High pressure aloft and weak offshore flow will bring elevated
fire weather conditions to the mountains and foothills today.
Locally gusty northeast to east winds with gusts to 25 mph will
occur this morning, decreasing this afternoon and evening.
Humidity will continue to be low inland today, with minimum
daytime humidity of 10 to 15 percent.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

PUBLIC/FIRE WEATHER...Connolly
AVIATION/MARINE/BEACHES...Schenk/SS