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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 230440
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
940 PM PDT Mon Oct 22 2018

.SYNOPSIS...
A series of weak Pacific troughs will bring seasonal weather through 
Wednesday. Night and morning marine layer clouds in the coastal 
zones and western valleys will retreat back to the coast each 
afternoon. It will turn much warmer Thursday and Friday as high 
pressure over the eastern Pacific builds into Southern California. 

&&

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

...Update...

Extensive high cloudiness moved into the area late in the day and
is covering the service area. Increased sky cover more to account
for this. Marine layer low cloudiness is developing along portions
of the coast and will continue to do so while moving into the 
inland valleys overnight. 

...Previous Discussion (Issued at 145 PM PDT Mon Oct 22 2018)...

High clouds will drift across Southern California tonight as a 
trough of low pressure over the Pacific moves inland. This trough 
brought stronger onshore flow and 3 to 5 degrees of cooling to the
coastal and valleys areas today. Mountain and desert temperatures
were about the same as yesterday.


The weather on Tuesday and Wednesday will be fairly similar to today 
as weak Pacific troughs move inland across SoCal. The first passes 
by Tuesday morning, followed by a weaker one Wednesday. The marine 
layer will stay intact and spread into the western valleys. There 
will also be scattered to broken high clouds at times. The IR loop 
this afternoon showed these high clouds starting to move into San 
Diego and Orange County at 1 pm. 

The onshore pattern Tuesday and Wednesday reverts back to a weak 
offshore pattern Thursday and Friday as high pressure over the 
Pacific builds in behind the departing trough. The pressure 
gradients turn offshore as a 1022 mb surface high builds over the 
Great Basin, strong enough for modest northeast winds in the 
mountains and foothills, but nothing too strong. The combination of 
ridging aloft and the offshore flow at the surface will raise max 
temperatures quite a bit in the coastal and valley areas Thursday 
through Saturday. The marine layer will be squashed and low clouds 
are not expected at the coast. The Inland Empire will see highs in 
the 90s Friday and Saturday, with widespread 80s in the coastal 
zones and San Diego Valleys. Mountain and Deserts highs will also be 
way above average for late October.  

The offshore flow weakens over the weekend and it won't be quite as 
hot west of the mountains on Sunday as onshore flow returns. But it 
will remain very warm/hot in the mountains and deserts. 

The upper ridge weakens early next week with a trough settling over 
the Great Basin bringing cooler weather, stronger onshore flow and 
the return of marine layer clouds to the coastal areas.  

&&

.AVIATION... 
230430Z...Coast/Valleys...High cloud bank will continue to affect 
the region overnight with OVC250 continuing through Tue morning most 
likely. SCT to BKN coastal stratus will build onto the coast after 
08Z and spread 10-20 mi inland through 12Z Tue morning. Bases will 
be approximately 1200-1800 ft MSL. VSBY down to 2 SM in patchy fog, 
especially in the inland valleys inc ONT and SBD.

Mountains/Deserts...OVC250 high clouds and unrestricted vis through 
Tuesday morning, then decreasing cloudiness through Tuesday.

&&

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

&&

.SKYWARN... 
Skywarn activation will not be needed this week.


&&

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

$$

PUBLIC...Gregoria (Update)/Moede (Prev Discussion)
AVIATION/MARINE...Brotherton