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Area Forecast Discussion (AFD)

Issued by San Diego, CA (SGX)

                            
000
FXUS66 KSGX 142103
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Sun Oct 14 2018

.SYNOPSIS...
Some stratus will occur mainly this evening along the coast. From 
late tonight through Tuesday, a Santa Ana weather pattern will bring 
strong gusty northeast winds to the mountains, valleys and even some 
coastal areas, along with low humidity and higher temperatures. The 
offshore flow will be much weaker Wednesday through Friday, but dry 
warm dry weather will continue. Upper low pressure could bring a few 
clouds this weekend.

&&

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

A few low clouds lingered this afternoon near the coast along with 
some cumulus over the mountains with temperatures mostly in the 
upper 60s to lower 70s west of the mountains.

The big change will occur late tonight and early Monday as a Santa 
Ana wind event develops. Winds will gradually increase from the 
northern mountain crests a little after midnight tonight south and 
southwest through the coastal foothills and valleys, including 
through and below passes and canyons. Winds likely will not arrive 
in the San Diego County Valleys until after sunrise Monday. 
Strongest support aloft will be late tonight and Monday morning, 
with high-resolution models, including the local WRF and Cansac WRF, 
indicating gust potential between 70 and 80 MPH in the strongest 
locations, mainly below Cajon Pass and in the Santa Ana Mountains in 
the 4 AM-noon PDT time range Monday. San Diego County should have 
somewhat weaker winds than farther north, with peak gust potential 
around 50-55 MPH in strongest locations. There will be much less 
support for strong winds Monday night and Tuesday, but local gusts 
over 50 MPH will still be possible Tuesday morning. Humidity will be 
low due to the offshore flow, below 10 percent at times. 
Temperatures will be higher once the offshore flow arrives with 
mostly 80s west of the mountains starting Monday.

The upper low which will move through the region from north to south 
Monday will remain over the SW US the rest of the week, with the 
interior SW being the most likely location of the low. This will 
keep us on the back side of the low with NE flow aloft and mostly 
weak offshore flow at the surface. Some model runs have the upper 
low moving west towards So-Cal or northern Baja next weekend which 
could enhance the offshore flow again, though that is dependent on 
the track of the low. Some moisture wraps around the low, based on 
the 12Z GFS solution, and that could even bring some precipitation. 
12Z ECMWF has some precip just to the north and east of our area. 
Have not added any precip for next weekend, but if models continue 
to show some precip in or near our forecast area, then I will add 
that to the forecast package Monday. MOS guidance shows it could be 
quite warm next weekend with 90s possible west of the mountains 
based on GFS MOS.

&&

.AVIATION... 
142100Z....Patchy stratus will continue over and west of the 
mountains, with bases 3000-4500 ft MSL and tops to 5000 ft MSL. 
Stratus will develop this evening with bases near 2500 ft MSL, then 
slowly clear in the morning once offshore winds develop. N-NE winds 
will strengthen this evening with sfc gusts 35-45 kt on the coastal 
mountain slopes and through and below the passes after 15/06Z, then 
increasing to 45-55 kt by Monday morning and spreading into the 
valleys and Orange County coastal plain. LLWS likely at SBD, KONT, 
and KSNA early Monday morning prior to winds surfacing. STG-SVR 
UDDFS like over and S/SW of the mountains. 

&&

.MARINE...
Northeast wind gusts to around 20 kt possible near and northeast of 
San Clemente Island Monday morning through Monday evening. No 
hazardous marine weather is expected Tuesday through Thursday.

&&

.BEACHES...
Locally elevated surf of 3 to 5 ft and strong rip currents will 
continue at the beaches through this evening from a south-southwest 
swell from 220 degrees. Swell and surf will begin to lower on 
Monday. A Beach Hazards Statement remains in effect through 10 PM.

&&

.FIRE WEATHER...
Critical fire weather conditions will occur at least Monday and 
Tuesday due to the Santa Ana Winds. Fuels which will be initially 
wet from the recent rains should dry out Monday as humidity will be 
10 percent or less in most low elevation locations, combined with 
winds 20-40 MPH with local gusts 55-75 MPH (Santa Ana Mtns and 
Inland Empire). Strongest winds will be Monday morning with winds 
somewhat weaker Tuesday. Mostly lighter winds are expected Wednesday 
through Friday, though humidity will stay low.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Red Flag Warning from 3 AM Monday to 8 PM PDT Tuesday for Orange 
     County Coastal Areas-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-Santa Ana Mountains-Including The 
     Trabuco Ranger District of the Cleveland National Forest.

     High Wind Warning from midnight tonight to 3 PM PDT Monday for 
     Orange County Inland Areas-San Bernardino County Mountains-
     San Bernardino and Riverside County Valleys-The Inland 
     Empire-Santa Ana Mountains and Foothills.

     Beach Hazards Statement until 10 PM PDT this evening for Orange 
     County Coastal Areas-San Diego County Coastal Areas.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...Maxwell
AVIATION/MARINE/BEACHES...JJT