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000 
FXUS66 KSGX 222048
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Tue May 22 2018

.SYNOPSIS...
A deep upper level trough will move northeast out of the area this 
afternoon and tonight, resulting in a gradual decrease in cloud 
cover through Wednesday. Another area of low pressure will through 
the region Friday through Sunday, so the below normal daytime 
temperatures will continue through the weekend with periodic low 
clouds west of the mountains. More marine layer low clouds are 
likely early next week as well.

&&

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

Marine layer depth ranged from 4000 feet above sea level in San 
Diego County to 5000 feet farther north this morning, with aircraft 
soundings showing a slight lowering this afternoon. We had partial 
clearing today, with greatest remaining stratus extent over Orange 
County and northern parts of the Inland Empire. Some cumulus were 
over the Big Bear area and the high deserts.

The upper low will move to the northeast mainly tonight and weaken 
while some ridging forms over the interior southwestern US. Some 
lowering of the marine layer will occur, with better afternoon 
clearing Wednesday, especially inland. With onshore flow continuing 
as well as the peak stratus season, we will still have a lot of 
stratus around, especially nights and mornings, most of the week. An 
upper level low will move into California Friday/Friday night, and 
this will bring more cooling to inland areas, though the marine 
layer effects here will depend partly on if we have a coastal eddy. 
Right now, the GFS is saying no to the eddy until Sunday, so we may 
end up with a decrease in stratus Friday/Saturday, especially with 
cooling above the marine inversion. Models are inconsistent for 
early next week, except for one thing--no significant ridging, and 
yes to continued onshore flow. Thus, coastal low clouds are likely 
to occur then, with temperatures at or a little below normal.

&&

.AVIATION... 
222030Z...Coast/Valleys/Coastal Mountain Slopes...Stratus deck 
hanging on at KSNA/KONT/KSBD while significant clearing has 
developed elsewhere. Expect continued erosion of the cloud cover 
with several hours of SCT conditions at the terminals through early 
this evening. The marine layer will be much shallower 
tonight/Wednesday morning. Expect low clouds to fill in again 
beginning 03-05Z coastal terminals and 06-10Z inland terminals with 
BKN IFR/MVFR conditions at the terminals thereafter. Will see bases 
900-1300 feet MSL and tops 1500-2500 feet late tonight/ Wednesday 
morning. Expect cloud deck to scatter out early Wednesday afternoon. 

Mountain Crests/Desert Mountain Slopes/Deserts...VFR conditions with 
clear skies through the period. Local west winds 15-25 kt with gusts 
25-35 kt will occur on the desert mountain slopes and through San 
Gorgonio Pass, with the strongest gusts late this afternoon and 
evening. 

&&

.MARINE...
No hazardous marine conditions are expected through Friday. Wind 
gusts over 20 knots are likely over the outer waters Friday night 
through Saturday night. 

&&

.BEACHES...
A long-period swell from 200 degrees and resulting surf on south 
facing beaches will peak today through Wednesday before subsiding 
slowly Thursday and Friday. Check the beach hazard statement for all 
the details.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement through Thursday afternoon for Orange 
     County Coastal Areas.

PZ...NONE.
&&

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