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Area forecast discussion 
National Weather Service San Diego California 
938 am PST sun Jan 20 2019 


Synopsis... 
another warm day today under an upper level ridge. A deepening 
trough will bring cooler weather on Monday as the marine layer 
surges back inland on westerly winds, which will become strong from 
the mountain tops to the desert slopes tonight into Monday. Cloudy 
skies and even a few light showers are possible along and west of 
the mountains tonight through Monday morning. Winds will turn 
northeast with a Santa Ana wind event expected Monday night through 
Tuesday. An upper level ridge will build over the West Coast mid- 
late week, leading to dry and warm conditions, and this pattern 
looks to extend at least into the early part of the following week. 


&& 


Update... 


No major changes were made this morning. Thick high clouds will 
continue to stream in through this afternoon from the SW out ahead 
of a strong inside slider trough which will move across the region 
late tonight through Monday. Very strong onshore winds will develop 
late tonight and continue through Monday morning with the potential 
for damaging wind gusts. 


Previous discussion, issued at 317 am: 


Highlights... 


* strong and potentially damaging winds tonight through Monday 
afternoon Mountain Ridge tops to the deserts 


* Santa Ana wind Monday night-Tuesday, strongest below the san 
bernardinos 


* few light showers Monday morning; 1-2" of snow San Bernardino 
County mountains and Mt. San Jacinto 


Today will be another nice day ahead of a vigorous shortwave which 
will be moving into norcal tonight, then moving southeast with its 
southern extent/axis moving across socal Monday morning. West winds 
will be increasing ahead of this feature with h70 winds to 60 knots. 
WRF shows mountain waves developing with strong winds to 80 mph late 
tonight-Monday morning along the Desert Mountain slopes. 
It also shows potential surfacing mountain waves onto the Lower 
Desert floor. So while the Coachella Valley and San Diego County 
deserts will see winds prevailing lighter tonight-Monday, mountain 
waves could suddenly surface and produce damaging winds. Strong 
winds will impact the high deserts as well, especially east of 
Apple Valley. The High Wind Warning was expanded to include all 
of the deserts. 


The west winds will lessen during the day on Monday, then will 
become northeast and strengthen along the coastal mountain slopes 
and through and below canyons/passes Monday night-Tuesday. This 
Santa Ana wind will favor northern areas to include the San 
Bernardino County coastal mountain slopes, through the western 
inland Empire and to the foothills of the Santa Ana Mountains. Wind 
gusts to 50 mph are forecast for cities in these areas with gusts to 
70 mph along the coastal mountain slopes. At least a Wind Advisory 
will be needed for this Santa Ana wind. 


There could be a few showers developing late tonight through Monday 
morning from the coast to the mountains. Showers will favor the 
coastal mountain slopes, especially of the san bernardinos near the 
Cajon Pass due to favored upslope flow there, where 0.25-0.45" of 
rain is forecast. Amounts elsewhere will mostly be 0.10" or less. 
The snow level will be above 5500 feet. 1-2" of snow is forecast for 
parts of the San Bernardino County mountains as well as Mt. San 
Jacinto. 


Winds will subside Tuesday afternoon-Wednesday. Then, the rest of 
the week will feature warming temps, dry conditions, and lighter 
winds as an upper level ridge builds along the U.S. West Coast. A 
warm, dry pattern looks to continue through the upcoming weekend and 
into at least the early part of next week. 


&& 


Aviation... 


201645z...coast/valleys...sct-bkn clouds above 20000 ft mean sea level and 
unrestricted vis through this evening. Broken-overcast cigs with bases 1000- 
1500 ft mean sea level could impact the coastal airports between 03z and 09z 
Mon...lifting to 1500-2500 ft mean sea level between 09z and 15z Mon. Areas of 
vis 3-5 miles in fog could impact elevated coastal terrain during 
this period. Low clouds become scattered aft 15z Mon. 


Mountains/deserts...sct-bkn clouds above 20000 ft mean sea level through 
tonight. West winds increasing to 20-40 mph with gusts to 60 mph 
after 06z Mon...producing strong up/downdrafts and low level wind shear over and 
east of the mtns. West winds weaken after 00z Tue before turning 
northeast. 


&& 


Marine... 
very windy tonight and Monday with northwest winds 20-25 kt gusting 
to 30 kt. Gale force wind gusts will be possible at times. A Small 
Craft Advisory is in effect from 2 PM today to 2 am Tuesday. The 
northwest winds will turn northeast early Tuesday morning and be 
strongest from San Mateo Point out to San Clemente Island with gusts 
to 20 kt through midday Tuesday. 


A west-northwest swell from 290-295 at 8-10 seconds will move 
through the coastal waters Monday and Monday night. The strong 
northwest winds and the ocean swell will produce combined seas to 6 
feet in the inner waters and 10 feet in the outer waters. 


&& 


Beaches... 
a west-northwest swell from 290-295 degrees with a period of 10-11 
seconds will bring surf of 4-6 feet through Monday. The surf 
combined with morning high tides of 6.5 to 7.0 feet could produce 
minor coastal flooding at flood prone beaches including Seal Beach, 
Sunset Beach, Cardiff, and Imperial Beach. A beach hazard statement 
is in effect through noon Monday for possible beach flooding during 
the early morning high tides. 


&& 


Skywarn... 
Skywarn activation is not requested today. However, spotter 
activation may be needed late tonight through Monday for the 
potential of damaging winds impacting the deserts. 


&& 


Sgx watches/warnings/advisories... 
California...High Wind Warning from 10 PM this evening to 2 PM PST Monday for 
apple and Lucerne valleys-Coachella Valley-Riverside County 
mountains-San Bernardino County mountains-San Diego County 
deserts-San Diego County mountains-San Gorgonio Pass near 
Banning. 


Beach hazards statement through Monday morning for Orange County 
coastal areas-San Diego County coastal areas. 


Pz...Small Craft Advisory from 2 PM this afternoon to 2 am PST 
Tuesday for coastal waters from San Mateo Point to the 
Mexican border and out to 30 nm-waters from San Mateo Point 
to the Mexican border extending 30 to 60 nm out including 
San Clemente Island. 


&& 






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