Ation DISCUSSION,
.SHORT TERM (Today through Saturday), A weak low pressure system over the eastern Pacific will move to near the West Coast on Saturday. It will maintain stronger onshore flow and a deeper marine layer into Saturday. Night and morning low clouds will spread inland across most of the valleys late each night. High temperatures for Friday and Saturday will be near average at sea level to as much as 5 to 10 degrees below average for the mountains and valleys. High temperatures for Friday and Saturday will range from the lower 70s near the coast to the upper 70s to mid 80s for the Inland Empire with 102 to 106 for the lower deserts. Southwest to west winds during the afternoon and evening for the mountains and deserts will be strongest on Friday with gusts to 30 to 40 mph and with gusts to 55 mph in the northern Coachella Valley below the San Gorgonio Pass.
A weak low pressure system moving to near the West Coast will spread cooling inland with high temperatures for Friday and Saturday as much as 5 to 10 degrees below average for the mountains and valleys. Night and morning low clouds will spread inland across most of the valleys late each night. Southwest to west winds during the afternoon and evening for the mountains and deserts will be strongest on Friday with gusts to 30 to 40 mph with gusts to 55 mph in the northern Coachella Valley below the San Gorgonio Pass. There will be a warming trend for next week. For Wednesday and Thursday of next week, there could be widespread major HeatRisk for the deserts and moderate HeatRisk for other non-coastal areas.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
(today through Saturday), A weak low pressure system over the eastern Pacific will move to near the West Coast on Saturday. It will maintain stronger onshore flow and a deeper marine layer into Saturday. Night and morning low clouds will spread inland across most of the valleys late each night. High temperatures for Friday and Saturday will be near average at sea level to as much as 5 to 10 degrees below average for the mountains and valleys. High temperatures for Friday and Saturday will range from the lower 70s near the coast to the upper 70s to mid 80s for the Inland Empire with 102 to 106 for the lower deserts. Southwest to west winds during the afternoon and evening for the mountains and deserts will be strongest on Friday with gusts to 30 to 40 mph and with gusts to 55 mph in the northern Coachella Valley below the San Gorgonio Pass.
(Sunday through Wednesday), Low pressure near the West Coast will weaken with high pressure over northern Mexico strengthening and expanding into the southwest states. The currently forecast 500 mb temperatures for San Diego for next Wednesday exceed the 90th percentile and would be near record levels. High temperatures will warm for Sunday through Wednesday with the greater warming on Monday and Tuesday and for the mountains and valleys. NBM 90th percentile high temperatures for next Wednesday range from the 70s near the coast to the 90s to 104 for the Inland Empire with 114 to 118 for the lower deserts.
Using NBM 90th percentile high and low temperatures for Tuesday through Thursday of next week would result in widespread major HeatRisk for the deserts for Wednesday and Thursday of next week and widespread moderate HeatRisk for the inland valleys, mountain elevations below 6000 feet, and inland Orange County.
Toward the end of next week, cluster analysis shows that the key to just how warm it gets and stays is dependent on the strength of low pressure near the Pacific Northwest coast. For Thermal for Friday and Saturday of next week, the NBM 10th percentile high temperatures are 109 and the 90th percentile 118. That's more than 5 degrees above average to around 15 degrees above average. Weaker low pressure near the West Coast toward the end of next week would allow the inland heat wave to at least persist if not also strengthen.
As high pressure aloft strengthens, the marine layer will decrease in depth. The farthest overnight inland spread of coastal low clouds will be limited to the western valleys by the middle of next week.
180930z, Coast/Valleys, Low clouds 1800-2400 ft MSL currently impacting coastal areas will move to cover most of the coastal basin by 12Z. Clouds will scatter for valleys 15-18Z and coastal regions 16-20Z. There will likely be some localized low clouds lingering along parts of the coast through most of the afternoon, highest chances in southern San Diego County vcnty La Jolla. There is a 30% chance KSAN could only partially/intermittently clear. Clouds with similar bases will become more widespread and move back into coastal regions after 00Z Friday, then back to cover most of the coastal basin again by 12Z Friday.
Mountains/Deserts, VFR conditions. Breezy westerly winds gusting 25-30 kts through mountain passes and into deserts 18Z through 09Z Friday. There could be temporary VIS restrictions due to FU (wildfire smoke) in an around the Coachella Valley area through Thursday evening.
No hazardous marine conditions are expected through Monday.
Elevated surf and strong rip currents continue through Friday. Surf of 3-5 feet with local sets to 6 feet are expected at south-facing beaches. Surf for southern San Diego County will be slightly lower, but hazardous swimming conditions with high rip current and longshore current risk will still exist. See the Beach Hazards Statement for more details.
Ca, Beach Hazards Statement through Friday evening for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
