Cooling will spread inland into the weekend with high temperatures cooling to around average on Saturday. High temperatures for the coast and valleys will be mostly in the 70s for Sunday through Tuesday. One low pressure system from the southwest on Sunday and a second from the north on Monday and Tuesday combined with tropical moisture will bring showers for late Saturday night through Sunday night with continuing chances for showers through Tuesday night. There will also be stronger southwest to west winds on Sunday.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
(today through Saturday), High pressure aloft will weaken into the weekend. Onshore will slowly strengthen and a shallow marine layer will slowly deepen into the weekend. Cooling of high temperatures will continue to spread inland. High temperatures for the deserts into the mountains will be a few degrees warmer today. Cooling will continue to spread inland today with high temperatures a few degrees cooler for coastal areas to around 5 degrees cooler for the western valleys in San Diego County. High temperatures on Friday will cool a few degrees for the deserts and around 5 degrees elsewhere. On Saturday, high temperatures will cool a few degrees near the coast to 8 to 12 degrees for the mountains, deserts, and inland valleys.
High temperatures for today will be around 10 to 15 degrees above average, ranging from the 80s near the coast to the upper 90s to 103 for the Inland Empire with 106 to 110 for the lower deserts. HeatRisk for the coast and valleys will be Moderate to locally Major and for the lower deserts Moderate to Major. On Saturday, high temperatures will cool to around average with high temperatures ranging from the 70s near the coast to the lower to mid 80s for the valleys with the lower deserts in the mid 90s.
A shallow marine layer will slowly deepen with patchy low clouds and locally dense fog developing across the coastal waters and spreading into adjacent coastal areas early this morning. Coverage of night and morning coastal low clouds and inland spread will increase for tonight and again Friday night.
(Saturday night through Wednesday), A closed low pressure system moving southward off the California coast will interact with a weakening tropical cyclone Rachel to spread moisture and precipitation into northern Baja and portions of southern California for Saturday night into Sunday.
NBM probabilities for 0.10 inch or more of rainfall for Saturday night through Sunday night range from 65 to 75 percent near the coast to 80 to 90 percent in the mountains with 50 to 70 percent for the deserts. NBM probabilities for 0.50 inch or more of rainfall for Saturday night through Sunday night range from 40 to 50 percent near the coast to 65 to 75 percent in the mountains with 30 to 40 percent for the deserts. NBM probabilities for 1 inch or more of rainfall for Saturday night through Sunday night range from 20 to 30 percent near the coast to 45 to 55 percent in the mountains with 15 to 25 percent for the deserts. NBM probabilities for 2 inches or more of rainfall for Saturday night through Sunday night are 15 to 25 percent for the mountains.
A second low pressure system moving southward along the California coast could bring additional showers for Monday and Tuesday. For Monday through Tuesday night, NBM probabilities for another 0.10 inch or more of rainfall range from 45 to 55 percent near the coast to 55 to 65 percent for the mountains with 15 to 35 percent for the deserts. For Monday through Tuesday night, NBM probabilities for another 0.50 inch or more of rainfall range from 20 to 30 percent near the coast to 35 to 45 percent for the mountains with less than 15 percent for the deserts. For Monday through Tuesday night, NBM probabilities for another 1 inch or more of rainfall range from around 10 percent near the coast to 15 to 25 percent for the mountains.
NHC has Rachel falling below tropical storm strength before landfall in northern Baja late Saturday night on a track that would take it into northwest Arizona late Sunday evening. Slight deviations from the NHC forecast are unlikely to cause any significant changes to the impacts to southwestern California for Saturday night through Sunday night.
Winds across the coastal waters are expected to shift to the west by Sunday afternoon with gusts to 20 to 30 mph. The tide gauge in the San Diego Bay shows water levels around 18 inches higher than those of a year ago, that higher current sea level the result of the thermal expansion of warmer water from a marine heat wave and the strengthening El Nino and the associated most recent Kelvin wave moving northward along the California coast. Those higher water levels combined with south to southwest swell and resulting surf from Rachel and surge from the winds across the coastal waters will increase the potential for coastal flooding, especially on Sunday.
Drying and warming is expected for next Wednesday with northwest flow aloft and weakening onshore lower-level flow.
081130z, Coast: Areas of low clouds and fog with bases around 400 feet MSL and vis 0-6SM will continue through 15-16Z. Low clouds and fog based around 600-800 feet MSL with vis as low as 2SM to redevelop after 07Z tonight and expand in coverage into Friday.
Otherwise, mostly clear today and tonight, except for shallow cumulus over mountains 19-01Z.
No hazardous marine conditions are expected through Saturday. The remnants of Rachel will bring a rapid increase in southerly swell along with gusty winds and choppy seas Sunday, diminishing somewhat on Monday.
Surf of 3-5 feet with sets to 6 feet is expected on south and southwest facing beaches through Friday. Elevated surf and strong rip and longshore currents will create hazardous swimming conditions. This elevated surf will combine with high tides during the mornings and evenings to generate local coastal flooding and beach erosion. Another south swell Sunday and continued morning high tides near 7 feet will maintain a threat of coastal flooding and beach erosion into Tuesday. The Beach Hazards Statement and Coastal Flood Advisory contain the details.
Ca, Extreme Heat Warning until 8 PM PDT this evening for Orange County Coastal Areas-Orange County Inland Areas-San Bernardino and Riverside County Valleys-The Inland Empire- San Diego County Coastal Areas-San Diego County Valleys- Santa Ana Mountains and Foothills.
Beach Hazards Statement through Friday evening for Orange County Coastal Areas-San Diego County Coastal Areas.
Coastal Flood Advisory until 2 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.
Extreme Heat Warning until 8 PM PDT Friday for Coachella Valley- San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
