San Clemente Island CA to Guadalupe Island from 60 NM offshore west to 120W Offshore Forecast
| Tonight...Nw Winds 10 To 15 Kt. Seas 4 To 5 Ft. |
| Wed...W To Nw Winds 5 To 15 Kt, Increasing To 10 To 20 Kt. Seas 3 To 6 Ft. |
| Wed Night...W To Nw Winds 15 To 25 Kt. Seas Building To 6 To 11 Ft. Chance Of Rain. |
| Thu...W To Nw Winds 20 To 30 Kt. Seas Building To 8 To 15 Ft. Chance Of Showers. |
| Thu Night...Nw Winds 10 To 20 Kt, Becoming N To Nw 10 To 15 Kt. Seas 8 To 14 Ft. |
| Fri...N To Nw Winds 5 To 15 Kt. Seas Subsiding To 6 To 10 Ft. |
| Fri Night...N Winds 10 To 20 Kt. Seas Subsiding To 5 To 7 Ft. |
| Sat...N To Nw Winds 10 To 20 Kt. Seas 5 To 6 Ft. |
| Sat Night...N To Nw Winds 15 To 20 Kt. Seas 5 To 6 Ft. |
| Sun...Nw Winds 15 To 20 Kt. Seas 5 To 6 Ft. |
| Sun Night...Nw Winds 10 To 20 Kt. Seas 5 To 8 Ft. |
| Area Forecast Discussion National Weather Service San Diego CA 911pm PDT Tuesday Mar 28 2023 Synopsis Low pressure moving south along the Coast through Thursday, will lead to widespread showers in mainly two waves. The first will be on Wednesday, and the second on Thursday. Accumulating snow will fall over the mountains, and gusty southwest to west winds will accompany the precipitation across the mountains and deserts. It will be quite cool both Wednesday and Thursday, then fair and slightly warmer for the coming weekend. For Extreme Southwestern California Including Orange... San Diego...Western Riverside and Southwestern San Bernardino Counties A few high clouds were drifting over SoCal this evening, otherwise it was clear. South winds were picking up over the mountains, in advance of the low pressure center that is slowly dropping south off the NorCal Coast. Peak gusts through 9pm were 35-40 MPH. Our 00Z Miramar sounding was still quite dry, but winds at all levels were now westerly. Looking up the Coast....Rain was falling as close as Santa Barbara County. Low clouds should be slow to return to coastal areas, and may not arrive until early Wednesday morning with the scattered shower development. The 02Z run of the HRRR (High-Resolution Rapid Refresh) shows showers arriving over O.C. by 14Z Wednesday morning, and then spreading SE through the morning. It still looks like a break in the activity late on Wednesday, followed by a return of numerous showers, later in the evening or overnight. A number of weather Advisories are in effect starting on Wednesday. See our website for specifics, and the Hydrology section below for precipitation details. No forecast updates this evening. From previous Discussion... A compact, strong low pressure system is off the coast of the Oregon-California border. The low will weaken and expand as it moves farther south tonight and on Wednesday, becoming an open wave and moving over Southern California on Thursday. Ahead of the system, winds will increase this afternoon through Wednesday across the mountains and desert slopes. Winds will peak Wednesday afternoon and evening before diminishing slightly, but will remain gusty through Thursday as the system exits the region to the east. Rain currently focused over central California will slowly progress southeastward, reaching Orange and San Bernardino Counties overnight, then spreading into Riverside and San Diego Counties near daybreak on Wednesday. This first round of rain will be modest, though locally heavy rainfall will be possible along the coastal mountain slopes. Snow levels will rise to above 6500 feet as precipitation develops late tonight, and will slowly fall through Wednesday. After a brief break in the precipitation later tomorrow morning and afternoon, more convective showers will develop late Wednesday night into Thursday, increasing from northwest to southeast. These cells will be more scattered in nature and isolated thunderstorms will be possible. With this second round of precipitation, snow levels will fall to 3500-4000 feet late Wednesday night into Thursday. Please read the Hydrology section below for further detail on expected precipitation. Temperatures will plummet tomorrow and on Thursday. Highs west of the mountains will struggle to reach 60 degrees, which will put high temperatures 5 to 20 degrees below normal. Thursday will be the coldest day of the week, when temperatures will run 10 to 25 degrees below normal. The system will exit the region to the east by Friday, leaving drier conditions in its wake. The 12z ensemble guidance shows a more zonal pattern by Saturday, with weak positive height anomalies, strengthening subtly on Sunday. This will support slight warming each day this weekend, though highs may remain up to 5 degrees below normal. Longer-range cluster analysis begins to develop discrepancies in the synoptic pattern for early next week, in regards to the extent and strength of the ridging over the central U.S. and how quickly Southern California will come under the influence of another trough. However, the general consensus is that a another strong trough with negative height anomalies could impact much of the western United States sometime next week. This would continue to leave the door open for chances of precipitation, gusty onshore winds and seasonally-cool temperatures to continue through the first part of April. Marine A storm system will bring rain and gusty winds Wednesday and Thursday. West winds around 20 kt with gusts 25 kt possible Thursday along with combined seas to 9 ft and steep waves. Isolated thunderstorms are also possible Wednesday night and Thursday, and these could create a waterspout. Beaches There is a slight chance of thunderstorms Wednesday night and Thursday at the beaches with cloud-to-ground lightning possible. Thunderstorms will most likely be isolated if they occur. Hydrology Light precipitation is forecast to reach Orange and southwest San Bernardino County just before sunup on Wednesday, and spread southeast through the morning, turning to scattered showers for the afternoon, except on the coastal slopes of the mountains, where upslope flow will maintain more widespread light accumulations. A second wave will arrive before sunup on Thursday and last throughout the day. This one will be more convective with isolated thunderstorms and heavier rainfall rates possible. For the first wave, rainfall rates under one-quarter inch/hour should be the rule, with isolated heavier amounts. For the second, one-quarter to one- half inch/hour rates can be expected at times. If thunderstorms develop, rates could be locally higher, but should be isolated. With the upslope enhancement on the coastal slopes, liquid equivalent precipitation totals of 1 to 3 inches can be expected. Around one-half inch is possible west of the mountains, punctuated by locally heavier amounts up to one inch where heavier showers/thunderstorms track. The high deserts could see around one-quarter inch, with somewhat less in the lower deserts. With wet soil conditions, there will likely be more instances of urban flooding and pooling of water in poorly drained areas. No main stem river flooding is expected. The snow level will rise above 6000 feet Wednesday morning, then fall to 3500 to 4000 feet late Wednesday night, then fluctuate around 4500 feet on Thursday. Snowfall of 6 to 10 inches is possible in the mountains above 5000 feet with locally 12 to 18 inches on higher peaks above 7500 feet. A few inches of snowfall is possible at elevations down to around 4000 to 4500 feet. Skywarn Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. NOAA San Diego CA Office: Watches - Warnings - Advisories CA...Winter Storm Warning from 4am Wednesday to 2pm PDT Thursday for San Bernardino County Mountains. Winter Storm Warning from 10am Wednesday to 4pm PDT Thursday for Riverside County Mountains. Wind Advisory from noon Wednesday to midnight PDT Wednesday night for San Diego County Mountains. Winter Weather Advisory from midnight Wednesday night to 4pm PDT Thursday for San Diego County Mountains. Wind Advisory from noon to 10pm PDT Wednesday for Apple and Lucerne Valleys. Wind Advisory from noon Wednesday to 2am PDT Thursday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...None. |
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