Periods of rain, wind, and mountain snow are expected through the week. There is a slight chance of thunderstorms through early Tuesday morning. Scattered showers will continue into Tuesday with strengthening west winds along the mountain crests and desert slopes, which peak Tuesday evening into Wednesday morning. A second round of rain and lower elevation mountain snow is expected late Tuesday into Wednesday. Cool with decreasing chances for showers for Thursday through Saturday. Chances of precipitation increase again into early next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Key Points: * A winter storm will bring widespread heavy snow to the mountains above 5500 ft creating hazardous travel conditions through Thursday. Snow levels as low as 3500 to 4000 ft Wednesday into Thursday may result in light accumulations through the Cajon Pass and along I-8.
* Stronger and potentially damaging west winds along the mountain crests and adjacent desert slopes Tuesday afternoon through Wednesday. Breezy conditions west of the mountains Tuesday night into Wednesday morning and wet soil will increase the risk of uprooted trees. * Ponding of water on roads and minor street flooding in urban areas possible this evening and again Tuesday night. Increased flows on rivers, especially the San Diego, Santa Margarita, and Santa Ana Rivers.
Evening update,
Scattered light showers continue tonight with a slight chance of thunderstorms, which could produce very localized brief heavier rainfall and small hail. Snow levels are currently around 5500-6000 ft and are forecast to fall to around 4700-5300 ft by Tuesday morning. An additional 3-6" of snow is possible above 6000 ft, and around 1-3" above 5000 ft. Rainfall amounts will range from around 0.10-0.30" west of the mountains overnight, with around 0.15" or less in the deserts. The Wind Advisory for the coastal areas, valleys, and high desert expire this evening, but will be in effect again Tuesday afternoon/evening into Wednesday morning/afternoon.
Previous discussion, The next shortwave is still on track to bring additional rounds of widespread rain, winds, and continued mountain snow Tuesday afternoon into Wednesday morning. Winds are expected to be stronger with this round shortwave for the mountain ridges and desert mountains slopes with gusts to 60 to 70 mph, potentially higher in wind prone locations. For the coast and valleys, peak gusts of 30 to 45 mph are expected and in the deserts gusts of 50 to 60 mph.
There will be lower chances for mostly lighter showers for Thursday into Friday. Chances for precipitation for next weekend are 10 to 15 percent, increasing to 20 percent for Sunday. High temperatures will warm slightly for Thursday and Friday, then gradually warm for Saturday through Monday with Monday high temperatures a few to around 5 degrees above average. High temperatures for next Monday will range from the mid to upper 60s near the coast to the lower to mid 70s for the valleys with the lower deserts around 80.
Scattered showers with rainfall rates up to 0.30" per hour tonight into Tuesday morning. Isolated lighter showers will continue into Tuesday afternoon, with the highest chances of precipitation in the mountains.
Another round of rain and mountain snow is expected Tuesday night into Wednesday. Hourly rainfall rates are expected to be 0.20-0.30" per hour. Forecast rainfall totals for Tuesday into Wednesday are 0.30-0.60" for the coast and valleys, 0.20-0.40" for the High Desert, and 0.05-0.45" for the low deserts, highest near the foothills. 1-2" of rain are expected in the mountains below the snow level Tuesday night into Wednesday. For Tuesday into Wednesday snow forecast has an additional 4-8" 5000-6000 ft, 8-15" 6000-7000 ft, and up to 2 ft above 7000 ft. The San Diego County mountains may see some accumulating snow above 5000 ft, with totals of 3-5", locally higher at the highest peaks.
The San Diego River at Fashion Valley and the Santa Margarita river are expected to reach monitor stage. The San Diego River is expected to reach monitor stage by 10 PM. The Santa Margarita River is expected to start responding tonight/early Tuesday morning, but is not expected to reach monitor stage until Wednesday. Interested parties should continue to closely monitor the river forecast and observed river levels this week. Current forecast indicates minor flood impacts to Avenida del Rio may occur. Please see the latest River Statement or CNRFC website for more information.
Scattered light rain and snow showers are possible Wednesday afternoon into Thursday as a third shortwave moves north of the area. Snow levels for Wednesday and Thursday are expected to be 3500-4000 ft so if any snow showers develop accumulating snow could impact the Cajon Pass and along higher portions of I-8.
There remains slight chances of precipitation Friday through the weekend ahead of the next trough set developing over the Gulf of Alaska. There remains considerable uncertainty in the details of the forecast but periods of unsettled weather looks possible next week.
170600z, Coast and Valleys, On and off post frontal showers remain possible through the overnight hours, eventually become much less numerous late Tuesday morning. Outside any precipitation, VFR conditions will generally prevail, with multiple clouds decks: a FEW- SCT deck around 2000-3000ft MSL and a more defined BKN deck around 3500-5000ft MSL. With any showers that pass through, VIS may briefly fall to 1-5 SM, with CIGs anywhere from 1500-2500ft MSL. A brief lull in shower activity is expected from 21z-03z Wednesday before shower activity returns to the region.
Mountains/Deserts, Cloud obscurations in the mountains and VIS reduced to 0-2SM as on and off SHRA/SHSN continues to move through. Shower activity should gradually wane after 12-15z. Southwest wind gusts of 20-30 kts with gusts up to 40 kts remain possible overnight tonight into Tuesday morning. Gusts gradually increase through Tuesday afternoon, with gusts 50-65+ kts expected for mountain peaks and desert mountain slopes after 00z Wednesday.
A bulk of the winds seen earlier today before the front have decreased this evening, with gusts generally 15-20 kts persisting over the waters. However, scattered showers are bringing down occasional gusts near 25-30 kts. With this, the Gale Warning remains in effect until 7 AM Tuesday morning, when shower activity becomes less numerous and winds stay below 20 kts.
After a brief lull in unsettled weather around mid-day Tuesday, come late Tuesday night, seas are expected to build to around 8-11 feet with wind gusts 25-35 knots, locally up to 40 knots. A second Gale Warning is in effect from 8 PM Tuesday until 1 PM Wednesday and contains more details. Seas and winds decrease to 5-7 feet and 10-27 kts Wednesday afternoon, but look to increase again come Thursday afternoon.
A series of strong westerly swell (9-11 feet with an average period of about 10-12 seconds) will produce large breaking waves up to 8-12 feet on most beaches across Orange and San Diego Counties through Friday night. Widespread, strong rip currents are also likely with these waves and dangerous swimming conditions expected. A High Surf Advisory is in effect until 10 PM Friday and contains more details.
Ca, High Surf Advisory until 10 PM PST Friday for Orange County Coastal Areas-San Diego County Coastal Areas.
Wind Advisory from 8 PM Tuesday to 8 AM PST Wednesday 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.
Winter Storm Warning until noon PST Wednesday for Riverside County Mountains-San Bernardino County Mountains.
Wind Advisory until 1 AM PST Tuesday for San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.
Wind Advisory from 10 AM Tuesday to 4 PM PST Wednesday for Apple and Lucerne Valleys-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.
PZ, Gale Warning until 7 AM PST Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm-Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
Gale Warning from 8 PM Tuesday to 1 PM PST Wednesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 10 nm-Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
