The final round of rain, snow, and gusty winds will be Thursday, with the main cold front moving through the area late Thursday morning through the early evening. There is a slight chance of thunderstorms Thursday afternoon and evening. Showers will diminish overnight Thursday with gusty winds diminishing by Friday morning. Frost is possible Friday and Saturday mornings. Dry conditions looking like they will prevail through the weekend. Chances of precipitation increase again mid-next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Update: Showers continue to taper off this evening and then there will be a bit of a lull tonight through tomorrow morning before the next wave approaches with another frontal boundary associated with it. Winds will also begin to increase again during the morning into the afternoon hours ahead of this boundary and as it passes through. There will be increasing showers ahead of this boundary, with more of a solid line of showers and possibly a few embedded thunderstorms developing along it which will be pushing through during the afternoon hours and may result in impacts to traffic during rush hour. There could be some rainfall rates of 0.50-0.80 inches per hour with some of the heavier showers and storms that move through, so there could still be some flash flooding concerns for areas prone to flooding. That being said, given the orientation of these showers as they are passing through will be coming in from the west, and therefore there should be less of a threat for the Bridge and Line burn scar areas. Showers/thunderstorms should be also moving through rather quickly, which should also help to mitigate the flash flooding potential, though it will still be closely monitored.
The main concern for tomorrow will be an increase of the winds again, which is shy the Wind Advisories have been extended into Friday morning. Some of these heavier showers and storms may also result in there being wind gusts that may approach 50 mph again for some of the inland areas. After then initial line moves through, showers will become more intermittent going into the late evening hours and overnight into Friday morning as they continue to taper off with high pressure building back in behind the exiting system, which will allow for drying conditions by the time we get to the weekend.
The other issue will be frost/freeze concerns within some of the higher based inland areas for Friday night, as we get clear skies with a much colder air mass in place. In addition, with the antecedent soil moisture from all of the recent rainfall, there could also be some patchy fog/freezing fog developing within some of these valleys. Snow levels will continue to drop from around 4500- 5500 ft to 3500-4500 ft by Thursday night into Friday evening, so there will likely be some additional snowfall amounts of 3-6 inches, especially for the San Diego mountains above 5000 ft. All of these showers will continue to taper off overnight into the early morning hours on Friday.
The rest of the forecast is trending drier for this weekend through the mid part of next week. The chance of precipitation towards the end of next week continues to lessen as ensembles for now showing overall drier solutions. There will also be a gradual warmup, with temperatures returning to be more seasonal for this time of year.
Previous discussion submitted at 119 PM:
Key Points:
*Gusty and potentially damaging west winds along the mountain crests and adjacent desert slopes Thursday into Friday morning. Gusty westerly winds expected for the coast and valleys during the day Thursday.
*3-8 inches of additional snow expected Thursday into Friday morning. Additional snow plus strong winds may result in blowing snow and limited visibility. Snow levels as low as 3500 to 4000 ft Thursday may result in light accumulations through the Cajon Pass.
*Light to moderate rain is expected Thursday. Ponding of water on roads and minor street flooding in urban areas possible. Thunderstorms may bring locally heavy rain, stronger winds, and small hail.
At 1 PM a few isolated showers were moving across the coastal basin. Any lingering showers this afternoon will produce light rain, with hourly rates less than 0.10" per hour. Winds are still gusting over the mountains and into the deserts. Gusts this afternoon are mainly 35-55 mph. A lull in the winds is expected overnight, but winds are still expected to increase again Thursday peaking in the afternoon and evening, continuing into early Friday morning. For the mountain ridges and desert mountain slopes peak gusts of 60 to 70 mph, potentially up to 75 mph in wind prone locations are expected. Wind gusts in the deserts will be 45 to 65 mph with the strongest winds near the mountain foothills. For the coast and valleys, peak gusts of 30 to 45 mph are expected. Winds for the coast and valleys are expected to peak with the passage of the cold front. The front will start to move through Orange County/San Bernardino County mid- morning, reaching San Diego county by the early afternoon.
Light to moderate precipitation is expected Thursday with the heaviest precipitation expected with the frontal passage or where any thunderstorms develop. For the coast and valleys and additional 0.25 to 0.50" of rain are possible with 0.10" or less in the deserts. Snow levels for through Thursday are expected to be 3500- 5000 ft with an additional 3 to 8 inches of snow expected across area mountains. Current forecast has a 60% chance of accumulating snow on I-15 at the summit of the Cajon Pass.
Dry conditions are expected by Friday, with diminishing winds. Dry conditions will prevail through the weekend. Conditions may be cold enough Friday and Saturday morning for patchy frost to develop in the valleys and High Desert. High temperatures will warm each day for Friday through Monday with high temperatures on Monday around 5 degrees above average. Shower chances begin to increase again Monday evening into Tuesday, with the highest chances of precipitation currently Wednesday.
190445z, Generally VFR conditions expected through Thursday morning with SCT-BKN clouds 3,000-6,000 feet MSL west of the mountains. Clouds begin to fill in and lower after 12-15Z Thu from the coast to the mtns as yet another round of light to moderate precip moves into the area. Current guidance indicates the main precip band will move northwest to southeast through the coastal basin from 18Z Thu to 02Z Fri. A few hours of MVFR cigs/vis is expected for the coasts/valleys. Mtns shrouded in FG through early Friday morning. Additionally, winds turn southwest and strengthen again after 18Z Thu as the system approaches. Gusts 25-35 kts through the coastal basin (locally 40 kts at the coast), 35-45 kts widespread for the mtns and deserts, and 50-65 kts along desert slopes.
Generally VFR conditions expected in the wake of the main band outside of the mtns. Winds also turn westerly and weaken through the coastal basin. However, strong westerly winds will continue for the mtns and deserts through late Thursday evening, particularly in San Diego/Riverside Counties.
A break in the gusty winds and hazardous seas is expected through tonight. However, hazardous conditions will redevelop ahead of the next system by late Thursday morning. Gusts up to 25 to 30 knots in the afternoon with steep, choppy seas. Conditions will slowly improve Thursday night into Friday morning.
High surf of 4 to 7 feet is expected with sets as high as 8 feet, highest in San Diego County today. A lull is expected tonight before high surf returns Thursday afternoon. Dangerous swimming and surfing conditions and localized beach erosion can be expected. A High Surf Advisory is in effect through 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 9 AM Thursday to 2 AM PST Friday 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 9 AM PST Friday for Riverside County Mountains-San Bernardino County Mountains.
Winter Weather Advisory until 9 AM PST Friday for San Diego County Mountains.
Wind Advisory until 9 AM PST Friday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, Small Craft Advisory until 10 AM PST Friday 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.
