Riverside, CA 92521 Weather

Synopsis

Cloudier and cooler weather will continue into the weekend. A weather system will move into the area, bringing the chance of widespread rainfall this weekend, heaviest of which will occur late Saturday into Sunday morning. Slightly warmer and drier weather is expected by Monday into at least the middle of next week.

Discussion

FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE: SAN DIEGO: WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES:

: UPDATED AVIATION DISCUSSION:

A low pressure system currently off the coast of the Pacific Northwest will lead to a greater troughing pattern over the West Coast into the weekend. Today will be dry with scattered clouds and temperatures near to slightly below average. As the low pressure system moves southward, an open wave trough will begin to form bringing in greater moisture from the southwest. PWAT values rise near one inch at San Diego. The marine layer will slowly become saturated tonight into Saturday, where hi-res models continue to show areas of light showers from the coastal slopes of the mountains to the coast. Since these seem to be isolated in nature, the forecast shows around 15-25% chance of rain for these areas Thursday night through Friday night.

A large area of moisture in the form of a subtropical low pressure system that we continue to monitor is slowly forming well off the coast. Models are beginning to agree on a more southerly track with the main swath of the heaviest rains going into Baja California, where IVT values near 300 kg/m/s (weaker values) for SoCal. Nonetheless, bouts of moderate to heavier rain are expected Saturday night into Sunday morning. With the model guidance of a more southerly track of the system, confidence remains high on San Diego County seeing the most precipitation overall, as well as all coastal mountain slopes. Confidence is not as high on rain totals further north, where there is a larger model spread. PWAT will peak near 1.5 inches in San Diego, as the subtropical low and low to the north pass through, so sufficient moisture will be in place.

The interactions between the subtropical low and the low pressure system to the north is still somewhat uncertain, where exact rain totals are still in question. Chances for 1 inch of rain in total over the weekend has stayed pretty consistent across San Diego County (50-60%), closer to 75% in the mountains. These chances decrease across the LA basin near 35-45%. Chances for one half inch in this area increases to 55-65%, 35-50% chance across desert regions. Some heavier bands of showers may occur over San Diego county closer to the core of the subtropical low, which may bring greater amounts locally. In terms of timing, light to moderate showers will push in from west to east sometime on Saturday afternoon into the evening. The period for the heaviest rainfall will be later on Saturday night into early Sunday morning. Rainfall will become more scattered about late Sunday morning through early evening, with peaks of sunshine starting to make a return in parts of the deserts and western LA basin as the system moves eastward.

Dry and sunnier weather is expected by Monday as weak high pressure moves over the area. This will bring a subtle warming trend, though keeping temperatures near normal readings for early November. This weather looks to continue into at least Wednesday. Another low pressure system may form somewhere off the California coast into the latter half of next week. This may bring a slight chance of light showers near the coast, though most of the region looks to stay dry for the rest of the week.

Aviation

300045Z: SCT-BKN clouds based 4000-6000 ft currently from the coast to the mtns with SCT-BKN high clouds near 8000-1000 ft regionwide. FEW-SCT low clouds based 2500-3500 ft MSL over coastal areas will spread over the coastal basin through this evening. Clouds will slowly rise through the night with bases mostly above 3000 ft MSL by early morning. However, ISO-SCT -SHRA will bring CIGs locally down to 2500 feet MSL between 08-15z, especially near the coast. Low clouds become more FEW-SCT in coverage 15-18z. ISO-SCT -SHRA redevelop Friday afternoon with highest coverage in Orange County.

Marine

No hazardous marine conditions are expected through Saturday. As a storm system moves through the coastal waters this weekend, shifting winds and seas are likely to increase by Sunday morning, possibly to hazardous levels, lingering into Monday. There is also a slight chance of thunderstorms Saturday night and Sunday morning. Stay tuned for updates.

Beaches

A Coastal Flood Advisory is in effect until 2 PM Friday. Friday's high tide is expected to peak around 7.25 feet near noon Friday which could produce minor coastal flooding as surf is expected to be around 3-5 feet.

The southwesterly swell (3 ft at 15 seconds from 200 degrees) responsible for the marginally elevated surf through the weekend will persist into Monday. As a storm system moves into the area for Sunday/Monday, increased winds could help bolster localized wave sets to 6 feet. While high tides will continue to wane into the weekend, tides will remain over 6 feet which could still lead to minor tidal overflow if breaking waves approach 4-6 feet.

Reported forecast tides have been corrected up by 1.4-1.6ft based on recent trends in tidal observations.

Skywarn

Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.

Watches, warnings and advisories

CA: Coastal Flood Advisory until 2 PM PDT Friday for Orange County Coastal Areas-San Diego County Coastal Areas.

PZ: None.