textproduct: San Diego

SYNOPSIS

Tropical Storm Rachel will approach the region Saturday evening into Sunday. Cooler weather will continue to spread inland this weekend into early next week as a stronger trough moves in from the north. These systems will bring showers and locally heavy rainfall, gusty winds, and coastal impacts to the region. Quieter and warmer weather will begin to move into the region for the latter half of next week.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

Mostly clear skies were seen over SoCal with cumulus clouds across the mountain areas. A trough is beginning to gain strength over the Pacific NW as Tropical Storm Rachel churns 800 miles to the SW of San Diego. The deepening troughing pattern over the West Coast will bring in more cooler air to the region by Saturday with a few degrees cooler than today near the coast, closer to 10 degrees cooler for all other areas. Widespread 70s and 80s will be seen for areas below 6,000 feet with 90s in the lower deserts. The marine layer will also build, bringing low clouds and less fog to coastal areas.

Tropical Storm Rachel is expected to make landfall somewhere near the US/Mexico Border late Saturday night. While there remains some uncertainty in the track, tropical storm level impacts have the potential to impact San Diego County. A Tropical Storm Watch is in effect for all of San Diego County, including coastal flooding, wind, and periods of heavy rain Saturday night into Sunday. There is expected to be a gradient in rainfall amounts with the higher amounts on the southeastern side of the storm. There still remains some uncertainty in the track, but a continued northern shift would increase potential for heavy rain across the county with a southern shift making it more localized. Areas of flash and urban flooding are possible, especially where the maximum rainfall rates occur some mountain areas 0.50-1.00 inch. The San Diego River at Fashion Valley is currently forecast to peak at 7.4 feet (which is just below monitor stage) Sunday afternoon.

Increased winds are expected with the onset and passage of Tropical Storm Rachel. Sustained winds of 39+ mph are expected on the southeast side of the storm. If the track continues to move further north, that would put more of San Diego county in a position to see winds of that magnitude. Based on the current track, more southern parts of the county are most likely to see winds of this magnitude. Regardless, strong sustained winds and wind gusts can be expected on Sunday. Winds may be enhanced by local terrain with gusts 40 to 55 mph on the desert slopes of the mountains and into the deserts. Local gusts up to 60 mph possible on mountain ridges.

Temperatures will continue to tumble on Sunday, dropping another 10 degrees from those of Saturday. Models continue to differ on the exact path of where the trough to the north goes by early next week. As of now, the coolest day of the week will be Monday with highs struggling to reach 70 west of the mountains with 50s and 60s for places below 6,000 feet. Colder temperatures will also be expected for the Big Bear region with highs in the 40s and lows in the 20s and 30s. Depending on the exact track of the low, chances for showers continue into Monday, possibly Tuesday. Models are in fair agreement on trough beginning to lift out of the area by Wednesday as high pressure off the coast gains strength. This will lead to a warmer and drier weather trend for the latter half of next week.

AVIATION

091820Z...Coast...Patchy low clouds returning to the coast after 03Z Saturday with bases closer to 1000-1500 ft MSL, best chance for cigs in San Diego County. Lower confidence on clearing times for low clouds, most likely sometime between 16-18Z Saturday.

Otherwise...Mostly clear with unrestricted vis through this evening. BKN high clouds AOA 20k ft moving into the region tonight into Saturday.

MARINE

No hazardous marine conditions are expected through Saturday. Gusty northwest to west winds 20-30 kts developing Sunday then weakening on Monday. Choppy seas with swells up to 8 feet and 8 second period will produce conditions hazardous to small craft on Sunday.

SKYWARN

Skywarn activation is requested for early Sunday morning through Sunday night. Weather spotters are encouraged to report significant weather conditions.

SGX WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Warning until 3 PM PDT Sunday for Orange County Coastal Areas-San Diego County Coastal Areas.

Tropical Storm Watch for San Diego County Coastal Areas-San Diego County Deserts-San Diego County Mountains-San Diego County Valleys.

Flood Watch from Saturday evening through Sunday evening for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Coastal Areas-San Diego County Deserts-San Diego County Mountains-San Diego County Valleys-San Gorgonio Pass near Banning.

Beach Hazards Statement from Sunday morning through Sunday evening for Orange County Coastal Areas-San Diego County Coastal Areas.

Coastal Flood Advisory from 3 PM Sunday to 2 PM PDT Tuesday for Orange County Coastal Areas-San Diego County Coastal Areas.

Extreme Heat Warning until 8 PM PDT this evening for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.

PZ...Tropical Storm Watch 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.