textproduct: San Diego

SYNOPSIS

Tropical Storm Rachel will impact Southern California through this afternoon. Cooler conditions expected into early next week. Widespread showers and locally heavy rainfall, coastal flooding, and increased winds are expected through this evening. Elevated winds over the mountains and into the deserts will continue into Monday morning. Scattered showers will continue across the coastal basin through the day Monday. Drier conditions expected for Tuesday onward, with an increase in temperatures and potential for Santa Ana winds during the latter half of the week.

..DISCUSSION FROM 10 PM YESTERDAY

Post-TS Rachel is now fully embedded within the upper level trough and the rainfall core, out ahead of the core, is actively decoupling with the low level circulation. As of 9PM, the rainfall core has moved into southern San Diego County and winds are increasing out of the east along the higher SD Co. coast facing slopes with gusts 25-50 mph. Farther east into Imperial County, clusters of thunderstorms are forming in a CAPE environment of 500- 1000 J/kg. These thunderstorms have the potential to move into the Coachella Valley and desert slopes through around 2 AM yielding to rain rates above 0.50"/hr and thus increased risk for urban and flash flooding.

By around 2 AM, the most widespread heavy rain bands start moving through the region from south to north. Models indicate widespread rain rates across all lower elevation areas of 0.2-0.5"/hr with pockets of more intense rain possibly over 1"/hr through mid-morning (~8-11AM). Areas receiving such rain rates are at an increased risk for urban and flash flooding; remain alert and heed advice of local officials. Simultaneously, northerly winds west of the foothills will increase throughout the night, gusting 15-35 mph (highest at the coast) through around 3-5AM Sunday. Easterly winds over the coastal foothills through the desert slopes will also increase significantly over the next several hours, from south to north, with wind gusts 45-65 mph, locally to 75 mph through passes and exposed ridges.

The strongest winds move through around 4/5 AM through 10 AM through SD County (~7AM-12PM for northern areas) as Post-TS Rachel makes a close approach. Wind gusts will increase to 25-45 mph across lower elevations and winds abruptly turn westerly and increase even more over the mountains, passes and desert slopes with gusts 50-80 mph (locally higher). By the afternoon, Post-TS Rachel will have moved north out of the region very fast. Precipitation scatters to showers across the lower elevations with more persistent (though weakening) showers and wind over the foothills and mountains for a few hours longer (through ~2-4PM). By evening, winds will be significantly reduced everywhere. Isolated showers continue for lower elevations, remaining scattered over the foothills/mountains through Monday morning. During the day Monday, the trough axis moves through, bringing a much more traditional round of light rainfall of around 0.05-0.25" through the coastal basin, with higher amounts in the mountains (light snow above ~8,000 feet) and rain shadowing the deserts (less than 0.05" and breezy downslope winds). Shower activity looks to persist until Tuesday morning before clearing out Tuesday afternoon.

As conditions clear out, morning temperatures Tues/Wed will drop noticeably inland into the low 50s/upper 40s and in the mountain valleys down into the low 30s and 20s.

High temperatures steadily rebound, returning to 80s across the lower elevation by Thursday and possibly into the 90s for coastal areas Fri/Sat courtesy of offshore winds.

AVIATION

111200Z...Coastal Basin...-RA/RA to continue across the area through around 16z, becoming SCT SHRA from the coast(~16z) to the far inland valleys (~19z), then becoming ISO SHRA by around 23z through the remainder of the TAF period. MVFR CIGs and VIS 3-6SM with SHRA/RA. Gusty SW winds gusting 20-25 kts (up to 35 kts in the foothills) through around 16-20z. Otherwise, SCT-OVC clouds based 3-5 kft through much of the TAF period.

Mountains and deserts...-SHRA/-RA/RA in the mountains through the TAF period, slightly more scattered Sunday evening. Gusty SW winds gusting to 35-55 kts over ridgetops, mountain passes and desert slopes through 03z Mon, becoming more localized thereafter.

MARINE

West winds gusting 20-30 knots expected throughout the coastal waters through Sunday afternoon. Large fresh swell from the northwest will combine with south swell associated with Tropical Storm Rachel and wind waves to create combined seas 6 to 10 feet today. Choppy, steep, mixed seas and gusty winds will produce conditions hazardous to small craft.

Calmer winds and seas expected Monday through the work week.

BEACHES

A fresh south swell associated with Tropical Storm Rachel in combination with a larger northwest swell will produce elevated to high surf today for all area beaches, peaking at 5 to 8 feet with sets to 9 feet. This will pose a hazard to swimmers and lead to very strong rip currents. In addition, morning high tides will continue to be 7 to 7.5 feet, continuing the threat for significant coastal flooding through this afternoon. A Coastal Flood Warning is in effect for these hazards through 3 PM this afternoon. Take the necessary actions to protect flood-prone property and avoid the beaches during high tide.

Both winds and swells subside for Monday-Tuesday, and surf will decrease to 3 to 6 feet, though strong rip currents will continue. Morning high tides will continue to be near 7 feet, meaning that minor coastal flooding will continue to be an issue through this period. The Coastal Flood Warning will be replaced with a Coastal Flood Advisory at 3 PM Sunday and continue through 2 PM Tuesday.

SKYWARN

Skywarn activation is requested.

SGX WATCHES/WARNINGS/ADVISORIES

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

Flood Watch through this 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 through this evening for Orange County Coastal Areas-San Diego County Coastal Areas.

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

Wind Advisory until 5 AM PDT Monday for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass near Banning.

PZ...Small Craft Advisory until 10 PM PDT this evening 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.