textproduct: San Diego

SYNOPSIS

Tropical Storm Rachel will impact Southern California tonight into Sunday afternoon. Cooler conditions expected into early next week. Widespread showers and locally heavy rainfall, coastal flooding, and increased winds are expected Sunday. 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...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Through this evening, showers ahead of now Post-TS Rachel moved through the region, bringing light totals (less than 0.10") for most of the coastal basin, with higher totals in the San Diego inland valleys(0.10-0.25") and SD County mountains (0.25-0.50"). The storms low level circulation is now tens of miles off the coast of Baja California and is expected to reach land around 10PM to midnight near Ensenada.

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

110500Z...All Areas...Bands of moderate precipitation from Tropical Storm Rachel are moving from south to north through the area this evening. While there is some uncertainty WRT timing, these are expected to continue to move through the region through about 15Z for coastal/western valley areas, and 16-20Z for inland valleys and mtns. Cloud bases lowering 2000-4000 ft and vis down to 3-5SM in heavy rain in general, with periods of cigs 700-1500 and vis 1-2 SM in heaviest rain. 30% chance for TSRA over any one point in low deserts/desert slopes, including vcnty KPSP, through about 15Z.

Towards 10-12Z, expect NW winds to increase, then shift to the WSW through mid morning for coasts and valleys. Gusty winds in San Diego County coast/valleys with a 40% chance of winds gusting over 30 kts at KSAN between 12-16Z. For mountains and deserts: brisk E winds 25- 35 kts over SD mtns and desert slopes 09Z through about 12Z, the SW winds increase after 12Z with gusts along all desert slopes 35-55 kts, gusts closer to 25-35 kts in all deserts. Very low certainty in wind directions in the Coachella Valley, including KPSP/KTRM, as localized wind circulations could change direction freq. Strong winds becoming more localized after 03Z Mon.

Showers becoming lighter and more scattered Sunday afternoon and evening with SCT-BKN mid level cloud cover lingering.

MARINE

Breezy northerly winds this evening will strengthen late tonight, then turn westerly later in the morning. Winds 20 to 30 knots expected throughout the coastal waters through late 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 Sunday. Choppy, steep, mixed seas and gusty winds will produce conditions hazardous to small craft on Sunday.

Calmer winds and seas expected Monday through the work week.

BEACHES

Fresh south swell associated with Tropical Storm Rachel will arrive late tonight through Sunday. This will combine with a larger northwest swell and strong winds to produce elevated to high surf Sunday 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 Sunday afternoon. A Coastal Flood Warning is in effect for these hazards through Sunday at 3 PM. 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 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 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 6 AM PDT Sunday 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.

Wind Advisory from 5 AM Sunday to 5 AM PDT Monday for Apple and Lucerne Valleys-San Bernardino County Mountains.

Wind Advisory from 2 AM Sunday to 5 AM PDT Monday for Coachella Valley-Riverside County Mountains-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.