The National Weather Service in San Diego has issued an update on the cooling trend and gusty winds affecting the region, as well as the onset of heavy rainfall expected to begin tonight. Temperatures are expected to progressively drop through the weekend, with high temperatures on Friday reaching the mid-60s to lower 70s for the coast and valleys, and around 80 degrees for the lower deserts. On Saturday, temperatures are expected to be even cooler. According to the NWS San Diego's forecast, the approaching cold front, paired with the tricky atmospheric river system, is anticipated to bring significant changes in weather patterns, resulting in uncertain rainfall totals that are likely to be updated with future forecasts.
Strong southwest winds will affect the mountains and deserts this afternoon and this evening with gusts of up to 35 mph, leading to a Pacific storm that ushers in increased chances of showers starting tonight, becoming heavy at times from late Friday afternoon through Saturday, and the looming prospect of thunderstorms for Friday night into Saturday evening. The National Weather Service's discussion points out that more widespread south to southeast winds are forecasted for Saturday morning with comparable gusts, which could impact areas beyond the mountains and deserts.
Hydrological concerns are escalating with this system, as parts of Orange and southwestern San Bernardino Counties might experience up to 3 inches of rain near the coast and 4 to 6 inches in the mountains, while San Diego County expects around 2.5 inches near the coast and 3 to 4 inches in the mountains; some areas may see even higher totals. These intense conditions could incite debris flows, flooding, and potentially make roads impassable. "These rainfall amounts along with the potential for periods of higher intensity rainfall for late Friday night through Saturday could produce debris flows in burn areas, significant ponding of water on roads and highways, and urban and small stream flooding," mentioned the NWS San Diego's hydrology section.
The forecast remains somewhat uncertain into next week with the potential for more showers, but the confidence in these details is notably less than the immediate forecast for the weekend. Meanwhile, snowfall is expected in areas with elevations above 6,000 feet, with snow levels anticipated to decrease after the weekend's events. These changes will also bring the risk of thunderstorms from Friday night through Saturday night for the maritime regions, affecting visibility during periods of heavy rain.
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