Two storm systems to hit California with rain and snow
Multiple mid-level shortwave troughs are expected to bring heavy rain and mountain snow to Central and Southern California from March 5 to 7, 2025. Forecasters warn of localized flash flooding and significant winter storm impacts, particularly in higher elevations.
Image credit: NOAA/GOES-West, RAMMB/CIRA, The Watchers. Acquired at 20:10 UTC on March 3, 2025
The first shortwave trough will reach the Southern California coast on March 5, interacting with residual moisture from a dissipating atmospheric river. This will create brief atmospheric river conditions over much of coastal Southern California, with a high probability of increased moisture transport, according to the Center for Western Weather and Water Extremes (CW3E).
CW3E’s AR Landfall Tool based on GEFS is indicating a high likelihood (>70% probability) of AR conditions over much of coastal Southern California.
While moisture levels are expected to remain moderate, the south-southwesterly flow could enhance precipitation over the Transverse Ranges.
A second storm system will follow late on March 6 into early March 7, bringing additional precipitation. Although moisture levels will be lower, orographic lifting over the Peninsular Ranges could lead to intensified rainfall.
The National Weather Service’s Weather Prediction Center (WPC) forecasts 25–50 mm (1–2 inches) of total rainfall across the Central Sierra Nevada and coastal areas, with 50–75 mm (2–3 inches) expected in the Southern Sierra Nevada and eastern Transverse Ranges.
Due to unusually dry soil conditions, rainfall exceeding 6.4 mm/hour (0.25 inches/hour) could trigger localized flash flooding, particularly in burn scar areas.
The WPC has issued a marginal risk (≥5%; level 1 of 4) for excessive rainfall in the Southern Sierra Nevada foothills, Central California Coast Ranges, Transverse Ranges, and Peninsular Ranges from March 5 to March 7.
Snowfall will also be significant, with over 30 cm (12 inches) expected in much of the Central and Southern Sierra Nevada. Some areas in the Southern Sierra Nevada could receive up to 61 cm (24 inches) by early March 6.
This could result in major winter storm impacts, affecting travel and infrastructure.
References:
1 Multiple mid-level shortwave troughs are forecast to bring rain and mountain snow to Central
and Southern California this week – CW3E – March 3, 2025
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