The National Weather Service (NWS) has issued an uncommon tornado risk alert for a portion of California’s Central Valley, highlighting the potential for isolated severe thunderstorms on Monday afternoon and early evening.
The forecast is based on a complex weather scenario involving a mid-level low situated in the eastern Pacific near the CA/OR border. A belt of robust southwesterly 500-mb flow extends from this system into California and Nevada. Simultaneously, a surface low will linger to the west of the northern CA/OR coast.
In particular, the Central Valley of California is identified as an area with a slight risk of severe thunderstorms. The latest HREF (High-Resolution Ensemble Forecast) convection-allowing model suggests the development of cellular storms during peak heating in the Central Valley.
While the NAM (North American Mesoscale) model exhibits a cool bias in surface temperatures, adjustments for slightly warmer conditions reveal the potential for moderate instability (250-500 J/kg MLCAPE) during the afternoon. The environment, characterized by elongated hodographs and moist boundary layers, appears conducive to the formation of transient supercells capable of rotation.