Northern California is set to experience another bout of active weather this week, following a weekend that saw a mix of moderate rain and mountain snow. According to the National Weather Service Sacramento CA, interior NorCal is bracing for periods of inclement weather with a few short reprieves between systems. There's potential for isolated thunderstorms especially in the Sierra foothills, where the likelihood of storm occurrence fluctuates between 15-25 percent.
The early hours of this morning saw a band of moderate precipitation laying heavy on the Sierra and adjacent foothills. Snow levels, which were at approximately 6000 feet, are set to plunge to the 4000 to 5000 feet range as the day progresses. Webcams from CalTrans reveal that snow is accumulating on roadways at pass levels, causing travel disruptions that are expected to spill over into the Monday morning commute. Accompanied by the precipitation, a distinct zone of clearing is underway, a brief breather before the next moisture wave, wrapped up within the trough, moves in around dawn.
Moving forward, conditions may shift, with snow levels anticipated to stabilize, sending most snowfall above the 4500 feet mark. "Resultant forecast snowfall totals have increased closer to 3 to 8 inches between 4500 and 6000 feet and 6 to 12 inches above 6000 feet," according to the NWS forecast. Elevations above 4500 feet in the Sierra and southern Cascades remain under a Winter Weather Advisory until Monday afternoon. Snowfall rates peaking at 0.5 to 1.0 inches per hour are expected at various times until Monday. Drier conditions should settle in region-wide entering Monday afternoon.
Looking further ahead, the National Weather Service predicts a second wave of precipitation arriving midweek, influenced by a trough from the Pacific Northwest expected to solidify into a closed low-pressure system. The Sierra, southern Cascades, and Coastal Range are bracing for widespread showers and mountain snow. The forecast anticipates a 40-70 percent chance of 6 inches of snow above 6000 feet, rain probabilities sitting between 10-50 percent across various counties, and potential thunderstorms Wednesday evening for most of the region with a 10 percent chance currently indicated. By Friday, the region should see a transition to mostly dry weather with a slight chance of northerly winds in the morning.
Aviation-wise, MVFR/IFR conditions linger in the northern Sacramento Valley till about 20z, as the recent weather system makes its exit. Scattered MVFR conditions persist due to rain showers in other areas, with VFR conditions forecasted to return across the Valley around 08z Monday. Valley sites can expect southerly wind gusts up to 25 knots continuing until 00z Monday, while mountainous areas may experience gusts reaching 35 knots.
