March 20, 2018 – Wet weather returns today and continues into the weekend.
Discussion
Clouds have increased overnight across interior NorCal. Current temperatures are milder (5-15 degrees warmer) compared to 24 hours ago and generally range from the lower 20s in the mountain valleys to the upper 40s to mid 50s across the Central Valley.
The low along 140W is beginning to slowly shift east. Satellite imagery shows a wide swath of clouds and deep moisture (TPW > 1.5 inches) approaching California from the southwest. Southern portions of the forecast area may see some sprinkles this morning with light precipitation becoming more likely later this afternoon. Initially, NorCal will be on the northern periphery of heavier precipitation as the focus will be into SoCal.
However, precipitation will be on the upswing across NorCal tonight as warm-advection and moisture increase further. Snow levels will high limiting accumulating snow to just the highest elevations.
Heavier precipitation is forecast to begin later Wednesday and continue Thursday as deeper moisture moves north into NorCal ahead of the approaching cold front and upper trough. The trend in the models has been a little slower with the trough allowing potential for higher QPF spreading further north. Snow levels will initially be rather high, 6500-7500 feet, but will tumble to below 4000 feet behind the front by later Thursday.
Periods of moderate to heavy precipitation will be possible, particularly over the mountains. Gusty winds are also possible on Wednesday across the region. A few thunderstorms will also be possible Wednesday and Thursday.
Precipitation forecast to taper Thursday night before the next system moves in on Friday.
Extended discussion (Saturday through Tuesday)
Upper low/trough along the West Coast with cyclonic flow will keep showers in the forecast over Interior NorCal Saturday. Snow levels Saturday will be low, 1500-2500 feet. Precipitation for the most part looks light and focused more over the foothills and mountains. Sunday is trending dry and warmer, as upper ridging develops with dry northwest flow. Dry weather continues early next week, with a warming trend as heights increase over Interior NorCal.