January 19, 2018 – Showers and a few thunderstorms will taper off across the region by this evening. The active weather pattern will continue with another system expected to affect the region early next week.
Satellite and radar imagery show the main band of precipitation along the frontal band shifting into central California early this morning. Moderate to occasionally heavy snow continues across the west slopes of the northern Sierra with accumulating snow impacting travel across the passes. Snow levels have lowered behind the front to around 3-4K feet.
Moderate to heavy snow expected to end in the northern Sierra by mid-morning as the front shifts further south. The cold upper trough moves onshore this afternoon, however, appears the best concentration of showers associated with the trough will move ashore to our south, so may need to reevaluate continuing the winter storm warning based on trends that develop later this morning.
The rest of interior NorCal will see a mixed bag of weather today a little bit of sunshine combined with a continuing chance for isolated to scattered showers. The Sacramento Valley may even see a chance for a few thunderstorms during the afternoon. next week. Heaviest amounts of snow are expected over the northern mountains, where 6 to 12 inches are currently projected through Monday. The northern Sierra is expected to see lighter amounts, more in the 2 to 5 inch range. EK A short-wave ridge moves in Saturday with the potential for clearing skies before the next weather making system arrives Sunday.
The next system will spread precipitation across the area beginning Sunday. Moisture riding over the existing cold air will give the potential for more significant snowfall across the northern mountains and may impact travel across Interstate 5 north of Redding. Stay tuned.
Extended discussion (Tuesday through Friday)
Unsettled pattern will continue through the extended period. Moisture is expected to spread across interior NorCal on Tuesday and impact the area through Thursday as troughing in the Gulf of Alaska dives southward. However, forecast guidance is still struggling with the overall progression of the system. Early QPF estimates suggest 0.5-1″ in the Valley, and 1-2″ over the mountains through early Thursday with the potential for accumulating snow over the mountains. Drier weather is expected by Friday afternoon as the trough axis shifts eastward, although lingering activity could persist over the mountains.