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January 6, 2021 – Areas of fog are possible again this morning. Light rain and light mountain snow today. A wetter system Thursday night through Friday could bring several inches of mountain snow. Dry weather is forecast for the weekend.

Discussion

Surface observations have indicated some patchy fog and mist this morning in the southern Sacramento and northern San Joaquin valleys. Satellite imagery has been showing some high and mid clouds passing through which have limited dense fog development so far. Some clearing is occurring now, though. This could bring a time period of more favorable conditions for fog to form over the next few hours before the main band of clouds currently off the coast moves in.

Clouds will continue to increase today as eastern Pacific shortwave moves inland. This is not a very moist system, but precipitation is expected to spread from the northern mountains in the morning to the northern and central Sacramento Valley by noon PST. Chances of rain showers reach the I-80 corridor around 3-4 pm PST. Rainfall amounts are expected to be fairly light, from a few hundredths of an inch around Sacramento to about 0.15″ at Redding, up to a quarter of an inch over the northern Coastal Range. Snow amounts range from a dusting over the northern Sierra to a few inches over Lassen Peak.

High temperatures today will generally be several degrees cooler than yesterday, ranging from the upper 40s in the northern Sacramento Valley to mid 50s elsewhere in the Valley.

Dry conditions will return again late tonight through the day Thursday as an upper level ridge briefly returns over the West Coast. This will probably lead to more morning fog for Valley communities. Afternoon temperatures will be a little warmer as skies clear in the afternoon.

A better chance of rain and snow will arrive Thursday night and into Friday. This system may be a bit wetter than the one today, but overall precipitation amounts still appear to remain on the light to moderate side. Valley amounts could range from a half inch for the north Sacramento Valley down to several hundredths for the northern San Joaquin Valley. The mountains could see a half inch to an inch of liquid, with several inches of snow above 5500 feet. This could bring some travel slow downs in the mountains, especially Friday morning.

Skies clear on Saturday, for the start of a clearing and dry weekend. Morning fog is again a possibility.

Extended discussion (Sunday through Wednesday)

Longwave ridging will result in mainly dry and mild weather for the region early next week. The far north end may see some light precipitation at times as the tail end of weak systems pass thru the ridge. Pattern favors late night and morning valley fog.