Wet Weather Continues Through Midweek

January 8, 2019 – An active weather pattern continues with the next system forecast to arrive in NorCal later today into Wednesday. This system may be followed by additional systems into next week.

Discussion

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Cloudy skies continue across the region early this morning as warm-advection ramps up ahead of the next system offshore. Temperatures are rather mild ranging from the lower 30s in the mountain valleys to the mid 40s to lower 50s elsewhere.

Weather radar indicates precipitation is knocking on the door and the dry weather overnight will end this morning across the northern half of the forecast area. Precipitation is generally expected to remain north of I-80 today before spreading southward tonight as the cold front moves inland.

Southerly flow will pick up across the area today as surface gradients begin to tighten once again. Stronger southerly winds are expected tonight and early Wednesday as the front approaches (with breezy winds continuing across the north on Wednesday), and a wind advisory has been posted for portions of the region.

QPF is expected to generally range from 0.75 to 1.50 inches in the valley north of Sacramento with 0.25 to 0.50 inches in the valley to the south of Sacramento while the foothills and mountains will see amounts range from 1 to 3 inches. Areas north of Redding and over eastern Butte County may see orographic enhancement result in amounts of 3 to 5 inches.

Snow levels are expected to be higher through this event, 7000-8000 feet today then lowering to 5500-6500 feet on Wednesday. Significant snowfall accumulation will be limited to the higher elevations where a foot or so of accumulation will be possible across the passes through Wednesday while the higher peaks may see up to 2 feet or more of new snow. A winter weather advisory has been posted for the northern Sierra passes.

Ridging returns Thursday and Friday resulting in drier weather across much of the region as the next system is forecast to dig southeast off the coast and head toward SoCal.

Extended Discussion (Saturday through Tuesday)

Guidance continues to show differing solutions in the extended period, leading to a rather low confidence forecast. Models similar in showing next system approaching the CA coast late this week. At this point, precipitation appears to be focused more over locations west of I-5 on Saturday, as main energy tracks south of the forecast area. Another system will approach the area Sunday into Monday. The latest GFS run paints a wet scenario, but the EC keeps the bulk of precipitation offshore. Have decided to lower PoPs, but will continue to monitor model trends. Tuesday looks mainly dry, except for some precipitation activity over the mountains.