February 24, 2019 – An active weather pattern will continue to set up over northern California this week. Heavy snow is forecast for the higher elevations of the mountains while increasing flooding potential remains the threat for the valley and foothills.
Low pressure area near British Columbia will drift southward to off the Oregon/Washington coast in the next day then will remain in a semi-permanent position through the middle of this week. This will allow for an abundant amount of moisture to stream into the region from the southwest to west. The models are in general good agreement into Monday with light amounts of precipitation moving over the interior…mainly for areas north of I-80. Snow levels will rise slightly this evening to near 4000 feet but some local snow down to 3500 feet may continue into the evening. General snow advisory conditions are expected into Monday ahead of the main band of precipitation over the northern mountain areas with some increased snowfall expected overnight for those areas.
Monday through Wednesday there are still some differences in the models on where the heavy precipitation will set up. The European has the heaviest from the Feather River Basin northward while the GFS brings heavier precipitation further south in addition to the heavier totals to the north. The European did increase its precipitation output a little today. The models are indicating anywhere from 8 to 12 inches of rainfall for the Feather River Basin over three days. Snow levels will be rising next week into the 5000 to 6500 foot range for the event as we get into Tuesday and Wednesday. Heavy snow is expected over the higher elevations and depending on where the focus of precipitation is flooding concerns will be on the rise. Rising rivers and the potential for major ponding of water throughout the interior from the lower mountain elevations into the valley will materialize. Some snow melt mainly below 4000 to 5000 feet will likely add to the water flowing into the rivers and streams as well as onto the roadways. Most rivers in the foothills continue to likely be cresting/peaking on Wednesday based on the latest forecast.
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Currently forecasting 6 to 10 inches of rain over Western Shasta County…8 to 12 inches through the feather river basin…5 to 8 over the mountains in Lake County…3 to 6 inches in the motherlode with local amounts up to 8 inches over the higher foothill elevations. The valley is forecast to have 2 to 5 inches with local higher amounts possible. Flash Flood watch issued for areas below 4000 feet and into the Redding area due to the amount of water expected on top of the already nearly saturated soils with a Flood Watch for the valley where the terrain is flatter.
Abundant snowfall accumulation will likely close major pass levels over the crest for an extended period of time so motorist might want to consider alternate routes if possible or avoid travel. 6 to 8 feet of new snow is expected near pass levels and above.
In addition breezy to windy conditions Monday into Wednesday will add to the problems with downed trees and limbs likely along with possible power outages. Heavy snow in the higher elevations of the mountains will replace the lower elevation rain related issues with trees and power outages.
Extended Discussion (Thursday through Sunday)
A cold front will be making its way through the region to start off the extended period. This will bring diminishing valley rain chances with lingering mountain showers. Snow levels will be lowering to 2000 to 3500 feet by late Thursday but overall additional accumulation should remain light. Chilly overnight lows are expected Thursday night as cold air builds in behind the front. Short wave ridging will bring quiet weather on Friday.
Our next system will start to move into the region on Saturday as a short wave trough approaches NorCal from the west. Precip chances are expected to continue throughout the weekend. The higher moisture does look to stay to our south but we will still likely see a steady rain at some point throughout the weekend. Given the expected rain this week this system would likely bring enough rain to bring some flooding concerns. Snow levels will start out between 3000 and 4500 feet Friday night but will raise to above 6000 feet by Saturday night.