Heavy Rain, Mountain Snow Events Target Northern California

Quincy Vagell
Published: January 13,2016
After an already wet first two weeks of January, another round of storm systems is set to impact California. This time, the most generous rain and mountain snow will target the northern part of the state along with the Pacific Northwest, where January has gotten off to a much drier start.
The active southern branch of the jet stream over the region is associated with the strong El Niño pattern. It will transport atmospheric moisture, at times via a so-called atmospheric river, toward California.
(MORE: El Niño Ties Strongest on Record)
The strongest in the series of storms could bring rainfall heavy enough to lead to flooding concerns by the start of next week. Meanwhile, the Cascades and Sierra Nevada are in line for several feet of snow over the next week or so from the weather pattern.

Atmospheric River Setup

The snow is great news for area ski resorts, and it's also great news for the long-term drought still entrenched over most of California.
Snow water content across the Sierra Nevada is essentially normal, sitting at 101 percent of average for this time of year as of Wednesday, according to the California Department of Water Resources. On the same date in 2015, that number was just 37 percent.
The snow cover itself is a substantial move in the right direction for drought relief, as snowmelt later in the season plays a big role with replenishing reservoirs and water tables in California. The region is in a much better position now than it was 12 months ago.
Recent weeks have already seen gradual lessening of drought conditions over parts of the West Coast, but more than two thirds of California remains in extreme to exceptional drought as of Jan. 5, according to the U.S. Drought Monitor.

Forecast Next 5 Days

Here is a look at how the next several days are expected to evolve.

Thursday and Friday

The first slug of moisture looks relatively modest, moving into portions of the Pacific Northwest and Northern California during the day on Thursday.
While some briefly heavy rain is possible in a few locations, flooding does not appear to be likely with rainfall amounts generally near or below 1 inch.
(FORECAST: Bend, Oregon | Eureka, California | Tacoma)
As for snow, winter weather advisories have been posted for Thursday afternoon and Thursday night by NOAA’s National Weather Service for portions of Northern California and the Cascades of Oregon, mainly for elevations above 3,000 feet. Some locations may pick up 6 to 12 inches of snow by early Friday.
A bit of the moisture may survive the trek across the mountains, bringing some light snow or snow showers into portions of Nevada, Utah and northern Arizona later Friday.

Saturday through Tuesday

Another quick round of generally light rain and mountain snow targets the region on Saturday, shifting somewhat farther north than the previous system.
However, a more potent storm system is projected to take aim at the West Coast on Sunday into Monday. It is this moisture that could potentially produce some localized flash flooding.

Monday's Forecast

Widespread moderate to heavy rain reaches Northern California later Sunday and persists into the day on Monday, with an additional 3 to 6 inches of rain possible in the area from this wave of moisture alone.
The heavier rainfall rates will raise the risk of flooding during this period, though the extent of the risk will depend on exactly how much rain falls and how quickly it does so.
The latest forecasts indicate that rain and snow may linger into part of Tuesday, though the heaviest of the precipitation would most likely be over by then.

Forecast Rain and Snow Through Tuesday

Meanwhile, substantial snowfall totals of 1 to 2 feet with locally higher amounts will plaster much of the Sierra and the Cascades. Some of the highest snowfall amounts by early next week in these areas could easily eclipse 3 feet.
Total rainfall amounts may exceed 6 inches along the coast of southwest Oregon and northwest California as well as northern portions of the Sacramento Valley.
To put it into perspective, Redding, California, may receive 6 inches of rain over the next week. While that may seem like an excessive amount of rain, January is typically their wettest month of the calendar year, averaging just over 6 inches of rain.
Farther north, similar rainfall amounts are forecast for Crescent City along the northwest California coast. January is typically an even wetter month at that location, picking up an average of more than 10 inches a rain. This is a sharp contrast to the minuscule 1.73 inches of rain reported at Crescent City in January 2015.
Given the overall pattern across the Northern Hemisphere and longer-range forecasts from the computer weather models, the West Coast could see this stormy setup continue into the latter portion of January.
Check back with weather.com for the latest forecasts and information.
MORE: Western Storms Slam California - January 2016