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Storms move in on California

Heavy snow, rain in store for California, impacts I-5

Dr. Mario Picazo
Meteorologist, PhD

Friday, January 19, 2018, 11:56 - After a wet start of the week for portions of northern California, the latest forecast points towards more unstable weather through the weekend into next week. Localized flooding, land and debris slides will be possible for low lying areas, where as snow will make for tricky travel conditions for higher elevations. Here's what you need to know.

A front moving across California on Friday will bring unstable weather to most of the northern half of the state although rain and snow showers are also expected to move into other sections of the south, as well. As the cold front associated with an east bound low moves south and east, it will drag much colder air behind causing temperatures to plunge and snow levels to drop significantly. 

Weather Highlights: 

  • Return to a wet pattern is expected to close out the week along the coast with inland snow. 
  • Chance of showers across Southwest California Friday night, with a threat of snow showers lingering into Saturday morning across the north facing mountain slopes.
  • Greatest threat of showers during this event will be along the Central Coast and north facing mountain slopes.
  • Significant travel impacts possible on the Interstate 5 near the Grapevine with snow showers accumulation 1 to 3 inches
  • Any shower activity over the devastated Montecito area is expected to be light, with accumulations less than a tenth of an inch.
  • Periods of heavy precipitation and high winds across portions of the Great Basin, the Northern Rockies, California, and the Pacific Northwest, Sun-Tue, Jan 21-Jan 23.
  • Another storm set to bring more rain, mountain snow and strong winds to Washington, Oregon and NorCal Sunday.

Click play to watch below: Precipitation forecast 

SAFETY: Six important flood safety tips

Snowfall outlook, potential travel impacts

A Winter Weather Advisory is in effect this Friday across many areas of California. Most counties in the northern third of the state are expecting snow above 3000 feet and occasionally at lower elevations. 

Coastal mountain ranges could see 2 to 3 inches in the higher areas before the day is over.

Snowfall forecast Friday through Sunday, courtesy the National Weather Service.

Heavier snow is expected across the northern Sierra's with 6 to 12 inches possible in the passes and gusty winds making road conditions even more treacherous. Snow levels in the high mountain region will be dropping to 3000 feet with winds gusts of 25 to 35 mph and occasionally stronger in high terrain.

low elevation rain exceeding 2 inches in 24 hours expected for Sunday. This image shows the quantitative precipitation forecast (abbreviated QPF), which is the expected amount of melted precipitation accumulated from Friday through Sunday night. Courtesy: WPC/NWS/NOAA.

Snow accumulation with this storm is going to be counted by the feet in the higher elevations of the Sierra Nevada range. 2 to 3 feet are expected before this system exists the state on Saturday.     

The main concern with some of the principal roads that traverse the range is along sections of I-80 at Donner Pass, Highway 50 at Echo Summit and Highway 88 around Carson Pass

Snow for areas further south

Further south temperatures will begin to drop during the second half of the day with winds chill values even lower as winds become stronger. Snow is expected above the 2500 to 4000 foot mark and accumulations will vary anywhere from 1 to 3 inches. North facing slopes could get up to 6 inches and wind speeds are expected to reach gusts of 50 mph in mountain passes and deserts. 

Snow is also expected to accumulate around the southern edge of the Sierra Nevada range into the San Gabriel, San Bernardino and San Jacinto Mountains. 

A large swath of snow is forecast to fall from Los Padres National Forest across to Angeles National Forest. This could affect travel along the always busy Interstate 5 (I-5) in and out of Los Angeles. This area is known as the Grapevine, and is normally affected by winter storms like the one moving across California. 

The I-5 becomes steeper at the mouth of the Grapevine Canyon as it ascends into the Tejon Pass and this stretch of road is always one to watch out for during winter weather. 

Fortunately, dry weather should also be the norm during much of the week for the Montecito-Santa Barbara area, as rescue teams continue to search for people missing since last week's dramatic landslide.

Meanwhile, gusty coastal winds and high surf can be expected through the weekend. Caution along the shores is advised.

Click play to watch below: Jet stream pattern

Adding to snowpacks

While many in Southern California will understandably keep a wary eye on additional rain in the forecast, a more active pattern will bring some welcome additions to this season's thus-far paltry snowpacks. As of January 19, the statewide snow water content - one way the snowpack is measured - only amounted to 21% of normal for the date. 


California receives most of its precipitation during the winter months, so snowpack serves as an important natural storage reservoir. In a typical year (or what used to be typical), the state's snowpack stores 15 million acre-feet of water, more than all the water used by California cities in 2010.

Significant mountain snow is expected to pick up through the week for the Sierra as well, as the second, another system moves into the coast. This pattern is expected to hold through much of next week, giving at least the northern and central Sierra a chance to develop some more significant snow depth. 

With files from The Weather Network meteorologist Caroline Floyd.

Additional sources: NRDC | NWS

Thumbnail image source: NWS/Los Angeles

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