NOAA: Atmospheric River Event for California Sunday-Monday

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Atmospheric River to impact California Sunday and Monday brining big snowfall to the Sierras.
Atmospheric River to impact California Sunday and Monday brining big snowfall to the Sierras.

NOAA is now calling this weekend’s storm coming to California an Atmospheric River Event.  Precipitation totals will be highest in the Sierra Nevada mountains during this event. A Winter Storm Watch is in effect for the Sierra Nevada mountains that is calling for up to 16-inches of snowfall on Sunday and Monday.

“An atmospheric river is currently impacting the Pacific Northwest, and will impact Northern California Sunday into Monday!

Confidence is high that the Sierra will see healthy precipitation totals with this weather system, as local spots could see over 2 inches of rain. The highest impact will likely to be travel across the Sierra, as drivers will likely be unaccustomed to driving in the snow. If you need to travel across the mountains, it may be best to avoid the late Sunday night through Monday period as snow levels drop.” – NOAA Sacramento, CA

Atmospheric River

Atmospheric Rivers (AR) are relatively narrow regions in the atmosphere that are responsible for most of the horizontal transport of water vapor outside of the tropics. While ARs come in many shapes and sizes, those that contain the largest amounts of water vapor, the strongest winds, and stall over watersheds vulnerable to flooding, can create extreme rainfall and floods. These events can disrupt travel, induce mud slides, and cause catastrophic damage to life and property. However, not all ARs cause damage – most are weak, and simply provide beneficial rain or snow that is crucial to water supply. This interesting feature will be impacting us late Sunday and into Monday. IR satellite imagery indicating the the low level circulation of OLAF will be lifted ENE along the front and will increase precipitation amounts and possibly raise snow levels above 8k feet at the onset. This video is from the latest run of the GFS displaying Precipitable Water and 700 MB moisture transport vectors. Very Impressive system coming across late Sunday and early Monday.

Posted by US National Weather Service Hanford California on Friday, October 30, 2015

NOAA video of the weather models for the coming atmospheric river event.

The Yosemite and Kings Canyon area will see 8-16″ of snowfall while the Lake Tahoe region will see 4-12″ of snow from this event. 

Snow levels will generally start out high and will drop to around 5,000-feet on Monday.  The heaviest snow will fall on Monday morning.

Map showing the exact areas that will be under the Winter Storm Watch in California on Sunday & Monday.
Map showing the exact areas that will be under the Winter Storm Watch in California on Sunday & Monday. Blue = Winter Storm Watch.

Be careful out there if driving during this storm.

Snow is forecast on Sunday and Monday for:

  • Donner Pass (hwy 80)
  • Echo Pass (hwy 50)
  • Lassen NP (hwy 89)
  • Carson Pass (hwy 88)
  • Ebbetts Pass (hwy 4)
  • Sonora Pass (hwy 108)
  • Tioga Pass (hwy 120)
Snow will fall on the entire Sierra Nevada this weekend.  Map of snow totals for the Sierras.
Snow will fall on the entire Sierra Nevada this weekend with 12-16″ of snow falling on the higher elevations (pink colored zones).

A powerful cold front will push through the Sierra and western Nevada with gusty winds through Sunday. Choppy conditions are expected on both Lake Tahoe and Pyramid Lake this weekend. Widespread rain and high elevation snow is expected for Sunday night into Monday morning. Anyone planning travel over the Sierra this weekend should prepare for winter travel conditions and pack winter clothing for their trip.” – NOAA Reno, NV

Tioga Pass and Sonora Pass most likely will close during this storm. We gotten word that Tioga Pass will close at 4pm on Sunday, possibly for the season. Up to 16″ of snow is forecast for Tioga Pass.

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE HANFORD CA
227 AM PDT SAT OCT 31 2015

-SIERRA NEVADA FROM YOSEMITE TO KINGS CANYON-

...WINTER STORM WATCH NOW IN EFFECT FROM SUNDAY EVENING THROUGH
MONDAY EVENING ABOVE 7000 FEET...

* HAZARD TYPES...HEAVY SNOW.

* ACCUMULATIONS...8 TO 16 INCHES ABOVE 7000 FEET. - NOAA Hanford, CA
Nearly all of California will receive precipitation during this Atmospheric River event.  This map shows liquid precipitation totals for the next 3 days.
Nearly all of California will receive precipitation during this Atmospheric River event. This map shows liquid precipitation totals for the next 3 days.

NOAA’s WINTER STORM WATCH for NORCAL TODAY:

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE SACRAMENTO CA
440 AM PDT SAT OCT 31 2015

...SIGNIFICANT EARLY SEASON SNOW POSSIBLE LATE SUNDAY NIGHT
THROUGH MONDAY EVENING FOR THE NORTHERN SIERRA NEVADA MOUNTAINS...

.A COOL STORM SYSTEM WILL SPREAD PRECIPITATION ACROSS THE AREA BY
LATE SUNDAY WITH POTENTIALLY THE FIRST SIGNIFICANT SNOWFALL OF
THE SEASON. SIERRA NEVADA MOUNTAIN SNOW IS EXPECTED TO BEGIN LATE
SUNDAY NIGHT AND CONTINUE THROUGH MONDAY. THIS STORM IS FORECAST
TO BRING SNOWFALL AMOUNTS AROUND 4 TO 7 INCHES TO THE SIERRA
PASSES AND UP TO A FOOT TO HIGHER TERRAIN SOUTH OF I-80. SNOW
LEVELS WILL INITIALLY BE AROUND 9000 FEET DURING THE DAY SUNDAY...
DROPPING TO PASS LEVELS BY LATE EVENING WITH SNOW ACCUMULATING
AFTER MIDNIGHT. THE HEAVIEST SNOW IS EXPECTED MONDAY MORNING. THE
SNOW WILL BECOME MORE SHOWERY THROUGH MONDAY AFTERNOON AND
EVENING WITH SNOW LEVELS DROPPING TO AROUND 5000 FEET.

-WEST SLOPE NORTHERN SIERRA NEVADA-

...WINTER STORM WATCH REMAINS IN EFFECT FROM SUNDAY EVENING
THROUGH MONDAY EVENING...

* IMPACTS: SIERRA TRAVELERS MAY EXPERIENCE VERY LONG DELAYS.
  CHAIN RESTRICTIONS PROBABLE.

* CONFIDENCE: HIGH CONFIDENCE SNOW WILL OCCUR ABOVE 7000 FEET.
  MEDIUM CONFIDENCE IN TIMING AND AMOUNTS.

* TIMING: SNOW LEVELS STARTING AROUND 9000 FEET SUNDAY
  AFTERNOON...REACHING PASS LEVELS LATE SUNDAY EVENING...5000 FEET
  DURING THE DAY MONDAY. HEAVIEST SNOW MONDAY MORNING.

* LOCATIONS INCLUDE: DONNER PASS ON I80...ECHO SUMMIT ON HIGHWAY
  50...CARSON PASS ON HIGHWAY 88...EBBETTS PASS ON HIGHWAY 4...
  SONORA PASS ON HIGHWAY 108.

* SNOW ACCUMULATIONS: 4 TO 7 INCHES AT PASS LEVELS...UP TO A
  FOOT OVER HIGHER PEAKS.


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