January 7-9, 2017 Atmospheric River Briefing – NWS Hanford, California


Hello, I’m Scott Rowe with the National Weather
Service in Hanford, California with a weather briefing for the atmospheric river event that
is poised to impact California from Saturday and into Monday. The information provided in this presentation
is valid as of 10 am , Thursday, January 5. For the most updated weather forecasts, watches,
warnings, and advisories, please visit weather.gov. With this weekend’s atmospheric river event,
we can expect a handful of potential hazards, including
Heavy snow above 9,000 feet. Heavy rain in the Sierra and foothills below
8,000 feet, with snow levels rising as high as 10,000 ft on Sunday. River flooding in the foothills and Yosemite
National Park. Flash flooding, mudslides, debris flows near
recent burn scars. Urban/small stream flooding in the San Joaquin
Valley. The heaviest precipitation is expected to
occur Saturday night and continue into Sunday. Here is a forecast model run showing the evolution
of the weekend’s atmospheric river event starting Thursday 10 am. Depicted here is integrated water vapor transport,
a variable used to measure the quantity of water vapor in the atmospheric column. The yellow and red colors indicate higher
integrated water vapor transport levels associated with the atmospheric river, which is expected
to begin impacting California as early as Saturday and continuing through the weekend. The latest snowfall forecast calls for significant
accumulations in the central and southern Sierra Nevada. Accumulations will be elevation-dependent,
as snow levels will rise over the duration of the event as warm, moist air moves into
the area. The highest elevations of the Sierra above
can expect to receive more than 3-6 feet of snow, with some locations approaching or exceeding
8 feet! The latest rainfall forecast calls for significant
accumulations below the snow levels in the Sierra Nevada and foothills where a flash
flood watch is in effect Saturday morning and continuing through Monday afternoon. 8-12 or more inches of rain is in the forecast
between Yosemite National Park and Sequoia/Kings Canyon National Parks. Recent burn areas will have an increased risk
of rock slides, mud slides, and debris flows. The high snow levels will also accelerate
snow melt below the snow levels as rain falls on the snow pack. With the heavy precipitation and high snow
levels, the threat of river flooding will be a concern in Yosemite National Park along
the Merced at Pohono Bridge. The current on forecast calls for the river
to exceed flood stage this weekend and crest over 15 feet on Sunday. This forecast is subject to revision over
the next few days. For the latest river forecast, please visit
the California Nevada River Forecast Center’s website. In summary, a wet atmospheric river will take
aim on California this weekend and continue into Monday. Very high impacts possible in the Sierra Nevada
with risk of river flooding, flash flooding, rockslides, mudslides, and debris flows. This concludes the weather briefing for this
weekend’s atmospheric river that is expected to bring significant impacts to central California. We invite you to visit the National Weather
Service’s webpage at weather.gov for the latest weather forecasts, watches, warnings,
and advisories. You can find us on Facebook by searching for
“US National Weather Service Hanford California” and on Twitter at the handle @NWSHanford. Thank you again, and be weather-ready we approach
the upcoming storm.

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