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Hi, My name is Mary Wister and I am the Science and Operations Officer at the National Weather
Service in Pendleton. The following slides will demonstrate why forecasters are anticipating
a busy weekend with snow, freezing rain, and sleet. Hopefully, this presentation will provide
a clearer picture of the complex weather pattern that has developed over the eastern Pacific
and the Pacific Northwest. To begin, this is a summary of the precipitation
forecast from Saturday through Monday. Basically, snow is expected tonight and Saturday for
all elevations. The heaviest precipitation is expected over north central and northeast
Oregon. The east slopes of the Washington Cascades will also see periods of moderate
to heavy snow Saturday night. By Sunday, another Pacific frontal system will bring widespread
precipitation to the east side of the Cascades. The challenge for Sunday will be the precipitation
type. Warmer air aloft will override cold air at the surface over central and eastern
Oregon, resulting in a mixture of snow, sleet and freezing rain. The warmer air will increase
on Monday. While Central Oregon as well as the John Day-Ochoco Highlands will observe
increasing snow levels with precipitation changing to rain for many areas on Monday,
the cold air will be slow to erode farther north. Take a look at the snow level forecast.
Notice how Central Oregon will have snow levels down to the valley floor on Saturday afternoon,
snow levels will increase to around 4000 feet by Sunday afternoon, then near 4500 feet on
Monday. However, northeast Oregon and central Washington will only observe a slight increase
in snow levels. The weather pattern is complex. A deep low
off the California coast is sending moisture across Oregon. MeanwhileĂ–an Arctic front
over southern British Columbia is spreading very cold air across eastern Washington. These
two fronts will collide and bring precipitation in the form of snow across central and northeast
Oregon and eastern Washington tonight and Saturday.
This image was created this morning that shows the forecast 24-hour snowfall through 4 PM
Saturday afternoon, March 1. Notice that only very light amounts of snow are forecast for
the Washington portion of the Lower Columbia Basin, Yakima Valley, and the Kittitas Valley.
Over central and northeast Oregon, many areas will receive 1-3 inches of snow with heavier
amounts in the mountains. Winter Weather Advisories are in effect for some areas. For the latest
forecast, check our website at weather.gov/pendleton. This water vapor image shows the next Pacific
front that will bring another round of precipitation late Saturday through Monday. The next slide
will explain why some areas will see a wintery mix of snow, sleet, and freezing rain with
this next front. This graphic is a cross section from one of
the forecast models showing the temperature profile from Madras, Oregon to the Tri-Cities.
This particular model is showing warmer temperatures between zero and three degrees Celsius overriding
much colder temperatures at the surface. This means that snow falling from the clouds will
partially melt or melt completely then refreeze before reaching the ground. This could mean
sleet and or freezing rain in some areas. Current forecast has a chance of snow, sleet,
and freezing rain over most of central and northeast Oregon and far south central and
southeast Washington expanding north Sunday night and Monday.
So, what are a few things you can do to be prepared?
Wait until next week to run errands. Warmer conditions are expected by Tuesday and Wednesday.
Roads will be wet or less hazardous.
If you must travel, check the latest forecasts and road conditions before departing. Dial
511 for the latest road conditions. WSDOT and ODOT have excellent websites providing
road conditions.
Have snow melt handy to place on sidewalks. Walking surfaces will be slick in many areas!
Let others know about any inclement weather in your area via NWS PendletonĂs Facebook
and Twitter pages. You never know how your information
could safe a life.
On behalf of the staff at the National Weather Service in Pendleton, I want to thank you
for listening. Have a safe weekend!