Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 157 AM EST Fri Dec 09 2016 Valid 12Z Fri Dec 09 2016 - 12Z Sun Dec 11 2016 ...Wintry weather expected for portions of the Pacific Northwest... ...Heavy snow possible across portions of the central and northern Rockies and Intermountain West... ...Lake effect snows expected to continue downwind of the Great Lakes... An active weather pattern will continue across much of the western U.S. through the short range forecast period. A frontal system moving onshore in the Pacific Northwest early this morning will continue to spread precipitation inland today. Cold air will linger in the valleys of Oregon and Washington this morning, and a mix of snow and freezing rain is possible. Temperatures will warm some by this afternoon, changing precipitation in the valleys to rain. As the cold front moves inland tonight, snow may once again fall across the inland valleys as colder air moves into the region. Across the Cascades, heavy snow is possible. Farther inland, an Arctic frontal boundary draped across the interior west, along with the approaching Pacific frontal system, will produce widespread snow today and tonight across portions of the northern Rockies and Intermountain West, spreading into the central Rockies on Saturday. Heavy snow is possible across these areas, particularly at higher elevations. Areas of snow are also possible on Saturday across the northern plains and the Midwest as a series of upper-level disturbances pass overhead, and a surface frontal zone strengthens east of the Rockies. Lake effect snows will continue today and Saturday downwind of the Great Lakes, as cold Canadian air streams across the relatively warm waters of the lakes. Snow may be heavy over localized areas, with gusty winds also possible. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php