Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 259 PM EST Thu Dec 17 2015 Valid 00Z Fri Dec 18 2015 - 00Z Sun Dec 20 2015 ...Heavy rain and snow continues to impact the Pacific Northwest and Intermountain West regions... ...Snow showers possible across the Great Lakes... The continuous pattern of storms impacting the Pacific Northwest will persist through the short term period. The first frontal boundary is currently moving onshore while causing moderate rain and high elevation snowfall across the Pacific Northwest and northern California. Moderate to heavy rainfall can be expected for the rest of Thursday and into Friday morning as the cold front begins to move inland. WPC currently has a slight risk for excessive rainfall valid through Friday morning -- please see that product for more details. As the northern portion of the cold front moves across the northern Rockies and Intermountain West on Friday with the southern portion pressing southward across California, precipitation will consequently increase in coverage throughout these areas. Thus, heavy snow can be expected in the higher elevations, especially the Sierra Nevada mountain range and the Sawtooth Mountains from Thursday evening and into Saturday. Ice will also impact the Washington and Oregon Cascades on Friday. By Saturday evening, as this front moves over the Intermountain West, another frontal system will be approaching the Pacific Northwest and will bring yet another round of precipitation to the region. The strong cold front moving toward the East Coast will continue to deliver showers and thunderstorms spanning from New England to Florida. This front will move offshore by Friday morning and much colder, December-like temperatures will follow suit and settle across the region. Showers and thunderstorms will linger in Florida as the front pushes south but expect the southern half of the Sunshine State to dry out by early Saturday morning. Meanwhile, the Great Lakes region will experience snow showers due to lake effect on Friday and Saturday as a result of the aforementioned strong front. Initially, the Upper Great Lakes will have prime conditions for lake effect snow on Friday. By Saturday, snow will also affect the Lower Great Lakes as well as the Upper Great Lakes. Fanning Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php