Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 303 AM EST Thu Jan 05 2023 Valid 12Z Thu Jan 05 2023 - 12Z Sat Jan 07 2023 ...There is a Slight Risk of excessive rainfall over parts of California on Thursday and Friday... ...Heavy snow for the Sierra Nevada Mountains and snow over parts of the Cascades, Great Basin, and Central Rockies... ...There is a Moderate Risk of excessive rainfall over parts of the California Coast on Wednesday and a Slight Risk of excessive rainfall over parts of California on Thursday... ...Temperatures will be 15 to 20 degrees above average over parts of the Northeast/Mid-Atlantic... A front will move onshore over the West Coast, bringing a plume of moisture over Southern California on Thursday. Furthermore, a second plume of moisture will move onshore over the Northwest and Northern California on Friday. A powerful atmospheric river continues to stream moisture over California on Thursday. In addition, extremely heavy snow rates above 3 inches per hour are nearly certain above 5000 feet, which will lead to dangerous, and at times impossible, travel in the mountains of Northern/Central California. Furthermore, considerable flooding impacts are likely, on Thursday. Rain rates over 1 inch per hour may lead to rapid water rises and mud/rock slides. Coastal areas of California and the Sacramento Valley are most at risk. Therefore, the WPC has issued a Slight Risk of excessive rainfall over California from Thursday into Friday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and burn scars the most vulnerable. Additionally, widespread wind gusts in excess of 50 MPH and saturated soils may make trees more susceptible to blowing down, with power outages also possible. On Friday, the stream of moisture will flow into Northern California, producing heavy rain. Therefore, the WPC has issued a Slight Risk of excessive rainfall over southwestern Oregon and Northern California Friday into Saturday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, small streams, and burn scars the most vulnerable. Moreover, snow will develop over parts of the Cascades, Great Basin, and Central Rockies from Thursday into Friday. Furthermore, coastal rain and higher-elevation snow will continue over the Pacific Northwest/Northern California into Saturday morning. Meanwhile, low pressure over the Great Lakes will linger over the region through Friday morning, producing snow over the area, with the heaviest snow over parts of the Upper Peninsula of Michigan and the northern Lower Peninsula. The snow will start to taper off on Friday. Snow will also develop over parts of the Central Appalachians and continue into Friday. Furthermore, snow will move into parts of the Northeast also on Friday. In addition, rain will develop over parts of the Northeast and pockets of rain/Freezing rain will develop over parts of Northern New England, with the freezing rain ending on Friday. The snow will result in reduced visibility and hazardous driving conditions. Additionally, temperatures will be 15 to 20 degrees above average ahead of the front over parts of the Northeast/Mid-Atlantic. Elsewhere, a front will move out of the Southern Rockies on Friday and move into the Southern Plains/Lower Mississippi Valley by Saturday morning. The system will produce rain over parts of the Middle/Lower Mississippi and Tennessee Valleys. Ziegenfelder Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php