Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 425 AM EDT Sat Oct 26 2024 Valid 12Z Sat Oct 26 2024 - 12Z Tue Oct 29 2024 ...Pacific Northwest... Days 2-3... Upper level ridging will give way to a broad upper trough, carved out by a series of shortwaves moving south of a low moving into British Columbia. This will support the return of unsettled weather and falling snow levels in the wake of a strong cold front moving from the Northwest into the northern Rockies on Sunday. Strong mid-to- upper level forcing and a shot of deeper moisture are expected to generate some of the heaviest precipitation across western Washington and Oregon Saturday night into Sunday morning. However, with snow levels above 6000 ft in most locations, winter weather impacts will be limited, initially. Snow levels are expected to steadily drop through Sunday, dipping to around 4500-5000 ft along the Washington and Oregon Cascades by Monday morning. Conditions will remain unsettled as onshore flow persists. WPC probabilities indicate that most significant snow accumulations will remain above the major Washington and Oregon passes through Monday Morning. Unsettled weather will continue across the Northwest through Monday, with snow levels dipping further as additional shortwaves move through the base of the broader scale trough as its axis shift inland. WPC probabilities indicate that potentially impactful accumulations will become more likely along the Oregon Cascades, with probabilities for accumulations of 4 inches or more climbing above 50 percent in some of the passes. Snow will also be spreading south into the Sierra Nevada and east into portions portions of the northern and central Rockies Monday into Tuesday. The highest probabilities for significant accumulations through Tuesday morning center over north-central Idaho and southwestern Montana and northwestern Wyoming -- in and around Yellowstone NP. WPC guidance shows at least low probabilities for accumulations of 6 inches or more in the higher elevations of these areas. The probability of significant ice across the CONUS is less than 10 percent. Pereira