Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 322 PM EST Thu Nov 7 2024 Valid 00Z Fri Nov 08 2024 - 00Z Mon Nov 11 2024 ...Central/Southern Rockies and Adjacent High Plains... Days 1-2... ...Heavy snow and major impacts continue for the Southern Rockies and Interstate 25 corridor through Friday... Deep low pressure drifting south over eastern AZ this afternoon will pivot east over southern NM tonight before swinging northeast up the eastern NM/TX Panhandle border Friday then shifts up the central Great Plains Friday night/Saturday. Pacific and Gulf of Mexico sourced moisture will continue to wrap in ahead of this low center and a developing surface trough extending from the southern Plains into central CO. Jet dynamics above frontogenesis along with topographical lift will allow renewed heavy precip over the Sangre de Cristos and adjacent High Plains by early Friday. This lift is through the DGZ which should allow large dendrites and rapid accumulation. Indeed the 12Z HREF mean 1-hr snowfall product features 1-2"/hr snow rates centered on the Raton Mesa 12Z to 22Z Friday. Day 1 PWPF for additional >12" is around 90% along the Raton Mesa to near the western OK Panhandle border. Please see updated Key Messages linked below. Snow shifts north over the eastern slopes and High Plains of CO on Friday, while a pivoting dry slow shuts off precipitation over NM. The strengthening theta-e advection will result in an impressive mid-level TROWAL pivoting NW into CO, which along with elevated instability, especially on the periphery of the dry slot, and upslope flow will driving heavy snow rates over central/eastern CO, especially where the DGZ deepens. The setup also supports a pivoting band of heavy snow around and perhaps north of the Palmer Divide south of Denver Friday evening. Day 1.5 PWPF for >8" are 50-80% over the Palmer Divide, but caution is advised with the decrease in values in the valley between the Palmer Divide and Raton Mesa where banding could easily overcome marginal thermal conditions and produce heavy snow in areas of central/eastern CO regardless of elevation. As the low occludes and shifts over Neb Friday night/Saturday, the moisture moisture fetch is shunted east and thermals farther east do not support snow, so the heavy snow threat generally ends in CO. The probability of significant ice across the CONUS is less than 10 percent. Jackson ...Winter Storm Key Messages are in effect... Southern Rockies and adjacent High Plains: https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png