Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 217 AM EST Wed Nov 4 2026

A closed 500mb low tracking east out of the Great Basin will reach the Central Rockies Wednesday afternoon, bringing an influx of anomalous moisture to the region. ECMWF guidance shows PWs topping the 90th climatological percentile traversing the Central Rockies Wednesday night. The region also lies beneath the divergent left- exit region of a ~110kt 250mb jet streak that will support enhanced upper-level divergence. In addition, 700mb winds in lee of the CO Rockies will gradually increase out of the east as the 700mb low tracks over central CO Wednesday afternoon, fostering enhanced upslope flow along the Front Range. The heaviest snowfall is likely to occur as the 700mb low passes through early Wednesday evening and coming to an end early Thursday.

Snowfall rates >1"/hr in the Sawatch/Mosquito ranges and into the higher CO Front Range peaks are likely (>70% per the 00Z REFS) and could even surpass 2"/hr at times (40-70%). The 00-06Z Thursday time period is likely to produce heaviest snowfall totals >8" at elevations above 11,000ft in central CO. The closed low will open up into a positively-tilted upper trough early Thursday morning and snowfall rapidly concludes before sunrise Thursday. The PPP shows moderate-to-high chances (50-70%) for snowfall totals >8" in the CO mountain ranges above 10,000ft. The peaks of the Sawatch and Mosquito Ranges do contain moderate chances (20-50%) for localized snowfall totals >12". The WSSI-P shows many of these remote mountain ranges as having 30-70% probabilities for Minor Impacts, which may include some locally hazardous travel conditions over nearby passes.

The probability of significant ice across the CONUS is less than 10 percent.