Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 427 PM EDT Sat Oct 13 2018 Valid 00Z Sun Oct 14 2018 - 00Z Wed Oct 17 2018 Day 1... ...Central Rockies into the Central Plains... A positively tilted upper trough will push south down the northern Rockies tonight. Synoptic lift within the right entrance region of a developing downstream trough will enhance snow tonight into Sunday associated with the surface cold front pushing south from WY to CO. The north flow will focus snow to the immediate east of the Rockies (with enhancement on east-west ridges) on the High Plains with some east side upslope enhancement to ranges like the Front Range in CO (where the WPC probabilities for 8" is above 60 percent) from a surface high over MT. The swath will ride the jet east across the Sandhills of NE tonight where WPC probabilities for 4" are above 40 percent. Late tonight into Sunday the front shifts farther south into NM with enhancements on the Sangre de Christos with kissing jets farther east across KS. However, despite the good upper level forcing over KS, the low level thermals became less favorable for snow with the 12Z suite of guidance. Therefore, probabilities have lowered over KS (while remaining high for the southern Rockies). The probability of significant icing (0.25 inch or more) is less than 10 percent. Day 2... ...Southern Rockies... The northern stream portion of the large trough over the west shifts east across the northern Plains with the southern stream accepting the trough and allowing a closed low to form over AZ Tuesday. Associated heavy snows will be limited to the higher mountains of southern CO and northern NM with subtropical air south of the low over AZ. The probability of significant icing (0.25 inch or more) is less than 10 percent. Day 3... ...Southern Rockies... Upper level low pressure settles over AZ Monday night/Tuesday with the snow elevation lowering to around 7500ft bringing some snow to higher portions of the Mogollon Rim of AZ and western NM. A cold front pushes south from the southern Rockies and into Mexico Sunday night. Low pressure then spins into the Sonoran Desert from the north Monday. Associated southwest flow looks to overrun the post-frontal cold air over west TX/the Rio Grande Valley and southern New Mexico Tuesday morning setting up potential icing. As of now the expected magnitude is around a tenth of an inch, though this will need to be monitored on ensuing shifts. Jackson