Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 307 AM EDT Sat Nov 02 2019 Valid 12Z Sat Nov 02 2019 - 12Z Tue Nov 05 2019 ...Great Lakes... Days 1-3... An occluded front will move across the Great Lakes, followed by winds across the upper lakes becoming W/NW Saturday into Sunday. The cold advection behind this front moving in favorable trajectory across the Lakes will produce lake enhanced snow showers in lee shore convergence areas downwind of Lake Superior and Lake MI. Light accumulations are expected Saturday in the eastern UP of MI and northern lower MI inland from the lake. Southwest flow across lake Erie results in lift and moisture fluxes into southwest NY, where light snow should develop inland from the lake. Temperatures above freezing near the lake suggest rain showers or a mixture of precip types, cutting down on potential for snow accumulations. Early Sunday, cross lake Ontario winds in westerly flow move onshore and upslope into the Tug Hill Plateau and the western Adirondacks. Enhanced moisture and loft combine to produce moderate snows in these areas. Spot totals to 6 inches are possible. The event winds down later Sun/Sun night as a ridge approaches from the Ohio Valley, with drying aloft and warming temperatures bringing an end to the LES. On Monday, a wave of low pressure departing the northern Plains crosses the upper MS Valley and Upper Great Lakes, then crossing into Ontario. Light snow is expected near the circulation center and in the post frontal air mass as lee shore convergence and moistening from lake Superior supports accumulating snow showers in the lee of Lake Superior in the western UP of MI. ...Northern Rockies... Days 2/3... Increasing RH through the column due to confluent mid/upper level flow will combine with coupled low level convergence/upper divergence in the right jet entrance region to produce an environment favorable for light to moderate snow. Upslope low-level flow behind the low level cold front will aid the synoptic ascent to produce periods of light snow, mostly in the higher terrain of the Bear Tooths. On Mon, the front/upper jet move slowly east northeast with light precip leading to modest snow totals, as the limited duration of snow limits the accumulation potential. The probability of significant icing (0.25 inches) is less than 10 percent all 3 days. Petersen