Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 357 PM EDT Thu Apr 25 2019 Valid 00Z Fri Apr 26 2019 - 00Z Mon Apr 29 2019 Day 2... ...Northern Plains and Upper Midwest... With the models moving into better agreement, the signal for a late season significant snowfall for portions of the region continues to increase. A shortwave trough sliding southeast from the eastern Pacific across the Pacific Northwest on Friday is expected to amplify as it moves east of the Rockies and into the northern Plains Friday night into early Saturday. A favorable upper jet couplet along with enhanced low level convergence along an inverted surface trough will support steady precipitation northwest of the low - enhancing the potential for rain changing to snow as cold air wraps around the backside of the deepening surface low. As has been the case, the NAM is amongst the colder solutions, with heavier amounts than the GFS along the North and South Dakota border into eastern South Dakota overnight Friday into Saturday. But given the dynamics, along with support from recent runs of the ECMWF, suspect the GFS may be underdone. To the east, models continue to show plenty of low to mid level dry air remaining in the wake of a downstream trough - supporting evaporative cooling and snow, or rain changing to snow, across portions of southern Minnesota and southern Iowa to southern Wisconsin. Models are showing marginal boundary layer temperatures across this region. However, low to mid level frontogenesis along with a coupled upper jet is expected to accentuate precipitation rates, raising the potential for a changeover and accumulating snows within this region. Despite the late date in the season, mesoscale banding setting up within this region could possibly produce a narrow axis of moderate to heavy snowfall accumulations. This is suggested by the WPC probabilities which show a Slight Risk accumulations of 8-inches or more for the Day 2 period (ending 00Z Sunday). Day 3... ...Northern Rockies and Plains... Models show another shortwave dropping southeast from western Canada into the northwestern U.S. Saturday night. Strong upslope flow west of a low dropping south from Alberta into eastern Montana may support some heavy accumulations along the ranges of northwestern Montana, with lighter accumulations spreading east across northern Montana into western North Dakota as the system turns east on Sunday. Pereira