From BOX AFD
Wednesday... It appears increasingly likely that at least part of southern New England could see its first widespread accumulating snow of the season. The dynamics are impressive. The 00z GFS shows a decent storm intensifying close to the 70W/40N benchmark with deformation band forming across the CWA. Omega within the favorable Dendritic Growth Zone of -12 to -18C looks to be in the 15-20 unit range, along with negative 700-500mb equivalent potential vorticity and good 700mb frontogenesis should help set up a decent mesoscale band sometime Wednesday afternoon into evening. The question will be whether it is cold enough for 1 inch per hour snowfall rate to materialize and how much snow can accumulate before potential mixing or changeover to rain especially along the Boston- Providence corridor. Ensemble model guidance (GFS, EC and GEM) have continued to advertize decent probability of 24 hour 3-plus inches snowfall, with consensus of at least 40-50 percent for Wednesday into Wednesday night across interior MA and CT, using uniform 10:1 snow to liquid ratio. Dependent on how impressive the cold air injection is, this ratio could potentially be a little higher. In fact, the GFS shows SLR of around 14 to 16:1. While it is still too premature to go into possible snowfall accumulation, would like to see greater signal for formation of deformation band across the CWA especially when the Convection- Allowing Models come into range by Sunday night/Monday morning. Given it is a fast-moving system, snowfall rates will likely have to approach or exceed an inch per hour for Warning criteria snowfall (6 inches averaged over a forecast zone in a 12 hour period). There is above average uncertainty with the Boston-Providence corridor because either it could be a mostly rain event or it could be the sweet spot for significant snowfall accumulation if the colder air holds its ground and the deformation band sets up in the vicinity. So plenty for snow lovers to ponder over and continually monitoring over the next couple of days. For now, really don`t have the confidence to come up with a snowfall map until the Hi-res ensemble guidance (HREF) comes into range but we have time to fine-tune the specifics.