Snow is expected to overspread the entire area between about 5 pm and 7 pm today. The snow will mix with rain across the lower Pioneer Valley even at the beginning of the storm, while it should be all snow to start with elsewhere across the region.
A change from snow to rain is likely to occur from south to north this evening, starting with areas near and south of the Mass Pike by 9 pm or so and then across areas north of the Mass Pike, but south of Route 62 by about the 10-11 pm time frame. Across areas near and north of Route 62, it appears that the changeover from snow to rain should occur around the midnight to 1 am time frame.
It should be noted that a few hours of freezing rain is likely across areas that are west of I-190. This freezing rain looks to occur from about midnight until about 3-4 am. That said, there could still be some spotty areas of freezing rain persisting in the northern Worcester Hills through sunrise Monday morning.
A change back from rain to snow looks to rapidly occur from northwest to southeast during Monday morning. This changeover from rain to snow looks to start in the northern Worcester Hills and the upper Pioneer Valley by 8-9 am and then reach areas around and south of the Mass Pike by 10-11 am Monday morning.
Snow is then expected to continue right through not only the midday hour, but also right through the afternoon hours of Monday. Some periods of moderate to heavy snow looks quite possible and this is something that'll need to be watched closely as it would be able to lay down an accumulation of snow on all surfaces leading to slippery roads and slow going during Monday afternoon.
Snow is expected to come to an end across the entire area between 6 and 8 pm Monday evening.
My latest forecast for snow totals are as follows:
Areas Near & South Of The Mass Pike, Including the Lower Pioneer Valley, the I-84 Corridor & the I-395 Corridor: 2 to 3 Inches. Most of that accumulation will occur from late Monday morning through Monday afternoon.
Areas North Of The Mass Pike, But South Of Route 62, Including The Worcester Metro, The I-290 Corridor & The Middle Pioneer Valley: 3 to 5 Inches. Most of that accumulation will occur from late Monday morning through Monday afternoon.
Areas Near & North Of Route 62, Including The Route 2 Corridor & the Upper Pioneer Valley: 5 to 8 Inches. It appears that about 1 to 3 inches of that accumulation will occur this evening before the changeover to freezing rain and rain with the rest expected from late Monday morning through Monday afternoon.