FINAL CALL 2/21 @ 12PM: I am calling this one in. We have seen a dramatic northward push on the models, starting last night around 00z timeframe. The models have really started to push the best QPF numbers along the Mass Pike and even into southern NH now. Now I know if you saw the 12z NAM, you went wow! But we have to figure that that model is up to its usual games again and that last minute it will diminish QPF nearly in half. Still would yield a good sized snowstorm. Then the 12z GFS came in farther north and much 'wetter' than before with warning type snows all the way up into southern VT and NH. However, when you get that huge northward push, we have to figure in some mixing issues. Now the area I have outlined in pink is where I think there will be a quick burst of 1-3" of snow in a short amount of time before you go over to sleet. Nantucket will likely go over to plain rain. The new 12z GFS brings mixing issues with sleet all the way up to the MA/CT and RI borders and even up to Brockton. I think that will fall a bit southward later today, thats been the trend this winter, so it will probably only make it to a line of Hartford to Providence to Bridgewater, but even here a decent 3-6" of snow will accumulate before any switch over to sleet. If we don't get the switch to sleet in these areas, then I wouldn't be at all surprised to hear amounts nearing 10" in this area. Then you get to where it will be all snow. North of the three cities I mentioned is where there will be all snow from this one. QPF numbers have been bumped up a bit, so I think a widespread 5-10" of snowfall will fall in this area. For now, I'm thinking that many towns will come in between 5-7" in this area, but a few lollies of over that will be possible with up to 10" of accumulation. The Berkshires look to do best with this setup, closing in on one foot of snowfall. Even SNH will see up to a half foot of fluffy snow from this with advisory type snows all the way up to North Conway, NH; where they have about 30-40" on the ground with snowbanks over 10-15 feet high on the sides of the roads. Amazing. A few inches will be nothing for them.
So to break it down...Here is a timeline.
Snow begins in SW SNE around 8-10AM. Then it will quickly spread ENE and reach Worcester between 9-11AM. I would expect it to be in the Boston metropolitan area between 11-2PM, the latest. I would suggest leaving early tomorrow. We remember what happened a little over two months ago. We don't want to make it a repeat. However, this time around, I do not think it will come in like a wall with having flurries over to heavy snow under 1/4 mile visibility in 6 minutes. I think this snow will build up in intensity gradually and may take a couple hours to be widespread moderate to heavy.
The snow will get moderate to heavy in the Boston area by 3-5PM, just in time for rush hour traffic. So, I STRONGLY suggest that if you have to work tomorrow, that you take a half day. In fact I URGE you to do so. Leave the roads for the plow operators after the first flakes, please. Now, we will have that moderate, steady, occaisonally heavy snow last until about 10PM; then it will gradually get lighter and transition to snow showers. However, by daybreak on Saturday, we will have another little packet of snow move through the area that could deposit another 1-2" of fresh snow on top of the accumulated snow from Friday. That is why I am going for a widespread 5-10" ATTM.
Now for my infamous guesses for towns from town to town...
Boston 6"; Worcester 8"; Lenox 10"; Waltham 7"; Wilmington 8"; Attleboro 5"; Hyannis 2"
Providence 5"; Warwick 6"; Newport 2"
Hartford 5"; Tolland 6"; Bridgeport 3"
Nashua 7"; Manchester 6"; North Conway 4"; Keene 8"
That's my call for now. I would expect Watches to be posted between 2-4PM today. Watches will transition to warnings and advisories by tomorrow AM. Have a good afternoon.