Two moderate to heavy snow events likely

Saturday and Sunday
---> As high pressure moves offshore tomorrow and low pressure moves north of the Great Lakes, warmer air will overrun cold air at the surface, resulting in isentropic lift. This will generate clouds throughout the day. Precipitation should hold off through the morning with dry air near the surface. By the afternoon, snow showers will develop across the region. The lifting force will remain in the region through Saturday night allowing moderate snow through the evening. Another factor to consider is low pressure development offshore, although it will likely occur to late and too far north for signficant effect. However there could be some slight enhancement. Currently, both the NAM and GFS have been consistent in showing at least .25" of water equivalent. And both have in the past run suggested near .5" of water equivalent. With good dendritic growth, suggesting up to 15:1 snow ratios, the potential exists for 2.5 to 4.5 inches of snow through midnight.

The snow total forecast gets trickier on Sunday. Cold front passage occurs mid morning, carrying moderate cold air advection. There is a good signal for a WINDEX (wintertime instability index) event in New England. Lifted indices drop below +5 and total totals approach 60. This is a good environment for snow squall developement, with embedded thunderstorms as well. This will support a few storms with 20 to 30 minutes of heavy snow and possibly white out conditions. The potential exists for a few places to pick up as much as 2 inches in 30 minutes. Where the concentration of squalls passes over, up to 4 inches could accumulation on Sunday, but because of the isolated nature of the event, will only tack on a half inch to the forecast.

Snow accumulation forecast: 3" to 5"

In addition to locally heavy snowfall Sunday, winds could be an issue in storms, and then more of a widespread issue Sunday Night as a second cold front passes. There could be a flash freeze event Sunday Night with this arctic front, along with winds gusting over 40mph. The newly falling snow could produce brief white out conditions.

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Tuesday through Wednesday Night
---> A storm system will move ENE out of the midwest Monday night, lifting a warm front northward toward New England. Warm air advection will develop precipitation along the front over the region during the day Tuesday. Precipitation type looks to be snow for southern NH, and northwest MA, although will still need to monitor it. Accumulations should be on the light side, less than .3" from the warm front. Cold front passage occurs Tuesday Night, and there could be some ptype issues just before the cfp, but should stay in the frozen form. Cold front will trigger some higher amounts, up to .4". From the primary storm system alone, we could see up to 4 inches of snow.

Again, there is a potentially a second part to the story. The GFS and EURO have been consistent in developing low pressure in the southeast along the cold front Wednesday morning. There are three effects this would have: 1) precipitation enhancement extending north along the front, 2) A delayed arrival of cold air, and 3) Signficant accumulations once the low reaches the region. There is still uncertainty with the track and strength of the secondary low. What would result with the GFS and EURO forecasts would likely be a change to sleet as upper level temperatures exceed freezing. In addition, this would add another inch of water equivalent to the total.

Initial guess for snowfall: 3" to 6"