Significant snow storm tomorrow

Models coming in line now with secondary development occuring along the Mid Atlantic coast during the day Sunday, and moving across southeast New England Sunday evening. Most importantly is the latest prognosis from the 00z ECMWF which is on this track as well. The NAM is the furthest south and east with a track closer to the outer Cape. This would result in more snow in CT, RI, E MA, and SE NH, while heavier totals in SW NH and NW MA.

Precipitation type will be a big issue for much of SNE south of I90 and 495. While thickness criteria supports snow, boundary layer temperatures will be in the upper 30's for much of the storm. This will cause precipitation to be briefly wet snow changing to a mainly rain event.

North of Rt 2, this will be a mainly snow event, and especially into the higher terrain of SW NH, should stay all snow. However, we still will be looking at high water content and relatively low ratios. Regardless, with QPF around .7" to .9", snowfall totals will easier eclipse 4" here, with 8" quite possible.

Secondary low pressure will rapidly intensify Sunday evening, contributing to crashing heights and a flash freeze for eastern New England later Sunday night. Meanwhile, this will also present the best timeframe for what could be a period of heavy snow in western New England as strong frontogenic forcing becomes the focus for 2"/hr rates, and potentially blizzard conditions. Depending on far south the secondary low develops, SW NH could cash in on some of this as well, and this will need to be monitored very closely. In addition, total totals in the low 50's supports the potential for some thunder.

Further north and east, into N NH and ME, jackpot accumulations of 10 to 18 inches are possible through Monday.

For Keene -
Light snow will begin to fall by 10am as the intial clipper system slides east. Accumulations will stay light through the early afternoon, with probably just an inch or two by 3pm. Between 4pm and 8pm, the coastal low will be bombing to our east and this will trigger an expanding precipitation field with bands of heavy snow. Additonal snowfall of 4 to 5 inches is likely through the evening. Scattered snow showers will continue through the night and into Monday morning as upper level cyclonic flow remains entrenched over the region. Total accumulations of 6" to 9".