MLK storm gaining support

Model guidance has trended northward over the last few days, extending light to moderate precipitation into southern New Hampshire. The GFS has been the most robust with low pressure tracking inside the benchmark. The 12z Euro recently shifted north, in relative agreement with the GFS. The UKMET and GGEM remain on the south side of the guidance but have come north considerably in the last 24 hours.

First point to make is that this storm is primarily southern stream. One general trend we've had this season is for southern waves to gain intensity over time on the model forecasts. We'll have a large moisture supply, with origins of low pressure near the Gulf of Mexico coast.

Second, guidance is suggesting multiple interactions with the northern stream: first over the southern plains, with energy phasing into the southern wave, and second with energy dropping southeast into the Great Lakes region Sunday night into Monday. If nothing else, this second disturbance will help drive back ridging to the west, helping the southern wave develop a negative tilt and more northward trajectory.

Looking at expected liquid equivalent accumulation, southern NH remains on the fringes, but support is increasing for a general .25" to.5". Amounts increase to the south, up to 1.5" across CT into SE MA. There, however, precipitation will fall as a wintry mix.

The pattern that has developed in the last week has shoved all the cold air in the CONUS, north into Canada. New England is holding onto the remains of the cold air as an east based negative NAO is just hanging on. High pressure to our north will help reinforce cold air at the surface, but warm advection ahead of the approaching low will raise temperatures aloft above freezing. This spells trouble with ice, primarily for areas of southern MA and northern CT. For southern NH, expect a mainly snow/sleet event.

AT THIS TIME, snow accumulation forecast for Keene: 2" to 4"

Keep in mind, it's still early, and changes to the forecast are inevitable through the weekend.