Special update this evening with the latest on our messy storm system moving into the region tomorrow. The storm track will be to our west meaning we are on the warm side of the storm so there will be a lot of rain. SE winds will be an issue as heavy precip could bring down strong winds just over our heads. Precip will start tomorrow morning and end Monday morning with the heaviest precip falling tomorrow night.
There will be two shots of snow with this storm, one at the beginning and one at the end. Very light snow at the beginning could drop a coating-2″ for most places. South of the red dashed line on the map, that’s all the snow that will fall and it will melt pretty quickly with the rain.
On the backside of the storm, intense upward motion, as seen here on the GFS’s vertical velocity map, will cause cold air aloft to be dragged down to the surface through dynamic cooling. All those big fancy words to say that the mountains are likely to see a quick shot of snow Monday morning that could drop an inch or two of snow. All in all, this won’t be a big snow producer but there will definitely be some flakes flying.
Winds will be another important factor to consider tomorrow night because they will be extremely strong only a few thousand feet up and any heavy bands of precip (there will be a few around) have the potential to bring down those winds. The map above shows the max winds in the lowest 1.5km of the atmosphere and not all of those winds will be mixed down. That being said, things are likely to get gusty along the coast and isolated 35mph wind gusts are possible. Winds die down and shift westerly Monday afternoon.
A general 3/4″ to 1.5″ of rain is expected for areas south of the mountains. The map above shows the total liquid as the NAM sees it which includes snow too. The higher rainfall amounts are likely to be found in the foothills where upsloping begins to take effect. Rain could be heavy at times but flooding concerns are minor as this will be a quick-hitting system and the snowpack should absorb most of the water.
Warm Air Advection will start late tonight and SW winds will begin to bring in some low level moisture. SE winds at the surface will bring in warmer air and cause the coast to change to rain fairly quickly. The airmass ahead of the storm will be enough to keep inland areas snow to start.
SE winds both at the surface and aloft will cause the rain/snow line to collapse inland rapidly tomorrow afternoon. Heavy rain is beginning to organize over SNE as the low passes overhead. The mountains will hang on to the snow the longest, but even there, rain will creep in late in the evening.
The peak of the storm will arrive tomorrow night as the low moves overhead. Rain will be tapering off over SNE as the storm moves north and the core of the rain moves to Maine. As the storm intensifies, dynamic cooling will cause the snow line to begin to collapse eastward beginning around 2-3AM. The cold will race the precip as the dry slot works in, beating the end of the precip in the mountains especially in NH. The cold arrives a little late for the foothills and the coast.
Precip will be racing NE Monday morning as the snow line moves SE. NW of Bethel stands the best chance for some accumulation with the back end snows. Winds will calm down and shift to the west as precip moves out Monday afternoon.