Yet another winter storm is headed our way so it is again time to break it down, impact by impact. Below I’ll take a look at some of the factors driving the storm and what these factors mean for the forecast.
Lets start with a look at the current radar showing the storm across the Great Lakes. Snow is already getting close to NYC which is right on track. Snow should arrive here in Maine early tomorrow morning. More details on the timing below the impacts section
There are several important factors I want to go over before putting out the snow map. I hope this will help you to understand some of the factors at play here and why this is a pretty tricky forecast for many areas.
Here is the GFS Low Level Jet map (courtesy of Accuweather) which helps to illustrate one of the factors that goes into the snowfall forecast and that is the coastal front. We get coastal fronts in most of our winter storms and they are basically a boundary between E/SE winds (warmer air) and N/NE winds (colder air). When winds collide like this (see map for wind arrows), the air has to go up and when air goes up, it snows harder. For this reason, higher totals are expected along the coastal front as this is one area to watch for mesoscale band development.
The HRRR temperature map for 8AM tomorrow (courtesy Weatherbell) illustrates two very important factors to consider when figuring out snowfall. First off is our coastal front I talked about earlier. Notice the extreme temperature gradient all along the coast. This thermal gradient is one of the important pieces of the coastal front and will likely drive heavy snow bands along the coast.
The other piece of the puzzle the temp map shows is the very cold temperatures across the area. This very cold air supports very high snow ratios on the order of 18:1-24:1 which is extremely fluffy. For reference, the blizzard brought widespread 20:1 snow ratios and the storm on Friday brought snow ratios closer to 10:1. Even though not a whole lot of liquid will fall, the snow ratios should more than make up for it.
It should be noted temperatures are not the only factor behind snow ratios, one could go into great detail about crystal type and snow growth (which by the way is excellent) among other things but temperatures are the main factor that drives fluffy snow vs wet snow.
Here is the snow map. Watch out for isolated 14-20″ amounts in the purple are, hence the + sign.
As with any coastal storm, wind will be a factor tomorrow. Winds will mainly be from the N/NE and could gust over 45mph at times along the coast. The map shown is the GFS wind gust map (Courtesy Accuweather) showing the highest winds zoned in on the coast. Keep in mind the numbers here are in knots so MPH values will be slightly higher.
High winds + dry fluffy snow = blowing and drifting. We’ve been here before and while no conditions experienced in tomorrow’s storm will rival that of the blizzard’s, localized whiteouts are possible especially along the coast where the highest winds are expected.
No sleet or freezing rain is expected to make it up here into Maine though areas south of the mass pike are at risk for sleet and ice which will keep totals down slightly. Cape Cod will mix with rain for a period of time as well so totals will be a good deal lower out there.
Normally coastal flooding would be an issue however the peak surge will occur during low tide so any coastal flooding impacts will be limited to isolated splashover/beach erosion.
Tonight: Increasing clouds, no snow yet. Travel impacts: None.
Tomorrow Morning: Developing Snow becoming moderate to heavy by midmorning. Winds will be picking up as well which will start the blowing and drifting. Travel impacts: Moderate/Major.
Tomorrow Afternoon: Moderate/heavy snow and wind. Travel impacts: Major.
Tomorrow Night: Snow winding down and tapering to flurries across SW areas. Moderate snow continues across NE areas. Travel impacts: Moderate/Major.
Tuesday Morning: Snow tapers to flurries everywhere, NW winds continue blowing/drifting. Travel impacts: Minor/Moderate.
All in all, nothing spectacular but it will make the snowbanks that much higher and the skiing that much better. More snow is possible Wednesday, more details on that in later updates.