Another storm is tracking up the Ohio River Valley this week and it will bring with it a mix of snow, sleet, freezing rain, and rain with the chance for a rumble or two of thunder. This storm is really two storms, one moving offshore tomorrow and another moving to our west Thursday. The first storm has the frozen precip while the second storm has the liquid precip. I’ll break down each and every impact below starting with some snow tonight into early tomorrow morning.
First Storm: Snow
Low pressure is moving NE offshore this evening and will bring us a round of precip tonight into tomorrow morning. Due to a cold dry airmass out ahead of the storm, this precip will start out as snow tonight with a couple inches of accumulation. Warm air will be blasting in aloft and will change snow over to sleet and freezing rain for the AM commute tomorrow. Before the changeover, a few inches of snow are expected but accumulations should remain fairly light. The snow combined with the icy mix will make for a very slick AM commute so be sure to allow extra time for slow travel tomorrow morning.
Here is what I expect for snowfall accumulations. The immediate coast could go over to rain fairly quickly so little accumulation is expected there. Most areas see 1-3″ but areas in the far north are likely looking at a good 3-6″ before warm air aloft finally gets up there mid day tomorrow.
First Storm: Ice
Warm air aloft will easily move in tomorrow morning. At the surface however, the cold will put up a solid fight. As a result, freezing rain is expected to be widespread tomorrow. This vertical profile of the atmosphere tomorrow afternoon near Rumford shows what I’m talking about. Snow will form and fall in the upper levels of the atmosphere which are below freezing (upper blue area). They will then fall into an above freezing layer which will feature temps near 5C (41F) and the snow will melt. Just before it falls to the surface, it will encounter more below freezing air. This won’t be cold enough for long enough to refreeze the rain back into sleet but it will be cold enough to allow the rain to freeze on whatever it hits. This is how we get freezing rain. As long as the lowest levels of the atmosphere stay below 32F, ice will continue to pile up. The greatest risk for solid ice accumulation is in the mountains and foothills where cold remains in place the longest. Closer to the coast, the very bottom of the atmosphere will warm faster but a sliver of below freezing air will remain between 500 and 1500 feet in elevation. If you live between those elevations anywhere in Maine, you are at risk for a fairly significant ice event.
Here are my thoughts on ice accumulation. Keep in mind, areas between 500 and 1500 feet in elevation run the risk of up to .5″ of ice even towards the coast. At lower elevations near the coast, less ice is expected and the immediate shorelines will likely escape the ice for the most part as temps quickly rise to above 32F. Also keep in mind that a half inch (.5″) of ice is enough to cause tree damage so power outages are definitely possible during this time in any areas that do get close to that half inch mark.
Second Storm: Rain
Strong southerly winds eventually get rid of any remaining holdouts of cold air. This will occur from SE to NW Wednesday evening into Wednesday night and the job won’t be completely done for the mountain valleys until the wee hours of the morning Thursday just before the heavy precip moves in. When the heavy stuff does move in, temps will be above freezing for all. While the frozen precip risk will be diminished at this point, we do still have two threats: rain and wind. Between 1 and 2″ of rain is expected for everyone across the area and this combined with warm temps could result in some minor drainage flooding. More impactful river flooding is unlikely though we do run the risk of ice jams on the bigger rivers which very well could cause problems. High winds will be possible with a line of heavy showers Thursday morning and a rumble of thunder cannot be ruled out. Heavy rain clears Thursday afternoon with just residual showers through Thursday evening. Gusty westerly winds will bring temps back below freezing Thursday night and an inch or two of upslope snow is likely during this time as well.
Second Storm: Wind
A band of strong winds aloft will be moving through at the same time the heavy rain will be and thus we run the risk of some of those winds being mixed down to the surface. While these winds could be strong, notice the lack of bright pink/purple we saw last week indicating these winds will be weaker. While I don’t expect any major issues with these winds, I am worried about scattered power outages especially in areas where ice from tomorrow has weakened trees. In terms of how strong I expect the winds to be, coastal areas could see gusts to 50 mph while the rest of the area sees gusts to 40 mph. Winds turn westerly Thursday afternoon and remain gusty but calm down into the 20-30 mph range which should limit any impacts after noon ish Thursday.
To recap, snow moves in tonight followed by ice tomorrow morning. Ice slowly changes to rain from SE to NW Wednesday night with everyone seeing rain by the time heavy precip arrives Thursday morning. Heavy rain will mix down some high winds Thursday morning causing scattered power outages especially in areas where ice on Wednesday has weakened trees. Rain and wind clears out Thursday afternoon as westerly winds bring in cooler and drier air. Upsloping will keep precip up and running in the mountains where an inch or two of snow is likely into Friday morning.
A cold front passes through Saturday night followed by a warm front Monday. Another cold front arrives Tuesday followed by colder temps.
Another update tomorrow morning.