For the third time in the past few weeks, Maine is in the cross hairs of a mixed precipitation event. Accumulating snow, sleet, ice, rain and wind will be thrown at the state beginning Monday night and won’t completely leave the state until Wednesday morning.
My previous update set the table of the storm along with the timeline that will effect the region over the next two days. The same concerns for cold air damming over the interior and an upper level warm air inversion to bring a mix of sleet and freezing rain is the main concern with this event for interior areas. For the coast, all of those elements, in addition to the wind, could make it an interesting start to the day on Tuesday.
The low level jet is indicated at roughly 1,700 feet above the surface indicates winds aloft in the range of 35-55 knots (40 – 63 mph). The wind, in conjunction with falling precipitation, may allow for gusts to exceed 50 mph along the immediate shorelines. This wind is dragging in an abundance of precipitation along with it. With cold air anchored on the ground thanks to a northeast wind at the surface, heat will rise into the atmosphere.
Sleet And Freezing Rain Make For A Tricky Forecast
I’m going to be right up front and just say the forecast is of low confidence and high bust potential, because that is the way these events always go. You may flip on the TV and see a meteorologist for WXYZ say “this is going to happen” and you may turn to another source and read “that is going to happen” which may confuse and frustrate you.
The reality here is we’re dealing with a “nose” of warm air aloft that will turn frozen precipitation to liquid, and pending how low the “nose” goes will indicate whether or not it remains liquid or not by the time it reaches the surface. It is this reality that models give ideas for, but the outcome may be different. We’re dealing with a matter of feet and a degree or two between an icing event, a sleet event, or a mix of the two.
Regardless of how cold the surface temperature is, freezing rain can and will occur with the right amount of warmth, with either the combination of the right velocity and/or the amount of feet above ground level where the temperature remains above 32°.
On the flip side, less warmth aloft or and/or more cooler air above ground level below the “nose”, the chance for sleet develops. It could be 50° and sleet (graupel is the actual term for it in this situation) could bounce off objects at the surface because temperatures aloft thaw, then refreeze, and cold air is close enough to the surface to keep the parcel in ice form at impact. This is more common in the spring when there is some sort of convection in the form of a strong cold front that causes that.
The Element Of Surprise For This Storm Is Very Real
Pictured above is the 12z (morning run) of the rather conservative GEFS ensemble (the ensembles of the American GFS models) with a precipitation mean accumulation value for this event. Since this storm is essentially a post-tropical cyclone, meaning it has tropical characteristics in core warmth, moisture and wind. For a third week in January storm, this is a very juicy event. The precipitation amounts depicted above range from a half inch in the western mountains of Maine to 2″ for the shoreline of Washington County.
With that being the case, if this were an all snow event, I’d suggest that folks start shoveling now. Measurements would likely need a yardstick in areas. In the past few days, some models have predicted a foot and a half of snow in areas. It appeared with every operational model run where models would do their usual flip-flop that the chance was there for some big snow somewhere, and in this case areas north and west of Chesuncook Lake in northern Maine was going to get clobbered. That area is indeed the jackpot area for this event as far as snowfall.
Again, since the region is dealing with a storm that for most of the state will be dealing with a matter of feet of the “nose” and a degree or two of warm air aloft, the outcome of this storm hinges upon it.
At first glance, this may not look like a big deal overall. It is a big deal given the fact sleet and freezing rain are going to play a big role in the outcome of this event and will likely impact snowfall totals. Some models are big on the freezing rain accretion, others think sleet is going to be the main precipitation type. Presented here is blend of ideas, which is what a forecast is made from. Arguments can be easily made for or against this solution. Keep in mind we’re dealing with a “nose” of warm air and a matter of feet and a couple of degrees. The forecast confidence remains low, the bust potential is high, and that is the reality.
Prepare for the worst, and don’t be surprised whichever way this turns out.
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Special thanks to Tropical Tidbits and Pivotal Weather for their written permission to use their graphics in this post. Use of WeatherTAP images used within their written permitted terms of media use policy. Additional forecast information supplied by the National Weather Service, WeatherBELL Analytics and AccuWeather Professional.
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