Expect a potential shift in forecast ideas
I mentioned on Facebook Tuesday afternoon that there is potential for shift in model ideas in regards to the late week storm, and that idea remains. The National Weather Service Gray office highlights the complex issue trying to forecast this one in its Wednesday morning discussion. The key point here is models are once again struggling to get valuable data from remote areas in northwestern Canada that are poorly sampled, and that is causing drifting and in some cases the flip-flopping of model ideas.
The European ensemble depiction of low pressure centers above shows a great deal of scattered ideas, which is rather alarming for an event that could begin within a 60 hours.
As a forecaster, my personal philosophy is to shoot straight with you, and over the past month or so it has been extremely frustrating at times to give you a "no bull" answer. The one thing I have said and will continue to say is model volatility remains high, so shifts in ideas can come fairly quick closer to the event. This is why it is important to stay on top of the forecast, regardless if you are getting it from the National Weather Service, local media, or from here.
What is going on here has to do with the timing of phasing with northern stream and southern stream, along with high pressure to the north. The thermal energy models use to figure out storm potential comes in the form of vorticity. I show those ideas once in awhile to make points, This upper level vorticity ties into how models depict the surface.
In this deterministic surface map idea from the Canadian RGEM model, it shows flat area of low pressure bringing a decent snow for southern New England, south of the benchmark 40°N / 70° W. The storm does not appear to phase and crank until south of Nova Scotia Saturday morning. It also shows a light amount of snow for the Maine coast, and that is about it. A jog west changes the ballgame from flurries to a 2-5" snow event for the shoreline counties.
The blunt force truth here is I don't trust any of the model ideas yet. The energy that needs to be sampled drops down into a sampling area Wednesday morning. A better idea should come Wednesday afternoon. If I have time, I will draft up a snowfall idea and post it on Facebook, and talk more about it here Thursday morning.
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