Synopsis- Likelihood of a moderate to heavy snowfall beginning Sunday morning into Monday has increased significantly. Details on how much, how far north heaviest snowfall extend’s is still low confidence at four days out.
Yesterday was a wild ride for model huggers. Data went from showing 8” of snow in Charleston SC and nothing in the Hudson Valley, to rain in SC and a snowstorm in NY in one six hour run.. That’s what happens when you are 5+ days out from a storm, details are irrelevant. Need to sort through it all and look for the nuances. What we noticed in the runs yesterday was that the southern piece of energy for the storm was a touch slower each run, and this allowed the northern piece to interact with it. This in return created the jet stream to amplify downstream, forcing moisture and lift further north with each consecutive run. Once this trend started, it only gained more momentum, then last night the models were also fed Air Force recon data, and thus poured gasoline on that trend.
The end result? All models have come north! The GFS came from SC to DC to Albany in three runs. The rest of the data a slowly nudged north. We are now four days out from the first flakes as most guidance says snow begins Sunday AM and persists well into Monday.
Are we done with the trends? Unlikely.
Will they be as substantial? Unlikely.
Ticks north and south will continue.
What does this mean for our region, probabilities for an impactful winter storm have increased significantly. Confidence on exactly how far north the light to moderate vs heavy snowfall pushes into the region remains low/moderate.
With pieces of energy now coming ashore, better sampling from recon flights and us entering into 96 hours or less window these details will continued to clarify with each 6-12 hour data period. As such we will continue to hone and dial in the details, such as first look snow maps, followed by prelim and final, we will hone down exact start/end time windows as well.
Keep in mind, while we don’t expect such wild variation in the future data, small adjustments in track, and the complicated evolution of what is now two separate low pressure systems, with a coastal redevelopment can and will impact the finer details that we are not addressing just yet.
Attached are the Euro,GFS and CMC which as you can see are finally getting along and playing nice with each other. This is the kind of data consistency that increases confidence, if models remain in lock step through the day, this would continue to increase probabilities and confidence. Four days is an eternity in a complex forecast that involves multiple pieces of energy coming together at all the right times and places to lead outcomes being forecasted in our little slice of the world.
Stay tuned, we will do both a morning and evening storm update beginning today, and some fireside’s as we begin to enter into Storm Mode. Everyone one have a great day, stay warm, keep calm and weather on!