Yummy! It’s not a bad storm by any means but the storm peaks during the morning commute. I’m pretty confident in 3″ of snow from Waterbury to Hartford along I-84. The higher amounts may verify if we can get into some mesoscale banding – we’ll see.
Along the shoreline the forecast is a bit more challenging. It appears a weak enough northerly ageostrophic drain will be in place to keep winds offshore (and therefore colder temperatures near the ground) but we’ll be tickling the freezing level about 5,000 feet off the ground through most of the event. A close call!
What we’ll have to watch is the warm layer sneaking around at 825 mb. You can see if on the 00z KIAD sounding to our south. This will advect north. More often than not when the shoreline straddles the danger zone they flip warm. I could see an extended period of sleet/freezing rain in the New Haven area with areas to the east tipping over the sleet/rain (>32F).
The SREF guidance I find useful within 12 hours of a storm. The QPF forecasts have come into decent agreement with a clustering on the plume diagrams of 0.4″-0.6″ from the Massachusetts border to the shoreline, respectively.
Synoptically, all of this is occurring as a baroclinic zone interacts with the right entrance region of a powerful 200+ knot jet streak on the U.S./Canadian forcing.
While there is synoptic scale ascent over the entire region the QPF field will likely be modulated by mesoscale effects such as banding and pockets of convection (Don’t get mauled by the MAUL!). There’s no one powerful PV anomaly/shortwave focusing QG forcing over a given area and spawning cyclogenesis or closing off a mid level low and focusing frontogenesis. This is a large, diffuse, somewhat-moisture laden zone of synoptic-scale lift that is producing a large area of precipitation. Expect some surprises both good and bad from this one.