Forecasting Becoming (Somewhat) More Clear

Our computer models have just been absolutely atrocious with this upcoming storm. Part of the reason for this is that there’s a very anomalous weather pattern developing which any computer model is going to have a tough time resolving. In situations like this the best thing to do is to use solid meteorology and figure out what makes the most sense in a given pattern. I’ll say right off the bat that confidence in this forecast is low.

The 18z GFS and 18z NAM seem to be on their own with a low WAY offshore by Wednesday morning with an inverted trough producing precipitation over southern New England. This is a very odd solution to me and I think the eastern outlier solution shown by the American models is due to convective feedback. I do not think this solution is likely to verify.

The 18z GFS is an almost all rain solution for most of the state outside of the hill towns, while the 18z NAM shows a slightly colder temperature profile with a mainly snow event in the hills and a decent accumulation of snow in Hartford’s northern suburbs. Since I think they’re off with the entire synoptic setup there’s probably not too much sense in diving into their temperature profiles in any detail.

The foreign models, on the other hand, are much more realistic. The GGEM, UKMet, and Euro not only are having a great winter but make sense given the developing weather situation across the country. They bring a surface low pretty close to the coast and deliver an impressive thump of precipitation as the low approaches southern New England. The GFS ensembles and actually a lot of the short range ensembles show this.

If we see a Euro-esque or UKMet solution I could see at least several inches of snow north of Hartford with a significant snow storm in the hills Tuesday into Wednesday. Boundary layer temperatures will be warm so it’s going to be a close call. I think we need to have a surface low move close to the coast in order to back winds out of the north (crank the ageostrophic flow). This is one of those strange setups where we’ll see a colder solution with a low closer to the coast than further off the coast. With an inverted trough winds at the surface will be straight out of the east (like the 18z GFS shows) and that’s going to be a torch for most of the state and change even the hills to rain.

Here’s what I’m expecting through Wednesday night (probabilistically) for Windsor Locks, Bridgeport, Torrington, and Groton:

Windsor Locks (BDL)

  • >1″ of snow – 60% chance
  • >4″ of snow – 30% chance
  • >8″ of snow – 15% chance
  • >12″ of snow – 10% chance

Bridgeport (BDR)

  • >1″ of snow – 30% chance
  • >4″ of snow – 15% chance
  • >8″ of snow – 10% chance


  • >1″ of snow – 20% chance
  • >4″ of snow – 10% chance


  • >1″ of snow – 70% chance
  • >4″ of snow – 50% chance
  • >8″ of snow – 30% chance
  • >12″ of snow – 20% chance



One thought on “Forecasting Becoming (Somewhat) More Clear

  1. Ryan,Thanks so much for your in depth analysis of all the computer models. What are your thoughts about the hills of NE Connecticut, in northern Tolland county? Thanks again…

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