As we outlined in our first call last night, the first snowstorm of the season is expected for tomorrow. This discussion will break down the trends in model guidance since we last updated you and also contains our final call snowmap.
Models and Trends
Since we last updated you, we have seen the model consensus stabilize on a moderate snow event for the state. Generally, the guidance has waffled back and forth between a slightly weaker solution that brings a warning level snow to the eastern portion of the state and advisory levels to the western portion and a stronger solution that brings warning level snows to nearly everyone in the state. This is well illustrated on the most recent two runs of the GFS – the 6z GFS on the left is the extreme solution (it’s actually far enough west to bring precipitation type issues to southeast areas) while the 12z GFS on the right is the more moderate solution. Both are still good-sized storms and will certainly be impactful to the state.
The other guidance is in generally good agreement on a moderate event for the state – modeled QPF is generally in the .4-.8” range with a few outliers on either side, but we’re not in a situation where one model has 1-2” and one model has 10-12”. One thing I’ve seen on the guidance that’s worth keeping in mind when making a forecast for this system is the likelihood that we will see a mid-level band of forcing set up somewhere along the northwestern flank of the storm and that could produce a classic band of heavier snows if it remains in the same location for a longer period of time. These are often tricky to forecast because it’s rare that the model will fully recognize the potential – you need to look for the signs and then extrapolate the model to figure out what the net impact on the surface may be. Here, my area of concern for a fronto band would be somewhere in the northwestern portion of the state – the Danbury to Hartford corridor could be a prime target as things stand now but again, as the storm moves so does the banding. It could show up almost anywhere in the state and I wouldn’t be shocked.
The trend on the most recent model guidance was to bring the storm slightly east as a result of less interaction between the streams – if that trend were to continue, we would probably end up on the low end of our snow amounts. However, should it correct back towards a stronger solution (which we have seen a couple of times already with this system), the higher amounts would be more widespread. We’ll see where this goes with the 18z and 0z guidance and will update if needed.
Forecast & Timing
Here’s our revised snowmap.
If the storm were to correct back west to something like a 6z GFS solution, we could see some brief mixing on the southeast coastline, but for now I’m going with an all snow forecast as that solution is an outlier in the grander scheme of model data. Should that occur, there would be enough snow before and after the changeover to still easily verify the forecast.
Forecast confidence here is moderate – much clearer consensus on a westward sol
As far as timing goes, expect snow to break out by 7 AM or so on the coastline and work its way north throughout the morning – should be snowing by noontime in all of the state at the latest. A steady snow continues through much of the day before tapering off later Saturday evening into early Sunday morning from west to east. Should have everything out of the state by daybreak Sunday aside from perhaps a couple of lingering snow showers.
As Don introduced yesterday, we are testing out a new graphic for our snow forecasts – the SCW Impact Scale. Here it is for this event – in the grand scheme of things, the impacts from this system should be fairly similar to how we envisioned them yesterday despite the increased snow amounts and so we have left the scale unchanged. We’d love your feedback on this new approach!