Well, March came in like a lion and never really showed it’s lamb side. We saw one of the biggest snowstorms of the season and some of our most sustained cold during the month, and never really got the spring side of March that we often see. In fact, it’s quite possible that March could end up having a colder average temperature than both January and February, which is certainly a rare sight. This month isn’t going out quietly either, as we’ve got a storm system on our hands to deal with for tomorrow into Saturday.
Models and Trends
We walked through the setup extensively last night here, and that hasn’t changed much if at all. The synoptics have remained remarkably consistent on the models, with a low pressure system moving northeast, running into high pressure to our north, and moving due east from that point to redevelop off the coastline. The difference in the guidance has been and continues to be the temperature profiles during the system, that is, how far north can midlevel warmth make it into the state before the storm starts to bomb out and dynamic cooling takes over? Let’s take a look at the various model solutions to that question.
Solution #1: The Snowstorm (GFS)
The GFS continues to be the snowiest solution. It tracks the storm along the PA/MD border, and holds warm air aloft well south of the area. As a result, the whole state save the immediate shoreline would see at least some snow from the system, and accumulations would be significant in the northern portions of the state, with the northern tier never flipping over to mix or rain.
Here’s a quick simulation of the progression of the storm from the GFS sim radar. Note that in a situation like this one where dynamics and marginal temperatures are in play, forecasting off a precipitation type algorithm will get you burned every time. As such, a disclaimer that we’re only using these maps for illustration purposes and to show the general progression from the various guidance.
In this solution, I would expect warning level (6”+) accumulations in the northeast and northwest hills, with at least a few inches of snow for most of the area away from the shoreline. I would weight the chances of this solution at 40%
Solution #2: The Icy Mix(RGEM, Euro, NAM)
In the second solution, the storm takes a bit further north of a track, allowing warmer air to intrude in the midlevels, resulting in a quick initial period of snow before a change to rain across most of the state. In the hills, however, colder air hangs on at the surface despite the warming temperatures, and so the result is an extended period of sleet/freezing rain at elevation. Here’s the simulated radar for that solution from the RGEM – again, remember this is for illustration purposes only J. In reality, I’d expect a bit more coverage of frozen precipitation if such a scenario were to verify as the model is likely being a bit too aggressive (as usual) in warming the last few hundred feet of the column.
Solution #3: Rain(GGEM)
Finally we have the GGEM. This solution is pretty straightforward; the storm tracks the furthest north of all the models, the midlevels and surface warm above freezing, and we see a day and a half of cold rain. Sounds like springtime in New England. While the trends have clearly been colder over the past day, we can’t completely rule this solution out, and therefore we’ll weight it at 10%.
Forecast and Timing
For this forecast, I essentially took a blend of the GFS and RGEM solutions, weighting slightly more towards the RGEM to account for the slim possibility that the storm could shift back warmer and the end result would be mostly rain. Here’s the end result on our forecast map.
Next, in the southern half of the state, I’m expecting mainly rain. However, we will likely see some snow at the start of the event and then potentially again on the backend as the low departs and colder air comes in from the northwest. That, combined with the chance of accumulating sleet, leads me to believe that at least some accumulation is a possibility there, and so I’ll go with a slushy coating to two inches for this zone.
For the Hartford metro area and north, there should be enough latitude to see a period of accumulating snow at the start of the event and again towards the end on Saturday. While snow will almost certainly mix with and then change to sleet/freezing rain/rain, a minor to moderate accumulation is expected, with 1-3” currently forecast. This area has the highest bust potential, as even a slight shift colder in the consensus towards the GFS would result in several inches of additional snow for the area and an increased risk of sleet & freezing rain as opposed to just plain rain.
Finally, in the elevated portions of the NE and NW hills, this should be a mostly frozen event. I expect periods of snow through most of the day tomorrow, and again on Saturday, with a changeover to sleet and freezing rain in the middle tomorrow night into Saturday morning. There is a non zero probability that this area could remain all snow, in which case amounts would be substantially higher, but for now, 3-6” of snow with accumulating sleet and ice in the middle seems like a safe bet to me.
Here’s the timeline:
Friday morning: Light precipitation moves in; rain for the shoreline and a wintry mix of snow/sleet/freezing rain for the rest of the state. We could see some slippery roads for the morning commute, especially in the Hartford metro and north
Friday afternoon: Precipitation gradually intensifies throughout the day, with a wintry mix expected in the north and mostly rain in the south. Again, could see some slippery roads for the PM commute in northern areas.
Overnight: Most of the state flips to moderate to heavy rain, with a wintry mix continuing in the hills. Ice accretions are possible in the hills.
Saturday morning: Precipitation begins to gradually taper to scattered showers. As the storm pulls away and colder air comes in, we could see a change back to snow in some areas.
Saturday afternoon: Scattered rain/snow showers persist through the afternoon before finally tapering off Saturday evening.
- A mixed bag of wintry precipitation, with plowable snow likely in the hills and possible in northern valley areas. NWS has issued Winter Weather Advisories for the northern four counties.
- Isolated slippery travel during both commutes tomorrow.
- Scattered power outages from heavy wet snow and icing.
- Minor flooding in areas that see mostly rain – 1-2” of QPF is likely.
As we’ve said throughout the discussion, this is a volatile forecast where small changes in the setup can have a big impact on the overall output. We’ll keep an eye on the models tonight and if needed, issue a final call tomorrow morning. As of now, I think that any bust potential is towards the snowier side, but if I were to go for a snowier forecast, I’d need to see another tick colder on the models tonight. We’ll see what happens!
As always, thanks for reading SCW!