A mix of winter weather headlines are up for the state in advance of our first significant snow event of the winter season. Most of the details seem sorted out, but the most important one, snow accumulation, is not settled yet. That said, it's time for our final call. Let's dive in.
Below: the current winter weather headlines for the state.
As a reminder, we get graded on the elements of this forecast. The overall setup has not changed. It was a warmer than normal and rainy Saturday as pre-frontal precipitation reached the area. A boundary will cross the region and the first press of Arctic air will arrive tomorrow, right as our storm system gets cranking to our south.
The expected track has shifted toward the state, increasing the chance we see more precipitation thrown back into the state. However, as we noted over the last few days, a closer track also introduces the risk of mixing at the start of the storm, especially along the shoreline.
Timing
While the individual models have bounced back an forth a little, there's not much change in my mind. I still think we see the onset of light snow and/or mixed precipitation between approximately 2pm-6pm on Sunday from SW to NE. The heaviest is likely to occur after sunset in a period between about 7pm and 1am, followed by tapering off between 3-5am.
Wind/Power Outages
No changes here. This doesn't look like a very windy storm. There's no big pressure gradient and the low itself isn't looking particularly powerful. Part of the reason for slightly increasing inland numbers is the likelihood of more powdery rather than wet snow. That reduces power outage risk. I think that'll be the case along the shoreline too, but it may take a little more time. I don't expect anything more than isolated power outages with gusts below 35mph.
Snow Accumulation
Last night I wrote that if I were to make an adjustment it would be up or down slightly. That ended up being the case. This gets weighed twice as much as the other factors, and it's a pretty close call here. There was never a real thought of taking numbers down, but there was a lot of consideration--which ended up winning out--of taking the numbers up slightly for interior CT. Let's briefly talk about why.
Most will end up with 5-8" I think, but the ceiling is higher if strong banding can cross over CT tomorrow night. I want to account for that. I also want to account for the possibility that we trend more amped in the last 24 hours, which often happens.
On the other side of that however is coastal CT. It'll likely be a significant storm there too, but the closer track means that there could be some mixing issues at the start. This is something that really needs to be respected. Any mixing cuts down on potential snow totals, and the possibility of banding adds another wrinkle as it means there will likely be areas of subsidence (read: dry slotting). That's extremely hard to predict this far out, but using frontogenesis forecasts we can get a sense of where the banding could be.
At the same time, the soundings tell the story of where things could be at the time. Let's quickly look at Hartford first. You have good lift through the DGZ--or dendritic growth zone (note on the left) with temperatures solidly below freezing. There's no mix risk here at this timeframe. If you get good enough snow growth inland, you can put up good numbers even in a quick hitter.
Bust Scenario: Widespread 1-2" totals (10%)
Above are the boom/bust scenario probabilities. No change from yesterday. Let's be clear here though. If you're in the 5-10" zone and you end up with 4", that's not ideal but it's not really a bust. The same goes if you end up with an isolated 11 or 12" report on the map. At the coast, 3" in a 4" floor isn't great but it's not terrible. Boom or bust scenarios require widespread errors.
The boom scenario happens if the models amp up at the last minute--which has happened fairly frequently in recent years once we've been able to bring a storm our way. The bust scenario happens if the storm cuts well to the west, which is unlikely, or it comes in even weaker at the last minute. That's something to watch but I think that's unlikely as well.
Impact
Overall, this still appears to be a moderate impact event. Travel conditions will deteriorate by late afternoon tomorrow with the worst happening Sunday night. Snow is likely to be moderate to heavy at times. Otherwise, the timing is actually great considering that Monday is a holiday and we don't expect powerful winds.
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Thank you for reading SCW.
-DB