In over a decade of forecasting, this is the toughest challenge I've seen. This is probably the latest SCW has made a final call forecast as well.
With more time, we're finally seeing things come into better focus. Somewhat.
Let's dive in.
The Overall Setup
It's the same as yesterday's forecast.
The powerful storm from the upper Midwest is rolling through the Great Lakes region, and is expected to phase (combine) with the southern stream of the jet. It's a high-end setup.
At the same time, our coastal low has formed off the Carolina coast, and is moving northeast, gradually intensifying. When the storm from the upper Midwest (northern stream of the jet) begins to phase, the intensification of the coastal low will become explosive. This, combined with blocking well to our north, will cause the storm to effectively stall and loop near Cape Cod before pulling away on Wednesday.
Not many changes here. We still think this is a long duration event, even though today is mostly rain. With cooling, snow is expected to break out in the elevated parts of Litchfield County this evening between 6-9pm. The rain/snow line will collapse south and east overnight, particularly between 12am and 7am.
The guidance has tried to coalesce around a cooler scenario for Tuesday. We lean toward a less than perfect phase that allows for snow in the northern four counties, but keeps the surface a little too warm for southern CT in the morning. However, everyone is likely to change to snow by Tuesday afternoon. Tuesday evening should still have all of CT as snow, and snow departs very early Wednesday morning, before 5am. I should note that the guidance has produced dry slotting in the state for part of Tuesday, and we will need to watch that closely.
Below is the 12z high resolution NAM, which highlights the general evolution of the storm (even though the details are still TBD).
When I woke up this morning, I thought our map might be in trouble and that we'd need to slash across the board outside of Litchfield County. Fortunately, patience prevailed.
The guidance, while still dramatically split over the overall outcome, have come back to Earth a bit with the extreme solutions in opposite directions. At the end of the day, our last call will mostly reflect our first, a testament (I think) to the experience and effort put into the first call.
There is high confidence in our 12+ zone. If you are located in this area, you will see over a foot of snow. In fact, someone may end up over 20". Now, most probably won't see the higher end of that range, but it's possible in isolated spots. Some guidance really goes crazy up there.
There is moderate confidence in our 6-12 zone. We still think elevation helps significantly in flipping you to snow earlier on Tuesday, and staying snow even if the low pressure lobe or some variation of it makes an appearance.
There is still low confidence in our 3-6" zone, and as I told SA this morning, I am worried about this zone. If the globals are to be believed, we see minimal snow here. If you take the high resolution guidance, a major snowstorm is on the way. Our 3-6 zone is the middle ground, and we're keeping it. As you will see below, in this case there is a big difference between 3" and 6" of snow.
There is moderate confidence in the 1-3" zone. Simply put, the temperatures are warmest here and this zone is last to flip to snow. Along the immediate shoreline, and I mean within a few miles of the beach, you may very well never accumulate if the low pressure lobe appears. However, we think it's more likely that you see at least a minor accumulation...and a lot of heavy rain. The northern part of the zone should see accumulating snow, and western CT could see snow outside of this zone if the low is more consolidated.
Below is the 12z GFS. It's a little more bullish in western and northern CT with heavy snow Tuesday, but with the low pressure lobe, it's mostly rain Tuesday morning in southern CT before a flip to snow.
As I mentioned yesterday, the combination of wind and heavy wet snow is a big issue, especially inland.
We anticipate maximum wind gusts between 35-45mph inland, and between 40-50mph along the shoreline. Highest gusts would be in eastern and SE CT. The winds are strongest in CT on Tuesday as the storm rapidly intensifies to our east. These aren't actually too bad in the whole scheme of things, but with dense snow, it becomes a problem if there's enough accumulation.
The combination of strong winds and heavy wet snow means that scattered power outages are possible in much of the interior. In our 12+ zone and 6-12 zone, we have particular concern that we see widespread outages.
Our concern has also increased in the 3-6" zone. If we see less snow than currently anticipated, or end up around 3", there are little power concerns. However, if we see a widespread area at or over 4-6", the risk of scattered to widespread power outages increases substantially.
Again, 12-18 inches of powder is far less impactful than 4-8+ inches of paste. The load on trees and power lines is a legitimate concern, even in areas expected to see less snow.
Overall, we still see a moderate to high impact event, with moderate impact in the 2-4 and 3-6 zones and high impact in 6-12 and 12+ zones. Based on the current forecast, we would see widespread cancellations statewide on Tuesday. There is minor coastal flooding expected, but we don't see a major impact with that.
Now is the time to follow radar trends and see what happens.
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.