Introduction and Synopsis
“It’s never that easy” is a good phrase to start off this afternoon’s discussion with. As most of you are probably aware of from reading our discussions, this has been an unusually low confidence winter for forecasters in that there hasn’t really been an event where it was clear what was going to happen even in the very short range. An event where one could go with one or two zones on the map and be confident that those zones would verify. As of yesterday, it seemed like we had finally found that event, with all forecast models in good agreement for 6-10” of snow across the state with little to no mixing to be seen. But, as we mentioned above, it’s never that easy, and we’ve seen a continued shift towards a further north solution as a result of the storm trending stronger out west and becoming more amplified sooner, allowing for it to track further to the north before it is shunted east with the cold air in place and the end result is a nasty mess for our forecast area and another situation where a shift of a few miles means a massive shift in the forecast. Wonderful. A storm is still very much coming, but now it will not only bring snow to the area, but sleet, ice, and perhaps plain rain as well.
Models and Trends
As stated above, the clear trend on the models has been for a stronger storm, hence a further north push of warm air in the midlevels and as a result a sloppier solution for the state. To see this, let’s compare the precipitation types valid at 10 AM tomorrow morning from the 0z NAM to the 12z NAM.
What is important to note however is that for the most part, the trend north is only in the midlevels. The surface has warmed slightly which will allow the shore to flip to plain rain at a point, but for most of the state away from the coastline, the surface will likely not warm above 32 until close to the end of the event, while the midlevels will warm much sooner. This means non-snow frozen precipitation will be a dominant precipitation type, either in the form of sleet or freezing rain. The icing threat for this event is real, especially in the typically colder portions of the area(Sheltered valleys/glens etc.). Some of the short range models are printing out over a half an inch of ice for some of the areas in the northern portions of the lower four counties, and while we don’t expect that much icing to verify, accretions of several tenths of an inch are possible. This, combined with heavy wet snow which will have already fallen, will create treacherous travel conditions and pose a risk of power outages.
As far as the actual models and our preferences, this forecast is based off a 50/50 blend of the RGEM and GFS models, which have been the most consistent for this event. We have discounted the Euro as a cold outlier, and have also discounted the GGEM as a warm outlier.
Here’s our forecast map for this event.
In the next tier north(Roughly the region between the Merritt and I84), we’re expecting four to eight inches of snow overnight and through the morning commute tomorrow, with rates of over an inch per hour possible late tonight and tomorrow morning. By 10 AM, we expect a changeover to have begun from south to north from snow to sleet/freezing rain, and soon after we expect most of this zone to be over to a mix of sleet and freezing rain. We are fairly confident in this area remaining below 32 degrees, and it is therefore this area where the most significant ice accretions are possible. Some forecast models show over half an inch of ice for parts of this area, and while we believe that is excessive, several tenths of an inch of ice is not an unreasonable forecast for the “lucky” areas. It is possible that temps will warm above 32 for a short period towards the end of the event, but the damage will have already have been done. Again, a changeover back to snow right at the end of the event is likely, with a minor additional accumulation possible. At the same time, however, temperatures will plummet as a cold front sweeps in, and a flash freeze is likely, allowing any melting or rain to freeze instantly and create very dangerous conditions. Use caution when heading out tomorrow night and Tuesday morning!!!
Finally, in the final tier of the state(Generally areas NW of I84), we are expecting precipitation to remain mostly snow, with six to twelve inches of snowfall expected overnight through mid-day tomorrow, with rates of over an inch per hour possible late tonight through mid-day tomorrow. Eventually, most should flip to a period of sleet, but the damage will have been done, as the vast majority of the QPF will fall as snow. The icing threat, while not non-existent in this region, is generally minimal, as most of the non-snow precipitation should be able to fall as sleet due to a generally cooler column overall. A flip back to snow is possible towards the end of the day with another minor accumulation possible. At the same time, however, temperatures will plummet as a cold front sweeps in, and a flash freeze is likely, allowing any melting or rain to freeze instantly and create very dangerous conditions. Use caution when heading out tomorrow night and Tuesday morning!!!
· A plowable snowfall for the entire state. The NWS has issued Winter Storm Warnings as a result for a combination of snow and ice for the entire state.
· Difficult travel from overnight tonight through tomorrow afternoon/evening, including the morning commute and likely the evening commute as well.
o This will likely lead to closings of schools and places of employment.
· Scattered power outages as a result of icing and winds(Which could gust over 30 miles per hour in some areas.
· Slippery surfaces due to icing.
· Difficult conditions Monday night into Tuesday from a flash freeze.
As always, we’ll be updating throughout the event as needed, with the first update of the day likely to come between 7 and 8 AM tomorrow and continuing every 1-3 hours or as needed throughout the course of the day. We also encourage you to let us know what’s going on in your town by sending us a message on Facebook, leaving a comment on one of our posts or discussions, or emailing one of us at spencer/tim/greg @ southernconnecticutweather.com. It really does make a difference in the forecast to know what is happening on the ground!
Stay safe, enjoy the storm, and thanks for reading SCW!