This is our official forecast for the Nor’ Easter that will be impacting the region tomorrow into Wednesday. This forecast will hold the latest precipitation type, accumulation, timing, wind speed, coastal flooding, and other forecast updates. The premium forecast, released slightly earlier, goes more in depth with an analysis of potential scenarios and impact analysis for specific power outage forecasts and school impacts, which you can get by either subscribing here or by purchasing the individual forecast for the storm here. However, the free forecast will similarly hold a wide range of information that we are going to dive into here, and there will be additional free updates throughout the storm as well, so stay tuned.
TUESDAY PRECIPITATION TYPE/TIMING: The timing with this storm, due to the various tracks and its specific direction, has been extremely hard to forecast. Thus, there are large timing changes both here and in the wind forecast for the storm. What we are looking at is some scattered flurries during the day today across the region that will stick instantly with temperatures below freezing. Tonight, temperatures rise through the night, meaning that precipitation starts around 4 or 5 AM in coastal locations as entirely rain. Further inland, precipitation starts around 5 AM as a freezing rain/snow mix before quickly turning over to just freezing rain and then rain. Current indications are that temperatures will rise fast enough so that only very far areas (north of I-84) could be dealing with any freezing rain issues by 6 or 7 AM. As seen here, the 12z NAM at 7 AM tomorrow has the freezing line at the top left in pink on the MA/CT border. However, the 34 degree line is still cutting through part of Fairfield County, leaving me concerned that a slight colder trend would result in more widespread freezing rain than most models are showing. Already today temperatures at the surface were significantly colder than many models expected, and if that were to happen again, we could have some moderate icing in far inland areas. The school impacts of this are discussed in the premium forecast. Anywhere south of Interstate 84 should not have any winter weather problems, and will just be seeing rain tomorrow morning. The largest timing change, however, is with the heavy precipitation. The heaviest precipitation now looks to be between 10 AM and 4 PM. Coastal areas will see it slightly earlier in that timeframe than inland areas, but the entire region should still see the heaviest precipitation during the day on Tuesday. There will be one major deformation band on the west side of the surface low pressure center, and wherever that sets up will see enhanced precipitation continuing through the evening tomorrow night, and maybe a mixture of snow. Right now, that looks to be over northern New Jersey or so, meaning that precipitation really dies down by evening across the area. However, that is something else I will be tracking very closely on our High Definition weather models. The result is that heavy rain comes a little later than expected, but that rainfall totals still fall inside the 1.5-2.5 inch range for the storm on Tuesday. At the heaviest, some minor flash flooding could occur, but this is not the largest threat that I am watching. Light rain will still continue through the night, however, as the low pressure center sits near the region and keeps the weather unsettled.
WEDNESDAY PRECIPITATION TYPE/TIMING: Very early Wednesday morning is when things again get interesting, as the exact placement of the low pressure center will determine how much cold air will be able to rush in on the back side of the low. The current consensus is that light precipitation continues into Wednesday morning, continuing as rain for most of the night with inland areas and areas further west turning over to snow likely just before daybreak. This is where the forecast gets even trickier, as models entirely diverge on the amount of snow that falls Wednesday, which relates directly to where the surface low pressure is, determining the amount of moisture and the surface temperatures, wind direction, etc. The premium forecast dives into this even more, but uncertainty remains very high. Still, the official forecast is for This is for inland 1-3 inches of steady, light snow through the entire day on Wednesday will be likely in inland Fairfield and Westchester Counties. In New Haven county and along coastal locations of Fairfield and Westcheter, the forecast is up for 2 inches of snow to fall, with it similarly very possible that little to no snow falls or accumulates. Regardless, there is the threat for snow through the day on Wednesday with the stalled low pressure center to our east and unstable conditions resulting in light precipitation, and further inland I would be surprised if we didn’t see at least some accumulations. Any light snow dies down Wednesday evening into early Thursday morning.
WINDS: The current wind forecast, at its peak, is for sustained winds of 25-30 mph at the coast with gusts to 50-55 mph and inland sustained winds of 20-25 mph with gusts to 40 mph. As I explained last night, the National Weather Service had to up their Wind Advisory to a High Wind Watch with expected gusts to 60 mph, but running the latest data I don’t believe that Southwestern Connecticut is at the biggest high wind threat, with Long Island being at risk instead. The NWS just recently saw the same thing, and lowered their Watch back to a Wind Advisory. With gusts only expected to get to 50-55 mph along coastal CT/Westchester and sustained winds only to 30 mph or so, I doubt we end up hitting High Wind Warning criteria (the most relevant of which is gusts to 58 mph). There remains a threat of that, but most models do not show that because the storm continues to look like it will go either over us or just to our east. If it were to trend west at the last second, then gusts to 60 mph along the coast would be possible, but that threat currently appears much more confined to Long Island. Still, as explained more in the Premium forecast, numerous impacts are possible from winds of the forecast speed even if they aren’t a little stronger. I want to detail the timing, which has shifted slightly. First, the start of the dangerous winds has been slightly pushed back as the storm slightly slowed down. Winds start to really pick up it seems now around 10 AM, with the strongest winds occurring between 12 PM and 2 PM and dying down around 4 PM. Gusty winds continue through around 7 PM, at which point they will have weakened enough so as to not cause any more damage. This means that the majority of impacts are likely to come between 10 AM and 4 PM tomorrow, and travel will be most impeded then, so coastal residents should plan accordingly. Once winds peak and begin to die down early tomorrow afternoon there will likely not be a second peak. This is something that we will easily be able to track, but I expect the early afternoon is where we observe peak power outages across the area. I’ll continue to track the winds very closely, though, as this is the aspect of the storm that for coastal residents will be far have the largest impacts.
COASTAL FLOODING: Coastal flooding will be a large threat due to the track of the low pressure center, and so I said the National Weather Service should upgrade their Coastal Flood Advisory. They have, and it is now a Coastal Flood Watch for coastal flooding 2-3 feet above average, in line with the expectations I laid out previously. High tide comes to Bridgeport and Stamford just past noon, so in immediate coastal areas be aware for some serious coastal flooding between 11 AM and 1 PM. It will be about a foot to a foot and a half higher than it has been already today, and I expect immediate coastal roads to be flooded over and become impossible. For those not right at the immediate coast this is not a large issue, but for those right at the coast this could actually be the largest impact of the storm. Again, we have seen worse with coastal flooding, but it will make coastal travel more difficult and result in problems for many for the beaches.
CONCLUSION: A very strong Nor’ Easter will be impacting the region tomorrow into Wednesday. Inland freezing rain could be the primary precipitation type tonight before the heavier precipitation comes in, resulting in icy conditions before sun-up north of I-84. Overall, 1.5-2.5 inches of rain is expected with gusty winds and coastal flooding at the coast, ending as up to a couple inches of snow inland and some flakes flying down to the coast. Impacts, though widespread, are not likely to be severe, though again the Premium forecast dives deeper into the actual impact forecast. At 1500 words, though, I feel I have covered all that I want to with this storm for now, and I hope you stay tuned for additional updates, and consider signing up for Premium if you haven’t already which has daily email updates with summaries of the latest posts and detailed impact analysis!