With every passing hour, the likelihood of our 1st significant winter storm of the season increases. The computer guidance is getting a better and better handle on the basic structure of this storm system, and how it will unfold. Because of the complexity of this storm’s structure… we will continue to have details to iron out, right up until the start of the storm. This will make pinpointing snow totals, timing, and impacts a bit tricky. So lets start digging in…
– 8am to 12pm Sunday : Snow/sleet begins
– 5pm to 9pm Sunday : Snow/Mix tapers
– Sunday Evening : Cloudy, scattered snow/sleet/rain showers
– 12am to 6am Monday : Snow redevelops
– 6pm Monday to 12am Tuesday : Snow tapers off
Total Snow Accumulation Probability:
– Over 1 inch : 95%
– Over 3 inches : 75%
– Over 6 inches : 65%
– Over 8 inches : 60%
(*probabilities based off Poughkeepsie area and Mid Hudson Valley. Chances increase as you go north and up in elevations, and chances decrease as you go further south)
– Zone 1,2,5&6: Snow… mixing with sleet Sunday afternoon. Mostly snow Monday
– Zone 3&4: Mostly snow on Sunday, some sleet possible… best chance for heaviest snow on Monday
– Zone 7&8: Snow… mixing with sleet and freezing rain Sunday afternoon. Mostly snow Monday
– Zone 9: Wintry mix, possibly light rain late Sunday. Changing to snow on Monday
Confidence : Medium
– Good handle on the basic structure of the storm
– Confident about timing for the first half of the storm
– Timing and location of Monday portion is lower confidence
The first half of this storm, the Sunday portion, we have a good handle on. It’s the 2nd half of the storm, on Monday, that could give us some unexpected surprises. But lets go through Sunday first.
The moisture likely arrives from mid to late morning from west to east. You can see the purple on the map is indicative of sleet… not snow. The reason is because there could be a thin layer of mild air in the atmosphere, that melts the snowflakes before they refreeze on their way to the ground. We will have to see how thick that layer of warmth is, and if it stays further south. But this could result in some parts of the region seeing a burst of snow, quickly change to a snow/sleet mix by late morning. It’s one of the details that we’ll be monitoring.
As the storm moves in, the entire region should be seeing snow and/or sleet falling by lunchtime on Sunday. Surface temperatures are expected to hold in the mid to upper 20s all day Sunday, plenty cold enough for frozen precipitation. The major question that we will be focusing on, is how much mild air at the mid levels of the atmosphere we get. That will determine whether we see snow, sleet or freezing rain. But as we look at the progress of the storm, you can see that the first half of this system begins to taper off late Sunday afternoon and early Sunday evening…
Futurecast Radar Loop : 7am Sunday – 1am Monday
The bulk of the moisture associated with the warm front moves through by around 7pm. This will result in most of the precipitation tapering off Sunday evening, and the Hudson Valley is left with scattered light snow, sleet and freezing rain showers. A rather icy Sunday night lined up for anyone with travel plans. But there should be a low pressure developing off the NJ coast, that will stall out south of Long Island. So just at the end of this radar loop, you can see some of the wintry mix changing back to snow, and the snow beginning to fill in a bit on the radar image. So when considering the first part of the storm (Sunday)… we’re leaning on the lighter side of accumulations. When considering total snowfall amounts… what falls on Sunday will likely be about 25% to 30% of the total snowfall accumulations this storm brings.
This leads us to the most uncertain part of the forecast.
Futurecast Radar: 1am Monday – 1am Tuesday
This is a futurecast loop of the final 24 hours of this storm, from 1am Monday morning. Notice how disorganized this storm system becomes. A coastal low pressure system develops as the Upper Level Low pressure moves to the coast. It results in the redevelopment of a steady moderate snow across much of NY and the Hudson Valley. This is easily the lowest confidence portion of our forecast. Because if the position of the upper level low is further south or north… the band of moderate snow could be outside of our area. If the coastal storm develops too late, the snow could be east of the Hudson Valley. There are a lot of tricky pieces here… and Upper Level Low pressure systems are notoriously difficult to forecast.
So when we talk about snowfall accumulations, if things play out just right, over 12″ of snow is certainly possible. At the same time, if the details are different from what we currently project… snowfall amounts could be significantly less than what you’re seeing and hearing. So this is something to keep in mind when thinking about this storm’s forecast… even as we roll out our preliminary snowfall forecast tonight. Remember… the 1st half of this storm… the Sunday portion… we have a moderately good level of confidence. It’s the Monday portion… that remains more of a wildcard. While a lot of guidance suggests the Hudson Valley is in the focal point of heaviest snow… like the GIF images above… we all need to take this into consideration.
Any way you slice it… this should be a wild start to the winter season! Thanks for your support!!