If you look at the radar… this storm looks like it’s really coming down across the Hudson Valley as we approach sunset. Unfortunately, that’s just not the case. Despite the moderate (dark blues & light greens) to even locally heavy (dark greens & yellows) snowfall returns coming in on radar… there is a patch of VERY dry air in the mid levels of the atmosphere. The result is that despite a very active radar… virtually no snow is reaching the ground north of Putnam and Rockland counties.
The magnitude of this dry air was no where near accounted for accurately. The question we were focused on, was how far north the snow band seen on radar would get. By all accounts, our forecast would have been on track if not for the unexpected strength of the dry air. But look at this newly modeled weather sounding…
Now this sounding has a lot of information on here that likely means nothing to most people, but the sounding is a useful tool for us to take a snapshot cross section of the atmosphere. The key take away are the red and green lines. The red line represents the air temperature from the top of the atmosphere, all the way down to the surface (1000mb on the left side of the graph). So it’s 36°F at this location. The dew point is 23° at this location, and so the air is quite dry. When dealing with a snow event, the dew point and the air temperature need to be fairly close… because we’d want to see humidity levels around 70% to 80% on average to get the snow to reach the ground.
But as dry as the air is at ground level… just go up into the atmosphere a bit, to around 850mb. Notice how the red and green lines go in opposite directions from each other. The further the lines are away from each other, the drier the air is, and the closer they are, the more humid the air. At 850mb (just below cloud level) the dew point and air temperature are over 20 degrees Celsius apart! The air is EXTREMELY DRY! Because if you notice, if you go up a little higher in the atmosphere, to 700mb… the red and blue lines are right on top of each other, roughly 100% humidity. The air is PLENTY moist enough to support the snow.
This is the entire problem… and it was not accounted for by any of the earlier computer guidance. The end result, is likely the following… if you haven’t seen snow yet, you’re likely not going to see any snow from this system.
That’s the truth of the matter, ladies and gentlemen. The air is just much too dry to erode that much dry air. Even with moderate precipitation falling into that dry air… it’s not moistening the air fast enough in most locations. So pretty much anywhere north of I-84, is likely to see no snow at all from this system, as a result of the dry air. Those areas weren’t going to see much anyway… but instead of 2 or 3… maybe 4 inches in places like Kingston, New Paltz, Poughkeepsie and Monticello… you’re likely going to see zero inches.
Now… in some parts of the Mid Hudson Valley, the snow will win out, and moisten up the atmosphere enough. There will be places where light to moderate snow falls tonight, near the I-84 corridor. The best chances will be for areas east of the Hudson River, but it’s really contingent upon banding of the snow. Where the heavier bands set up on radar, will determine where the best chances of snow falling are. It wouldn’t surprise us to see someone get a couple inches in parts of southern Dutchess county.
This map may be a little too pessimistic, but you get the general picture. All the accumulating snow is focused near and south of I-84… because the magnitude of the dry air is just so strong. So anyone near or south of I-84… expect snow to develop if it hasn’t already… and an inch or two is likely near the I-84 corridor. As you go further south, into zones 8 & 9 (Rockland, Putnam and Westchester), an additional 2 to 4… maybe 5 inches of snow could fall tonight. That would be enough to get those areas into the low end of the forecast range… but it is certainly a possibility there.
The dry air has completely evaporated this snowstorm for the Hudson Valley. There will be some snow tonight in the Mid Hudson Valley and points south, but exactly how much depends on the resilience of the dry air. Unfortunately, it’s extremely difficult, if not impossible, to tell just how long the dry air will hold ground. Most indicators are that it will give way to the moisture and snow will fall… but there is uncertainty for sure. We’ll have more updates as the night continues.
This storm is not pulling any punches. Not only was it a major challenge to decipher where the banding of snow would set up… we’re now trying to iron out if and when this dry air will ever ease it’s grip on the Hudson Valley.
The radar looks great for the southern half of the Hudson Valley at this hour… but the observations tell a completely different story. Everything north of the black line is evaporating before reaching the ground… because the air is so incredibly dry across the Hudson Valley. So areas like Newburgh, Middletown, Montgomery, Fishkill, even Poughkeepsie… it may look like the snow is falling or is about to fall… but it’s really just cloudy, breezy and cold.
The dry air was always a concern for the northern Hudson Valley and Catskills… where it’s safe to say there will be no snow from this system.
Basically… the areas where we originally highlighted as a coating to 2 inches…
those areas will officially see nothing. We were always skeptical of the snow pushing into those areas, and it’s all but been confirmed now, that the snow will never reach the Catskills or the northern Hudson Valley.
The areas where we originally had 2 to 6 inches forecasted…
there we have added another wildcard factor, in the form of very dry air. The snow band has pushed into parts of this area on radar… but the dry air is causing it to evaporate before reaching the ground. As the snow continues to fall into the atmosphere, it should moisten the air and begin reaching the ground at some point… but exactly when, is anyone’s guess. Our latest guidance suggests that as the storm rotates eastward tonight, it will swing bands of moderate snow northwestward… into the Hudson Valley. So periods of snow are certainly possible late this afternoon and tonight… but the strength of this dry air is the wildcard.
The areas where we had originally forecasted 6 to 12 inches
Those areas still stand to see a decent snowfall from this system. The snow has eroded much of the dry air in these areas, and you’re now looking at 8 to 12 hours of steady snowfall. As a result, as these bands of snow rotate in, snowfall rates could exceed 1 inch per hour at times. We think a general 4 to 8 inches is likely… with some areas possibly reaching 12 inches down by I-287. The extreme southern Hudson Valley could see someone come in with a foot of snow.
Bust of a Storm…
We spent 2 solid days trying to drive home the unpredictability with this storm system. We published our snowfall forecast, but really did not want to focus on the totals… because there were just too many variables at play. Figuring out the exact progression and cutoff of the northern edge of the snow, was always going to lead to areas getting “ripped off”… but the question was exactly where.
A lot of schools closed today… and the rest opted for early releases… and it’s very likely that not a single flake will have fallen by the end of the normal school day. “Wait and see” was a message we tried to convey, to minimize the number of cancelled and altered plans in areas where the weather remained cloudy and dry.
This storm got a LOT of air time from the news networks, because the NYC area stands to get clobbered by this system, along with the southern most portions of our viewing area. But the northern half of the viewing area was never expected to be majorly impacted by this storm… and we did our best to communicate that.
When dealing with such complex and complicated storm systems… it’s crucial to listen to the details of the forecast… especially when the forecasters are emphasizing the conflicting data and uncertain data that they’re seeing.
Still Some Surprises Yet to Come…
This storm isn’t over… not by a LONG shot. Now, for some parts of the area (Catskills & Northern HV), this was never your storm to begin with, so we’re not talking to you per say. However, in the mid and lower Hudson Valley… you need to keep watching this storm.
It may not have done what you expected so far today… honestly, it wasn’t expected to do all that much by this point regardless… but we need to watch as this system wraps up off shore this afternoon. The low pressure will sit and rotate off shore for the next 12 to 18 hours… and as it does, it’s expected that bands of snow will rotate in NW off the ocean.
So you see… there will be snow to contend with for many parts of the Hudson Valley later today and into tonight. So we’ll have more updates as the day progresses.
We mentioned on Tuesday in the evening live stream, that this storm reminded us of the blizzard a few years back that shut down the Hudson Valley. That storm also expected a sharp cut off across the mid-Hudson Valley, and we weren’t sure exactly where it would be. In that storm, Montgomery and Newburgh got 0.0″ of snow… but a half hour drive to your south… in Warwick, they saw 12″ of snow. When all is said and done, this storm will likely look a lot like that… we shall see.