First Snow of the Season?!

Based on the latest information it seems like someone in our area is going to see their first snowfall of the season. The emergence of high latitude blocking in the EPO and NAO domains will bring about a very potent trough across the east coast. This does not have the look of a classic east coast storm. The formation is quite odd actually. But essentially upper level energy gets squeezed between the SE ridge (hence our mild weather lately) and a west based -NAO. The phasing of these energies happens early on, and what ultimately heads our way is a matured upper level low packing tons of vorticity. The trickiest part of this setup is determining where the secondary low forms, and how much cold air it can generate and for who.

Right now, my thinking is the secondary forms at or inside the 40/70 benchmark. Normally this is considered a good thing for coastal areas to see some snow, but not in this type of a setup where the primary ULL is well to our N&W. See below.



This location of the 500mb ULL normally keeps our boundary level temperatures too warm. However, some guidance has the mid center doing a loop - thanks to the blocking aloft - south of NYC and going back off the coast. This will make things very interesting for those N&W of NYC. Ultimately, I think the setup for accumulating snow along the coast is not a great one, but perhaps our first look of snow falling (and maybe even at a good clip at some point) is in the cards. It does seem like those in peak elevations are in for a nice accumulation if everything holds as is right now. Let’s see what happens!

Elevation is going to play a big role in who gets any real accumulations. Looks to me like NW NJ, eastern PA and the Catskills could see some decent accums.

To keep things simple I’m going to segment this system into two parts. Part I is Thursdays rain and Part II is Fridays potential snow.

For part I, we’re looking at a widespread 1-1.5” rainfall event. Some models are projecting a squall-like like. Check out this 700mb vorticity map. Gorg.

hyde345 wrote:Elevation is going to play a big role in who gets any real accumulations. Looks to me like NW NJ, eastern PA and the Catskills could see some decent accums.

NWS so far agrees with you.Eastern PA has WSW up for 3 to 7 inches.My forecast here has shifted pretty much to an all rain event in Monroe NY.Will welcome anything to reduce the wildfire risk.

I woke up to this

Frank_Wx wrote:I woke up to this

are we sure the models are set to the right year? its not just doing test runs on data from 40 years ago?

I have to say, it is fascinating the gap between what some models are showing and what the public forecasts are. There are models showing several inches of snow, if not a foot, in areas where the public forecasts are for all (or mostly all rain). In those particular areas someone (or something in the case of the models) will be very wrong - or at least late to the party.

billg315 wrote:I have to say, it is fascinating the gap between what some models are showing and what the public forecasts are. There are models showing several inches of snow, if not a foot, in areas where the public forecasts are for all (or mostly all rain). In those particular areas someone (or something in the case of the models) will be very wrong - or at least late to the party.

Yea…

Snow maps don’t do well with elevation events. Take them with a massive grain of salt. It’s going to be a tricky forecast regardless.

I don’t want to overstate it, but I just don’t typically see models THAT far out of synch with the public forecasts. Usually it’s a matter of slight degrees. Not (to take my backyard for example) a forecast of all rain and no snow, when the models show anywhere from 4-14” of snow (depending on which model and run). If nothing else a good example of being careful not to take models verbatim - or will it be the forecasts that should not be taken verbatim? Hmm.

heehaw453 wrote:Please use the snow depth delta maps for this. The 10:1 maps have no concept of surface temps which imo there will be a lot of white rain outside of highly elevated areas. I will be happy to see flakes and get a coating.

Excellent advice - on both fronts.

billg315 wrote:

heehaw453 wrote:Please use the snow depth delta maps for this. The 10:1 maps have no concept of surface temps which imo there will be a lot of white rain outside of highly elevated areas. I will be happy to see flakes and get a coating.

Excellent advice - on both fronts.

Thats still impressive for NW NJ, 3-5 in mid Nov, I am sure anyone there will be happy to take that. Shoot I had a yearly total of 5 inches last year, if I got 3-5 (I know we will just see rain here, it's okay) this early I would think at least last year would be smushed. I really hope we do not have a repeat of the last 2-3 winters here in NYC area. Good luck to those in elevation, my dad is going to VT on Fri, says chance snow but not going to be any real accumulation, any thoughts on this as some GFS runs have shown nearly 2-3 ft in mountains which is where their second home is.

6Z EURO


IF TRUE BL temps are marginal and it will stick with teh ehavier rates to cold surfaces and especially elevation areas



Dew Points at Freezing will help cool the boundary layer and allow stickage to ocld surfaces


Positive Snow Depth - Isn't any and all snow POSITIVE??




This is like a mid-late March storm - elevations are going to do well.

Great gaphic representation of snow and elevations this time of year

Early season #snow event likely for Northeast. Matches topography well since airmass is marginally cold for snow at the surface. As my professor always said..."2 ways to get to cold air, travel a few hundred miles north, or a few hundred feet up in elevation." #winter pic.twitter.com/2EOCwnMzLU

— Tom Niziol (@TomNiziol) November 19, 2024

SNOW WILL DUMP with this FRONTGENESIS

Sorry, folks, been really busy today. Good discussion in here, as always. Bill, you raise a great point about the disparity between media forecasts and operational guidance, and heehaw raised a great parallel point about using actual accumulation maps versus raw output. My $.02 is that it’s a combination of factors. First, I think it’s a fear to be “that guy” who is “hyping” a particular forecast, as the media tend to do often. But, by the same token, they create their own problem by just presenting raw model output and using it as their own forecast. When it busts, they look bad and instead of owning the moment, they just blame the models. There’s a difference between hype and supporting a bold forecast with sound analysis and supporting evidence, but the folks in the media continuously fail to do this. I think if they took more responsibility for their forecasts and held themselves accountable, the general public would be much more understanding (to a point - if you’re not a good forecaster, you’re just not good and have to figure out how to improve, and it is all about ratings at the end of the day). Explain WHY they busted in a 15-second teachable moment. But they don’t. And this leads to my second point: A lot of them don’t use what they learn in school about the hard science and apply it to the models, which are TOOLS for a forecast, not a forecast themselves. So, when it comes to situations like this, where meteorologists can actually demonstrate their skill above raw guidance, they don’t seize the opportunity. The NWS is different; they rarely stray from guidance to take the “big stands” because it creates a lot of headache for them internally, and is why they can be so late to the party sometimes. Caveat to this: Mount Holly WFO. They are usually phenomenal.

To heehaw’s point about the maps, I think you really need to be observant and understand how different areas behave in certain situations. For example, this exact same situation occurred in November 2016 as I posted earlier. I was way out on a limb with that when I called for elevations to see 3-5”, and I still busted too low. As soon as the rain turned to snow, accumulations started almost immediately. How? Well, a couple reasons. First, the snow was falling at night, so even in a very marginal airmass, the lack of insolation aided with slight surface radiational cooling. Secondly, wet snow is much more efficient at removing heat from the surface than dry snow because of the much higher water content. Because of water’s very high specific heat, it takes a lot of energy to change its state, in this case from solid (snowflake) to liquid during the melting process when it hits the ground. This makes it highly efficient at cooling the surface just enough so that the rate of melting becomes less than the contact rate. The maps can approximate this, but it’s up to the meteorologist to adjust for these factors all over their forecast area. And I just don’t think a lot of people in the media take the time to look into such specifics and the whole picture. They’re on for 3-5 minutes, and that’s it.

I’m sticking with my idea that anybody outside the urban corridors and north of I-78 will see accumulations from this by Friday morning. Firstly, because I think this ends up further south than current guidance indicates. Secondly, I’ve learned to NEVER underestimate these strong upper-level lows, especially when they are so negatively tilted. Funny things seem to happen around them lol we shall see - 12z operationsals shifted ever so slightly north today. I don’t see it. As heehaw noted previously, the NAO blocking has continued to trend stronger and further south, and the anomaly maps show the effect on the trough. I think this is a signal that the operationals are too far north on today’s 12z’s.

So far, my thoughts mentioned above regarding the southward shift of tonight’s runs is 3/3 - NAM, RGEM, and ICON all followed through. GFS and GEM up next.

While we wait, take a look at the below image, which is an analysis of critical thicknesses (fancy name for various atmospheric thermal proxies for the rain/snow line throughout different sections of the vertical profile). Basically, they can help identify where there are any warm tongues aloft depending on where each line is in reference to the others. Now, if you recall from my video, I mentioned that I felt that this front would very steep throughout the column rather than more gently sloped, which would mean that once the front goes through, there would be a pretty rapid transition to snow behind it, and that the front and precipitation shield would arrive simultaneously. Well, if you look at the below image and note how the critical thicknesses are stacked on top of one another (except the 1000-850mb thickness, which is heavily skewed by the surface temps, and easily overcome for getting snow at the surface), this is pretty clear confirmation in-situ that my ideas were correct I just wanted to demonstrate what it looks like in reality rather than just a conception.

Thanks, CP! If nothing else, at least I can say that my ideas have had merit up to this point. I can’t ask for more than that.

Just checked, and at 3am I am officially getting snain, so the changeover is underway, right on schedule.

Frank saw your Snow Index, you think theres a 15% chance NYC sees 1 inch of snow? How? It is far too warm and as far as I can see the furthest south any kinds of watches, warnings or HWO is around monticello, NY. But just the fact that we are talking of this in Nov. is better than past years. And good luck to those up north! Anyone in the warning around monticello? Could see 12-18 in the highest elevations thats nuts for Nov. 22nd, or am I just forgetting what a normal winter is usually like lol

CPcantmeasuresnow wrote:For probably the first time in my life I look at a setup like this and I am not agonizing over the rain snow line which I seem to be on the edge of in every run. At 600 asl and 50 miles NNW of NYC I'm teetering on that line. Why don't I care, because we need precip desperately, (For the fires, this isn't a commentary pro or con on climate change) as long as we get 1-2 inches of qpf I'll be happy. Of course I'd be even happier if a good portion of that is white, but for once I won't agonize over it.

Nice job as always NJ Strong crew. Special thanks to RB who was on this very early. I still don't think this will play out as white as he's thinking but his analysis as always is sound.

After getting alerts last week here as a result of the wildfires in Greenwood Lake some 10 miles away from me, agree with you CP on the precip to help alleviate the risks.
Rb and the crew were on this but I agree with you, think this is an Eastern PA-Catskill special for measurable snow.Will be a nice surprise tomorrow morning if we get the ground covered.Right now light rain, 44 and calm winds.