Upslope Snows

[bobbutts]

Scott from skivt-l is talking about some significant snows for N. VT
http://list.uvm.edu/cgi-bin/wa?A2=ind1012A&L=SKIVT-L&T=0&F=&S=&P=27715

 

[Glenn]

Looks like there's some coastal action on Sunday/Monday...but it may stay out ot sea.

 

[Puck it]

Looks like there's some coastal action on Sunday/Monday...but it may stay out ot sea.

May take a day next week off if this holds for some snow.

 

[psyflyer]

Woke up to two inches here at Burke. Hoping for more this week-end.

 

[billski]

Would you please explain what upslope snow is? dmc patiently explained last year, but I seem to have lost it. Sorry & Thanks.

 

[deadheadskier]

If that holds true, I might have my sites set on Jay for 12/11

 

[drjeff]

Would you please explain what upslope snow is? dmc patiently explained last year, but I seem to have lost it. Sorry & Thanks.

Here you go Billski, as simply as I can put it.

When you take an air mass thats flowing along at a low altitude, smoothish surface (like say over a lake or some other body of water), it will pick up some moisture (heck even if it doesn't flow over a body of water it will still have some moisture in it)

When that air mass hits something with some elevation, like say some mountains, that moisture ladened air flowing smoothly along the surface in relative "warm" lower air gets forced up into the colder, dryer air of the elevation. As that moisture ladened air gets forced up, the moisture gets squeezed out of it, and if it's cold enough at elevation, you get snow fall in the lee of the object that forced the air upwards.

It's quite similar to lake effect snow, in both how it happens and also how wind direction specific it can be.

 

[WinnChill]

Yep, you pretty much got it DrJeff! When you force air upwards against mountainsides, it cools...when it cools to saturation, it precipitates out or rains/snows. The more you force it upwards, the heavier the showers get.

You're hearing the "upslope" forecast a lot since we're getting into a persistent northwest flow the next several days which is prime (over the long haul) for northern resorts (especially NEK). We try to fine tune accumulations up a little more for N/NW facing slopes and lower end ranges for S/SE facing slopes in this particular pattern.

 

[billski]

Yep, you pretty much got it DrJeff! When you force air upwards against mountainsides, it cools...when it cools to saturation, it precipitates out or rains/snows. The more you force it upwards, the heavier the showers get.

You're hearing the "upslope" forecast a lot since we're getting into a persistent northwest flow the next several days which is prime (over the long haul) for northern resorts (especially NEK). We try to fine tune accumulations up a little more for N/NW facing slopes and lower end ranges for S/SE facing slopes in this particular pattern.

I've got it. Well, just a little bit. Is upslope snow independent of a storm snow? For example, we see this big honker of a system in the mid central states, barreling towards us. Is this considered up-slope snow, or just regular snow? Are not these large storm clouds fairly high in altitude so there's nothing "up" about it? Is up-slope only a "local" phenomena?

What mountains in the Northeast traditionally benefit from upslope snow? Let me guess, Jay, Bolton, maybe Stowe. All because of Champlain, right? What about Southern VT? NH?

So an upslope snow usually only benefits one side(s) of the hill, right? It's all dumped out before it gets to the top?

 

[WinnChill]

I've got it. Well, just a little bit. Is upslope snow independent of a storm snow? For example, we see this big honker of a system in the mid central states, barreling towards us. Is this considered up-slope snow, or just regular snow? Are not these large storm clouds fairly high in altitude so there's nothing "up" about it? Is up-slope only a "local" phenomena?

What mountains in the Northeast traditionally benefit from upslope snow? Let me guess, Jay, Bolton, maybe Stowe. All because of Champlain, right? What about Southern VT? NH?

So an upslope snow usually only benefits one side(s) of the hill, right? It's all dumped out before it gets to the top?

Like DrJeff said, depending on moisture, it can occur on its own but it can also enhance snow/rainfall during a more significant storm too. Yeah, Jay/Stowe and Bolton make out the best in a dominant northwest flow...some southern VT peaks can get it in a westerly flow. Upslope is diminished with lower hilltops of NH though but can still be a factor in a southeasterly flow.

 

[riverc0il]

All because of Champlain, right? What about Southern VT? NH?

Champlain has minimal effect on NoVT snow, it is not wide enough to have dramatic impacts like the great lakes. Minimal, perhaps. Up slope doesn't need a catch, as far as I understand it, so the lake and upslope are not related.

 

[deadheadskier]

Champlain has minimal effect on NoVT snow, it is not wide enough to have dramatic impacts like the great lakes. Minimal, perhaps. Up slope doesn't need a catch, as far as I understand it, so the lake and upslope are not related.

I wonder if there's a way to measure/quantify Lake Champlain's effect.

The Lake is 12 miles across at it's widest and it's probably only 30-40 miles between the Northern Greens and the Dacks. Yet, during that stretch systems load up and drop 100+ more inches of snow on the Northern Greens than the Dacks.

Then on the other side of the Greens, you've got an even wider swath of flat land (not as flat as the Champlain Valley, but still pretty flat) before it hits the Presidentials, yet save for Mt. Washington, they receive 100 + inches less than the Northern Greens.

 

[riverc0il]

I wonder if there's a way to measure/quantify Lake Champlain's effect.

The Lake is 12 miles across at it's widest and it's probably only 30-40 miles between the Northern Greens and the Dacks. Yet, during that stretch systems load up and drop 100+ more inches of snow on the Northern Greens than the Dacks.

Then on the other side of the Greens, you've got an even wider swath of flat land (not as flat as the Champlain Valley, but still pretty flat) before it hits the Presidentials, yet save for Mt. Washington, they receive 100 + inches less than the Northern Greens.

Not really flat at all in NoNH. There are a crap ton of mountains all the way from the NoVT spine to the Presis. I think it is more the flatness hitting a wall than the lake. I read somewhere you needed a significantly fetch than Champlain provides to get lake effect (at least significant). The 100"+ difference between NoVT and NoNH isn't due to the lake.

Edit: Wikipedia says a fetch of about 62 miles is required (http://en.wikipedia.org/wiki/Lake_effect_snow). Plus, parts of Champlain freeze during the winter.

 

[deadheadskier]

as I said, relatively, but not as flat as the Champlain Valley.

This is a shot from the top of Mansfield last winter. The Presis do very much look like a wall and Washington averages what 300? Wildcat across the street reports 200, but I think that's inflated.

 

[kingdom-tele]

Champlain has minimal effect on NoVT snow, it is not wide enough to have dramatic impacts like the great lakes. Minimal, perhaps. Up slope doesn't need a catch, as far as I understand it, so the lake and upslope are not related.

right steve.

Bill, I always looked at this way, upslope snow is related to wind direction and the moisture that is being transported IN the atmosphere - elevation = more squeeze = higher snow totals. even places like holland, vt will end up with 2-3x the snow lower elevations like newport will have

lake effect is snow is just that, elevation doesn't play as much of a roll because the moisture doesn't need the squeeze to = higher totals

I think

either way - heres hoping for some magical terrain induced snow totals over the next week.

 

[UVSHTSTRM]

Just my non meteorlogical take on the northern greens vs the whites.

Greens get to squeeze out the last drops of moisture from moisture laden clouds that re-form just after the dacs and then hit the northern greens where they finally meet their demise. Also doesn't lake Champlain freeze over?

 

[WinnChill]

Just my non meteorlogical take on the northern greens vs the whites.

Greens get to squeeze out the last drops of moisture from moisture laden clouds that re-form just after the dacs and then hit the northern greens where they finally meet their demise. Also doesn't lake Champlain freeze over?

Yep, you got it. The orientation of the Greens really get the best first shot at them in W-NW flow...less makes it over to the Whites unless it's more NW-N. With these next waves of moisture retrograding (moving east to west) this weekend and early next week, both the Whites and northern Greens will get a fair shot at some snow.

 

[Huck_It_Baby]

Relevant link from Ski the East:

http://www.skitheeast.net/blogs/bd/...-Kooks-.DSH.-Northwest-Flow-and-Upslope-Snow/

 

[billski]

Relevant link from Ski the East:

http://www.skitheeast.net/blogs/bd/...-Kooks-.DSH.-Northwest-Flow-and-Upslope-Snow/

I like it, complete with pictures!

 

[rocojerry]

Is the moisture from this weeks event most likely from the hudson bay? or wrap around from the atlantic?

One things for sure, I love it!

Edit: Link above says Atlantic!