NNE Fall Thread

[alex]

I'd take it...

[adk]

2 hours ago, klw said:

GFS says:

That's totals through Sunday night....4-8 in highest greens modeled to fall from sky...yea...that makes sense. I think it will verify to 3-5" under foot above 2500ft. 

I do agree that some high elevation ADK terrain will get 10"

[J.Spin]

Lots of great snow talk in the latest BTV AFD:

 

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...

As of 351 PM EDT Wednesday...Still plenty of uncertainty during this time period with evolution of mid/upper level system...associated track of surface low pres...how quickly cold air advects on backside and amount of qpf. This uncertainty also presents complication in snow levels for Saturday into Sunday...along with potential impacts. Using a blend between the faster gfs with the cold air advection and warmer ecmwf solution and later arrival of cold air...still supports some accumulating snowfall across the higher terrain this weekend.

 

A prolonged upslope/backside deformation precip event is expected Saturday into Sunday with additional precip amounts of 0.50 to 1.5 across our region...with highest amounts in the mountains...especially northern dacks and northern/central vt mountains and parts of the Northeast Kingdom.

 

The 12z Ecmwf is stronger and closes off 5h/7h circulation over eastern PA by 12z Saturday...with our cwa still in the warm sector...until 00z Sunday...delaying arrival of mountain snow. Meanwhile...gfs is quicker with progged 850mb temps dropping below 0c by 12z over the dacks and across the entire region by 18z Saturday. Given closed 5h/7h circulation...expecting plenty of deep layer moisture advecting back into our region...with very favorable upslope signatures present. This includes northwest between 925mb to 850mb of 35 to 45 knots...strong 850 to 700mb uvv`s...and good 850 to 500mb moisture. The difficult question is how quickly the cold air advects into the region and associated lowering snow levels. Current forecast shows snow developing between 12z-15z dacks summits and between 18z-21z for the northern Green Mountain Summits. NAM/GFS bufkit soundings show freezing levels dropping to 1500 feet overnight Saturday into Sunday...with snow levels lowering to base areas. How much snow will stick with extremely warm ground temps...and potential impacts with leafs on the trees and power outages is still too early to tell. The potential for 6 or more inches is possible at summits with several inches of heavy wet snow across the higher mountain towns of the northern dacks/green mountains.

 

Eventually the vertically stacked area of low pres lifts toward the canadian maritimes by early next week and moisture profiles dissipate. Will mention pops near 100% for Saturday into Sunday in the favorable upslope areas...and taper off to chance by early next week. Expecting a large temp contrast from valleys to summits with highs mainly 30s mountains and 40s valleys on Saturday and upper 20s mountains to mid 40s valleys on Sunday. Slightly warmer weather arrives by early next week...as clouds and precip dissipate.

[powderfreak]

Yeah great AFD...let Taber take the wheel and we get an awesome snow discussion.

[CoastalWx]

Ugh at the warm ground talk. Haven't we learned yet?

[Lava Rock]

2 hours ago, adk said:

That's totals through Sunday night....4-8 in highest greens modeled to fall from sky...yea...that makes sense. I think it will verify to 3-5" under foot above 2500ft. 

I do agree that some high elevation ADK terrain will get 10"

I love how all of VT, most of NH and some of MA have snow probability, but most of ME, aside from mtns get nothing.

[Hitman]

so refreshing to hear talk of snow.  near 80f down here today.

[powderfreak]

36 minutes ago, CoastalWx said:

Ugh at the warm ground talk. Haven't we learned yet?

I do think it's valid here.  It's not like we are jamming a -10C 850 airmass in here.  If I'm getting 36F -SN in town on Sun AM that's not sticking. 

I think you'll need to be 32F or lower to accumulate in this.  A couple inches of rain and then some 34F snows will struggle unless it's like 1-2"/hr.

[CoastalWx]

9 minutes ago, powderfreak said:

I do think it's valid here.  It's not like we are jamming a -10C 850 airmass in here.  If I'm getting 36F -SN in town on Sun AM that's not sticking. 

I think you'll need to be 32F or lower to accumulate in this.  A couple inches of rain and then some 34F snows will struggle unless it's like 1-2"/hr.

36 and -SN won't really stick any time of year. I don't care if a super nova happened an hour before it snows.....if it comes as modeled, it's sticking when it drops to 32.  With all that talk of dynamics, I wouldn't worry about ground temps..especially when cold rain already chills it off.

[powderfreak]

2 hours ago, CoastalWx said:

36 and -SN won't really stick any time of year. I don't care if a super nova happened an hour before it snows.....if it comes as modeled, it's sticking when it drops to 32.  With all that talk of dynamics, I wouldn't worry about ground temps..especially when cold rain already chills it off.

See I disagree.  If the ground is frozen and its been cold before hand, 33-36F snow will stick, even at 1.5sm -SN.  Heck you can still get freezing rain for a while at like 35F if it was -10F the day before.  I've seen plenty of times where its really cold ahead of WAA and its snowing and sticking well into the mid-30s.  Or the ground was frozen and cold prior to a cutter and you get 6-12 hours of above freezing before it changes back to -SN and its sticking at 33-36F. 

You will need to be in the deformation band in this event and rates will determine it.  Once its below 32F of course it'll stick...its the warm ground and marginal temps at whatever elevation band that ends up being where it'll be an issue.  If we've got cold, frozen ground at all elevations, you lean towards the higher end of guidance, even at elevations well below the progged freezing level.  In October, unless its either below freezing or precipitating at 0.1"/hr+, its going to struggle to accumulate.

The warm ground debate to me isn't an issue to elevations or spots that are 29-31F and snowing...its the spots below the freezing level where it'll make a big difference.  I think we all assume below 32F will stick fine.  Sometimes accumulations occur like up to 1500ft lower than the freezing level if the ground is cold and frozen in mid-winter...with warm ground, maybe its only the freezing level (or up to 500ft lower) that sees anything stick.  That's how I look at the warm ground argument.  It's not simply warm ground = no snowfall, but it does have an impact when dealing with elevation events in how low the accumulating snow gets.

Practically, I look it at like if it snows all Saturday night at 34F at the office/base area village/1500ft (freezing level say 925-950mb)...with a cold/frozen ground in January that accumulation will be much better, than it would be in October following a torch and inches of rain.

[wxeyeNH]

Back a few years ago on Memorial Day weekend  I got 3" of snow. Heavy thundersnow that started at around 35F and fell to 32F when it ended 3 hours later. Accumulation was about 7 to 10pm so it was dark.   Grass was entirely covered and stayed covered halfway through the next day.  Obviously at the end of May the sun angle is very high.  I don't know what the surface layer temperature was before that snow event but it must have been pretty darn warm but the snow sure did stick.  So I don't give the warm ground temperature thing too much credence.   

[dryslot]

9 hours ago, tamarack said:

51 at my place with 0.02" of condensed mank thru this morning.  I spent yesterday in the woods about 75 miles north of home, and the mid 40s with fresh east winds and no sun made things a dite chilly.

Mid 40's on an east wind is not very pleasant, Most should get a taste of those high 40's at the beginning of next week

[Lava Rock]

Local mets already knocking rain totals down. Seems so predictable anymore. Be lucky to get 1". Better than nothing.

[adk]

12 hours ago, powderfreak said:

See I disagree.  If the ground is frozen and its been cold before hand, 33-36F snow will stick, even at 1.5sm -SN.  Heck you can still get freezing rain for a while at like 35F if it was -10F the day before.  I've seen plenty of times where its really cold ahead of WAA and its snowing and sticking well into the mid-30s.  Or the ground was frozen and cold prior to a cutter and you get 6-12 hours of above freezing before it changes back to -SN and its sticking at 33-36F. 

You will need to be in the deformation band in this event and rates will determine it.  Once its below 32F of course it'll stick...its the warm ground and marginal temps at whatever elevation band that ends up being where it'll be an issue.  If we've got cold, frozen ground at all elevations, you lean towards the higher end of guidance, even at elevations well below the progged freezing level.  In October, unless its either below freezing or precipitating at 0.1"/hr+, its going to struggle to accumulate.

The warm ground debate to me isn't an issue to elevations or spots that are 29-31F and snowing...its the spots below the freezing level where it'll make a big difference.  I think we all assume below 32F will stick fine.  Sometimes accumulations occur like up to 1500ft lower than the freezing level if the ground is cold and frozen in mid-winter...with warm ground, maybe its only the freezing level (or up to 500ft lower) that sees anything stick.  That's how I look at the warm ground argument.  It's not simply warm ground = no snowfall, but it does have an impact when dealing with elevation events in how low the accumulating snow gets.

Practically, I look it at like if it snows all Saturday night at 34F at the office/base area village/1500ft (freezing level say 925-950mb)...with a cold/frozen ground in January that accumulation will be much better, than it would be in October following a torch and inches of rain.

I'm with Scott on this one. Warm wet ground eats up snow and compacts it quickly.  That warm moisture perspires upwards and compacts snow too.

 

[CoastalWx]

12 hours ago, powderfreak said:

See I disagree.  If the ground is frozen and its been cold before hand, 33-36F snow will stick, even at 1.5sm -SN.  Heck you can still get freezing rain for a while at like 35F if it was -10F the day before.  I've seen plenty of times where its really cold ahead of WAA and its snowing and sticking well into the mid-30s.  Or the ground was frozen and cold prior to a cutter and you get 6-12 hours of above freezing before it changes back to -SN and its sticking at 33-36F. 

You will need to be in the deformation band in this event and rates will determine it.  Once its below 32F of course it'll stick...its the warm ground and marginal temps at whatever elevation band that ends up being where it'll be an issue.  If we've got cold, frozen ground at all elevations, you lean towards the higher end of guidance, even at elevations well below the progged freezing level.  In October, unless its either below freezing or precipitating at 0.1"/hr+, its going to struggle to accumulate.

The warm ground debate to me isn't an issue to elevations or spots that are 29-31F and snowing...its the spots below the freezing level where it'll make a big difference.  I think we all assume below 32F will stick fine.  Sometimes accumulations occur like up to 1500ft lower than the freezing level if the ground is cold and frozen in mid-winter...with warm ground, maybe its only the freezing level (or up to 500ft lower) that sees anything stick.  That's how I look at the warm ground argument.  It's not simply warm ground = no snowfall, but it does have an impact when dealing with elevation events in how low the accumulating snow gets.

Practically, I look it at like if it snows all Saturday night at 34F at the office/base area village/1500ft (freezing level say 925-950mb)...with a cold/frozen ground in January that accumulation will be much better, than it would be in October following a torch and inches of rain.

Then why have the big weenie disco for catpaws at 36F? They are worried about the dynamics and the potential for brief heavy snow and the warm ground argument becomes BS. Again if it's 36F, you aren't getting much snow anytime of year. Find me an example of when 36F gave 3-4" of snow. I'm not talking about coatings. Wxeye gave an example of what I am saying. The dynamics and combination of the energy used to melt, naturally gets the temp as close to 32F as possible. Now of course 5SM -Sn at 32 this time of year won't do anything, but that AFD wasn't written because they are thinking catpaws might not stick...the issues are if a band of heavier snow develops which renders the warm ground argument useless.

[CoastalWx]

1 hour ago, Lava Rock said:

Local mets already knocking rain totals down. Seems so predictable anymore. Be lucky to get 1". Better than nothing.

You should do well.

[CoastalWx]

I guess it's how you interpreted that AFD. If it's just some -SN at 35F than yes, the ground temp would matter of you wanted small accumulations. But if something like the 00Z euro op happened in extreme nrn VT, that's a classic example of how ground temps would mean absolutely nothing. That is a quick 40F -32F paste job. All you need is a skim coating on the ground and it's off to the races. That 00z solution was nuts for nrn VT.

[powderfreak]

12 hours ago, wxeyeNH said:

Back a few years ago on Memorial Day weekend  I got 3" of snow. Heavy thundersnow that started at around 35F and fell to 32F when it ended 3 hours later. Accumulation was about 7 to 10pm so it was dark.   Grass was entirely covered and stayed covered halfway through the next day.  Obviously at the end of May the sun angle is very high.  I don't know what the surface layer temperature was before that snow event but it must have been pretty darn warm but the snow sure did stick.  So I don't give the warm ground temperature thing too much credence.   

Yeah, because you had thundersnow and extremely heavy rates.  If that happens, anyone is going to accumulate.  Even hail at 85F accumulates when it comes down hard/convectively.  

[powderfreak]

19 minutes ago, CoastalWx said:

I guess it's how you interpreted that AFD. If it's just some -SN at 35F than yes, the ground temp would matter of you wanted small accumulations. But if something like the 00Z euro op happened in extreme nrn VT, that's a classic example of how ground temps would mean absolutely nothing. That is a quick 40F -32F paste job. All you need is a skim coating on the ground and it's off to the races. That 00z solution was nuts for nrn VT.

Yeah maybe we just see it differently.

Ive seen plenty of elevation events each year and a lot of times I've seen it pouring snow at 34F but really struggling to accumulate in the base area.  You end up with widely different snow totals and like 4" of translucent slop in the parking lots.  

Theres only so far it can dynamically cool if the freezing level is at like 3000ft.  I think that's where the warm ground comes in.  A lot of early/late season upslope events don't have the power of a deform band but can still tick off 0.1"/hr QPF.  You end up with the snow level getting stuck somewhere mid-slope but a frozen ground would help in those areas seeing snow at 33-35F.  

[CoastalWx]

11 minutes ago, powderfreak said:

Yeah maybe we just see it differently.

Ive seen plenty of elevation events each year and a lot of times I've seen it pouring snow at 34F but really struggling to accumulate in the base area.  You end up with widely different snow totals and like 4" of translucent slop in the parking lots.  

Theres only so far it can dynamically cool if the freezing level is at like 3000ft.  I think that's where the warm ground comes in.  A lot of early/late season upslope events don't have the power of a deform band but can still tick off 0.1"/hr QPF.  You end up with the snow level getting stuck somewhere mid-slope but a frozen ground would help in those areas seeing snow at 33-35F.  

I agree. I guess in the scheme of hazards when talking about trees and powerlines being down...they were worried about the potential for heavy, wet snow in spots. If that's the case, warmer ground really means nothing. Even that late April 2010 event comes to mind. But, all you need is a cold rain and then flip to paste...and it's off to the races, if rates suffice. You can also easily have a 2-3K isothermal 32F layer thanks to the power of melting. We see that here on the coast a lot.  But overall it comes down to rates. Clearly 34-35 and 4SM -SN won't do anything. Not sure if you saw the 00z euro, but that was mighty snowy in extreme nrn areas..maybe just a bit north of you. Jay Peak crusher. There is a lot of uncertainty with the deformation and upslope signal it seems.

[powderfreak]

15 minutes ago, CoastalWx said:

I agree. I guess in the scheme of hazards when talking about trees and powerlines being down...they were worried about the potential for heavy, wet snow in spots. If that's the case, warmer ground really means nothing. Even that late April 2010 event comes to mind. But, all you need is a cold rain and then flip to paste...and it's off to the races, if rates suffice. You can also easily have a 2-3K isothermal 32F layer thanks to the power of melting. We see that here on the coast a lot.  But overall it comes down to rates. Clearly 34-35 and 4SM -SN won't do anything. Not sure if you saw the 00z euro, but that was mighty snowy in extreme nrn areas..maybe just a bit north of you. Jay Peak crusher. There is a lot of uncertainty with the deformation and upslope signal it seems.

Yeah it's all rate dependent.  I also look at warm ground as maybe the difference between 6-8" and 3-5"...maybe you lose .1-.2" QPF allowance on getting that initial layer down.  I guess the thing with the warm ground is how that's been used in several big time events to justify NO accumulation over the past few years.  I look at it like it's going to snow but even steady 0.5-1"/hr would obviously benefit from cold ground.  But it won't make or break the event, just something to consider when nailing down accums.  I'm sure on Sunday I'll be able to find examples of where a colder ground surface would've helped at some elevation band.

Anyway, in my mind the snow threat is with upslope for here.  The deform will be too far northwest to me, taking a model blend.  But that backside wind dynamics, strong closed mid-level lows, and decent low level moisture will get a good response from the mountains at some point.  It'll matter more if it can get going for 6 hours or more like 12 hours in a steady state.  

[eyewall]

I am definitely excited to find some elevation on Sunday whether it is 2 inches or 6 that falls up there. Anyway this is what greeted me this morning ahead of the rain:

 

[CoastalWx]

44 minutes ago, powderfreak said:

Yeah it's all rate dependent.  I also look at warm ground as maybe the difference between 6-8" and 3-5"...maybe you lose .1-.2" QPF allowance on getting that initial layer down.  I guess the thing with the warm ground is how that's been used in several big time events to justify NO accumulation over the past few years.  I look at it like it's going to snow but even steady 0.5-1"/hr would obviously benefit from cold ground.  But it won't make or break the event, just something to consider when nailing down accums.  I'm sure on Sunday I'll be able to find examples of where a colder ground surface would've helped at some elevation band.

Anyway, in my mind the snow threat is with upslope for here.  The deform will be too far northwest to me, taking a model blend.  But that backside wind dynamics, strong closed mid-level lows, and decent low level moisture will get a good response from the mountains at some point.  It'll matter more if it can get going for 6 hours or more like 12 hours in a steady state.  

6z GFS puts you in the deformation area as well later Saturday.

[ORH_wxman]

Warm ground argument is complete bunk if you are actually getting heavy snow. It only matters in marginal rates.

[eyewall]

I would agree. If the rates are high enough it will stick. 

[ORH_wxman]

Just now, eyewall said:

I would agree. If the rates are high enough it will stick. 

Like 1 mile vis snow (while quite steady and normally accumulates in winter) will def have trouble at 34F in October. Even occasional moderate/heavy bursts that go back to light snow will have trouble...sometimes when the snow level is struggling to descend, you'll get this I have noticed. It will all of the sudden burst down in huge flakes to 1/2 mile or even briefly lower and you get stickage, but then it lightens back to 1 mile vis with smaller flakes and the temps is like at that 33-34F mark...during the time it lightens up, you'll actually lose accumulation from the heavier burst. But none of that qualifies as heavy snow, so that all falls under marginal rates...and the snow level itself is probably contributing. It might be consistent 1/4 mile another 1000 feet higher.

 

But get under true heavy snow and warm ground is powerless to stop accumulations. You'll also not typically get heavy snow at 34F except for the first few minutes to perhaps as long as an hour...the temps lowers to 32-33F fairly quickly because of the latent cooling from melting.

[eyewall]

1 minute ago, ORH_wxman said:

Like 1 mile vis snow (while quite steady and normally accumulates in winter) will def have trouble at 34F in October. Even occasional moderate/heavy bursts that go back to light snow will have trouble...sometimes when the snow level is struggling to descend, you'll get this I have noticed. It will all of the sudden burst down in huge flakes to 1/2 mile or even briefly lower and you get stickage, but then it lightens back to 1 mile vis with smaller flakes and the temps is like at that 33-34F mark...during the time it lightens up, you'll actually lose accumulation from the heavier burst. But none of that qualifies as heavy snow, so that all falls under marginal rates...and the snow level itself is probably contributing. It might be consistent 1/4 mile another 1000 feet higher.

 

But get under true heavy snow and warm ground is powerless to stop accumulations. You'll also not typically get heavy snow at 34F except for the first few minutes to perhaps as long as an hour...the temps lowers to 32-33F fairly quickly because of the latent cooling from melting.

Very true and I have witnessed this many times. 

[alex]

New cam is up:

http://moose-lodge-1.click2stream.com/

I'm definitely in for the standard angle, but I'd like to get it to be a bit brighter

[CoastalWx]

27 minutes ago, ORH_wxman said:

Like 1 mile vis snow (while quite steady and normally accumulates in winter) will def have trouble at 34F in October. Even occasional moderate/heavy bursts that go back to light snow will have trouble...sometimes when the snow level is struggling to descend, you'll get this I have noticed. It will all of the sudden burst down in huge flakes to 1/2 mile or even briefly lower and you get stickage, but then it lightens back to 1 mile vis with smaller flakes and the temps is like at that 33-34F mark...during the time it lightens up, you'll actually lose accumulation from the heavier burst. But none of that qualifies as heavy snow, so that all falls under marginal rates...and the snow level itself is probably contributing. It might be consistent 1/4 mile another 1000 feet higher.

 

But get under true heavy snow and warm ground is powerless to stop accumulations. You'll also not typically get heavy snow at 34F except for the first few minutes to perhaps as long as an hour...the temps lowers to 32-33F fairly quickly because of the latent cooling from melting.

Right, that's my point. It's the most ridiculous argument ever. That's fine in marginal rates, but given the issues of power outages and tree damages etc that the AFD was mentioning, warm ground is the least of the issues. Latent cooling is a powerful process. 

[ORH_wxman]

10 minutes ago, CoastalWx said:

Right, that's my point. It's the most ridiculous argument ever. That's fine in marginal rates, but given the issues of power outages and tree damages etc that the AFD was mentioning, warm ground is the least of the issues. Latent cooling is a powerful process. 

 

Probably the single most useful sentence to use as a baseline about warm ground is:

 

-Warm ground impeding accumulations is almost entirely rate-dependent

 

You can just pin that on the 10 commandments of forecasting right below "Thou shalt not forecast over 12" in a SWFE".