NNE Winter Thread

[powderfreak]

Temps will rise again tonight. There is stronger SW flow in the OH valley that will reach NE.

Yep...BTV had a comment about that in the AFD. Highs were reached early in the day east of Champlain, with slowly falling temps, while in NY temps will start to rise as thicknesses rise ahead of the next system.

Interesting little pattern though as usually we don't see such rapid transitions between CAA and WAA.

[Nittany88]

Ah Spring time in Vermont...any snow we had is melted, went for a run outside in shorts, great time of the year.

Oh wait.

It's December 3rd.

[ctsnowstorm628]

Meh. All my snow is melted, and its not even a torch. 37F. Woooo.

Last night's high Td's FTL.

[J.Spin]

I really did not think it was supposed to be this cold... not even close to our hourly forecast.

At noon we are forecast to be:

3,600ft...36F

2,600ft...40F

1,500ft...44F

Actual is:

3,600ft...26F

2,600ft...28F

1,500ft...32F

It keeps dropping too... temp has fallen about 5-8F across the board since 5am.

We'll be 10-12F lower than guidance today.

That’s pretty cool from a snow preservation standpoint – I checked the Bolton Valley Weather Station at 2,100’ and it’s similar on the west side as well; sub freezing at that elevation:

[dryslot]

Well, At least 1 less torch day this week as today failed........

[Lava Rock]

Well, At least 1 less torch day this week as today failed........

Really? We pegged 50F. What did you hit?

[dryslot]

Really? We pegged 50F. What did you hit?

46F, Was suppose to be 50F

[Nittany88]

AS OF 346 PM EST MONDAY...FOR TUESDAY...INCREASING SOUTHERLY FLOW

AHEAD OF AN APPROACHING COLD FRONT IS EXPECTED AS A 925-850MB

40-50KT JET TRAVERSES THE REGION. UNSEASONABLY WARM TEMPS ARE

EXPECTED AND WILL BE EVEN WARMER THAN THE PREVIOUS DAYS IN THE

LOWER TO MID 50S...SOME 10-15 DEGREES ABOVE NORMAL FOR EARLY

DECEMBER! SHORT-TERM GUIDANCE CONTINUES TO BE IN GOOD AGREEMENT

ON LATE TIMING OF FRONTAL PRECIP WHICH LOOKS TO IMPACT THE REGION

AFTER 21Z TUESDAY THROUGH TUESDAY NIGHT. MUCH LIKE THE LAST

FRONT...MILD TEMPS AHEAD OF THE BOUNDARY WILL KEEP RAIN AS THE

PREDOMINANT PRECIP TYPE...BUT COOLER AIR BEHIND THIS FRONT WILL

BEGIN TO TRANSITION PTYPE TO SNOW SHOWERS LATE AT NIGHT OVER THE

NORTHERN MOUNTAINS...ESPECIALLY THE ADIRONDACKS.

A COOLER AND MORE SEASONABLE AIR MASS WILL USHER IN BEHIND THE

FRONT DURING THE DAY WEDNESDAY WITH A NORTHWESTERLY LOW-LEVEL

FLOW REGIME SETTING UP. HIGHS WILL GENERALLY OCCUR DURING THE

MORNING HOURS AND SLOWLY FALL THROUGH THE DAY. ANY RAIN/SNOW

SHOWERS IN THE VALLEYS WILL TRANSITION TO SNOW SHOWERS BUT THE

MAIN FOCUS WILL BE ACROSS HIGHER TERRAIN AS A TRAILING SHORTWAVE

AND UPPER TROUGH MOVE ACROSS THE REGION LATE IN THE DAY/EVENING.

CONDITIONS CONTINUE TO FAVOR UPSLOPE SNOW SHOWERS ACROSS THE

ADIRONDACKS AND NORTHERN GREENS... WITH SEVERAL INCHES OF SNOW

EXPECTED. FORECAST FROUDE NUMBERS INDICATE FLOW WILL BE UNBLOCKED

SO EXPECT MUCH OF THE PRECIPITATION WILL FALL CLOSE TO THE

MOUNTAIN SUMMITS AND ON THE LEE SIDE...FAVORING LOCATIONS SUCH AS

JAY PEAK...NEWPORT AND THE REST OF THE NORTHEAST KINGDOM.

MOISTURE DOES THIN THROUGH THIS TIME-FRAME AS WELL THOUGH SO IT

WILL LIKELY BE A QUICK BURST OF SNOW FROM 00-03Z THURSDAY...THEN

WANING AFTER MIDNIGHT.

[powderfreak]

Some nice undercast skies at times today above 3,500ft....

[Nittany88]

Some nice undercast skies at times today above 3,500ft....

That second shot is amazing!

[powderfreak]

A COOLER AND MORE SEASONABLE AIR MASS WILL USHER IN BEHIND THE

FRONT DURING THE DAY WEDNESDAY WITH A NORTHWESTERLY LOW-LEVEL

FLOW REGIME SETTING UP. HIGHS WILL GENERALLY OCCUR DURING THE

MORNING HOURS AND SLOWLY FALL THROUGH THE DAY. ANY RAIN/SNOW

SHOWERS IN THE VALLEYS WILL TRANSITION TO SNOW SHOWERS BUT THE

MAIN FOCUS WILL BE ACROSS HIGHER TERRAIN AS A TRAILING SHORTWAVE

AND UPPER TROUGH MOVE ACROSS THE REGION LATE IN THE DAY/EVENING.

CONDITIONS CONTINUE TO FAVOR UPSLOPE SNOW SHOWERS ACROSS THE

ADIRONDACKS AND NORTHERN GREENS... WITH SEVERAL INCHES OF SNOW

EXPECTED. FORECAST FROUDE NUMBERS INDICATE FLOW WILL BE UNBLOCKED

SO EXPECT MUCH OF THE PRECIPITATION WILL FALL CLOSE TO THE

MOUNTAIN SUMMITS AND ON THE LEE SIDE...FAVORING LOCATIONS SUCH AS

JAY PEAK...NEWPORT AND THE REST OF THE NORTHEAST KINGDOM.

MOISTURE DOES THIN THROUGH THIS TIME-FRAME AS WELL THOUGH SO IT

WILL LIKELY BE A QUICK BURST OF SNOW FROM 00-03Z THURSDAY...THEN

WANING AFTER MIDNIGHT.

This is just an awesome AFD. Always love the details of the upslope events.

Nittany, maybe you know this as you seem to be "in-tune" at BTV, but what are the Froude Numbers? And how does that relate to "indicating that the flow will be unblocked"?

That's the one thing I've never been able to understand or forecast, is where the heaviest upslope precipitation will fall. Its fairly easy to see synoptically when it will occur, but does the heaviest fall on the west side or the east side? Of course, the heaviest almost always falls right on the Spine at the ski resorts like Jay/Smuggs/Stowe/Bolton (except extreme events like Jan 1-3, 2010 when the heaviest was BTV, well removed from the Spine), but as far as inhabited areas, sometimes the heaviest precipitation falls in lee communities (like Waterbury, Stowe, Johnson, up RT 100 corridor) and then there's the type of event that smokes West Bolton-Underhill-Cambridge while lee side towns see flurries.

Just sample QPF from past events... but a lot of times the heaviest QPF ends up falling right on the spine and west like the rain event last June:

Then there are the events where the heaviest falls here east of the spine. In most events, both sides of the spine will get appreciable QPF, but trying to figure it out the favored side for each event has always been a puzzle to me.

[J.Spin]

CONDITIONS CONTINUE TO FAVOR UPSLOPE SNOW SHOWERS ACROSS THE

ADIRONDACKS AND NORTHERN GREENS... WITH SEVERAL INCHES OF SNOW

EXPECTED. FORECAST FROUDE NUMBERS INDICATE FLOW WILL BE UNBLOCKED

SO EXPECT MUCH OF THE PRECIPITATION WILL FALL CLOSE TO THE

MOUNTAIN SUMMITS AND ON THE LEE SIDE...FAVORING LOCATIONS SUCH AS

JAY PEAK...NEWPORT AND THE REST OF THE NORTHEAST KINGDOM.

Glad to see this getting some discussion, as I was going to ask about it – seems like they are knocking it up a notch in terms of the technicalities of upslope forecasting. This is the first time I’ve seen the discussion allude to the unblocked flow and Froude Numbers (which are velocity ratios as far as I can see – but hopefully one of the meteorologists on the board can fill us in on how they are used in this meteorological context).

[Nittany88]

This is just an awesome AFD. Always love the details of the upslope events.

Nittany, maybe you know this as you seem to be "in-tune" at BTV, but what are the Froude Numbers? And how does that relate to "indicating that the flow will be unblocked"?

That's the one thing I've never been able to understand or forecast, is where the heaviest upslope precipitation will fall. Its fairly easy to see synoptically when it will occur, but does the heaviest fall on the west side or the east side? Of course, the heaviest almost always falls right on the Spine at the ski resorts like Jay/Smuggs/Stowe/Bolton (except extreme events like Jan 1-3, 2010 when the heaviest was BTV, well removed from the Spine), but as far as inhabited areas, sometimes the heaviest precipitation falls in lee communities (like Waterbury, Stowe, Johnson, up RT 100 corridor) and then there's the type of event that smokes West Bolton-Underhill-Cambridge while lee side towns see flurries.

Just sample QPF from past events... but a lot of times the heaviest QPF ends up falling right on the spine and west like the rain event last June:

Then there are the events where the heaviest falls here east of the spine. In most events, both sides of the spine will get appreciable QPF, but trying to figure it out the favored side for each event has always been a puzzle to me.

CONDITIONS CONTINUE TO FAVOR UPSLOPE SNOW SHOWERS ACROSS THE

ADIRONDACKS AND NORTHERN GREENS... WITH SEVERAL INCHES OF SNOW

EXPECTED. FORECAST FROUDE NUMBERS INDICATE FLOW WILL BE UNBLOCKED

SO EXPECT MUCH OF THE PRECIPITATION WILL FALL CLOSE TO THE

MOUNTAIN SUMMITS AND ON THE LEE SIDE...FAVORING LOCATIONS SUCH AS

JAY PEAK...NEWPORT AND THE REST OF THE NORTHEAST KINGDOM.

Glad to see this getting some discussion, as I was going to ask about it – seems like they are knocking it up a notch in terms of the technicalities of upslope forecasting. This is the first time I’ve seen the discussion allude to the unblocked flow and Froude Numbers (which are velocity ratios as far as I can see – but hopefully one of the meteorologists on the board can fill us in on how they are used in this meteorological context).

The Froude Number is a measure of whether the flow can make it over the mountains or not. It is basically a test of stability versus the wind perpendicular to the mountain trying to push it over. If the Froude Number is low, the air will not make it over the mountain and the precip backs up. If it is high, the air will flow freely over the mountains and deposit the heaviest precip on the east side.

[J.Spin]

The Froude Number is a measure of whether the flow can make it over the mountains or not. It is basically a test of stability versus the wind perpendicular to the mountain trying to push it over. If the Froude Number is low, the air will not make it over the mountain and the precip backs up. If it is high, the air will flow freely over the mountains and deposit the heaviest precip on the east side.

Nice – PF, you should find out how to calculate/use the appropriate Froude Numbers in your snowfall forecasting, then we could compare to all the snowfall obs and see how well they work in determining east side/west side snowfall numbers in upslope events.

[powderfreak]

The Froude Number is a measure of whether the flow can make it over the mountains or not. It is basically a test of stability versus the wind perpendicular to the mountain trying to push it over. If the Froude Number is low, the air will not make it over the mountain and the precip backs up. If it is high, the air will flow freely over the mountains and deposit the heaviest precip on the east side.

Cool, thanks! I'll have to do some work with the "google machine" but is that number something that the meteorologist calculates, or do the models spit out a value (like they do for say various t-storm indices)?

I guess I'll have to do some reading on it, but is it tied into lapse rates and inversion levels... or a parcels ability to rise to a certain height relative to the horizontal wind velocities acting on it?

[MaineJayhawk]

Sweet pics Freak! I was wondering if you'd post some when you mentioned fog at the surface but the summits were in the clear. You never disappoint!

[NEK_VT_Upslope_Event]

I feel like I am getting such mixed messages on the upcoming pattern for NNE. Is there a meteorologist who can summarize where things stand for the 7th-15th period based on the long range models? I have some personal business that is largely dependent on this outcome and it would help me plan immensely to know a more detailed snapshot. FYI, this is in the NEK of VT. Thanks in advance.

[N. OF PIKE]

Froude numbers hmmm. Interesting key to unlock upslope sides to be favored.

[Nittany88]

Cool, thanks! I'll have to do some work with the "google machine" but is that number something that the meteorologist calculates, or do the models spit out a value (like they do for say various t-storm indices)?

I guess I'll have to do some reading on it, but is it tied into lapse rates and inversion levels... or a parcels ability to rise to a certain height relative to the horizontal wind velocities acting on it?

Check your messages.

[weatherMA]

Down to 33F. Not very torchy.

[ctsnowstorm628]

I feel like I am getting such mixed messages on the upcoming pattern for NNE. Is there a meteorologist who can summarize where things stand for the 7th-15th period based on the long range models? I have some personal business that is largely dependent on this outcome iand it would help me plan immensely to know a more detailed snapshot. FYI, this is in the NEK of VT. Thanks in advance.

Where are you at dude?

[adk]

I've looked into the Froude numbers and the Green spine and found no real benefit and simply some added complexity. IMO the lee side of a mountain is almost always going to have greater snow depths than the windward side. No, maybe it's not from the "synoptic" (i know upslope is mesoscale but I'm using synoptic to mean snow falling from the sky) snow as the flow is blocked and deposits more on the windward side but rather from wind transport after the event. In the Greens and dacks, snow is usually followed by prevailing north, northwest or west winds. Those winds are going to quickly move powder up and over treeless summits and ridges, depositing them into leeward side gullies and bowls. Also, the wind block caused by the ridge helps the dendrites. oN the windier east sides, some of the snow crystals get battered about pretty good and lose their fluffy shape. On the leeward side there tends to be less wind and better snow dendrites.

It's no surprise that before all this fancy computer and radar technology, the old timers who built resorts built them on the leeward side in VT.

I think getting beyond that rule in my mind doesn't add a lot to a forecast. I don't need to give people GPS coordinates to the lollipop of snow that exceeds the average.

As for Wednesday into Thursday...yes, upslope pattern looks good. I'd say a good 3-4 of upslope is possible. I esp. like that the -10c isotherm is progged to move through the region. As PF and I have talked about, that's the isotherm that makes fluffy snow. And we like fluffy snow. Esp. on top of the snow brick currently draped over the mountains.

[powderfreak]

I've looked into the Froude numbers and the Green spine and found no real benefit and simply some added complexity. IMO the lee side of a mountain is almost always going to have greater snow depths than the windward side. No, maybe it's not from the "synoptic" (i know upslope is mesoscale but I'm using synoptic to mean snow falling from the sky) snow as the flow is blocked and deposits more on the windward side but rather from wind transport after the event. In the Greens and dacks, snow is usually followed by prevailing north, northwest or west winds. Those winds are going to quickly move powder up and over treeless summits and ridges, depositing them into leeward side gullies and bowls. Also, the wind block caused by the ridge helps the dendrites. oN the windier east sides, some of the snow crystals get battered about pretty good and lose their fluffy shape. On the leeward side there tends to be less wind and better snow dendrites.

It's no surprise that before all this fancy computer and radar technology, the old timers who built resorts built them on the leeward side in VT.

I have to disagree on a few things man... first the leeward side to me does get less pure snowfall quite often during upslope events, but what the leeward side does is preserve snow. That's why the resorts were built on this east side... where was the last place the snow melts in April/May? East side thanks to cold air damming. I'm also becoming less and less convinced that wind transport means anything below like 3,000ft. That is why ski patrol and myself measure snow down at that 3,000ft location during the bulk of the season, to try and mitigate stuff blowing off the ridge. But I think that's a fairly localized phenomena and not something the NWS is going to forecast heavier snow on the east side everytime because of. Its like the snow that blows off MWN ends up in Tuckerman's but I'm skeptical that Pinkham Notch 2,000ft below Tuckerman's sees any of that. Sort of like my 1,550ft snow board and stake at the base aren't seeing inflated totals from snow that has fallen in Underhill and is now being blown up and over the mountain 2,500ft higher and a couple miles away.

When I was at UVM and living on the otherside, I had plenty of days when the Underhill State Park (Teardrop) had twice as much fluff as Stowe. The 2010-2011 winter (especially early on) was huge on the west slope. Everyone I ski with was telling me how much more snow the Underhill side had (like twice the snowpack) as the east side in Dec/Jan 2010-2011. That winter the Underhill village CoCoRAHS observer came in with 220" while the Stowe village guy had 150". A 70-inch difference between one side and the other is fairly significant, IMO.

But I think this is also where we differ sometimes because you primarily focus on forecasting for the high elevations immediately along the spine. That's what I try to do for work but I'm really also fascinated with what happens down in the inhabited areas around the mountains... like why Underhill gets hit hard one time and then the next time its the RT 108 area in Stowe. You are mainly talking about that top 1,000 verts where yes, the Sunset Ridge rocks are swept clean on the west, while the Kitchen Wall to the east has a 15 foot snowpack. But below that top rocky 500-1,000ft, the snowfall can vary drastically from west slope to east slope.

We also have to realize that while the NWS has been great at pointing out snowfall for the mountains in their AFD and products, there's a reason they don't issue headlines for high elevation snow because no one lives there. Talking with Nittany, I have a very good feeling that the Froude numbers are something worth paying attention to if you are forecasting for inhabited areas on eitherside of the Spine... hopefully a certain study gets posted to BTV's website in the coming weeks that proves this...

[weatherMA]

Torch cancel. Only 32F under cloudy skies and I doubt we make it past 40F.

[powderfreak]

Torch cancel. Only 32F under cloudy skies and I doubt we make it past 40F.

36 degree rain showers moving through over here.

Maybe we'll be off to the races after this as this prcp is the warm front moving east... you guys further east may fare better today like we did up here yesterday. It'll be interesting to see how much everyone warms up this afternoon after this warm front lifts into Canada north of New England.

[NEK_VT_Upslope_Event]

Where are you at dude?

Peacham/Danville area

[adk]

I have to disagree on a few things man... first the leeward side to me does get less pure snowfall quite often during upslope events, but what the leeward side does is preserve snow. That's why the resorts were built on this east side... where was the last place the snow melts in April/May? East side thanks to cold air damming. I'm also becoming less and less convinced that wind transport means anything below like 3,000ft. That is why ski patrol and myself measure snow down at that 3,000ft location during the bulk of the season, to try and mitigate stuff blowing off the ridge. But I think that's a fairly localized phenomena and not something the NWS is going to forecast heavier snow on the east side everytime because of. Its like the snow that blows off MWN ends up in Tuckerman's but I'm skeptical that Pinkham Notch 2,000ft below Tuckerman's sees any of that. Sort of like my 1,550ft snow board and stake at the base aren't seeing inflated totals from snow that has fallen in Underhill and is now being blown up and over the mountain 2,500ft higher and a couple miles away.

When I was at UVM and living on the otherside, I had plenty of days when the Underhill State Park (Teardrop) had twice as much fluff as Stowe. The 2010-2011 winter (especially early on) was huge on the west slope. Everyone I ski with was telling me how much more snow the Underhill side had (like twice the snowpack) as the east side in Dec/Jan 2010-2011. That winter the Underhill village CoCoRAHS observer came in with 220" while the Stowe village guy had 150". A 70-inch difference between one side and the other is fairly significant, IMO.

But I think this is also where we differ sometimes because you primarily focus on forecasting for the high elevations immediately along the spine. That's what I try to do for work but I'm really also fascinated with what happens down in the inhabited areas around the mountains... like why Underhill gets hit hard one time and then the next time its the RT 108 area in Stowe. You are mainly talking about that top 1,000 verts where yes, the Sunset Ridge rocks are swept clean on the west, while the Kitchen Wall to the east has a 15 foot snowpack. But below that top rocky 500-1,000ft, the snowfall can vary drastically from west slope to east slope.

We also have to realize that while the NWS has been great at pointing out snowfall for the mountains in their AFD and products, there's a reason they don't issue headlines for high elevation snow because no one lives there. Talking with Nittany, I have a very good feeling that the Froude numbers are something worth paying attention to if you are forecasting for inhabited areas on eitherside of the Spine... hopefully a certain study gets posted to BTV's website in the coming weeks that proves this...

Great points PF. I'm going to take this into consideration. Be great to keep this discussion up this year and reach some consensus. We should pick this back up in person soon.

Looking nice downstream in BTV. Sun coming out. Might be a springy afternoon on the hill.

[weatherMA]

33F and a light rain shower moving through.

TORCHHH!

[J.Spin]

As for Wednesday into Thursday...yes, upslope pattern looks good. I'd say a good 3-4 of upslope is possible. I esp. like that the -10c isotherm is progged to move through the region. As PF and I have talked about, that's the isotherm that makes fluffy snow. And we like fluffy snow. Esp. on top of the snow brick currently draped over the mountains.

It was interesting to hear Roger Hill’s early broadcast this morning – he seemed to write off (or certainly strongly deemphasized) any snow potential with these next 2-3 systems (his discussion focused on the positive tilt of these troughs and time spent in the warm sector). For tomorrow’s system, the only mention of snow was, “tailing off with a few wet snowflakes”, and that was similar for the potential weekend/early next week system(s). He could have been focusing on a general low-elevation population forecast, but usually he’ll mention when there’s the potential for the mountains to get accumulations. The BTV NWS still seems to have the same/similar discussion that they’ve been posting over the past couple of days, with a good chunk of a paragraph allotted to the snowfall. A quick look through the models (GFS/ECMWF/NAM) does show some variation with respect to the coincidence of the cold air/moisture, but a blend of those certainly suggests some snow to me. Roger did seem intrigued by potential changes that take place after the 12^th of the month however.

[weatherMA]

Nice advisory event on the 12z GFS for Monday.