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powderfreak

NNE Fall Thread

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5 minutes ago, CoastalWx said:

COuld be a nice slug of snow tonight up in VT. Pretty strong s/w moving in with decent lift in the DGZ and some instability aloft. 

Yeah that's a good shortwave. Could even get some snow showers further south into S NH and maybe MA. 

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1 hour ago, wxeyeNH said:

Brief light to moderate snow shower past through last hour.  Temps 34F.  Tried to whiten the ground but a bit too warm.  Ridges above me got a bit white while down in Bristol 700 feet below it was raining with mixed cat paws. 

Looking at  Alex's webcam looks like a  couple of inches up in BWoods.....

Look at all of those kids ruining the snowpack. Devastating.

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10 minutes ago, alex said:

Omg don't get him started!

Looks like your going to get a refresher tonight with the next front.  Add a couple more inches.  Then a warm up in a couple of days to melt the fake upslope fluff.  Now the Euro looks totally different late week with a much weaker system but much colder too with a snowy scenerio.  No consistency so will take each day at a time. 

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Event totals: 1.1” Snow/0.16” L.E.

 

Details from the 1:00 P.M. Waterbury observations:

 

New Snow: 0.6 inches

New Liquid: 0.03 inches

Snow/Water Ratio: 16.7

Snow Density: 6.0% H2O

Temperature: 31.6 F

Sky: Light Snow (2-5 mm flakes)

Snow at the stake: 1.0 inches

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This was a perfect event for skiing.

It was all wet and pasty and dense with small flakes until about halfway through the flakes started getting bigger.  Still a decent amount of graupel too.

Then topped with an inch of sparkling stuff.  This was no upslope fluff, my guess is the average ratios would be under 10:1.  

A couple shots around the 1500ft Stake.

IMG_7463.JPG.3d2e66adce09fa7076e806d32110b120.JPG

IMG_7464.JPG.86c4c15f6d8dc417e772e2ee602bfaf2.JPG

And I was wrong in that I was estimating 3" at the base but the Stake showed an additional 3" to the 1" this morning so total would be 4" at that elevation in the photos.  I'm going to leave the snow report as 3" though for 1500ft as I sort of low-balled myself and it makes no sense to up the amounts now.  

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19 hours ago, powderfreak said:

As usual the 3km NAM/WRF is on crack and juiced up to like 1.4" QPF... which it does every time it seems. 

Something to watch over the next 48 hours though... in a relatively boring pattern we'll take some flakes and hopefully get the ground back to white in the mountain valleys after today's torch finished it all off.

There is something fundamentally wrong with how that model produces precipitation in terrain. There are plenty of other hi-res models that don't go as wild as the nested NAM. 

Some of the WFOs out west have hypothesized that it produces QPF in sub-saturated situations when you might expect rime to form on the mountains in a cloud, but no actual precip.

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Tonight could be sneaky, especially around onset. The DGZ is pretty deep to start, and models want to warm the low levels through the night. So if that doesn't happen, and the lower levels stay cold, the DGZ stays deep and the ratios might be pretty good, even with the low QPF event.

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1 hour ago, wxeyeNH said:

Looks like your going to get a refresher tonight with the next front.  Add a couple more inches.  Then a warm up in a couple of days to melt the fake upslope fluff.  Now the Euro looks totally different late week with a much weaker system but much colder too with a snowy scenerio.  No consistency so will take each day at a time. 

Big work week so I'll be in Boston tonight through Thursday... We'll see what I come back to!

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1 hour ago, OceanStWx said:

Tonight could be sneaky, especially around onset. The DGZ is pretty deep to start, and models want to warm the low levels through the night. So if that doesn't happen, and the lower levels stay cold, the DGZ stays deep and the ratios might be pretty good, even with the low QPF event.

The HRRR is drilling some QPF right to the coast... with some good snow growth could have some folks waking up to white lawns even out away from the mountains.

W3hVt4X.png

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3 minutes ago, powderfreak said:

The HRRR is drilling some QPF right to the coast... with some good snow growth could have some folks waking up to white lawns even out away from the mountains.

It wouldn't really surprise me.

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1 hour ago, OceanStWx said:

There is something fundamentally wrong with how that model produces precipitation in terrain. There are plenty of other hi-res models that don't go as wild as the nested NAM. 

Some of the WFOs out west have hypothesized that it produces QPF in sub-saturated situations when you might expect rime to form on the mountains in a cloud, but no actual precip.

 

I just saw a post the other day related to this topic - Jim Steenburgh and his group have been looking at it as well:

 

http://wasatchweatherweenies.blogspot.com/2017/11/precipitation-overprediction-problems.html

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18 minutes ago, J.Spin said:

 

I just saw a post the other day related to this topic - Jim Steenburgh and his group have been looking at it as well:

 

http://wasatchweatherweenies.blogspot.com/2017/11/precipitation-overprediction-problems.html

Yep, that study was referenced in the discussion. I mean it is important to note that the HRRR is the same resolution (3 km) and it doesn't seem to have the same problem.

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11 minutes ago, OceanStWx said:

Yep, that study was referenced in the discussion. I mean it is important to note that the HRRR is the same resolution (3 km) and it doesn't seem to have the same problem.

That's a great point... the HRRR doesn't go buck wild like the NAM.  What you said about riming situations seems right... because the model just goes apesh*t at the terrain but you can tell its out to lunch when it has 0 precip around the peaks and then wants to try and bring 0.1"/hr liquid to the peaks.  There's just a certain look when you know to take it seriously and when its too ridiculous.  The precip gradients around here are crazy but even the NAM situations are too much.  It'll just try to crush 0.1"/hr for like 12 hours while there's really no other precipitation anywhere else....and as we know it can be localized but if it's going to be doing that type of QPF it would also be occurring upstream or downstream to some effect.

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Just now, powderfreak said:

That's a great point... the HRRR doesn't go buck wild like the NAM.  What you said about riming situations seems right... because the model just goes apesh*t at the terrain but you can tell its out to lunch when it has 0 precip around the peaks and then wants to try and bring 0.1"/hr liquid to the peaks.  There's just a certain look when you know to take it seriously and when its too ridiculous.  The precip gradients around here are crazy but even the NAM situations are too much.  It'll just try to crush 0.1"/hr for like 12 hours while there's really no other precipitation anywhere else....and as we know it can be localized but if it's going to be doing that type of QPF it would also be occurring upstream or downstream to some effect.

And relatively speaking, we don't even have it that bad. Out west, it's spitting out feet of powder above 5,000 feet that never happens.

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2 minutes ago, OceanStWx said:

And relatively speaking, we don't even have it that bad. Out west, it's spitting out feet of powder above 5,000 feet that never happens.

Ha yeah... here its usually only 1-1.5 feet off ;). 

Going off the 18z runs... the HRRR has 0.3" QPF for Mansfield, while the 3km NAM has 0.9". 

That's about par for the course...we all know this clipper-like thing isn't bringing anyone 0.9" QPF but for the peaks 0.3" seems a bit more reasonable, even if that might be a little high.

 

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4 minutes ago, powderfreak said:

Largest snowfall to date for the summit station with 6.0" finding its way into their precip can.  Rare for their elevated precipitation can to top my ground based method.

23844365_10103243012583650_4189266428866

MWN up to 0.47" and 4.7" for the event, with some additional definitely between 18-00z. 

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This afternoon’s thoughts on the upcoming event from the BTV NWS forecast discussion are below:

 

Area Forecast Discussion

National Weather Service Burlington VT

347 PM EST Sun Nov 26 2017

 

.NEAR TERM /THROUGH MONDAY NIGHT/...

As of 345 PM EST Sunday...12Z guidance still locked in on a mid level trough and related weak surface low just to our north tonight. The trough can be seen on water vapor imagery northwest of Ottawa moving rapidly southeast. The associated clouds will be reaching the St Lawrence Valley by sunset, with light snow developing between 5-7pm as warm air advection commences. Elsewhere light snow should quickly overspread the entire region during mid to late evening. Not a lot of moisture with this system, basically a few hundreths in the valleys to near a quarter inch in the mountains and southern St. Lawrence county. Looking at somewhere about 15-20:1 SLR so thinking a dusting to 1" at lower valley elevations except some of the snow may become lake- effect enhanced off Ontario from 01-08z in southern St. Lawrence county with a bit more accumulation (2-4") there. Orographic lift across the northwestern slopes of the Adirondacks and western slopes of the central/northern Green Mountains with upwards of 2-4" at higher summits with 1 to 3" at the bases.

 

I just took a look at the radar and you can already see moisture pushing into the area:

 

26NOV17A.gif

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Well, that was pretty quick in terms of the precipitation shown on the radar.  The air probably hadn’t dried out too much from the previous event, but it was already snowing here at the house as of ~7:00 P.M.

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18 minutes ago, J.Spin said:

This afternoon’s thoughts on the upcoming event from the BTV NWS forecast discussion are below:

 

Area Forecast Discussion

National Weather Service Burlington VT

347 PM EST Sun Nov 26 2017

 

.NEAR TERM /THROUGH MONDAY NIGHT/...

As of 345 PM EST Sunday...12Z guidance still locked in on a mid level trough and related weak surface low just to our north tonight. The trough can be seen on water vapor imagery northwest of Ottawa moving rapidly southeast. The associated clouds will be reaching the St Lawrence Valley by sunset, with light snow developing between 5-7pm as warm air advection commences. Elsewhere light snow should quickly overspread the entire region during mid to late evening. Not a lot of moisture with this system, basically a few hundreths in the valleys to near a quarter inch in the mountains and southern St. Lawrence county. Looking at somewhere about 15-20:1 SLR so thinking a dusting to 1" at lower valley elevations except some of the snow may become lake- effect enhanced off Ontario from 01-08z in southern St. Lawrence county with a bit more accumulation (2-4") there. Orographic lift across the northwestern slopes of the Adirondacks and western slopes of the central/northern Green Mountains with upwards of 2-4" at higher summits with 1 to 3" at the bases.

 

I just took a look at the radar and you can already see moisture pushing into the area:

Good sign that MSS is at 3/4SM.

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