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February the climo snow month


Ginx snewx
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1 hour ago, tamarack said:

Both morning and afternoon P&Cs from GYX offer a measly <1/2" for my area, far from the 3"+ on that map, which seems based on all snow here while the AFD says otherwise.

The GYX snowfall map seems a tad bearish to me. They are overplaying the rain angle I think. The latest AFD is not inspiring, to say the least. More fog talk than anything. LOL

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11 minutes ago, PhineasC said:

@CoastalWx @dendrite

Stupid question. what level should I be looking at typically for wind direction to determine downsloping risk for here? It’s kinda complicated by the peaks in the way, sometimes the moisture flow seems more affected than other times. 

There’s a lot that factors into it, IMO.  Veering in the low levels under 850mb, speed/velocity, inversions, stability, etc.  That’s why BTV studies the Froude number so much.  In some events a certain wind direction at 850mb can result in a downslope, but then in another event that same wind direction seems to be pushing the moisture over the barrier so effectively it’s a QPF jackpot.

Here sort of explains it... if there’s blocking then the Lee side down slopes, if it’s unblocked the Lee side actually jackpots.  BTV often references it on NW flow but it goes for all wind directions... sometimes I think we do great with an east flow in a synoptic storm only to find the precip maximum ended up on the west side because it was unblocked...likewise sometimes we jackpot in NW upslope on the east side.  It’s not as simple as just looking at a straight wind direction.

“The Froude Number represents the flow of air when it comes in contact with a barrier, in Vermont's case, the Green Mountains. It is an estimation of whether the flow can make it over the mountains or not and is basically a ratio of the wind perpendicular to the mountain chain versus the atmospheric stability.

Under northwesterly flow, if the Froude Number is low (< 1), or subcritical and blocked, the air will not make it over the mountain and the precipitation will back up and fall primarily along the spine of the Green Mountains and the western slopes. If it is very low (< 0.5), the precipitation will back further west into parts of the eastern Champlain Valley and the western slopes of the Green Mountains.

If the Froude Number is high (> 1), or supercritical and unblocked, the air will flow freely over the mountains and deposit the heaviest precipitation on the east side. A Froude Number near 1 is critical and the heaviest precipitation will likely fall along the barrier.”

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15 minutes ago, powderfreak said:

There’s a lot that factors into it, IMO.  Veering in the low levels under 850mb, speed/velocity, inversions, stability, etc.  That’s why BTV studies the Froude number so much.  In some events a certain wind direction at 850mb can result in a downslope, but then in another event that same wind direction seems to be pushing the moisture over the barrier so effectively it’s a QPF jackpot.

Here sort of explains it... if there’s blocking then the Lee side down slopes, if it’s unblocked the Lee side actually jackpots.  BTV often references it on NW flow but it goes for all wind directions... sometimes I think we do great with an east flow in a synoptic storm only to find the precip maximum ended up on the west side because it was unblocked...likewise sometimes we jackpot in NW upslope on the east side.  It’s not as simple as just looking at a straight wind direction.

“The Froude Number represents the flow of air when it comes in contact with a barrier, in Vermont's case, the Green Mountains. It is an estimation of whether the flow can make it over the mountains or not and is basically a ratio of the wind perpendicular to the mountain chain versus the atmospheric stability.

Under northwesterly flow, if the Froude Number is low (< 1), or subcritical and blocked, the air will not make it over the mountain and the precipitation will back up and fall primarily along the spine of the Green Mountains and the western slopes. If it is very low (< 0.5), the precipitation will back further west into parts of the eastern Champlain Valley and the western slopes of the Green Mountains.

If the Froude Number is high (> 1), or supercritical and unblocked, the air will flow freely over the mountains and deposit the heaviest precipitation on the east side. A Froude Number near 1 is critical and the heaviest precipitation will likely fall along the barrier.”

Thanks man! Will need to study this post further. 

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1 hour ago, PhineasC said:

Thanks man! Will need to study this post further. 

Yeah that was a good explanation from PF. He's the king of knowing this stuff. I'd say in your area, I might not want the flow too blocked..although you have the big mtns to your south and southeast, so even a blocked flow is ok there I'd say. The biggest thing is lacking a N-S 4k barrier that acts to lift and pummels the areas around it.  

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58 minutes ago, klw said:

Here is a good discussion of the Froude with lots of graphics.  Its a Green Mountain thing.

https://www.weather.gov/btv/froude

 

Isn't your biggest issues around downsloping going to occur with E or SE winds?

Due S winds. I get crushed on E winds. I love those events. Not been enough of them this winter.

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1 hour ago, mahk_webstah said:

I was surprised to see 2-4 of snow in my forecast for tomorrow. I hadn't been on here much very good Maybe it'll be 1 of those things that they say it's gonna change to rain but it doesn't really do that till the end and we end up with a nice snw.  Ends up being a pretty snowy February.

Yea I think you have a nice little thump before the drizzle. Not doldrums

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33 minutes ago, CT Valley Snowman said:

Pack is taking a hit here.  The open sunny areas and main roads are really showing ground now.  Some more urbanized areas are completely bare. However, the neighborhoods and wooded areas still have solid snow cover but it is down to just a few inches.  

IMG_20210225_175100796.jpg

I'm sure this isn't news to you guys locally, but cover was definitely spotty when I was on I-91 and I-90 yesterday. South of about Deerfield Mass coverage went down pretty quickly. Brattleboro VT still had 10" solid eveywhere. 

Medians on highways are going to torch first obviously, but long stretches of nothing.

20210225_115510_compress14.thumb.jpg.c851c972af50ea746fbbbe5ab625f621.jpg

 

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