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Bonafide SWFE 2/7-8


weathafella

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8 minutes ago, Bostonseminole said:

i hope so, I would toss my weather station if that verified

That map is BS....its snowfall algorithm is entirely temperature derived, thus it underestimates snowfall in in marginal conditions.

I'm not sure why anyone would post that in lieu of the 10:1 map in this situation.

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What a complicated setup. I do lime Ryan's idea on the potential for some prolonged icing down this way if we can keep colder air locked in at the surface and that is a really tough call right now. If the sfc low does develop and track just to our south icing could be a pretty big issue. Since this system isn't overly strong this should prevent a stronger push of warmer air just above the surface to work too far inland (unless of course the sfc low develops further NW). 

I keep looking how far back the main energy is though in association with the surface low and I wonder what kind of  influences that will have on anything outside of playing a factor in a stronger storm (obviously not the biggest factor). 

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2 minutes ago, 40/70 Benchmark said:

That map is BS....its snowfall algorithm is entirely temperature derived, thus is underestimates snowfall in in marginal conditions.

It gives like 5 to 1 or 6 to 1 ratios for a good portion of the front end thump...prob because during the heaviest precip before the flip, there's a layer that is barely below freezing, like -1C or something. In reality, its prob gonna be closer to 10 to 1. I think icing could be a big concern though in this one...more than the usual SWFE.

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1 minute ago, ORH_wxman said:

It gives like 5 to or 6 to 1 ratios for a good portion of the front end thump...prob because during the heaviest precip before the flip, there's a layer that is barely below freezing, like -1C or something. In reality, its prob gonna be closer to 10 to 1. I think icing could be a big concern though in this one...more than the usual SWFE.

Yes, that high is optimal.

I like Kevin's area in n CT for that.

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The front end thump of snow could could be rather impressive down this way. Could see a several hour period of extremely heavy wet snow falling. GFS bufkit for Waterbury is rather impressive with some great omega into the SGZ. Wish we had some higher RH values within the zone but if we get several inches of heavy, wet snow followed by ZR there could be some issues.

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Just now, 40/70 Benchmark said:

Yes, that high is optimal.

I like Kevin's area in n CT for that.

The sfc low also starts to become a bit strung out NE to SW...which will intensify the northerly component of the ageo flow. In a lot of other SWFEs, we have a dying primary way up into like CLE or BUF so the low becomes stretched more E-W as it tries to redevelop...this one seems to be trying to jump ship around PIT or even a bit south and it's forming almost a little mesolow out ahead in the CAD sig...so it def screams for locking in the cold air.

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3 minutes ago, ORH_wxman said:

The sfc low also starts to become a bit strung out NE to SW...which will intensify the northerly component of the ageo flow. In a lot of other SWFEs, we have a dying primary way up into like CLE or BUF so the low becomes stretched more E-W as it tries to redevelop...this one seems to be trying to jump ship around PIT or even a bit south and it's forming almost a little mesolow out ahead in the CAD sig...so it def screams for locking in the cold air.

Maybe I am just looking too much into this but when you have a situation where you have upper energy lagging behind a sfc low quite a bit what kind of influences would that have on the storm in general? 

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6 minutes ago, ORH_wxman said:

The sfc low also starts to become a bit strung out NE to SW...which will intensify the northerly component of the ageo flow. In a lot of other SWFEs, we have a dying primary way up into like CLE or BUF so the low becomes stretched more E-W as it tries to redevelop...this one seems to be trying to jump ship around PIT or even a bit south and it's forming almost a little mesolow out ahead in the CAD sig...so it def screams for locking in the cold air.

I cited the developing n ATL ridge node as a reason that would likely happen in my blog on Saturday.

Do you think that is at least partially attributable?

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4 minutes ago, weatherwiz said:

Maybe I am just looking too much into this but when you have a situation where you have upper energy lagging behind a sfc low quite a bit what kind of influences would that have on the storm in general? 

It means the storm is very "tilted"...the sfc is far SE of the upper levels. It's not uncommon in SWFEs...that's why we often get snow to start and then flip to IP/ZR even though we might have a sfc low tracking to our southeast which on a very elementary level would suggest we all get snow. But since the system is so tilted to the northwest, we are getting warm sectored aloft and we flip to sleet/ZR (and rain on coast)....of course, this could still shift a little and we either end up snowier or end up warmer and icier for some folks.

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2 minutes ago, ORH_wxman said:

It means the storm is very "tilted"...the sfc is far SE of the upper levels. It's not uncommon in SWFEs...that's why we often get snow to start and then flip to IP/ZR even though we might have a sfc low tracking to our southeast which on a very elementary level would suggest we all get snow. But since the system is so tilted to the northwest, we are getting warm sectored aloft and we flip to sleet/ZR (and rain on coast)....of course, this could still shift a little and we either end up snowier or end up warmer and icier for some folks.

Thanks! This makes a ton of sense. I was trying to like over-analyze the whole thing and completely overlooked the basic aspect to this. We went over this whole idea in really good detail last year in one of my classes. 

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43 minutes ago, 40/70 Benchmark said:

That map is BS....its snowfall algorithm is entirely temperature derived, thus it underestimates snowfall in in marginal conditions.

I'm not sure why anyone would post that in lieu of the 10:1 map in this situation.

Here you go Ray.   I didn't realize how it struggles with marginal.  So the 10:1 is surely further south....

10.jpg

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1 hour ago, ORH_wxman said:

Yes it does...I'd prob bring the whole thing about 20-30 miles south. It's def still got a lot of non-snow frozen precip though on this run...as Ryan mentioned, it's still blowing the mid-level warmth to the NH border. But the algorithm prob flipping precip to IP/ZR a bit too fast during the WAA phase.

Euro kuchie could be missing a warm layer between H7-H85 too.

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2 minutes ago, snowgeek said:

Thanks, but I only see maps through 48 hours.  How do ya get the 84 hour extended?  I'm confused lol. 

You have to manually change the hour number in the address bar, but you first need copy the location of the actual image which is different than what is in the address bar....so for example, the snow precip is located here:

http://img.meteocentre.com/models/gemreg_amer_qc_12/accum/SN_000-048_0000.gif

 

Change that 48 near the end to an 84 and you'll get the extended map. You can change it to anything else too like 60 hours or 54 hours.

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8 minutes ago, 40/70 Benchmark said:

Thanks, Gene.

Sorry, I hope that didn't come off the wrong way.

Not much change.

No prob at all.  I'm always learning.  Usually, up here we are so cold so don't have as many marginal systems, although last night was one.  Maybe someone can explain why the Kuchera algorithm is not tweaked to take into account the marginal "edges" of a system.  Now I know to really look at both before jumping to conclusions.  Thanks...

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1 minute ago, wxeyeNH said:

No prob at all.  I'm always learning.  Usually, up here we are so cold so don't have as many marginal systems, although last night was one.  Maybe someone can explain why the Kuchera algorithm is not tweaked to take into account the marginal "edges" of a system.  Now I know to really look at both before jumping to conclusions.  Thanks...

The map lowers ratios when it records a temp near freezing in the column. The formula starts "punishing" your snow ratio once you hit any temps in the column that is warmer than -2C.

 

Sometimes its a good way to lean...esp when you have a warm layer that is quite elevated (like up near 800 and 750). But when the warmer layers are lower (esp near the sfc), it can under predict snow accumulations badly. It will assume awful ratios because the model output is like 33F at the surface when it reality the temp verifies at 30 or 31.

 

In this case, our elevated warm layer is kind of low compared to regular SWFEs, so kuchara is prob over-punishing 850-900mb temps near -1C or something.

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