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Arctic front and some rain showers changing to snow showers


ORH_wxman

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We'll continue the discussion pertaining to the arctic front, snow showers (or even a burst of steadier snow) and very cold temps in here.

 

My quick thoughts:

 

1. The biggest story will be the cold. It won't be long lasting (about 2 days), but high temps may not make it above freezing on Wednesday. Record low maxes are in jeopardy for some.

 

2. The arctic front shoul dhave a band of precip just behind it that will probably start as rain showers for most...but then transition to snow before ending. The soundings briefly become isothermal between about 600-700mb at -10 to -11C...this could allow for a burst of steadier snow that starts to accumulate before it end...we'll have to watch that.

 

 

I feel like I should know this, but what exactly is the significance of that isothermal layer when it comes to steadier snow falling? 

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I scanned back and didn't see any mention. Also, I tried google and was right away successful at finding, but this bares some resemblance to the fabled grid-lock morning of Dec, 2003, when an arctic boundary and attending snow squalls dropped a half inch, which immediately melted, then within moments sheen-ed over, sending cars careening.

Not sure the profiles are the same, but the general gist of having a sharp boundary and crashing temp/thickness reminds me of that.

Yeah, MPM, Scooter , and Jerry mentioned it yesterday or Saturday
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I feel like I should know this, but what exactly is the significance of that isothermal layer when it comes to steadier snow falling? 

 

 

If you have a deeper layer that is in the snow-growth region, then you increase the chances of the best lift hitting that snow-growth region.

 

Typically the best lift is between about 750-600mb (though sometimes it extends a little higher)...so if you have an isothermal layer that is ideal for snow growth (between -10C and -16C typically), then you really increase the chances at big snow growth and better snowfall rates.

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If you have a deeper layer that is in the snow-growth region, then you increase the chances of the best lift hitting that snow-growth region.

 

Typically the best lift is between about 750-600mb (though sometimes it extends a little higher)...so if you have an isothermal layer that is ideal for snow growth (between -10C and -16C typically), then you really increase the chances at big snow growth and better snowfall rates.

 

 

Oh okay. So it's not the fact that it's isothermal in itself -- but the fact that it's isothermal at a snowgrowth layer between those more ideal snow growth temperatures is what really helps. I'd imagine that having that layer be isothermal at like -6 or -7C wouldn't do much. 

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Not sure where you are but I'm 1/2mi S of the airport so my expectations are not as high but I've been surprised before. Everything looks lined up for a nice 1st snow event of the season though.

I live over in northwest taunton, past the industrial park. Right on the norton line, very close to Attleboro is well. Like you said if all goes well we will both be seeing white tomorrow, which is welcome in any capacity

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Oh okay. So it's not the fact that it's isothermal in itself -- but the fact that it's isothermal at a snowgrowth layer between those more ideal snow growth temperatures is what really helps. I'd imagine that having that layer be isothermal at like -6 or -7C wouldn't do much. 

 

Yes...it was having that semi-deep layer that was -10C or a bit colder that was standing out.

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I scanned back and didn't see any mention.  Also, I tried google and was right away successful at finding, but this bares some resemblance to the fabled grid-lock morning of Dec, 2003, when an arctic boundary and attending snow squalls dropped a half inch, which immediately melted, then within moments sheen-ed over, sending cars careening.

 

Not sure the profiles are the same, but the general gist of having a sharp boundary and crashing temp/thickness reminds me of that.     

I remember that event.  It was the same week as the major noreaster that buried much of new england with 1 to 3 ft of snow.

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Oh okay. So it's not the fact that it's isothermal in itself -- but the fact that it's isothermal at a snowgrowth layer between those more ideal snow growth temperatures is what really helps. I'd imagine that having that layer be isothermal at like -6 or -7C wouldn't do much. 

 

 

I think what is fundamental here is not just the isothermal, but that the psuedo-adiabat is achieved (saturation  --> instantaneous crystallization), and that requires the WB temp be at or less than freezing where it intersects with omega.    Will's right about the more efficiency crystal growth, but I just wanted to mention the DP/temperature relationship. 

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hi-res euro snow algorithm drops 1-1.5" over SE MA/Cape...for whatever those garbage things are worth.  

 

 

It wouldn't shock me if places like Foxborough, Walpole, etc where they have about 300 feet of elevation wind up with an inch or so if things pan out. But I'd be a bit surprised if the Cape got that this early in the season on an anafrontal event. But I guess you never know if there's a quick burst heavy enough.

 

ORH hills might be able to do it if they can get a burst...they'll be able to take advantage of the low level cold more obviously and maximize the qpf output. I'd still think that most get <1" though at this point.

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I remember that event.  It was the same week as the major noreaster that buried much of new england with 1 to 3 ft of snow.

 

 

Yup,  that arctic boundary heralded in the air mass change the set the stage.  In fact, some 3 or 4 days prior there was a southerly gale type system that transported DPs close to 70F with wind swept rains.  It ended with a polar boundary that knocked things back to average, but the models had been pegging the big storm post arctic invasion for a few days at that point.  So the arctic boundary comes through, the high settles across NNE, and cyclogen took place to our S.  Viola.   I had 18" in Winchester Mass from that  

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It wouldn't shock me if places like Foxborough, Walpole, etc where they have about 300 feet of elevation wind up with an inch or so if things pan out. But I'd be a bit surprised if the Cape got that this early in the season on an anafrontal event. But I guess you never know if there's a quick burst heavy enough.

 

ORH hills might be able to do it if they can get a burst...they'll be able to take advantage of the low level cold more obviously and maximize the qpf output. I'd still think that most get <1" though at this point.

i'm thinking a coating on the grass out here. i do think it'll flip and be steady for a short time.

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Yeah if the guidance is correct, it should be a wintry morning. Watching steady snow fall (even if light) is always one of the more exciting parts of the early season...that first time where you see more than just a flurry or few mangled flakes.

 

So far, it appears the system is behaving itself off to the west.

 

Yup!

 

Just got off the phone with a co-worked in Cedar Rapids.  She was complaining that the snow there was beginning to accumulate.

 

Congrats to the southerners and easterners--things seem to be tipping in your direction.

 

44.7/26

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Surprised folks are ruling out 1-2 inch amounts in the hills and Se areas. Enough qpf is there and with moderate snow falling for a few hours should be enough to get the kids sleds out in a  lot of spots

 

 

Some of the qpf is going to be wasted on rain...even in the hills I think. So you have to keep that in mind. I'm definitely not "ruling out" 1-2" of snow anywhere...but I think if those amounts happen, it would be confined to a small area that gets lucky.

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