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Wintry 2/3-2/4 Mixed Bag NC, SC, NE GA

Shawn said:
There's no way heavier rates won't release enough latent heat (from liquid turning ti ice, it gives off heat) to keep the surface at 32F. Serious ice storms generally need to be 28-29F or so with heavy precipitation.

Of course, I am just going by that one sounding.
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So per that, sounds like we would warm up if it sleets, or even if the rain starts to freeze. However, if it gets to 30 or 29 somehow, it would be way worse, but I can't see that happening.
 
ForsythSnow said:
So per that, sounds like we would warm up if it sleets, or even if the rain starts to freeze. However, if it gets to 30 or 29 somehow, it would be way worse, but I can't see that happening.
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Yeah, the scariest thing to see sitting around the temperature of 31-32F is light freezing rain or drizzle for a prologned period of time.
If you get under some of the heavier bands and something screws you, keeping you right at 30F or below, you're in trouble.

Looking at the charts above for the upstate are a bit unsettling, as it's wanting to have that situation happening as you can see in the > 1 " ice accumulation maps. The Canadian suite of modeling does handle CAD better. This isn't an arctic plunge or anything, that it could be way over doing as we usually see from the model.
 
I looked back to February 2015's ice storm and saw that the low track is quite similar to this system's. However, the big difference is that it will be raining morning into afternoon versus day into night.
 
Latest HRRRs have backed off on the more problematic ice scenarios in the Upstate, which is a good thing. RGEM may be on it's own.
 
Yeah these temps don't look promising. Might hit 32 but the wedge should scour out rather quickly. Temps don't support a significant event. RGEM thinks I'm at 31 right now..I'm currently at 35

We rain
 
Okay, cloud clover and winds starting to work their magic. Temperatures up to almost 40 around the area. Whew.
 
Temperature currently at 37

RGEM thinks I'm at 31..lol

Reality starting to set in. Should be one of the coldest rains so far this season. This winter rocks!
 
Shawn said:
Yeah, the scariest thing to see sitting around the temperature of 31-32F is light freezing rain or drizzle for a prologned period of time.
If you get under some of the heavier bands and something screws you, keeping you right at 30F or below, you're in trouble.

Looking at the charts above for the upstate are a bit unsettling, as it's wanting to have that situation happening as you can see in the > 1 " ice accumulation maps. The Canadian suite of modeling does handle CAD better. This isn't an arctic plunge or anything, that it could be way over doing as we usually see from the model.
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Based on my experiences with ZR, sometimes heavier ZR leads to warmer 2 meter temperatures. I wonder if that would likely be due to the heavier rain pulling down warmer temperatures from aloft. Or even if the 2m temps didn't warm, the heavier rain might have still had more trouble accumulating. It seems that the highest ratios of accretion to ZR are often favored with lighter ZR. If for no other reason, think about a higher % of heavier rain dripping off branches too quickly for it to freeze on those branches.

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GaWx said:
Based on my experiences with ZR, sometimes heavier ZR leads to warmer 2 meter temperatures. I wonder if that would likely be due to the heavier rain pulling down warmer temperatures from aloft. Or even if the 2m temps didn't warm, the heavier rain might have still had more trouble accumulating. It seems that the highest ratios of accretion to ZR are often favored with lighter ZR.
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As liquid mass turns into ice, it releases heat. Basically think of it as a solid changing to a liquid, the energy "trasnfer" has to give off some sort of warmth. Anything in motion will give off some form of heat.

As the liquid mass freezes on contact, the energy expunged creates a tiny little pocket of heat. As the rates become heavier, more heat is released and eventually the ground level comes above freezing.

Lighter ZR is letting less heat off as fast, because the droplets are smaller or the rate of precipitation as a whole, is lighter. From what I have seen, the bigger ice storms that have occurred in heavy precipitation scenarios were when the surface was too cold (26-28F) to be overcome by the liquid to solid change, and the end result being destructive ice accretion.

At least this process is what I was taught in my reading.

@Webberweather53 will hopefully, have a better response to this process.
 
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Shawn said:
As liquid mass turns into ice, it releases heat. Basically think of it as a solid changing to a liquid, the energy "trasnfer" has to give off some sort of warmth. Anything in motion will give off some form of heat.

As the liquid mass freezes on contact, the energy expunged creates a tiny little pocket of heat. As the rates become heavier, more heat is released and eventually the ground level comes above freezing.

Lighter ZR is letting less heat off as fast, because the droplets are smaller or the rate of precipitation as a whole, is lighter. From what I have seen, the bigger ice storms have occurred in heavy precipitation scenarios, when the surface was too cold (26-28F) to be overcome by the liquid to solid change, and the end result being destructive ice accretion.

At least this process is what I was taught in my reading.
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Consider this possible more simplistic reason heavier ZR may tend to accrete on branches at a lower rate: If for no other reason, a higher % of heavier rain likely drips off branches too quickly for it to have time to freeze on those branches. I'll exaggerate to make a point: What if somebody were to rapidly pour a bucket (representing extremely heavy ZR) of supercooled water on a branch? Wouldn't almost all of it go right to the ground below the branch? Compare that to pouring it very slowly over said branch. Wouldn't more of it accrete?
 
As the event is getting pretty close to starting, let me remind you of the 1/3 rule; a nifty way to get an approximation of your wet bulb temperature. First, find your dewpoint depression. This is temperature minus dewpoint. For example, 38F with a dewpoint of 16F gives 38 -16 = 22. Second, take your dewpoint depression and divide it by 3, so 22/3 = 7.3333 degrees. Finally, take your standing temperature and subtract from the value to got above; 38 - 7.3333333 = 30.666 F. Concisely, 1. standing temperature - dewpoint temperature. 2. dewpoint depression divided by 3. 3. standing temperature minus previous value obtained above. Good luck everyone with the event. wetbulb.gif
 
Man what a close call! Currently sitting at 33.4 with a cold cold rain. DP is 29. I don’t think I’ll see 32 though. Wasn’t expecting 33.4 either lol. Hope everyone else in the ice path is warm and safe!


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Got lucky here in Dahlonega, got down to 32.2, now it's ticking back upwards slightly with the heavier rain. Can't get much closer than that.
 
32.2/32.2. Just missed ice by .2 degrees although I am sure in the tall pines it’s probably 32. But needless to say it’s pouring in sheets and this is one of the coldest rains I can remember in a while! Beat the forecast low by 3 degrees almost. Already picked up .92”’of rain so far. I couldn’t imagine getting that much in ice...geez!


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