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Wintry ❄The Christmas Miracle❄(12-24/12-25)

Weather Underground/aka, The Weather Channel algorithm:

Thursday Night 12/24
53% / 1.3 in
Rain and snow showers in the evening transitioning to snow showers overnight. Low 27F. Winds WNW at 5 to 10 mph. Chance of precip 50%. Snow accumulating 1 to 3 inches.
 
SETNwx said:
Always bet pivotal over Weatherbell Euro maps.. why are they so different, just curious.
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The pivotal map there is 10:1. The WB map is using the Kuchera Ratio, which approximates how much snow falls based on temperatures. Once temps get into the upper 20s or lower and if upper levels are also very cold, it takes less than .10 of qpf to make an inch of snow. With really frigid 850s and temps in the lower 20s and upper 10s we can get 20:1 ratios at times. A few places see ratios of 40:1 at times. When you get cement wet snow falling at 34 or 35 it can go down to 4 or 5:1.
 
John1122 said:
The pivotal map there is 10:1. The WB map is using the Kuchera Ratio, which approximates how much snow falls based on temperatures. Once temps get into the upper 20s or lower and if upper levels are also very cold, it takes less than .10 of qpf to make an inch of snow. With really frigid 850s and temps in the lower 20s and upper 10s we can get 20:1 ratios at times. A few places see ratios of 40:1 at times. When you get cement wet snow falling at 34 or 35 it can go down to 4 or 5:1.
Click to expand...
Thanks, I was wondering about the difference.
 
John1122 said:
The pivotal map there is 10:1. The WB map is using the Kuchera Ratio, which approximates how much snow falls based on temperatures. Once temps get into the upper 20s or lower and if upper levels are also very cold, it takes less than .10 of qpf to make an inch of snow. With really frigid 850s and temps in the lower 20s and upper 10s we can get 20:1 ratios at times. A few places see ratios of 40:1 at times. When you get cement wet snow falling at 34 or 35 it can go down to 4 or 5:1.
Click to expand...
So, now I'm calling you out.. lol What do you think the rates are going to be? Where are you leaning...
 
MRX is slow tonight with their updated discussion.. last night's was interesting though:

"Again, guidance is in poor agreement regarding how quick the
cold air filters into the area as well as any potential surface low
organization to our south. Of particular interest, however is that
the 12Z ECMWF, and its ensembles have trended cooler with a bit more
wrap around precipitation. Obviously this kind of disagreement
leaves the forecast with low confidence. As the event becomes
closer, guidance should begin to converge on a particular solution."
 
BufordWX said:
I like what I’m seeing from FFCView attachment 58956
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FFC discussion is quite interesting this morning. Maybe a little bullish?


Very cold air spills in behind the
front by late in the day Thursday with the main short wave swinging
through overnight into early Friday. Should be enough moisture for
some precipitation across portions of the forecast area, especially
across the north. With the cold airmass settling into the region,
some mixture/change-over to wintry precipitation is likely across the
north and not impossible across portions of central Georgia. Just
how much moisture will be available and how far south it reaches
remains quite uncertain at this time.
 
SETNwx said:
So, now I'm calling you out.. lol What do you think the rates are going to be? Where are you leaning...
Click to expand...

The temperatures on the Euro during the snow are falling. The surface in Chattanooga falls from 40 to 26 as the changeover moves through until the snow ends, it looks like. 850s go from 4c to -9c to -12c with 700mb going from -2 to -12 to -15c as the snow moves through. The column looks pretty saturated all the way up to 500mb so the snow growth zone is saturated and very cold for several hours over the area. The ratios crash from probably under 10:1 to around 15:1 as the event unfolds. Vertical velocity also plays a factor too. The Kuchera looks like it's averaging about 12:1 over East Tn based on the accumulation map differences between Pivotals 10:1 totals and the Kuchera totals. Higher by a bit in the mountainous areas.
 
John1122 said:
The temperatures on the Euro during the snow are falling. The surface in Chattanooga falls from 40 to 26 as the changeover moves through until the snow ends, it looks like. 850s go from 4c to -9c to -12c with 700mb going from -2 to -12 to -15c as the snow moves through. The column looks pretty saturated all the way up to 500mb so the snow growth zone is saturated and very cold for several hours over the area. The ratios crash from probably under 10:1 to around 15:1 as the event unfolds. Vertical velocity also plays a factor too. The Kuchera looks like it's averaging about 12:1 over East Tn based on the accumulation map differences between Pivotals 10:1 totals and the Kuchera totals. Higher by a bit in the mountainous areas.
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Kick ass answer.. thanks, man.
 
A little sleet and freezing rain in Highlands, NC last night. I’m at 4K ft and it’s not a big deal...looking up at Shortoff MTN at just over 5k ft looks to be more icy. December has been cold and we have seen flakes several times but nothing has been able to get over the mountains to the East...hoping this Christmas storm manages to do it...the pic in my Avatar is from 2010 in Highlands on Christmas Day...as I recall the forecast at this stage was not much better than what we have now. It can change as everyone note...sometimes it does change towards MORE snow...bring it.
 
Good morning, IDK about this threat but the Sunday/Monday has my attention. Onset will be interesting.
 
What has happened to me COLD AIR? The other day GFS had me Christmas Day @ Hi 19 Low of 10..... Now looks like I want even get down into the teens at all?

Thursday
Rain. Highs In The Upper 50s. Chance Of Rain
90 Percent.

Thursday Night
Rain In The Evening, Then Rain Likely With A
Chance Of Snow After Midnight. Lows Around 30. Chance Of
Precipitation 90 Percent.

Christmas Day
Mostly Sunny With A Chance Of Rain Showers. A
Chance Of Snow In The Morning, Then A Chance Of Snow Showers In
The Afternoon. Much Cooler. Near Steady Temperature In The Lower
30s. Chance Of Precipitation 50 Percent.

Friday Night And Saturday
Mostly Clear. Lows in the lower 20s
Highs In The Lower 40s.
 
BIG FROSTY said:
What has happened to me COLD AIR? The other day GFS had me Christmas Day @ Hi 19 Low of 10..... Now looks like I want even get down into the teens at all?

Thursday
Rain. Highs In The Upper 50s. Chance Of Rain
90 Percent.

Thursday Night
Rain In The Evening, Then Rain Likely With A
Chance Of Snow After Midnight. Lows Around 30. Chance Of
Precipitation 90 Percent.

Christmas Day
Mostly Sunny With A Chance Of Rain Showers. A
Chance Of Snow In The Morning, Then A Chance Of Snow Showers In
The Afternoon. Much Cooler. Near Steady Temperature In The Lower
30s. Chance Of Precipitation 50 Percent.

Friday Night And Saturday
Mostly Clear. Lows in the lower 20s
Highs In The Lower 40s.
Click to expand...
The 6z was the coldest run yet, I didn't look at 0z. That forecast seems more similar to the Euro but even warmer than it
 
SD said:
The 6z was the coldest run yet, I didn't look at 0z. That forecast seems more similar to the Euro but even warmer than it
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To add to this it looks likely we still get the cold but it's just pushed back. Our coldest night might very well be Saturday into Sunday areas west of us might be Friday into Saturday. Still wouldn't be surprised to see a decent amount of upper teens Sunday morning but I might be chasing waterfalls
 
SD said:
The 6z was the coldest run yet, I didn't look at 0z. That forecast seems more similar to the Euro but even warmer than it
Click to expand...
Doesn't get out of the 20's Christmas day or if it does, barely but doesn't go above freezing
 
111
SD said:
View attachment 58960

Euro to me is likely squeezing out some flurries and light snow showers Christmas morning into the afternoon as temps crash aloft and sfc temps cool. Reminds me a bit of the early December system but possibly a little more widespread
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That’s a good point. Snow growth region will be much lower than usual with those very cold 850’s.
 
deltadog03 said:
111

That’s a good point. Snow growth region will be much lower than usual with those very cold 850’s.
Click to expand...
Euro brings in a pocket of ridiculous 850s. This set up seems to really work well for Tn/Al/Ga and obviously the mountains. East of the apps it's usually hit or miss
850th.us_ma.png

In a perfect world we would find a way to get this energy a few hundred miles south tracking from southern Ms and exitingnear CHS but that probably ain't happeningfloop-ecmwf_full-2020122000.500hv.us_ma (1).gif
 
That clipper system looks so good on the gfs in Christmas day then the mountains destroy it. Ugh mountains kill everyone's hope of snow in nc

Sent from my Pixel 3 using Tapatalk
 
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