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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
Click to expand...
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.
Click to expand...
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.
 
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