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The Jan 9-10 Storm Part 2


MotoWeatherman

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Someone (Beanskip?) asked me for a history of 6"+ official S/IP at Atlanta (ENSO phase included):

3/24/1983 SEN

1/12-14/1982 (heaviest any one day 4" on 1/12) NP

1/23/1940 WEN

1/29-30/1936 NP

1/28/1904 WLN

2/11-12/1899 WLN

12/2/1896 SEN

2/15-16/1895 WLN

2/24-5/1894 MLN

1/18-19/1893 SLN

2/21/1889 SEN

12/3-6/1886 MLN

2/12-15/1885 (heaviest any one day 4" on 2/15) NP

12/29/1880 NP

Interesting info. It's been a while. Thanks.

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Tons of moisture in LA @57 on this run compared to the 12z, more north with the precip shield.

it really dumped in central Tex, over 3" under the ULL there. Someone in Texas will probably get a major snowfall, though localized. Dynamic cooling could come into play there. Still puzzled why the model don't have moisture shield further north than shown, to fit the dynamics. At 60, there is almost extreme divergence over southern Tenn and northern Alabama. That alone would argue for heavy precip there.

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it really dumped in central Tex, over 3" under the ULL there. Someone in Texas will probably get a major snowfall, though localized. Dynamic cooling could come into play there. Still puzzled why the model don't have moisture shield further north than shown, to fit the dynamics. At 60, there is almost extreme divergence over southern Tenn and northern Alabama. That alone would argue for heavy precip there.

This run looks like it's going to be a mix of the 6z and 12z, so maybe it's starting to catch on.,,,6z was probably closer to what should be going on.

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it really dumped in central Tex, over 3" under the ULL there. Someone in Texas will probably get a major snowfall, though localized. Dynamic cooling could come into play there. Still puzzled why the model don't have moisture shield further north than shown, to fit the dynamics. At 60, there is almost extreme divergence over southern Tenn and northern Alabama. That alone would argue for heavy precip there.

Robert,

When you have time, can you explain the "scenarios" of WHY the precip is not shown more north, even with the divergence there? Thanks!

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Around 4 inches with that storm for KATL I believe, more south and pretty much no snow Northwest of Atlanta.

Had 5" IMBY (Lilburn) on that storm...That had a SW to NE band of Snow that setup right through Atlanta and to the Northeast. Like you said, NW and most of N. GA saw nada with that storm. It was a 28/29 degree Snow that covered everything.

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Robert,

When you have time, can you explain the "scenarios" of WHY the precip is not shown more north, even with the divergence there? Thanks!

Maybe the precip totals are lagging the divergence. I would expect to see more, though.

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@66 it looks like that heavy glob of QPF is making a bee line straight to WNC.

The only issue I have is that the North and Northeast sections of the precip are a lot lighter. On 6Z, it was a lot more defined, heavier. Maybe I am just blind or not looking at something correctly.

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it really dumped in central Tex, over 3" under the ULL there. Someone in Texas will probably get a major snowfall, though localized. Dynamic cooling could come into play there. Still puzzled why the model don't have moisture shield further north than shown, to fit the dynamics. At 60, there is almost extreme divergence over southern Tenn and northern Alabama. That alone would argue for heavy precip there.

During the Christmas storm, wasn't pretty much that same set up occuring as what you just said? The models (NAM, GFS) showed little to no moisture around the southern Tennessee line up until 24-36 hours until the event. It seems in that time frame, moisture always shows up with a low crossing the gulf like this. Do you think this might be a different set up or do you believe more moisture will be available?

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Made a quick post on the blog, but a big key for the Carolinas is the rate of weakening of our disturbance. The 12z Euro is nearly identical in strength and placement of the disturbance in the Lower MS Valley, but today's runs weaken it quicker as it approaches the Carolinas.

I get into that, plus put up my precip type outlook maps.....just some general outlines that most on here already know.

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QPF verbatim this looks like a much better run for us in WNC and CLT, but not as good for ATL...either way this is the trend we want to see, I can't see ATL and points north really missing out on the jackpot.

Back to the 6z solution. You can see the difference at 500 with the s/w holding its own longer with more downstream ridging providing more lift. This is proving Robert's assertion that the northern precip shield will trend stronger.

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Robert,

When you have time, can you explain the "scenarios" of WHY the precip is not shown more north, even with the divergence there? Thanks!

i put it in scattered parts of this thread, but basically its dynamics aloft haven't matched the surface, what should happen, but I don't know why, other than this might be a bias or a reflection of the strong high pressure in the Ohio Valley, and the strong 50/50 confluence, which we don't have much of, so since this is a rare situation, its hard to say. We just don't get many setups like this, but when we did in the past, the precip shield just traversed right along, basically up 85 for us. However this time we've got the incoming rockies system so that is messing with the model's physics. But, once again, this is similar to the Jan 1983 system, somewhat, but not an exact setup, so who knows what really happens. I'm inclined to think the usual will occur with what happened in the past. And that blended with the dynamics and track and setup I'm seeing is that snow will stretch from northeast Texas to southern third of Arkansas and spread east/northeast from there, and I'd ad the heavies snow might be north Texas, southern Ark, to central/north Miss, and probably would include n. Alabama, n. Ga and once we get into the western Carolnas it just depends on how much lift carries east. Normally, I'd say good setup but with the models all dropping amounts suddenly here, that gives me pause. We really need more time to see the trends, and not get gung ho on the amounts yet. It could still easily be a big snowfall here, but theres never a guarantee on any one specific spot, esp right here, which might be the hardest spot in the U.S. to accurately forecast a snowstorm becuase of the extreme complex mtn. interactions we have.

Just looking at the rest of the 18z run, it appears its a good bit wetter here , with a general look of the JMA and SREF ensembles, on the precip shield orientation. I noticed it held the 5H vort together stronger clear through Tennessee and northern GA. But its an off run of NAM, obviously we'll be watching the 00z closely. Nothing is certain, good or bad , here.

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It could make sense with upper level dynamics, not a strong surface low, driving the show. Not saying this run is correct, but it is not insane.

The NAM has less moisture further south.. closer to the low and gulf.. makes total sense.. lol

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Back to the 6z solution. You can see the difference at 500 with the s/w holding its own longer with more downstream ridging providing more lift. This is proving Robert's assertion that the northern precip shield will trend stronger.

@81 it's still keeping the heavy precip just to our south...either way this is a good trend, baby steps from here on out.

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