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Wintry January 8-9, 2018 Ice threat

bud006 said:
Just catching up on the board today and haven't really looked at models for Monday (other than the kind analysis of the screenshots y'all have provided; thank y'all for that).

There are two major reasons why I am rooting -- actively -- for WAA and no winter precip:

1. Freezing rain, as we have discussed repeatedly, is a mess. Does not take much to provide a disruptive event for travel and daily activities. Add in just how cold it has been for a full week leading into the event, and it will not take very much precip at all to really make things messy. No 60 degree highs a couple of days before the potential event.

2. Monday is a huge day in Atlanta, with the national championship game that evening, heaven knows how many tens of thousands of people visiting downtown (some I would guarantee do not have tickets to the game, but are there to soak up the atmosphere) ... I remember the freezing rain when Atlanta hosted Super Bowl XXXIV in January 2000 (I'll save my moving story from the NE Ga mountains to the southern suburbs that week for banter one of these days). Net-net: that event was a huge headache and the city's response left a lot to be desired.

Wedges are very tricky. How strong is it? How far SW does it extend? How quickly does the high work east? How much moisture works N and NE and how much WAA does it bring to erode the wedge? Models typically do not handle wedge temps and resulting warmup well.

This certainly bears watching. I'd be willing to bet given the influx of folks coming to town is why FFC was quite uncharacteristically bullish in this afternoon's AFD.

--30--
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To FFC's credit, I've seen them be bullish on winter storms at this range numerous times before over the past few years. Even the storms that didn't materialize as planned (here in Atlanta that is) like January 2017 for example. There was another storm around President's Day where they went all in 6-7 days out (might have been February 2015?) I thought they had completely lost their minds they had a high chance of snow/sleet in the forecast for Atlanta/N. GA. It didn't take too many model runs later for that forecast to change to rain for us. lmao
 
Weatherlover92 said:
To FFC's credit, I've seen them be bullish on winter storms at this range numerous times before over the past few years. Even the storms that didn't materialize as planned (here in Atlanta that is) like January 2017 for example. There was another storm around President's Day where they went all in 6-7 days out (might have been February 2015?) I thought they had completely lost their minds they had a high chance of snow/sleet in the forecast for Atlanta/N. GA. It didn't take too many model runs later for that forecast to change to rain for us. lmao
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Well IMO I think FFC being "bullish" at this point is pretty prudent. . Since "Snowjam 2014" FFC has really been focused on "impact" forecasting and with the combination of cold ground temp, along with a "National" sports event Monday, I truly feel it's the right call.
 
gawxnative said:
Well IMO I think FFC being "bullish" at this point is pretty prudent. . Since "Snowjam 2014" FFC has really been focused on "impact" forecasting and with the combination of cold ground temp, along with a "National" sports event Monday, I truly feel it's the right call.
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Agreed, I'm not saying they're wrong to be bullish, just saying I don't feel it's that out of the ordinary as it's being made to seem.
 
StoneMtnWx said:
Here is end of 12KM 18z NAM fwiw. ZR back I'm Alabama/Tennessee at edge of precip line.
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Sent from my SM-N950U using Tapatalk
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Show me a strong low pressure that takes a southern track in January with very cold soil temps and an arctic air-mass already well established, and I will show you a winter storm for the CAD areas. It will all come down to the amount of moisture that falls and when it begins. Recall that freezing rain is a “self limiting” process. If there is no source for sustained cold air advection, then the latent heat of freezing associated with freezing rain will gradually increase surface temperatures to the freezing mark. Once the temperature reaches 32 degrees, ice no longer accumulates. Now, with the low center passing well south of your particular location, you could have a weak source of cold air advection due to the NE winds over the present snow-pack to our north. That's my 2 cents... for now.
 
The 18z NAM has the high pressure off shore at 84 hours, while the GFS has it in VA. interesting
 
Weatherlover92 said:
Agreed, I'm not saying they're wrong to be bullish, just saying I don't feel it's that out of the ordinary as it's being made to seem.
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@Weatherlove92: That's fair. I've been reading AFDs from FFC for years and it's not easy sometimes to shake the years of ultra-conservative approaches. Not fair on my part. I do remember the January 2011 system they were honking on it Friday afternoon for an event that hit Sunday night (they were right!). Certainly since Jan. 28, 2014, they have tended at times to be more aggressive, for better or worse.

Good call-out and I acknowledge it. Thank you. Still, it seems that 84 hours out is a bit early, but as I said and @gawxnative mentioned, with what's happening in Atlanta on Monday evening (Go Dawgs!), it is the right call to raise the flag early.

--30--
 
Precip moves in earlier across AL, freezing rain/sleet as far east as NE side of Birmingham by hr 78. Freezing rain spreads in Atlanta metro 3hrs later by 9z Monday.

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EDIT: Notice the HP sitting over the western Carolinas at hr. 81
 
Snowflowxxl said:
Precip pretty much dies at 84
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Kinda weird isn't it? Especially since this run of the NAM closes off our s/w over the Arklatex region and keeps it closed to the very end of the run. I would have thought that would argue for an increase in Gulf moisture, but idk. Wait, it's the 84hr NAM, who cares it'll change anyway.

MuR6LVJ.gif
 
Precip seems to die due to the dewpoints being extremely low. It's too far out to tell I think since we would only know if it's truly died out beyond that time frame at hour 84.
 
Weatherlover92 said:
Kinda weird isn't it? Especially since this run of the NAM closes off our s/w over the Arklatex region and keeps it closed to the very end of the run. I would have thought that would argue for an increase in Gulf moisture, but idk. Wait, it's the 84hr NAM, who cares it'll change anyway.

MuR6LVJ.gif
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Flow goes SSW out in front!
 
The NAM has very strong wedging which ends up destroying precipitation. Kind of like areas that had a virga storm yesterday with the snowfall.

Either way, there is a 1032 sitting right over North Carolina trying to pull away. The image that Chris just posted of the 2M Dewpoints, argues a much more aggressive situation that would anchor the cold air at the surface for quite a while if heavier precipitation were to occur.

Dare I say, yesterday's 12z Canadian Operational look.
 
Out to hr 54, 00z GFS looks like it will be slower than 18z and way slower than 00z NAM. The s/w is digging pretty far SW into south/central California. 00Z Nam for comparison had the s/w centered over UT/CO at the same timeframe.
 
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