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Wintry January 29th-30th ARCC Slam Dunk Winter Weather Threat

SoutheastRidge said:
Serious question. What's it gonna take for Atlanta to get a major 6"+ event out of this ? Do we need a low pressure forming to enhance the precip ?
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It would take a low pressure forming along the front. But like someone else side on here you want to keep the low pressure weak. If the low gets to strong you will have to start worrying about WAA..
 
FFC:
The longwave trough deepens again over the southeast on Monday night
into Tuesday. As the surface high pressure moves out of the area, a
sharp cold front will approach and is expected to enter the forecast
area on Tuesday morning and move southeastward through Georgia
throughout the day on Tuesday. The main concern with this system is
how much precipitation will coincide with the cold air on the back
side of the system. GFS and ECMWF models both indicate that the bulk
of the precipitation associated with this system will pass through
our area throughout the day on Tuesday. However, there are still
slight disagreements between model solutions, as ECMWF offers a
wetter, but slightly faster solution than the GFS. The possibility
still exists of the cold front slowing and becoming elongated and
moving through the area Tuesday night into early Wednesday, so I
maintained some slight chance PoPs in on Wednesday to account for
this possibility. Overall, the upper level flow does not indicate
deepest moisture aligning with the sub-freezing temperatures behind
the front. Nonetheless, some wintry mix and a transition to light
snow is possible with some shallow moisture behind the cold front,
but confidence remains low.
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For Carolina folks, if we can get the front to slow down about another 6-9 hours ish and push the timing of some of the heavier precipitation to the overnight or early morning hours, it seems feasible that more of the board in this area would see more snow and accumulation efficiency would also improve. However that would come at a cost to areas further west. Diurnal timing alone will possess winners and losers here.
 
ATLwxfan said:
That’s probably generous. Looks like maybe a dusting inside the perimeter. But that could change. Maybe the 0z will bring the goods.


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As someone who lives ITP, I wouldn't expect more than a dusting to a half inch based on what we've seen thus far. Might even be better to temper the expectations even less to say maybe we'll see some flakes falling. Just not quite enough to suck this ITP skeptic in at this point.
 
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Showmeyourtds said:
As someone who lives ITP, I wouldn't expect more than a dusting to a half inch based on what we've seen thus far. Might even be better to temper the expectations even less to say maybe we'll see some flakes falling. Just not quite enough to suck this ITP skeptic in at this point.
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I’m not skeptical for any other reason than that clippers don’t really get to us.


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I know this is the long range NAM but here the precip map for Tuesday morning.
nam_mslp_pcpn_frzn_us_28.png
 
Interestingly, this week and next week were depicted as very cold for the eastern US by the long range models a few weeks back. I guess that those fantasy range forecasts can at least show trends.

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Huntsville disco this afternoon.

Issued at 250 PM CST Fri Jan 25 2019

Uncertain is a good way to sum up the extended forecast at this
point. A strong and very cold upper level system will start to make
it`s way SE Monday into Tuesday. Good warm air advection ahead of
this feature will allow temps Monday afternoon to warm into mid to
possibly upper 50s. This will occur ahead of a Arctic front currently
forecast to move in Monday night into Tuesday morning. Timing
differences between the latest operational runs of both the GFS/ECMWF
continue to result in some uncertainty and lower confidence for the
forecasted QPF and any snowfall amounts. Much of the precip will be
post-frontal and based on the thermal structure of the front and
temperatures aloft, this will allow for a very quick transition to
snow on Tuesday. The biggest issue is when will the heaviest precip
occur, the GFS would suggest much of the snow occurring shortly
before sunrise Tuesday. While the ECMWF is slower and would put the
best chances for snow after sunrise Tuesday. In either case we are
looking at impacts to morning commutes Tuesday morning. With an
extended warm period from Saturday through Monday, road surfaces
should be on the warmer side and any initial snow might melt.

Ensemble members still indicate varying solutions for QPF and
snowfall amounts for Tuesday. Sticking closer to the means but also
recognizing that some of the outliers could be pulling the ensemble
means higher have tried to nudge amounts a bit lower due to the
lingering uncertainty. This would put snowfall amounts generally
around 1 inch for much of the TN Valley. Some of the higher terrain
in TN and NE AL could see upwards 1.5 inches. Want to reinforce this
point though: the confidence in those amounts is low. We still have
awhile to go and would like to see better consistency in the
guidance before we could increase our confidence. For what it is
worth, ensemble probabilities of 1 inch of snow have steadily been
increasing.
 
Fairly healthy QPF from the WPC. 1/4"+ for most of the board west of the Apps with a max of 1/2"+ in the higher elevations in southeast TN. Good trends.

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DarkKnight said:
Huntsville disco this afternoon.

Issued at 250 PM CST Fri Jan 25 2019

Uncertain is a good way to sum up the extended forecast at this
point. A strong and very cold upper level system will start to make
it`s way SE Monday into Tuesday. Good warm air advection ahead of
this feature will allow temps Monday afternoon to warm into mid to
possibly upper 50s. This will occur ahead of a Arctic front currently
forecast to move in Monday night into Tuesday morning. Timing
differences between the latest operational runs of both the GFS/ECMWF
continue to result in some uncertainty and lower confidence for the
forecasted QPF and any snowfall amounts. Much of the precip will be
post-frontal and based on the thermal structure of the front and
temperatures aloft, this will allow for a very quick transition to
snow on Tuesday. The biggest issue is when will the heaviest precip
occur, the GFS would suggest much of the snow occurring shortly
before sunrise Tuesday. While the ECMWF is slower and would put the
best chances for snow after sunrise Tuesday. In either case we are
looking at impacts to morning commutes Tuesday morning. With an
extended warm period from Saturday through Monday, road surfaces
should be on the warmer side and any initial snow might melt.

Ensemble members still indicate varying solutions for QPF and
snowfall amounts for Tuesday. Sticking closer to the means but also
recognizing that some of the outliers could be pulling the ensemble
means higher have tried to nudge amounts a bit lower due to the
lingering uncertainty. This would put snowfall amounts generally
around 1 inch for much of the TN Valley. Some of the higher terrain
in TN and NE AL could see upwards 1.5 inches. Want to reinforce this
point though: the confidence in those amounts is low. We still have
awhile to go and would like to see better consistency in the
guidance before we could increase our confidence. For what it is
worth, ensemble probabilities of 1 inch of snow have steadily been
increasing.
Click to expand...

Ground temps for the win !!!


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From the New Orleans NWS office:

The big story going into next week for the country will be the punch of cold air expected to move into the eastern United States and the chance of snow across the Deep South. A front will move through the region on Tuesday. Guidance suggest that there could be some moisture available as the front comes through and with cold air rushing in behind it for a changeover to wintry precipitation as the front exits the area. I have not included this in the official forecast as the guidance is hard pressed to suggest wintry precip this far south. The GFS is warmer than the ECMWF. I have tried to maintain a blend of guidance. Will have to watch this as more guidance comes in house, but for right now we are expecting all rain for our immediate area. If the GFS show a colder signal over the next few days, my confidence would increase at the possibility of wintry precip in our area...however...models do sometimes struggle with cold air progression and depth.

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