SnowDawg

Yep even normal winter temps and this is a huge winter storm with a potentiay great ULL track to add more on the backside. What could've been....

Who knows if we have enough time to trend far enough but all guidance has ticked back south and east this morning. If it goes far enough that deform band will have a much better angle of approach into the area. Things are bleak, but I'm gonna stay hopeful for a surprise given that the dynamics are at least in place to produce one.

For whatever it may be worth, the HRRR looks a lot better at least as far as precip coverage goes with the deform band. As long as we can secure heavy rates under that upper level cold pool then we should at least get to see some heavy wet snow fall for a while.

It is though in the part of the storm that matters, when the upper level cold pool is over head. Remember even in those good NAM runs yesterday almost all of the snowfall was in the deform band. But with the more northerly track/angle of approach that band now tries to track over the mtns from the Tennessee side completely wringing it out. We ideally need to see things trend back south/southeast, a touch weaker, and probably a touch faster.

Was just looking at the same thing very confused. Totals cut across the board, rightfully so but still lol

In some ways for sure. But it was the first run in a while on any model to come colder aloft. Something to at least keep an eye on cause despite the stronger vort cutting north quicker, logic also says it should have better dynamics for cooling if it can overcome the poor daytime timing.

I'm more or less just glad to see it go to perhaps be more optimistic going into next winter.

That upper level cold just continues to arrive later and later and look more and more stale.

So just looking at the 06z Euro, I start by looking at the upper level chart and see that it ticked noticeably stronger with the ULL with a nearly identical track. I assumed this would lead to a better pull of upper level cold to work with but instead it did the exact opposite and continued to reduce the extent and intensity of the 850 mbar cold pool. Is this unfortunately just the models playing catch up on the ULL being cutoff from any real cold source to pull from?

In my experience HRRR is garbage on thermals. Good with convective processes and precip pattern when in range, but terrible with thermals. I remember it being off by 5-10 degrees at the surface for the ULL snow in February 2020.

Love the honesty in the Atlanta AFD this morning. As of now, even on Day 3, there remains an abundance of questions that we don`t quite have answers for, and frankly, may not fully know until the event is underway. How deep and in what location will the upper-level low set up? Cutoff upper lows are notoriously hard to predict given the lack of steering flow aloft, yet the positioning will determine where and when wintry precip begins. What will temperatures be in the mid-levels of the atmosphere? Up until this point, temperature profiles cooled continuously with elevation, but now some models are showing temperatures above freezing between the 700-850 hPa levels, right where the warm, moist conveyer belt will set up which could turn wintry ptypes from snow to sleet. Will the surface low drive a wedge front through the region and if so, how far and how deep? This question could have significant impacts for the I-20 corridor NE of Atlanta in terms of ptype duration late Sunday morning and afternoon. How much snow will be able to accumulate with temperatures in the mid 30s? How much will temperatures drop if heavier snow does make it to the ground? We have a lot of questions that will begin to slowly come into view, but honestly, several wintry parameters are forecast to be on a knife`s edge throughout this event and could easily go one way or another. While we`re not anticipating any more impacts outside of elevations over 1500 feet at this time, it`s still important to be prepared, just in case, so please check back for future updates.

NAM was just a massive jump for a single run, similar to what the Euro did yesterday moving the jackpot zone all the way west of knoxville. Hopefully it's one of those windshield wiper over-corrections and it'll tick back east over its next few runs. Trends have honestly been poor across most guidance since mid day yesterday. Which is not necessarily a bad thing as its rare to ride the jackpot zone all the way from 60+ hours out. I'd rather it do so now than a rug pull in the final 24 hours.

I gotta say, I think ground temps are talked about way too much in these situations. Ambient air temps matter and will be a problem for some, but I wouldn't worry too much about ground temps as long as the rates are there. Plus in my experience in top down cooling scenarios, if the rates are persistent they can literally drag freezing air to the surface. Warms up as soon as it moves out, but still aids in accumulation.

It's all the way at the end of its range for one, but honestly it doesn't look all that different from the 12k at the same timeframe. If rolled forward it would probably produce similar results, just finer details obviously. Now I know the NAM wasn't great for everybody but that's a whole different story.

Yeah give them time. They usually react after the first few inches are on the ground lol.

Three cheers for the death of La Niña!!

GSP basically just went with the Canadian for now. It may not be what they said in the discussion, but it's definitely what's in their forecast grids. Don't you just love forecasting winter weather in the south lol? Euro and GFS both with 4-12 across the county about 60 hours from onset. Official forecast...all rain lol. Not even bashing them for it, it's the safest play for now.

Final snow map on NAM:

Forecast grids still haven't updated best I can tell. I'm sure it'll be out soon.

EPS mean: Similar to how the GEFS eliminated some of its eastern outliers the EPS eliminated some of its western ones. Seems they are trying to meet in the middle maybe.

So GFS/NAM show a way for us to score with a super amped dynamic system and the Euro shows a way to score with a weaker one as long as the track is right, hence it's big jump away from the Tennessee snow it was showing. Seems weak and west leads to the worst outcomes. Still a ways to go but hard to complain about where things are as we stand.

It seems to just be almost completely missing the dynamic cooling. I mean it has places going up 5+ degrees while it's puking snow through a -2 to-4 850 layer.

GEFS Mean:

With models now showing most if not all of our snow coming from a deform band type feature as the upper level energy swings through behind the surface low, I guess we pretty much wanna go all in on as strong and dynamic of a system as we can get, even if it means more rain from the beginning of the storm.

I guess it's just the closer surface low track making the difference there? I know the vort is a little weaker than on the NAM but it has temperatures rising in spots that should be dynamically cooling given the upper air temps.