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Wintry Machine Learning Mauler 1/30-2/1

We already have well over an inch already on cold surfaces in Blacksburg. Roads are starting to get sticking again as night falls. Report from my parents in Roanoke is that all they have seen is flurries. Elevation makes all the difference with weak shortwaves like the one we have seen in VA today! 2200 feet vs 900 feet is a sizeable drop but Roanoke County and Montgomery County (Blacksburg) border each other. Just wild!
 
The 18z GFS(s) compared to 12z.

18z GFS did have a dry slot but filled in time:
1769810772227.png

12z GFS:
1769810813393.png

But the 18z AI GIS increased QPF in the north:
1769810662891.png

12z:
1769810595455.png

Probably the last time I use the GFS for this storm. Short-range or nowcasting...
 

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I went with 10.1 inches for Charlotte earlier in the forecast contest. That would be the 7th biggest storm at CLT since 1930.

We'll see how it goes, but this is what I liked:
1. Strong upper wave bottoming out in the trough - that's when fireworks go off
2. Mid-level lows are closed and 'spinny' as they track across SC
3. Upstate mesolow formation and associated mid-level convergence
4. Highly anomalous soundings with very cold profiles, deep dendrite growth zone (DGZ), and mid-level frontogenesis co-located in the DGZ

The last holdout to me was the QPF inching up on the modeling, and I thought what we saw today was noteworthy. Good luck to all!


Jan 29 CLT Top 10.png
 
griteater said:
I went with 10.1 inches for Charlotte earlier in the forecast contest. That would be the 7th biggest storm at CLT since 1930.

We'll see how it goes, but this is what I liked:
1. Strong upper wave bottoming out in the trough - that's when fireworks go off
2. Mid-level lows are closed and 'spinny' as they track across SC
3. Upstate mesolow formation and associated mid-level convergence
4. Highly anomalous soundings with very cold profiles, deep dendrite growth zone (DGZ), and mid-level frontogenesis co-located in the DGZ

The last holdout to me was the QPF inching up on the modeling, and I thought what we saw today was noteworthy. Good luck to all!


View attachment 192070
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10.1 would be the 4th largest for CLT in my 49 years. February 2004, January 1988, and March 1983 are the top 3.
 
JalenW25 said:
View attachment 192078


View attachment 192079
Start of 21z Rap on top, current radar on bottom. Now granted i'm not sure how much of that if any of it at all is actually hitting the ground and sticking but Kat Campbell did say they had saw snowflakes on the Kerr Lake Skycam
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Yep. Lots of investing a single runs that aren’t even initializing right. Crazy stuff.
 
Am I the only person understanding that the SLRs will be 15:1 up to 20:1, i believe the models have a bias of 10:1 LSR, here at CAE they are calling for 6 to 9 inches, which is correct based on the ratio, just honestly never read any one talk about the dry fluffy snow, please correct me if I am wrong.
 
ragtop50 said:
More interesting discussion from RAH this afternoon on the setup (and the potential dry slot)...

Snow should really increase in coverage and intensity beginning
Saturday morning, with the event likely peaking in the afternoon and
evening as the mid/upper low interacts with the deepening coastal
low and a band of 850 mb frontogenesis sets up. With very cold
temperatures in place, the snow will be of the dry and fluffy
variety as snow to liquid ratios through the event generally range
from 12:1 to 20:1, lowest in the SE and initially, highest in the NW
and by Saturday evening/night. Liquid equivalent QPF for the event
is generally expected to range from a third to three quarters of an
inch, lowest N and highest SE. This generally translates to 4 to 8
inches across most of central NC, but a band of 8 to 12 inches is
likely to set up somewhere over the state with the best chance along
and east of I-95. There is also a scenario where many spots receive
lower amounts that will have to be monitored, which is explained
below.

Despite only being 24 hours from the event, there is still quite a
bit of discrepancy among the models on where exactly the band of
heavier snow will be, and it will depend on where exactly the
elevated frontal zone sets up, as well as how far south the
mid/upper low tracks. This is a complex setup and small shifts in
track and intensity can have a huge effect on how much snow falls.
If the mid/upper low tracks farther south, it will take longer to
interact with the coastal low, keeping the 8+ inch amounts to our
east, and potentially resulting in lower than expected snowfall
totals across a good portion of central NC. This is the scenario
depicted by the 12z NAMNest and 18z HRRR, which depict very light
amounts stretching from the northern Coastal Plain into the NE
Piedmont due to a gap in forcing between the mid/upper low to our
west and the coastal low to our east, a signal that has shown up on
some model runs since yesterday. This is a concerning trend that
will have to be monitored to see if it continues. But until there is
more consistency from run to run, it`s hard to take this one
scenario with too much weight. High-res models have been waffling
back and forth, with a notable shift east in the axis of heaviest
snow in some of the 12z and 18z runs compared to 06z. However, if
the mid/upper low and coastal low interact sooner, as depicted by
models like the 12z GFS and lower-resolution NAM, a larger area of
moderate to heavy snow will develop over central NC. Bust potential
is fairly high and this may be a nowcasting situation where we don`t
know exactly how far inland the heaviest snow will get. For now, a
Winter Storm Warning continues from this evening through Sunday
morning.
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I think this discussion sums up the situation for KRDU and surrounding areas very well. This looks to be an almost all or nothing storm depending on where that dry slot sets up. Model runs show some of the most discrepancy I have ever seen before a winter weather event. On the edges of the dry slot there might be some very high totals. I'm hoping for the higher totals but I aware that there is a chance that this storm could be a comparative bust compared to other areas. Best of luck to everyone!
 
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