Everything about it was marginal but for once it all barely worked out. 26 hours of snow with 850s and surface temps right at or barely above freezing.
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Pattern January 2021 - Joyless January
- Thread starter TheBatman
- Start date
@138 more precip into ga, may be an improvement over 6z?
Storm5
Member
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more precip than 6z for sure
More Precip, also colder in Carolinas Wow?more precip than 6z for sure
EastAtlwx
Meteorologist
I mean overrunning is essentially just isentropic upglide due to differential advection and the air parcel conserving it potential temperature.. so in a way is it correct to say that CAD is a spatially controlled form of this by terrain resulting from less than 1 froude number
Need harder returns over South Carolina.
Nah, we are just to warm. Wet bulb is not ideal.
soundings down into sc look pretty good, sfc a little warm but otherwise not bad.
I know we need some low level help....but it could have some legs...
Webberweather53
Meteorologist
CAD can be characterized as subset of overrunning sure I agree with that, but I want to clarify that they definitely aren't the same thing because CAD involves a geostrophic & hydrostatic adjustment process of cold air building up against the lee side of terrain (causing local sfc pressure rises) w/ the low-level flow that's blocked by the terrain, and acquiring a northerly component as a result. That doesn't always happen in overrunning in general, you can actually get overrunning w/ southerly sfc winds, which isn't possible in CAD. You see southerly wind overrunning more frequently in the northern US in the heart of winter where it's cold enough to support wintry precip almost regardless of wind direction
At least we continue to be pretty active. We have had a lot of minor events, sure. But Winter has stayed active. This looks to be yet another storm to talk about the remainder of the week.
MichaelJ
Member
This far out you probably be reciting the mantra, "it is the GFS". Even the EURO at this range is highly inconsistent. The pattern does look good for the final 11-12 days of the month but we don't always score even when it is.
I see no way this can improve for those outside of the favored climo regions (***of the southeast***). Without some cold high pressure, we will continue to track marginal events that will end up being slop storms that yield illusions of grandeur and end in great disappointment. I can't wait to be proven wrong, but I highly doubt I will be.
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Thor
Member
Waco texas got the most snow its had since 1982 the other day.
EastAtlwx
Meteorologist
Oh yeah I totally forgot about the geostrophic & hydrostatic components of CAD.. yet I’m sitting here using froude numbers which are ground in the hydraulic principles ??
Thor
Member
hahaha about as much as usual. But it's kind of luck of the draw. I know my night time lows have been below freezing more than most years but just haven't lined up a storm with that.
Getting there 
Webberweather53
Meteorologist
Well, no, cold highs to the north usually give you CAD and there are more winter setups than CAD here in the Carolinas. Miller A cyclones rarely have cold highs in the right position or directly to the north.
If the sfc low intensifies, you end up w/ more precipitation & cold air advection on the backside & it's not gonna take much to make that happen.
There's plenty of cold air in the low-levels w/ 850s like these being progged, just not right at the sfc because the precip is too light on the model verbatim but we're still like 5-6 days out. More precip and a deeper sfc low to create an isallobaric effect w/ enhanced northerly low-level winds and you end up w/ legit storm over the piedmont.
This could certainly go to hell in a hand basket no doubt, but it's really not anywhere near as bad as you're leading people to believe.
CMC has a close miller A sort of setup 
Stormlover
Member
I had about 1 1/2 inches yesterday. Great start and definately think things can happen soon, maybe as soon as sun night/mon
This to an extent does remind me of February 2020, because that storm had a very dominant southern stream that got cut off in the pacific, and as we got closer, the northern stream strengthened and allowed for a storm.
Stormlover
Member
exactly!
Webberweather53
Meteorologist
Oh yeah I totally forgot about the geostrophic & hydrostatic components of CAD.. yet I’m sitting here using froude numbers which are ground in the hydraulic principles ??
I honestly never really thought about CADs being a subset of overrunning but it's 100% true actually. It's akin to saying every square (CAD) is a rectangle (overrunning), but rectangles (overrunning) aren't squares (CAD).
Can’t wait to see the GEFS, hope it keeps the strong signal
?
Storm5
Member
Here comes the freezer on the gfs 
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and of course, it seems as though moisture is always over performing right now... I think the rain we had overnight was supposed to be very light and I went out this morning to find .75 inch in my rain gauge
Webberweather53
Meteorologist
The models are clueless with all these upper lows flying around
HSVweather
Member
There was a big spread in amounts from Athens to SE Huntsville. I had about .5 on county line but Athens had much more. Not much in south and east.
tennessee storm
Member
Here comes the freezer on the gfs
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Not buying yet. Sure it will get pushed backHere comes the freezer on the gfs
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Pretty big decrease on the GEFS, lol
looks pretty decent for those of us in Mississippi and Alabama. Be interesting to see individual members
Webberweather53
Meteorologist
Just came across a very interesting research that shows in GFS ensemble re-forecasts over the last 30 years that the worst forecasts and lowest predictability in the model tends to occur during major jet regime shifts (extension to retraction) and during the development and maintenance of high-latitude blocking in the N Pacific (-EPO/WPOs) & that this high-latitude blocking (-EPO/-WPO) are underforecast ~25% of the time.
Basically, we're fixing to encounter a period w/ very low predictability in the N Pacific in late January, and historically these blocks are often underestimated vs reality. Given this aforementioned information and that the GEFS is more aggressive w/ this -WPO/-EPO than the EPS, I'm tempted to lean towards the GEFS here but sometimes it can be overcooked beyond 300+ hrs.
Coupled w/ the increasing tendency for -NAO in the medium range, this ought to be fun to see what unfolds.
"The Development of the North Pacific Jet Phase Diagram as an Objective Tool to Monitor the State and Forecast Skill of the Upper-Tropospheric Flow Pattern"
https://journals.ametsoc.org/view/journals/wefo/34/1/waf-d-18-0106_1.xml
Basically, we're fixing to encounter a period w/ very low predictability in the N Pacific in late January, and historically these blocks are often underestimated vs reality. Given this aforementioned information and that the GEFS is more aggressive w/ this -WPO/-EPO than the EPS, I'm tempted to lean towards the GEFS here but sometimes it can be overcooked beyond 300+ hrs.
Coupled w/ the increasing tendency for -NAO in the medium range, this ought to be fun to see what unfolds.
"The Development of the North Pacific Jet Phase Diagram as an Objective Tool to Monitor the State and Forecast Skill of the Upper-Tropospheric Flow Pattern"
https://journals.ametsoc.org/view/journals/wefo/34/1/waf-d-18-0106_1.xml
The last look is really not far from something significant at all. The problem is like has been talked about, the models are having such a hard time with all the energy flying around you see the wild swings that we see here. That’s why I really feel like we’re in a pattern that we could see a winter storm pop up only 2 days out.
I don't think we're as far apart as you may think. What I am saying is that for those of us outside of the more favored climo areas of the southeast, it is a mighty fine needle to thread without a parent high of any kind and it is much more likely to end up with a snowfall distribution like 12/18-12/19/2009. That one sucked like heck and many areas looked to be right on the line for days ahead of that one only to end in a few meaningless flakes considering areas just to the west got clobbered. Of course anything is possible with a lot of cold air aloft around, but it requires more help than if a parent high were in play. Anyway, I hope like heck I am wrong.
