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Pattern November Knock-Out

SD said:
Hmmm
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SD said:
Hmmm
054b93776ea49bb333c8bb61c2470c19.jpg


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blocking anyone.... see if that holds....
 
Webberweather53 said:
Just your run of the mill 1045 hPa high over southern Quebec and Ontario... Yikes that's nuts for the heart of winter much less early-mid November.
:eek:
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Remember last year, all through winter we were seeing like 1018 highs when we were about to get a a winter storm and hope it would make it to 1020/1023 in future runs!? A 1045 in a perfect spot, is a great start! Dec 2002 redux!??
 
Webberweather53 said:
The GFS usually does a piss poor job of sniffing out CAD in the short-medium range (due in large part to its overzealous mixing bias), the fact that it's already seeing a bonafide CAD event nearly a week out is a little alarming...
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Canadian actually does well with regards to temps on possible CAD
 
It’s been a long time probably 2002 since we had a cad that beefy.


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I remember the temperature dropped from the mid 50s to the mid 20s in a couple of hours.


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Tarheel1 said:
Canadian actually does well with regards to temps on possible CAD
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Yeah the GFS, like most other NWP has a mixing bias, meaning that it will erode CAD domes too quickly (because the primary mechanism to erode them is thru turbulent mixing)...
The model support is unusually strong that this high is going to be a beast... The Canadian has a 1035 sitting over north-central VA. Ouch
gem_mslpaNorm_eus_25.png
 
Webberweather53 said:
Yeah the GFS, like most other NWP has a mixing bias, meaning that it will erode CAD domes too quickly (because the primary mechanism to erode them is thru turbulent mixing)...
The model support is unusually strong that this high is going to be a beast... The Canadian has a 1035 sitting over north-central VA. Ouch
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Is there any chance that the models are underdoing the wedge as usual? I fear that if they are, the temps could be a lot colder than predicted.
 
Has there ever been a significant ice storm, involving a wedge, all the wayinto GA, this early in November? Around the 12th??
 
ForsythSnow said:
Is there any chance that the models are underdoing the wedge as usual? I fear that if they are, the temps could be a lot colder than predicted.
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Even if the air mass were to remain as strong as currently forecast, yes there's a lot of room for the wedge to trend stronger & last longer than forecast. Of course, the models in general have actually been deepening this trough over SE Canada and New England in the medium range, thus this airmass may get even colder and consequently, the accompanying arctic high pressure may become more intense as verification nears.

gfs-ens_z500trend_namer_14.png


As I also alluded to earlier, it also is a little worrisome that the coarse spectral global NWP models are already picking up on a very stout CAD event 6-7 days in advance... Even if this general setup holds as is and the incoming cP airmass and high pressure don't intensify at all between now and then, I can imagine those along and NW of I-40/85 in NC and SC could end up having to contend w/ precipitation type issues in some way, shape, or form...
 
Webberweather53 said:
Even if the air mass were to remain as strong as currently forecast, yes there's a lot of room for the wedge to trend stronger & last longer than forecast. Of course, the models in general have actually been deepening this trough over SE Canada and New England in the medium range, thus this airmass may get even colder and consequently, the accompanying arctic high pressure may become more intense as verification nears.

View attachment 1501


As I also alluded to earlier, it also is a little worrisome that the coarse spectral global NWP models are already picking up on a very stout CAD event 6-7 days in advance... Even if this general setup holds as is and the incoming cP airmass and high pressure don't intensify at all between now and then, I can imagine those along and NW of I-40/85 in NC and SC could end up having to contend w/ precipitation type issues in some way, shape, or form...
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Hi Eric. Got a question. Are you seeing what everyone else is seeing with potential high latitude blocking developing toward mid -end of November? Is that a legit possibility or is it not worth getting excited about?
 
I'm on the southern edge of where CAD usually sets up. While I know I won't see anything wintry here in this case, I've found in my case I can often throw out the temp predictions during CAD events. If a CAD event is going to occur I suspect I'll be in the mid to high 50s for it with it being a raw/gray day.
 
The 12/2002 event was well modeled far out! All I had to go by was TWC 7 day on the local forecast and the event was being shown on there from about Sat/Sun and the event was that Thur/Fri!
 
I said over a month ago that this would be a winter with plenty of ice/mix storm chances due to cad, but I didn't expect an event to be showing up on the models already. This is still a week away. I'm not too concerned. However, I can't remember a November "7 day model run" with a wedge signature as strong as this one.
 
Is it possible that the potential HP could be relocated little west of whats being modeled? That would put Alabama at least cooler than whats shown.
 
I was around three years old during the 2002 storm, from what I could remember and from what my Mom told me we ended losing power early on and had to go to South Carolina.

Anyway, is anyone else staying up for the 00z models?
 
SimeonNC said:
I was around three years old during the 2002 storm, from what I could remember and from what my Mom told me we ended losing power early on and had to go to South Carolina.

Anyway, is anyone else staying up for the 00z models?
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Staying up is no big deal anymore thanks to the time change. :)
 
Tarheel1 said:
Has there ever been a significant ice storm, involving a wedge, all the wayinto GA, this early in November? Around the 12th??
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I have some info on this and will get back to you when i have the chance.to find my data.
 
Webberweather53 said:
Wait what? The Euro actually looks significantly colder on the new run especially over the Carolinas...

Yesterday's 12z run

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Last night's 0z run
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I was talking about the highs for Saturday and Sunday. across GA and SC. It's colder for NC only. In addition, the precipitation times are different as are the directions they come in and amounts.
 
At least it looks to go down to near average late this week, which is all you can ask for when you have record highs this time of year.
 
ForsythSnow said:
I was talking about the highs for Saturday and Sunday. across GA and SC. It's colder for NC only. In addition, the precipitation times are different as are the directions they come in and amounts.
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Ah okay, it wasn't clear what areas and times the models were warmer. GA and SC are near the periphery of the CAD wedge and it's often very fickle/shallow equatorward of the base of the Appalachians, and NWP models are notorious for poorly estimating the extent and initial timing of precipitation in CAD/overunning events characterized by moist WSW-SW flow aloft and shallow, gentle isentropic lift over the CAD dome...
ecmwf_uv700_east3_28.png

The erosion of the CAD on this Euro run is directly attributable to the increased mid level cold air advection, which disrupts and weakens the low-mid level inversion by enticing more mixing hence eroding the CAD dome faster especially in SC and GA...
ecmwf_t850_dt_nc_28.png
 
The GFS has a much weaker high over southern Quebec and Ontario this run although it's arguable the 1045 hPa high it was showing on yesterday's 12z run was very unrealistic to begin with... Regardless, anything over 1030 hPa is still argues for a very formidable, classic CAD event this weekend and we're safely well above that figure on all NWP models... Not to mention it's also going to be the 2nd week of November, anything so much as a token snowflake, sleet pellet, or freezing drizzle is a big win this early on in the fall and winter...
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Webberweather53 said:
The GFS has a much weaker high over southern Quebec and Ontario this run although it's arguable the 1045 hPa high it was showing on yesterday's 12z run was very unrealistic to begin with... Regardless, anything over 1030 hPa is still argues for a very formidable, classic CAD event this weekend and we're safely well above that figure on all NWP models... Not to mention it's also going to be the 2nd week of November, anything so much as a token snowflake, sleet pellet, or freezing drizzle is a big win this early on in the fall and winter...
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TWC obviously going with warmer solution! Has my high 58 on Sunday!
 
12z GFS forecast lows for Saturday and Sunday morning. First hard freeze of the season possible for parts of NC, perhaps even upstate SC on Saturday morning if guidance trends a tick cooler...
gfs_t2min_nc_21.png

gfs_t2min_nc_24.png
 
CMC has a much stronger CAD wedge than currently shown on the GFS in spite of its weaker source region high in Quebec/southern Ontario... Temperatures are near-below freezing across the western and northwestern piedmont of NC as some of the initial overrunning precipitation encroaches, likely in the form of very light rain/freezing rain

cmc_t2m_nc_25.png
 
Via Tomer Burg, record low 850 hPa temps (for this time of the year) are currently being forecast by the GFS for New England this weekend, hence the CAD potential...
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Webberweather53 said:
Via Tomer Burg, record low 850 hPa temps (for this time of the year) are currently being forecast by the GFS for New England this weekend, hence the CAD potential...
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Yeah, I have to wonder what a 1038 - 1039 high and 850 temps up there reaching -15 to -25 across a lot of the area could do down this way. I remember just over a week ago the temps were originally forecast to be in the upper 40s and with clouds, barely hit 40. If we get a wedge in overnight and clouds roll in, then we can do the usual "forget the models" and expect a chilly day.
 
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