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Wintry 2/11-2/12 ULL Magic or More Cold Rain

Review of the Feb26,-27 2004 Macdaddy ULL:

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Review of the Feb26,-27 2004 Macdaddy ULL:

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The big difference between this event and Feb 26-27 2004 is the Feb 2004 had a nice 50-50 low south of Atlantic Canada to keep some feed of cold air going into the cut-off upper low. There's a ridge in its place this time, which means there is going to be even less cold air to work with here. Not a good sign for big snow outside the mountains.

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NWS RKE not biting yet.

.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 220 AM EST Wednesday...

Drier and warmer for early next week...

On Sunday the closed low moving across the Deep South will skirt
our area to the south and move offshore Monday. This system
presents the best chance for precipitation over the next 7 days,
although most of the rain will mainly be over NC and eastern
VA.
I really don't understand KBCB sometimes. I can understand not mentioning snow at this time. But they are even pessimistic about precipitation period.
 
No. All of that cooling is being driven by lift + dynamical cooling aloft from heavy precipitation. There's no legitimate cold air anywhere in sight for this upper low to tap into.
There is colder/drier air to the north with the push from new england. 35 knot jet at 925mb is helping to cool the piedmont. It's the only reason they're getting snow on the GFS... if you can't see that, then I dunno what to tell you. We can argue how "legitimate cold" it is I guess. But it's clearly colder than locations west of the apps.
 
Despite all the pretty 10:1 SLR maps from the GFS suite, I'm still having a hard time seeing how this works out in a big way for areas outside the mountains. I still can see some snow for sure, but I think it's going to be a very sloppy, low-end event in the best case scenario here.

I can't find any really good examples where an upper low totally cut off from the mean flow like this & crushed the piedmont + coastal plain. Cut off upper lows are fine but you usually still need at least a little injection of cold air continuing to funnel into the ULL.

This is a composite of 15 upper low cases I could find since the 1950s that actually worked out for folks east of the mountains. Notice the ridge anomaly to the west of the cut-off over the Upper Midwest & southern Canada helping to keep some injection cold air going into the base of this cut-off upper low.
View attachment 132471



Notice in our setup however, the ridge completely comes over the top and basically shuts off the tap of cold air from the north & you're having to rely entirely on precipitation rates to cool the column to freezing. If you're hoping for a big snow outside the mountains, this pattern isn't a good one for setups like these.


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Just to reinforce what I was talking about w/ the upper low composite in this previous post. You can see the high to the NW of the cut-off upper low over Minnesota & Manitoba feeding continental polar air into the base of the upper low. Yes, the upper low is also making its cold air, but it's not completely cut off from a cold air source & has a way to advect more in as heavy precipitation is ongoing. This weekend's setup doesn't have this tap of cold available to it, it's going to be that much more marginal for folks outside the mountains.



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There is colder/drier air to the north with the push from new england. 35 knot jet at 925mb is helping to cool the piedmont. It's the only reason they're getting snow on the GFS... if you can't see that, then I dunno what to tell you.

That cold air over New England is not getting advected into the upper low. This cold air is leftovers from the midwest & OH valley.
 
That cold air over New England is not getting advected into the upper low. This cold air is leftovers from the midwest & OH valley.
I'd disagree because every push south with the confluence over new england has lead to a shift south in temperature isotherms for the northern piedmont of NC. All of that helps even at mid levels.. colder 850's are good.

Nobody is going to argue with you that this isn't a marginal setup with no decent cold air source. But it's the best opportunity we've had all year... we'll track and hope for the best. Mountains seem like a lock for a solid hit either way.
 
I'd disagree because every push south with the confluence over new england has lead to a shift south in temperature isotherms for the northern piedmont of NC. All of that helps even at mid levels.. colder 850's are good.

Nobody is going to argue with you that this isn't a marginal setup with no decent cold air source. But it's the best opportunity we've had all year... we'll track and hope for the best. Mountains seem like a lock for a solid hit either way.

You can disagree with me all you want, but the facts are this air mass is not coming from New England, as the backward HYSPLIT trajectories from the GFS show.

It's stale, leftover table scraps from the midwest.

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Despite all the pretty 10:1 SLR maps from the GFS suite, I'm still having a hard time seeing how this works out in a big way for areas outside the mountains. I still can see some snow for sure, but I think it's going to be a very sloppy, low-end event in the best case scenario here.

I can't find any really good examples where an upper low totally cut off from the mean flow like this & crushed the piedmont + coastal plain. Cut off upper lows are fine but you usually still need at least a little injection of cold air continuing to funnel into the ULL.

This is a composite of 15 upper low cases I could find since the 1950s that actually worked out for folks east of the mountains. Notice the ridge anomaly to the west of the cut-off over the Upper Midwest & southern Canada helping to keep some injection cold air going into the base of this cut-off upper low.
View attachment 132471



Notice in our setup however, the ridge completely comes over the top and basically shuts off the tap of cold air from the north & you're having to rely entirely on precipitation rates to cool the column to freezing. If you're hoping for a big snow outside the mountains, this pattern isn't a good one for setups like these.


View attachment 132470
Spot on and that's what worry's me webb is where having to rely on surface temps to cool enough during precip to either make it or break it. Someone is going to get plastered while a few miles down the road it's a cold rain. I'd only be confident at this point if I was above 2500".
 
NWS RKE not biting yet.

.LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 220 AM EST Wednesday...

Drier and warmer for early next week...

On Sunday the closed low moving across the Deep South will skirt
our area to the south and move offshore Monday. This system
presents the best chance for precipitation over the next 7 days,
although most of the rain will mainly be over NC and eastern
VA.
They are always wait until last second campers, I remember one system we had that I myself thought we would get 2-4 inches and they had a trace for us. Then I was right and they were late to put out an advisory.
 
No one is derailing this discussion.
Actually as the argument between two posters continues, it does derail the discussion... sometimes it best to make a point then move on from it. It isn't a competition in here.
 
The 925mb jet can crush the hopes and dreams of Oconee and Pickens county as seen here with that God awful snow hole. I've seen it happen before, but it's not set in stone yet. We need a further west track to avoid getting the turn towards NNE winds at this level. Not only does it cut off the Cold air feed from the Northeast, but as the winds turn more northerly we start downslope warming.

A track more like the ICON keeps that from happening until after the precip pulls out though.
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Actually as the argument between two posters continues, it does derail the discussion... sometimes it best to make a point then move on from it. It isn't a competition in here.

The argument is about this setup and where the cold air is actually coming from, but yea I guess that's somehow off topic for this thread.
 
The 925mb jet can crush the hopes and dreams of Oconee and Pickens county as seen here with that God awful snow hole. I've seen it happen before, but it's not set in stone yet. We need a further west track to avoid getting the turn towards NNE winds at this level. Not only does it cut off the Cold air feed from the Northeast, but as the winds turn more northerly we start downslope warming.

A track more like the ICON keeps that from happening until after the precip pulls out though.
View attachment 132481View attachment 132482
The ole Highway 25 cutoff is brutal. I've said for a long time that mountains of SC are nice to get some big snows like Caesar's Head but I still stand on that you want to live north of 85 and east of highway 25 in SC if you want to continually have good chances for snow or frozen in general. Oconee and Pickens get hit hard with downslope and are always fighting warm air in the valley as shown by that map. Routinely Eastern Greenville, Spartanburg, and Cherokee counties hold on CAD longer, tend to fight off warm noises more, and can get hit with downslope, it's not nearly as pronounced.
 
The ole Highway 25 cutoff is brutal. I've said for a long time that mountains of SC are nice to get some big snows like Caesar's Head but I still stand on that you want to live north of 85 and east of highway 25 in SC if you want to continually have good chances for snow or frozen in general. Oconee and Pickens get hit hard with downslope and are always fighting warm air in the valley as shown by that map. Routinely Eastern Greenville, Spartanburg, and Cherokee counties hold on CAD longer, tend to fight off warm noises more, and can get hit with downslope, it's not nearly as pronounced.
We’re in a crap spot for sure. It is what it is. I’ve come to terms with it over the last 30 years. We’ve actually done pretty well the last 3-4 years. We’re due for screw job.
 
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Here was the EPS mean image from 00z that I found. Definitely more westward than the GEFS. Imo I would favor this closer to game time especially with NW trend still in the cards (and BL issues). Although let’s see if it trends more to the GEFS mean, maybe we will get lucky.
 
I'd disagree because every push south with the confluence over new england has lead to a shift south in temperature isotherms for the northern piedmont of NC. All of that helps even at mid levels.. colder 850's are good.

Nobody is going to argue with you that this isn't a marginal setup with no decent cold air source. But it's the best opportunity we've had all year... we'll track and hope for the best. Mountains seem like a lock for a solid hit either way.

The mountains will jackpot here. That’s where winter has a fighting chance. These rate driven, cold core set ups seem to give us either cold rain or very cold rain these days.


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We’re in a crap spot for sure. It is what it is. I’ve come to terms with it over the last 30 years. We’ve actually done pretty well the last 3-4 years. We’re due for screw job.
Unless you are literally right on the mountains on the border in that county, it's extremely hard in Oconee and Pickens and even Anderson north of 85. Cold air just seems to bleed better east of Hwy 25. I've watched changeovers take place routinely bleed down western Spartanburg and Eastern Greenville counties. 0Z GFS from last night actually showed that for a frame. I never expect a global model to pick up on the microclimates, but it's just funny that the look you see below in SC is usually where the changeover starts and spreads east and that's why places like Campobello, Landrum, Greer, Inman, Fingerville do really well when we can get it to snow (on top of the elevation plusses in these towns).
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Good write-up from RAH last night.

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 230 AM Wednesday...

Friday through Sunday: The upper trough and embedded shortwaves
should extend from the western Great Lakes, southwestward through TX
by Fri morning. Central NC will be under deep southwesterly flow,
situated between the trough to the west and the sub-tropical ridge
to the east. A persistent moist axis will set up from the Gulf
Coast, through the Southeast and southern mid-Atlantic as the high
amplitude trough progresses eastward Fri/Fri night. The two waves
within the trough begin to separate Fri/Fri night, with the southern-
most low closing off over the mid/lower MS Valley, while the
northern-most wave remains open over the Great Lakes/Northeast. The
northern wave will continue to progress eastward through the
Northeast and away from the CONUS on Sat, while the low over the
lower/mid-MS Valley deepens and becomes cutoff over the Deep
South/TN Valley. The model guidance continues to be variable with
the strength and track of this low Sat night/Sun, which thus lowers
forecast confidence
. Generally expect the low to swing through the
Deep South/Southeast and lift north-northeastward through the
Carolinas and off the mid-Atlantic coast through Sun night. At the
surface, while the occluding low over the Northeast/southeast Canada
drifts eastward on Fri, a low will develop over the Southeast, along
the attendant cold front extending SW from Maine to the Mouth of the
Mississippi. While the front from VA to ME will generally progress
eastward, the southern half from VA to the Gulf will become nearly
stationary, with the low lifting northeastward along it through the
day Fri. The cold front should finally collapse southeast through
the area Fri night, but linger along the Southeast US coast on Sat
as yet another low develops over GA/SC. High pressure extending from
the southern Plains to the Great Lakes will migrate eastward, making
more progress through the OH Valley and Northeast than the Deep
South Sat/Sat night. Both the GFS and ECMWF solutions deepen the low
over the Southeast US coast late Sat, which then migrates northeast
along the Carolina coast Sat night and Sun, then off the mid-
Atlantic coast Sun night.

"Precipitation: There will likely be multiple rounds of precipitation
from Fri to Sun. The first will be generally be convective, along
and ahead of the cold front Fri/Fri night. Have kept the chance for
thunder in Fri/Fri eve, generally along and east of US-1/I-95 where
the best instability is progged to be (though still very limited).
Rainfall amounts of half an inch to an inch NW to SE are expected.
The Piedmont may get a brief respite from rain late Fri night/early
Sat, while rain could persist across the Sandhills and Coastal
Plain. The next round of precipitation will spread northward through
the area Sat and Sun as the upper low swings through the Southeast
and the coastal low at the surface lifts along the Southeast US
coast. The exact track of the coastal low and also if and how
strongly the ridge is able to build southward into the area Sat and
Sun will have the greatest impacts on the weather across central NC
over the weekend. Should the ridge and CAA be stronger over the
Piedmont, there could be a period of wintry precip over the northern
Piedmont late Sat night/early Sun. Otherwise, precip should be
predominantly rain, with another half an inch to an inch expected.
"


So we need to hope the ridge trends stronger. There will be some cold air to pull from, but as Webber has talked about right now that gets shut off. I'll be very interested in future model runs looking at dew points (for colder/dryer temp trends) which would correspond with a stronger ridge.
 
Unless you are literally right on the mountains on the border in that county, it's extremely hard in Oconee and Pickens and even Anderson north of 85. Cold air just seems to bleed better east of Hwy 25. I've watched changeovers take place routinely bleed down western Spartanburg and Eastern Greenville counties. 0Z GFS from last night actually showed that for a frame. I never expect a global model to pick up on the microclimates, but it's just funny that the look you see below in SC is usually where the changeover starts and spreads east and that's why places like Campobello, Landrum, Greer, Inman, Fingerville do really well when we can get it to snow (on top of the elevation plusses in these towns).
Super tight a normal as you mentioned. In Rutherford places like caroleen down 120 back to 221 to Rutherfordton always has a tight line between the good the bad and the ugly.
 
Super tight a normal as you mentioned. In Rutherford places like caroleen down 120 back to 221 to Rutherfordton always has a tight line between the good the bad and the ugly.
Yes sir. Couldn't of said it better my self. Hopefully will be on the good side of this one. Your elevation will help you a little more than me in this one. It will be close if we can get the intense heavier rates to pull the cold air down from aloft. Least we have a shot at something the way things have been.
 
Fwiw, sure looks like the NAM going to close this off sooner, way south, but too soon for some of us that's for sure. Really would love to see the Ukie and Euro hold this longer on the 12z runs
 
Fwiw, sure looks like the NAM going to close this off sooner, way south, but too soon for some of us that's for sure. Really would love to see the Ukie and Euro hold this longer on the 12z runs
Actually not that far south, I don't think I'm going to like this NAM run..... on to the next one lol
 
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