brooklynwx99

we've seen that Rex block look with a monster -EPO trapping a black hole over San Fran multiple times over the last few years. sickening

I agree. the reason why these patterns can appear cold and dry for a time before threats pop up is because of setups like this... this is the type of vort that can easily trend more amped and lead to miller B or strong clipper

FWIW the 12z models have shown some interest in allowing the Dec 1 wave to become more of its own entity, as seen on the GEFS. the airmass is much better and the -NAO is more established, so this is worth watching IMO

FWIW the 12z models have shown some interest in allowing the Dec 1 wave to become more of its own entity, as seen on the GEFS. the airmass is much better and the -NAO is more established, so this is worth watching IMO

models start bringing the baroclinic zone northward with more precip around the 5th. luckily we should have a cold airmass established unlike with the Thanksgiving storm

also, I agree with your point about the first week of Dec... there's a signal for a large 50/50 ULL and decaying block over the Davis Strait. climo is better and cold air is more firmly in place. this is probably the main window to watch if I had to pick one at this juncture

the timeframe around the 5th looks conducive for something bigger regionwide... anomalous 50/50, a decaying block over the Davis Strait, and persistent cross-polar flow. combine with an active STJ for split flow and there's a lot to like here

that's why I think holding the shortwave back with stronger confluence makes more sense. the GFS tried but it was just a bit too sloppy. I like its general evolution

FWIW the NAO pays off as it decays later in the run:

offshore. the overall synoptic setup was more favorable... Wiz is saying the same thing

right? that -NAO really slows down the flow. I think we want to see a more hung back vort overall, but seeing the confluence trend stronger is also important

i know we've been burnt over the last few winters but come onnnnnn

GFS has a much more interesting solution for next week... holds the main wave back and allows the block to go to work more. we've seen confluence and the -NAO trend stronger, which is nice to see

similar progression occurred in 2010

yup, it was in the "good phases" in Feb 2012 as well

yeah, the stronger that gets, the better if you can nose that -NAO more into central Canada you can also pop transient HP

my initial impression of late Nov into early Dec so far is that the persistently +AAM that's being forecasted combined with +EAMT event is extending the Pacific jet more than is typical of La Nina. extensions are often favorable for us, and I believe these factors are overriding the largely unfavorable MJO passage this general pattern favors +EAMT into early Dec, allowing for a persistently extended Pacific jet that leads to an Aleutian trough. the MJO isn't a silver bullet, and i do think we're seeing a break in the typically strong MJO correlation

my initial impression of late Nov into early Dec so far is that the persistently +AAM that's being forecasted combined with +EAMT event is extending the Pacific jet more than is typical of La Nina. extensions are often favorable for us, and I believe these factors are overriding the largely unfavorable MJO passage this general pattern favors +EAMT into early Dec, allowing for a persistently extended Pacific jet that leads to an Aleutian trough. the MJO isn't a silver bullet, and i do think we're seeing a break in the typically strong MJO correlation

my initial impression of late Nov into early Dec so far is that the persistently +AAM that's being forecasted combined with +EAMT event is extending the Pacific jet more than is typical of La Nina. extensions are often favorable for us, and I believe these factors are overriding the largely unfavorable MJO passage this general pattern favors +EAMT into early Dec, allowing for a persistently extended Pacific jet that leads to an Aleutian trough. the MJO isn't a silver bullet, and i do think we're seeing a break in the typically strong MJO correlation. never been happier to be wrong about a forecast, let me tell you

nothing about this says 60s to me. all of the cold air is on this side of the globe and cross polar flow remains established

@ORH_wxman and to your point, both Greenland and the N Pac have only trended better over the last few days opposite of the last few years

yup. you’d have to turn the clock a back a decade for looks like these

Although it's early in the year, next week's setup is a good one, as there is a potent ridge over AK that's reaching all the way into Siberia, promoting cross polar flow. Perhaps most notably, there is a developing Greenland block that forces a 50/50 ULL (ULL over Nova Scotia, basically). As a vort gets ejected from the Rockies, the confluence from the 50/50 ULL may push colder, drier air into the flow and can prevent the main energy from shooting north. This is more of an overrunning to coastal or SWFE type event rather than a potent Nor'easter, to be clear. This is a favorable setup for snowfall, even down to the Mason-Dixon line. If it was late Dec instead of late Nov, I would be more open to workable coastal snowfall, though that is a difficult ask given how warm waters are. The main points of contention are: 1) how quickly does the vort get ejected? 2) how much of the vort gets ejected? and 3) how strong is the confluence? I would argue that the confluence is the most important part of the setup... if it vanishes, there is not enough press from the cold air and the setup is DOA. However, if the vort comes out too early, it won't matter. This is unlikely, though... if anything, the vort would come out of the Rockies too late or too sheared rather than before confluence forms. How the 50/50 ULL trends is crucial to this setup and I will be watching that closely. These cross polar flow patterns are pretty much the only ones cold enough to allow for snow at this time of year, and there is very high confidence in one developing. We are still at the range where the vort can get sheared to nothing, so the storm can still "disappear." Just don't write the threat off due to the time of year.

Although it's early in the year, next week's setup is a good one, as there is a potent ridge over AK that's reaching all the way into Siberia, promoting cross polar flow. Perhaps most notably, there is a developing Greenland block that forces a 50/50 ULL (ULL over Nova Scotia, basically). As a vort gets ejected from the Rockies, the confluence from the 50/50 ULL may push colder, drier air into the flow and can prevent the main energy from shooting north. This is more of an overrunning to coastal or SWFE type event rather than a potent Nor'easter, to be clear. This is a favorable setup for snowfall, even down to the Mason-Dixon line. If it was late Dec instead of late Nov, I would be more open to workable coastal snowfall, though that is a difficult ask given how warm waters are. The main points of contention are: 1) how quickly does the vort get ejected? 2) how much of the vort gets ejected? and 3) how strong is the confluence? I would argue that the confluence is the most important part of the setup... if it vanishes, there is not enough press from the cold air and the setup is DOA. However, if the vort comes out too early, it won't matter. This is unlikely, though... if anything, the vort would come out of the Rockies too late or too sheared rather than before confluence forms. How the 50/50 ULL trends is crucial to this setup and I will be watching that closely. These cross polar flow patterns are pretty much the only ones cold enough to allow for snow at this time of year, and there is very high confidence in one developing. We are still at the range where the vort can get sheared to nothing, so the storm can still "disappear." Just don't write the threat off due to the time of year.