February 4th-6th Overunning & Possible Coastal Threat

[IsentropicLift]

We have a few lose ends to clean up before the middle of next week but the guidance is overwhelmingly pointing towards a threat for a major storm system to affect much of the eastern half of the United States starting early next week and lasting for several days.

 

The ensemble guidance continues to be the most consistent. Despite the 00z ECMWF operational keeping the system well to our south, the ensemble mean is quite a bit further north tracking a low off the Carolina or mid-atlantic coast.

 

The 00z GGEM ensemble mean generally supports the 00z GGEM operational with a heavy over running snow event flipping to a heavy wintry mix tracking a low off the Delmarva coast and then towards Cape Cod.

 

Now onto the GFS which has been the most consistent model of the pack. The last several runs of the GFS outside of yesterdays 12z run have shown significant snow events for a majority of the region.

 

One improvement in the last few model cycles seems to be that the possibility of a cutter is slowly diminishing. That's not to say that the threat of a cutter is zero, but at this time it looks like the bigger thereat would be to keep this suppressed.

 

These gradient patterns can be both very tricky to forecast and also very rewarding if you can get the chips to fall in the right places.

 

The GFS first showed this potential at day 15, that's pretty impressive. And while the Euro has waivered back and forth, the GFS has been very consistent with this threat. Hopefully we can cash in on this one, could be not only the biggest storm of the season but the biggest one in a few years.

[earthlight]

Pasting this from the other thread to continue discussion:

 

It has been a while. 1-6-94 to 2-11-94 was one of my favorite examples where we had numerous overruning
events with the bulk of the blocking back near Alaska to the pole like we are seeing in the forecast next week.


94.gif

f180.gif

Really nice analog find. I think much of this set up is going to come down to the amplitude and timing of the polar vortex and associated energy over Central Canada. The newer model runs which are showing the snowy scenarios have the PV lobe swinging southward at a favorable time to push the big ejecting shortwave southeastward and force secondary development along the baroclinic zone. The older runs had this same lobe a little more delayed, so not only was there less cold air available but the SE Ridge was able to amp up as well.

The good sign is that most guidance seems to agree on the same major players being on the field. This can be a great overrunning set up for our area with lots of moisture if it is timed well. I don't buy the Euro trapping the shortwave back in the Baja, either. But we need the PV timing to be correct as mentioned above in this set up I think. Without any blocking we are relying on that to keep this from taking a warmer track.

[REDMK6GLI]

We have a few lose ends to clean up before the middle of next week but the guidance is overwhelmingly pointing towards a threat for a major storm system to affect much of the eastern half of the United States starting early next week and lasting for several days.

 

The ensemble guidance continues to be the most consistent. Despite the 00z ECMWF operational keeping the system well to our south, the ensemble mean is quite a bit further north tracking a low off the Carolina or mid-atlantic coast.

 

The 00z GGEM ensemble mean generally supports the 00z GGEM operational with a heavy over running snow event flipping to a heavy wintry mix tracking a low off the Delmarva coast and then towards Cape Cod.

 

Now onto the GFS which has been the most consistent model of the pack. The last several runs of the GFS outside of yesterdays 12z run have snow significant snow events for a majority of the region.

 

One improvement in the last few model cycles seems to be that the possibility of a cutter is slowly diminishing. That's not to say that the treat of a cutter is zero, but at this time it looks like the bigger thereat would be to keep this suppressed.

 

These gradient patterns can be both very tricky to forecast and also very rewarding if you can get the chips to fall in the right places.

 

The GFS first showed this potential at day 15, that's pretty impressive. And while the Euro has waivered back and forth, the GFS has been very consistent with this threat. Hopefully we can cash in on this one, could be not only the biggest storm of the season but the biggest one in a few years.

very good thinking on starting this thread buddy, this threat I will say now officially has some legs but still TONS to iron out. biggest factor in my opinion to getting to take a BM track or thereabouts with multiple lows is the PV orientated correctly since the SE ridge will be in play. No blocking that PV will be beyond crucial. besides though its refreshing to have a great threat to follow for notoriously when we get some of our biggest snows, in February

[REDMK6GLI]

Pasting this from the other thread to continue discussion:

 

Really nice analog find. I think much of this set up is going to come down to the amplitude and timing of the polar vortex and associated energy over Central Canada. The newer model runs which are showing the snowy scenarios have the PV lobe swinging southward at a favorable time to push the big ejecting shortwave southeastward and force secondary development along the baroclinic zone. The older runs had this same lobe a little more delayed, so not only was there less cold air available but the SE Ridge was able to amp up as well.

The good sign is that most guidance seems to agree on the same major players being on the field. This can be a great overrunning set up for our area with lots of moisture if it is timed well. I don't buy the Euro trapping the shortwave back in the Baja, either. But we need the PV timing to be correct as mentioned above in this set up I think. Without any blocking we are relying on that to keep this from taking a warmer track.

 

earthlight could not agree with you more on the emphasis on the PV being that we have no worthy blocking to speak of to prevent the storm track from going to the north or the SE ridge ruining the snow for us. this storm is still very volatile and pretty much in my opinion depends on the cold push from the PV to keep this to the south for the snowier solution. I know the 1-94 analog had the same Alaska/poleward block but with no established -NAO it really does throw that uncomfortable monkey wrench into the equation

[earthlight]

The 00z Euro Ens were impressive for this event once again. A few things to note as we continue moving forward here. They tightened the confluent gradient to the north which is an impressive sign. So with the PV in a better position, the surface high is strengthening on the ensemble mean. The surface low also trended deeper (likely only a sign of more members picking up on the threat). There are still likely some northward leaners with the 850 0c line getting up to about Trenton, but that data is essentially noise on the ensembles at this point. The signal is strong and hasn't budged in two days now.

 

The one thing I will say is that we are still far in the extended range. 180 hours out is not close at all. So we need to be really careful and understand the synoptics around the threat before we start getting attached to any specific solutions.

 

The Euro ensembles also had light snow from 120-144 hours with that lead vort.

[earthlight]

earthlight could not agree with you more on the emphasis on the PV being that we have no worthy blocking to speak of to prevent the storm track from going to the north or the SE ridge ruining the snow for us. this storm is still very volatile and pretty much in my opinion depends on the cold push from the PV to keep this to the south for the snowier solution. I know the 1-94 analog had the same Alaska/poleward block but with no established -NAO it really does throw that uncomfortable monkey wrench into the equation

 

If we get the PV timed well I think we are in business. So long as the models aren't completely mishandling something (never totally out of the question) there is very good agreement on that pacific energy diving into the Southwest US. You can even argue that the SE Ridge amplifying a bit is going to aid in tightening the baroclinic zone too..there could be some pretty significant precipitation along the gradient and if the models are correct in modeling the shortwave, the impressive lift will give somebody a lot of snow.

[REDMK6GLI]

If we get the PV timed well I think we are in business. So long as the models aren't completely mishandling something (never totally out of the question) there is very good agreement on that pacific energy diving into the Southwest US. You can even argue that the SE Ridge amplifying a bit is going to aid in tightening the baroclinic zone too..there could be some pretty significant precipitation along the gradient and if the models are correct in modeling the shortwave, the impressive lift will give somebody a lot of snow.

 

im taking into account also the models as a whole outside of 120 hrs really have not been too consistent. I know the pattern we were in was making it hard to concentrate on just one perturbation. I just feel until we are inside of 120 hrs, preferably 96 hours we can start getting excited or disappointed. the run of the EURO was impressive and improved but waiting till Super Bowl Sunday there "should" be a good amount of agreement then as to what to expect. Long Range still and nothing is set in stone as of now

[IsentropicLift]

FWIW the DGEX continues to show a major event

 

[jm1220]

Hopefully the energy coming out of the Southwest stays positively tilted and sheared out, kind of like the storm that just passed us. With more of a SE ridge, that kind of a setup would be very favorable for us if the PV cooperates, like Earthlight was saying. In the progressive pattern we've had, I'd say that's fairly likely. But if the PV is modeled wrong and isn't in place at the right time, or if this storm breaks the mold and is a consolidated, sharp trough this can still end up being a cutter or too warm for many of us to see a lot of snow. With southern stream involvement though, this should be a very wet system and there should be a lot of snow for somebody. It's still way too far out though for specific details. Any high latitude blocking would also be a huge help.

[+SNfreak21]

The ensembles are consistent and the operational runs are slowly catching on, and if you see the 1994 analog to now it looks almost the same, let me tell you why I think the PV will not move north, those massive heights over Alaska and the arctic will keep the PV close enough to us, you also see an elongated 50/50 low stretching to Iceland, it keeps the cold air source and drills HP from eastern Canada due to the confluence of the SE ridge

[earthlight]

So much of this has to do with the eventual evolution of the PV lobes and associated disturbances in Central Canada. So despite the fact that we are seeing some modeling consistency with the disturbance moving from the Pacific into the Southwestern US, my confidence is still extremely low on any specific solution and lower than it usually would be even at this range. The forecast models have struggled tremendously with handling the individual features and evolution of the pattern over Canada for the greater part of the past two months. 

 

The models which show colder, snowier solutions; i.e the ones that force the baroclinic zone to tighten farther south and have coastal development, have increasing confluence over the Great Lakes and Southeast Canada as a piece of the PV swings southeastward and essentially acts as a block to prevent any northwestward progression of the surface low. The warmer model runs from yesterday had this feature much farther west and even lobing southward and interacting with the Southwest US disturbance, allowing for height rises over the Southeast US and all the way into New England. 

 

My point is that at this range it is hard to say which solution is correct and which isn't. The encouraging sign right now is that ensemble guidance has been consistently pointing to a moderate winter storm threat in our area. Additionally, the EPO ridge positioning may argue for favorable positioning of the Canadian features which are a wild card in this set up -- and they additionally may help to increase low level cold air support. The guidance picking up on confluence at this range is always a good sign. 

 

Just some morning thoughts. Lots of time...and lots of ridiculous OP model solutions to go. I strongly suggest you all become well versed in understand ensemble guidance and trends over the next week...you're going to need it if you want to stay sane. 

 

[Sn0waddict]

The 00z Euro Ens were impressive for this event once again. A few things to note as we continue moving forward here. They tightened the confluent gradient to the north which is an impressive sign. So with the PV in a better position, the surface high is strengthening on the ensemble mean. The surface low also trended deeper (likely only a sign of more members picking up on the threat). There are still likely some northward leaners with the 850 0c line getting up to about Trenton, but that data is essentially noise on the ensembles at this point. The signal is strong and hasn't budged in two days now.

 

The one thing I will say is that we are still far in the extended range. 180 hours out is not close at all. So we need to be really careful and understand the synoptics around the threat before we start getting attached to any specific solutions.

 

The Euro ensembles also had light snow from 120-144 hours with that lead vort.

Perhaps I'm wrong, but I thought I read earlier that we would want the low to stay weaker.

[earthlight]

Perhaps I'm wrong, but I thought I read earlier that we would want the low to stay weaker.

 

The ensemble mean had a very weak, broad surface low depiction at this range because of the 51 different members showing varying solutions. So the fact that we are starting to see some consolidation of a surface low on the ensemble guidance is encouraging, as it at least tells us that more members are picking up on the surface low being in that general area. 

[Weathergun]

Main questions here are:

 

1. How strong the southern stream energy will be?

2. How much of confluence or 50/50 low will get out the PV over Hudson Bay/SE Canada?

 

They are too many run to run differences on operationals. The ensemble means have been more consistent. But they have ensemble members that show cutters and 40/70 BM tracks.

[Sn0waddict]

The ensemble mean had a very weak, broad surface low depiction at this range because of the 51 different members showing varying solutions. So the fact that we are starting to see some consolidation of a surface low on the ensemble guidance is encouraging, as it at least tells us that more members are picking up on the surface low being in that general area. 

Makes complete sense, thanks!

[IsentropicLift]

Out of the 00z GEFS members that I can see here was the breakdown:

 

1/12 with a true cutter

1/12 with an apps runner

8/12 that look very similar to the 06z GFS OP

2/12 that look like the 00z ECMWF

 

4 or 5 out of the 8 which looked like the GFS looked as strong or stronger that the op.

[PB GFI]

IF YOU WANT SNOW , HERE YOU GO , 

Part 1 ,

You can see  here How as the WPO  pops POS  allowing the the PV to relax allowing the SE Ridge to send the Sat`s system west .

Then you see as the WPO heads NEG  starting around the Sun- Mon time frame it pumps the heights across the pole and forces the  PV  S creating confluence 

By the time we are out to day 6  we are 3 SD below normal and the PV should offer enough confluence that this doesnt cut .

 

Part 2 , If the troughs are Pos tilted they come under . 

[earthlight]

The Euro has been very consistent with developing that lead wave as well. We'll have to see if any more models catch on by increasing the amplitude of it over the southwest US by Day 3-5. We'll have to think about making a specific thread for that system as well if that is the case.

[Saturn510]

Would the lead wave if it developed more per say screw everything up after it or help us out more?

[96blizz]

The Euro has been very consistent with developing that lead wave as well. We'll have to see if any more models catch on by increasing the amplitude of it over the southwest US by Day 3-5. We'll have to think about making a specific thread for that system as well if that is the case.

And at 126, it's there on the GFS with some decent precip back in WV...  A bit colder too --- see if she climbs a bit.

[96blizz]

...and squashed by 132.

[IsentropicLift]

12z GFS is more amplified than 06z with the SW trough. It's going to phase in a piece of the PV at 150. Low over Mississippi. Think this is going to be a big hit.

[PB GFI]

...and squashed by 132.

Could set up the Baroclinic zone thru the M / D line , u want to shunt the SE  ridge . 

[IsentropicLift]

Over running beginning hour 153, or Tuesday afternoon.

[earthlight]

The GFS has again wildly changed its handling of the PV to the north of our area -- the split now allows interaction to occur well to far west. If this occurs you can hedge your bets on a warm evolution for our area.

[earthlight]

12z GFS is more amplified than 06z with the SW trough. It's going to phase in a piece of the PV at 150. Low over Mississippi. Think this is going to be a big hit.

 

There is too much warm air advection to play around with phasing anything West of the Mississippi. You don't want that to occur at all.

[IsentropicLift]

Cutter, low over eastern KY at 159.

[IsentropicLift]

Most of NNJ is ZR 159-162 but likely going to flip to rain on the next frame.

[IsentropicLift]

Low heads for western PA, low level cold air hanging tough in the NW interior. Probably a major ice storm for places like Sussex County NJ.

[SnoSki14]

No point worrying about every model run right now as it'll just drive you crazy. Still going with cutter though.