12/20-12/21 Moderate/Intense Clipper Event?

[cyclone77]

FWIW, the new RGEM is similar to the 12z GFS. What's interesting is the IWX WRF model posted above. It's in agreement with the new NAM, and it's over 12hrs old. As T-snow and others have mentioned, we should have our final answers tonight with the 00z suites.

[L.B. LaForce]

06z ukie:

[cyclone77]

Well first, our last 3 winters have had 50" or more of snow....

With this unusually long lasting Greenland block type pattern again this season who knows what to expect. I guess expect the unexpected. Maybe we'll see some bizarre storm evolutions later in the winter. Last winter we had that 6 day long Christmas storm that did a complete loop over Minnesota for example.

[Hoosier]

First, it's weather forum and while you may consider me "poo poohing the system" I call it a realistic view and forums are for discussing varying points of view. Fact is, this appears to be a quick hitting Warm advection snow event with a 4-6 hour window with a 1-3 inch snowfall ending as drizzle. While I am not a pro met I have seen these type of systems plenty in my lifetime. The one thing that argues for more is sometimes these systems can out do what modeling projects ..but the further north and east one gets this will be more diffiult to do. I for one am not a fan of over hyping the event either..see last Sunday's system(OVER HYPED) and for that matter the system that dropped nil on the Chicago area Wednesday eve.(2 days out maybe 2-4" when I felt it was pretty easy to see that the dry air in place was going to lead to a virga fest). My ap;ogies if you cannot deal with realities that sometime it snows and sometimes it doesn't. One more note; when was the last time our area got three 50 inch snowfall years in a row? Gimme a break...dude.

I think your original post was overstating things though. Guess there's no real defintion for "slop fest" but I don't consider 27-30 for 95% of the event and almost all of the precip falling as snow to be that.

[Thundersnow12]

LSX WRF

[cyclone77]

12z 4km WRF

[Thundersnow12]

With this unusually long lasting Greenland block type pattern again this season who knows what to expect. I guess expect the unexpected. Maybe we'll see some bizarre storm evolutions later in the winter. Last winter we had that 6 day long Christmas storm that did a complete loop over Minnesota for example.

If someone can get in the sweet spot with this system and the xmas eve system then someone end up with a quick 12" of snow in under a week.

[L.B. LaForce]

LSX WRF

Oh yeah? MQT's WRF!

Not a fan of this one, its screws me over.

[cyclone77]

If someone can get in the sweet spot with this system and the xmas eve system then someone end up with a quick 12" of snow in under a week.

Yeah that's definitely a good possibility, especially considering how wet that xmas eve storm could be. This is the wrong thread to discuss it, but if that storm slows down just a little bit the QPF will quickly go up.

This has been an excellent start to the season as far as having systems to track. There's essentially been no down time since late November.

[Thundersnow12]

Oh yeah? MQT's WRF!

Not a fan of this one, its screws me over.

can you link me to that? thanks!

[Thundersnow12]

Yeah that's definitely a good possibility, especially considering how wet that xmas eve storm could be. This is the wrong thread to discuss it, but if that storm slows down just a little bit the QPF will quickly go up.

This has been an excellent start to the season as far as having systems to track. There's essentially been no down time since late November.

Ya its really been a fun pattern to follow and should continue.

[baroclinic_instability]

The red circle is it..

The pink looks like another piece of energy.. Maybe baro can confirm that?

Can see the pressure falls in CA/OR/NV here.

So yeah i believe the 00z runs will have it fully.

That big plume is the massive Pacific jet driving this whole beast. Some MADIS satellite derived winds are picking off 180+ KT winds in there at 250.

http://www.star.nesdis.noaa.gov/smcd/opdb/goes/winds/gifs/trwnd96.gif

As almost always, higher than the models predict.

[baroclinic_instability]

CMC finally got a clue what the heck is going on. Came in way stronger and amplified with the S/W ejecting into the plains. The CMC finally overcame its crappy bias to dissipate strong waves over the American mountain west. That takes a tiny bit of the variability out.

[A-L-E-K]

This smells like a lot of the other clipper-esque systems we've seen. For chicago area guys, heaviest snows should set up west with the band weakening as it pushes into our area. 1-4 is a good general call with highest far NW.

[goknights]

Really sharp gradient on the cmc as well. With some serious precip falling just north of that cutoff

[Northern_IN_Wx]

No change from my thinking yesterday...1-3" for most of the IWX FA...heaviest northwest. And then drizzle/freezing drizzle. Just a quick hitting WAA event here. Next...

[baroclinic_instability]

A few comments to make here. Most higher resolution guidance such as SREF/NAM generally develop some of the heaviest QPF early, likely some convective early, and rapid intensification. As usual, models almost always underestimate the strength of the Pacific jet as it is over water, and I expect fully that the ejecting S/W will be in pretty good shape and mostly one strong wave as it ejects into the plains. In other words, the strongest solutions seem to be the most believable, and I have a feeling the NAM is generally right in dropping the brunt of the very heaviest QPF into the Dakotas and western MN and farther N with falling off amounts heading east, I also find a slightly slower track a better bet given the strength of the eventual system and that these almost always "wrap up" and track a little slower

[Chicago Storm]

First, it's weather forum and while you may consider me "poo poohing the system" I call it a realistic view and forums are for discussing varying points of view. Fact is, this appears to be a quick hitting Warm advection snow event with a 4-6 hour window with a 1-3 inch snowfall ending as drizzle. While I am not a pro met I have seen these type of systems plenty in my lifetime. The one thing that argues for more is sometimes these systems can out do what modeling projects ..but the further north and east one gets this will be more diffiult to do. I for one am not a fan of over hyping the event either..see last Sunday's system(OVER HYPED) and for that matter the system that dropped nil on the Chicago area Wednesday eve.(2 days out maybe 2-4" when I felt it was pretty easy to see that the dry air in place was going to lead to a virga fest). My ap;ogies if you cannot deal with realities that sometime it snows and sometimes it doesn't. One more note; when was the last time our area got three 50 inch snowfall years in a row? Gimme a break...dude.

A new Alek

[A-L-E-K]

A new Alek

I'm busting high all over the place this year

[baroclinic_instability]

One final comment. All "dynamic" and poorly sampled storms such as these with rapidly ejecting low amplitude waves will have some "surprises" for someone. That is a guarantee. 0Z data will help but it won't be nearly enough time to fully correct the models and as they catch one new part of the storm with the sampling system at 0Z, this storm will be rapidly developing across the mountains and already different than what the models are simulating....in other words, they will always be a step back with this system and will never latch on to a "definitive" solution. It will be a lot of nowcasting come Monday morning...similar to the massive plains blizzard. 4dVAR data assimilation won't even save the Euro/UK here.

[TimChgo9]

I have been watching this system.

I have a tendency to think that any warming is underdone, and the possibility of a "slop fest" is very real. I base this on the fact that after 45 years living here, I can pretty much say how things are going to go. Big snows in December generally don't happen. December storms tend to be mix events, either on the front end, or the back end. Our temps are going to be borderline tomorrow, with a high of 31 forecast, and a low of 28. Not too much margin of error, if you ask me. I think we are going to get about 1-3" on the front side and that might be pushing it. If temps were forecast to be 5 degrees lower, I would feel better, but, this close.. nope. High of 31, with a plus or minus of 2 degrees. Same with the overnight temps. I figure a high of 33, and the overnight low near 30-31. I would not be surprised at all if we saw a 34 or 35 degrees tomorrow. Yeah, I think it's gonna get sloppy.

When forecasting WAA snows, and what not for this area always remember the WAA is always underdone. I have see this stuff way too much in my lifetime to buy into an "all snow" event.

It's not the right thread, but for the Christmas Eve potential, LOT is showing the storm track through C IL. Move that sucker between here and MKE, and that's your track. Unless I am wrong...which is very possible.

[csnavywx]

I'm busting high all over the place this year

Not hard to do with near misses. Trick is knowing when to pull the trigger. This storm doesn't look like too much more than the quick clipper we got before the big storm last week, maybe a bit stronger and wetter. The trend towards the hard south cutoff and slightly warmer thicknesses is evident. In fact, the 850-700mb thicknesses get high enough to make me worry, but BUFKIT suggests that the low levels stay somewhat below 0C...

Thinking RFD sees 3", ORD sees 2" atm. MSN and ARX may see closer to 4-5"

[cyclone77]

One final comment. All "dynamic" and poorly sampled storms such as these with rapidly ejecting low amplitude waves will have some "surprises" for someone. That is a guarantee. 0Z data will help but it won't be nearly enough time to fully correct the models and as they catch one new part of the storm with the sampling system at 0Z, this storm will be rapidly developing across the mountains and already different than what the models are simulating....in other words, they will always be a step back with this system and will never latch on to a "definitive" solution. It will be a lot of nowcasting come Monday morning...similar to the massive plains blizzard. 4dVAR data assimilation won't even save the Euro/UK here.

It does seem that the GFS and GEM are awfully quick with this thing. The slower NAM may be the way to go with this, but it's probably too far south. This is just pure speculation, as I'm sure the 00z and tomorrow's 12z will have some additional tricks to throw at us lol.

[baroclinic_instability]

I have been watching this system.

I have a tendency to think that any warming is underdone, and the possibility of a "slop fest" is very real. I base this on the fact that after 45 years living here, I can pretty much say how things are going to go. Big snows in December generally don't happen. December storms tend to be mix events, either on the front end, or the back end. Our temps are going to be borderline tomorrow, with a high of 31 forecast, and a low of 28. Not too much margin of error, if you ask me. I think we are going to get about 1-3" on the front side and that might be pushing it. If temps were forecast to be 5 degrees lower, I would feel better, but, this close.. nope. High of 31, with a plus or minus of 2 degrees. Same with the overnight temps. I figure a high of 33, and the overnight low near 30-31. I would not be surprised at all if we saw a 34 or 35 degrees tomorrow. Yeah, I think it's gonna get sloppy.

When forecasting WAA snows, and what not for this area always remember the WAA is always underdone. I have see this stuff way too much in my lifetime to buy into an "all snow" event.

It's not the right thread, but for the Christmas Eve potential, LOT is showing the storm track through C IL. Move that sucker between here and MKE, and that's your track. Unless I am wrong...which is very possible.

You make a few interesting comments worth replying too. First, I certainly can't replace your 45 years of experience, but I always warn against analog forecasting which I have seen some commenters make here. Such analogs as "never snows hard in Decemember" or "WAA is ALWAYS overdone". Every storm is different and must be analyzed as such. I honestly haven't looked too hard down that way, but one thing to always consider with intense systems with low static stability is intensity driven snow which can overcome warm pockets at the surface as the wet snow flakes can easily rapidly accumulate and turn everything into a big mess. Not saying that will happen, but it is never a good idea to forecast with analogs only as it will set one up for some very big busts. Think Halloween 1991 storm. 30 inches of snow should never fall in October, right? Of course can't compare that storm to this and every storm should be analyzed without making broad assumptions based off past storms. Either way, I don't blame anyone here for being pessimistic.

[Hoosier]

One final comment. All "dynamic" and poorly sampled storms such as these with rapidly ejecting low amplitude waves will have some "surprises" for someone. That is a guarantee. 0Z data will help but it won't be nearly enough time to fully correct the models and as they catch one new part of the storm with the sampling system at 0Z, this storm will be rapidly developing across the mountains and already different than what the models are simulating....in other words, they will always be a step back with this system and will never latch on to a "definitive" solution. It will be a lot of nowcasting come Monday morning...similar to the massive plains blizzard. 4dVAR data assimilation won't even save the Euro/UK here.

I'm not familiar with everything about 4dVAR but I thought that the Euro still ingests obs/data after 00z, hence why it usually has an edge and doesn't start running until well after the other 00z runs. Is this wrong?

[baroclinic_instability]

I'm not familiar with everything about 4dVAR but I thought that the Euro still ingests obs/data after 00z, hence why it usually has an edge and doesn't start running until well after the other 00z runs. Is this wrong?

Exactly And it still won't save it, I don;t think. Too fast of a rapidly developing storm.

[csnavywx]

I have been watching this system.

I have a tendency to think that any warming is underdone, and the possibility of a "slop fest" is very real. I base this on the fact that after 45 years living here, I can pretty much say how things are going to go. Big snows in December generally don't happen. December storms tend to be mix events, either on the front end, or the back end. Our temps are going to be borderline tomorrow, with a high of 31 forecast, and a low of 28. Not too much margin of error, if you ask me. I think we are going to get about 1-3" on the front side and that might be pushing it. If temps were forecast to be 5 degrees lower, I would feel better, but, this close.. nope. High of 31, with a plus or minus of 2 degrees. Same with the overnight temps. I figure a high of 33, and the overnight low near 30-31. I would not be surprised at all if we saw a 34 or 35 degrees tomorrow. Yeah, I think it's gonna get sloppy.

When forecasting WAA snows, and what not for this area always remember the WAA is always underdone. I have see this stuff way too much in my lifetime to buy into an "all snow" event.

It's not the right thread, but for the Christmas Eve potential, LOT is showing the storm track through C IL. Move that sucker between here and MKE, and that's your track. Unless I am wrong...which is very possible.

Storm should start with a surface temp of around 27-28 at start time in ORD, maybe a touch warmer lakeside, and come in at night. With a decent snowpack fetch, I doubt Chi-town goes above freezing during the event. It would surprise me. Some PL or FZRA/FZDZ mixing in at the end would not shock me though.

[A-L-E-K]

Storm should start with a surface temp of around 27-28 at start time in ORD, maybe a touch warmer lakeside, and come in at night. With a decent snowpack fetch, I doubt Chi-town goes above freezing during the event. It would surprise me. Some PL or FZRA/FZDZ mixing in at the end would not shock me though.

Count me as not worried about rain, any brief period of fzra at the end won't be of much consequence. Your call above seems pretty safe.

[Chicago Storm]

12z ECMWF comes in with about the same QPF placement to the 0z, but is a bit wetter. A nice pocket of 0.50"+ up towards MSP into the extreme E. Dakotas.

[Hoosier]

I have been watching this system.

I have a tendency to think that any warming is underdone, and the possibility of a "slop fest" is very real. I base this on the fact that after 45 years living here, I can pretty much say how things are going to go. Big snows in December generally don't happen. December storms tend to be mix events, either on the front end, or the back end. Our temps are going to be borderline tomorrow, with a high of 31 forecast, and a low of 28. Not too much margin of error, if you ask me. I think we are going to get about 1-3" on the front side and that might be pushing it. If temps were forecast to be 5 degrees lower, I would feel better, but, this close.. nope. High of 31, with a plus or minus of 2 degrees. Same with the overnight temps. I figure a high of 33, and the overnight low near 30-31. I would not be surprised at all if we saw a 34 or 35 degrees tomorrow. Yeah, I think it's gonna get sloppy.

When forecasting WAA snows, and what not for this area always remember the WAA is always underdone. I have see this stuff way too much in my lifetime to buy into an "all snow" event.

It's not the right thread, but for the Christmas Eve potential, LOT is showing the storm track through C IL. Move that sucker between here and MKE, and that's your track. Unless I am wrong...which is very possible.

I can think of 3 significant December snows for your area without even having to think about it. 12/11/00, 12/8/05, 12/15/07.