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

[Jim Martin]

Here is a snippet from the area forecast discussion from the NWS in Cleveland:

SITUATION MON NIGHT THROUGH TUE NIGHT SHOULD BE MORE INTERESTING AS MODELS HAVE CHANGED COURSE AGAIN AND NOW ARE PROGGING A LOW TO MOVE EAST ACROSS OHIO TUE.

GFS AND ECMWF KEEP LOW FAR ENOUGH SOUTH TO KEEP US IN THE COLDER AIR AND THEREFORE LOOKS TO BE A SNOW EVENT...POSSIBLY EVEN A DECENT ONE.

HOWEVER...GIVEN THAT THE MODELS HAVE BEEN HAVING A HARD TIME LOCKING IN ON A SOLUTION NOT VERY CONFIDENT IN HOW THIS WILL PLAY OUT YET.

[cyclone77]

The RGEM only goes out to 48hrs, but it looks much stronger with that first little wave tomorrow night. Drops 5-10mm of precip (~2-3 inches of snow) over Iowa and points east towards northern Indiana. How this effects the evolution with the main wave later Monday is unclear.

Edit: I should point out the RGEM was too quick to saturate the column with that last clipper, and eventually backed off on amounts. That may be the case this time too, as the initial wave will really be fighting the dry air.

[Harry]

Are we talking about the Xmas storm here? Because for the first clipper the block has shifted west due to the rapid deepening of that Atlantic cyclone. In fact, that's why the NAM is showing that strung out piece of garbage. As it takes a further north track initially, it has to shear out quicker once it runs into that area of confluence over the Eastern Lakes/NNE.

Talking more so further out and or January. But yeah depending on how quick it all takes place it could have implication on the Christmas storm.

IT IS possible this thing ends up far to the north via cutting/closing off. I doubt it but it is possible. I'll feel better tomorrow about the track etc. Not much lead time but whats new this year. lol

What are your thoughts for us here in SW Mich. on Mon/Tues.? I think it's looking pretty good for us. Unfortunately this winter has had everything going northwest or southwest of us...so I'm a bit hesitant to bite.

By the way, snowing pretty good here now with the Lake effect/enhanced precip. Looking forward to getting a couple inches.

Like you i am not ready to bite on anything yet. Probably better to ask tomorrow. I will say the chances of us getting something decent out of it are higher then what we have seen recently.. Yeah i know thats not saying much..

And yeah you look good for atleast a few inches today/tonight and perhaps tomorrow as well. Gonna be close here but whats new. May end up just missing me to my wnw/north. Hoping the flow is more west vs sw. lol

[L.B. LaForce]

From IWX's WRF model

[TugHillMatt]

Talking more so further out and or January. But yeah depending on how quick it all takes place it could have implication on the Christmas storm.

IT IS possible this thing ends up far to the north via cutting/closing off. I doubt it but it is possible. I'll feel better tomorrow about the track etc. Not much lead time but whats new this year. lol

Like you i am not ready to bite on anything yet. Probably better to ask tomorrow. I will say the chances of us getting something decent out of it are higher then what we have seen recently.. Yeah i know thats not saying much..

And yeah you look good for atleast a few inches today/tonight and perhaps tomorrow as well. Gonna be close here but whats new. May end up just missing me to my wnw/north. Hoping the flow is more west vs sw. lol

It seems this winter that once the systems begin the north jog, they don't stop moving north until they're practically in Canada (so hopefully that won't happen)...."sigh" it is what it is...

Hey, don't wish my heavier snow away. haha! Atleast with these more westerly events a larger area gets "spray painted" over, although it's often not as heavy as the northerly, pencil-thin bands of snow.

[csnavywx]

Talking more so further out and or January. But yeah depending on how quick it all takes place it could have implication on the Christmas storm.

IT IS possible this thing ends up far to the north via cutting/closing off. I doubt it but it is possible. I'll feel better tomorrow about the track etc. Not much lead time but whats new this year. lol

Like you i am not ready to bite on anything yet. Probably better to ask tomorrow. I will say the chances of us getting something decent out of it are higher then what we have seen recently.. Yeah i know thats not saying much..

And yeah you look good for atleast a few inches today/tonight and perhaps tomorrow as well. Gonna be close here but whats new. May end up just missing me to my wnw/north. Hoping the flow is more west vs sw. lol

Jet placement leads me to believe that this will start out as lee cyclogenesis then transition to a low further north (within the more favorable left exit region). Either way, we're looking at primarily a strong WAA snow event, which rarely under-produce, and given the strength of the WAA and fetch of moisture, the higher QPFs are favored. While the RGEM is probably a bit too wet, it wouldn't surprise me to see a nice belt of WAA driven snows starting tomorrow night. NAM and GFS hint at this, but are very weak with it.

[Northern_IN_Wx]

Early call for my backyard would be 1-3" of wet snow transitioning to drizzle/freezing....as it looks like models are trending towards this being only a WAA event locally with better chances for advisory amounts north where deformation settles in. Still early though. Subject to revisions...

[Northern_IN_Wx]

Jet placement leads me to believe that this will start out as lee cyclogenesis then transition to a low further north (within the more favorable left exit region). Either way, we're looking at primarily a strong WAA snow event, which rarely under-produce, and given the strength of the WAA and fetch of moisture, the higher QPFs are favored. While the RGEM is probably a bit too wet, it wouldn't surprise me to see a nice belt of WAA driven snows starting tomorrow night. NAM and GFS hint at this, but are very weak with it.

This is interesting as local studies over here show that model QPF is almost always overdone for purely WAA events. Maybe these events perform better just off to the west given better baroclinicity before waves shear out in downstream confluence.

[buckeye]

Because that block is starting to shift some. Once it does get out of the way we go back to the typical worrying over systems tracking to the nw ( aka some se ridging ) vs what we have. For how long that lasts ( worrying over too far nw ) depends on who you ask.

I can't see this going to much more nw....(famous last words right?...lol)....but if you look at the jet config on the gfs and note a storm is right on it's tail coming into the southern rockies the first clipper shouldn't have enough time to dig and screw. We may warm but it might not be until after the brunt of whatever comes thru. Should be a nice waa event for some, those are infamous for front end frozen followed by backend drizzle, (assuming it warms enough).

[buckeye]

gfs actually looks a tad more south with the xmas storm

[csnavywx]

This is interesting as local studies over here show that model QPF is almost always overdone for purely WAA events. Maybe these events perform better just off to the west given better baroclinicity before waves shear out in downstream confluence.

Is that seasonally based, or just overall (any time of the year in general)? And you may be right on with the shearing-out bit, as this seems to happen quite a bit in the winter season.

Having said that, this event won't be totally WAA based, I would expect some frontogenesis-based forcing too, especially given the snowpack in place to help reinforce the baroclinic zone.

[Harry]

Jet placement leads me to believe that this will start out as lee cyclogenesis then transition to a low further north (within the more favorable left exit region). Either way, we're looking at primarily a strong WAA snow event, which rarely under-produce, and given the strength of the WAA and fetch of moisture, the higher QPFs are favored. While the RGEM is probably a bit too wet, it wouldn't surprise me to see a nice belt of WAA driven snows starting tomorrow night. NAM and GFS hint at this, but are very weak with it.

To tell the truth i have not given much thought to the *possible* WAA snows the rgem is showing? Will be very interesting to see where it sets up if it does.

This is interesting as local studies over here show that model QPF is almost always overdone for purely WAA events. Maybe these events perform better just off to the west given better baroclinicity before waves shear out in downstream confluence.

Problem up this way is these type of events always seem to come in further north. Could be why the models typically over do QPF down that way? Ofcourse this is not the typical situation either. lol So yeah not even sure what to think as far as this goes. Past history does tell me though that wherever the snows fall with this WAA that it will be the same general area that sees the best snows from the system/storm itself.

I can't see this going to much more nw....(famous last words right?...lol)....but if you look at the jet config on the gfs and note a storm is right on it's tail coming into the southern rockies the first clipper shouldn't have enough time to dig and screw. We may warm but it might not be until after the brunt of whatever comes thru. Should be a nice waa event for some, those are infamous for front end frozen followed by backend drizzle, (assuming it warms enough).

See csnavywx post.

One thing i do know is that i'll be happy to be rid of this pattern once it is gone. What a pain in the ass it has been trying to figure where the systems etc are gonna go. Even if i score a nice hit i'll still be happy to see it go..lol

[mnweather]

The 12Z UKMET has a low in MN at 72 hours.

[Stevo6899]

To tell the truth i have not given much thought to the *possible* WAA snows the rgem is showing? Will be very interesting to see where it sets up if it does.

Problem up this way is these type of events always seem to come in further north. Could be why the models typically over do QPF down that way? Ofcourse this is not the typical situation either. lol So yeah not even sure what to think as far as this goes. Past history does tell me though that wherever the snows fall with this WAA that it will be the same general area that sees the best snows from the system/storm itself.

See csnavywx post.

One thing i do know is that i'll be happy to be rid of this pattern once it is gone. What a pain in the ass it has been trying to figure where the systems etc are gonna go. Even if i score a nice hit i'll still be happy to see it go..lol

My thoughts exactly. Why do the models have such a hard time with pacific NW and canadian energy? They seem weaker and you would think the models would handle the weaker (northern tracks) storms better than the larger Sw lows, panhandle hookers and colorado lows. Perhaps they do sturggle sometimes with larger storms, but it seems moreso with the clipper type storms like we've had this year. I would say that several Great lakes and Midwest mets are on track in saying that the heavier snows will most likely come in Jan-March.

[buckeye]

well at least the canadian has some precip showing up over ohio now......as opposed to last nites run where it petered it out completely.

[buckeye]

The 12Z UKMET has a low in MN at 72 hours.

but it has a stronger low over Oklahoma as well

[csnavywx]

Did anybody see the 1084-1088mb high over Greenland this morning on the NAM's 0 and 6hr plots?

Too bad there's not a station up there to record that, otherwise I think that might be close to a world record (if true, of course).

OT aside, the system following this one looks interesting as the GoA/EPAC trough weakens and comes onshore as a progressive wave.

[Northern_IN_Wx]

Is that seasonally based, or just overall (any time of the year in general)? And you may be right on with the shearing-out bit, as this seems to happen quite a bit in the winter season.

Having said that, this event won't be totally WAA based, I would expect some frontogenesis-based forcing too, especially given the snowpack in place to help reinforce the baroclinic zone.

Yep, I keep track of QPF verification for all winter events, so I'm not sure about summer/fall/spring events. Looking at cross sections you are right that there could be some banding given low static stability just above a sloped area of frontogenesis. But still, this goes down as a WAA event in my book, and in our area models normally over-estimate QPF no matter the forcing. Again, this might just be a local thing as Harry mentioned above.

[Harry]

The 12Z UKMET has a low in MN at 72 hours.

Here for all to see.

[L.B. LaForce]

This is interesting...

[buckeye]

ggem just not too impressed with a xmas storm.

i'll tell ya what....if we lose the block and that se canadian vortex, we are gonna TORCH after xmas. Models starting to go crazy with a western trough and storminess.

[Harry]

ggem just not too impressed with a xmas storm.

i'll tell ya what....if we lose the block and that se canadian vortex, we are gonna TORCH after xmas. Models starting to go crazy with a western trough and storminess.

It is THIS model that says to me BE CAREFUL. Reason being is because it usually is better with northern stream events/stuff up north and not as great with southern/sw stuff. NAM/UK look like what i would expect to see with THIS model. Thus something stinks with one of them. Hard to say which..

Why again i'll wait till the 12z runs tomorrow.

[csnavywx]

Yep, I keep track of QPF verification for all winter events, so I'm not sure about summer/fall/spring events. Looking at cross sections you are right that there could be some banding given low static stability just above a sloped area of frontogenesis. But still, this goes down as a WAA event in my book, and in our area models normally over-estimate QPF no matter the forcing. Again, this might just be a local thing as Harry mentioned above.

Interesting. I should start keeping hard numbers here, just to check the perception vs. reality factor, as my statement is pretty much as good as anecdotal given no hard numbers to back it up. How far out are you verifying against? T minus 12, 24, 48 hr timeframes?

My general rule of thumb is to go under model QPF averages anyways, but less so with WAA events than with deformation/dynamical based events, due to the bust factor with the latter. It would be interesting to see how off the modeling typically is with WAA events over here and see if that thumb rule has real statistical validity or whether I should be cutting it back further.

[Moneyman]

How does the GEM look for this storm in a few days? Not sure where to look for it etc.

[baroclinic_instability]

How does the GEM look for this storm in a few days? Not sure where to look for it etc.

The global GEM looks like a big pile of poo and it is holding to its typical bias I mentioned a number of posts back regarding the cyclone breakdown and energy dissipation of a baroclinic wave across the intermountain W. First main difference is the CMC essentially sends a number of weak upper tropospheric disturbances through the intermountain W and they come out across the plains as a series of weak non-distinct waves that interact weakly with the strong baro zone in the plains then fall apart under the influence of the stronger east coast trough. The first bias is a noted one with the CMC as it seems to have significant issues with this setup. RIght now I am giving it much less consideration and it is no longer being backed up by any global guidance, GFS ensemble guidance, or the NAM.

[Harry]

Can add the euro to the UK/NAM collection with one northern piece of energy and a south one as well. Difference is the northern ends up going back se from MN across WI/sw MI to N.OH where it is about washed out. The southern energy goos poof and thus vanishes as it heads towards se MO.

.25+ from the GRR zones/MI-IN line on west across all of WI/MN and far northern IA/ND with a zone of .50+ in N.ND just south of the Canadian border. Less then .25 for points south and east of here back to Chicago..

[baroclinic_instability]

The EURO/UK/NAM look almost identical with the S/W trough and all feature a very sharp S/W over northern MN with the exception of some speed differences. Right now it looks like a rather quick hitting event.

[mnweather]

The EURO/UK/NAM look almost identical with the S/W trough and all feature a very sharp S/W over northern MN with the exception of some speed differences. Right now it looks like a rather quick hitting event.

There looks to be a better chance of snow for me now compared to yesterday. I am still unsure on this. Should be interesting.

[Hoosier]

Did anybody see the 1084-1088mb high over Greenland this morning on the NAM's 0 and 6hr plots?

Too bad there's not a station up there to record that, otherwise I think that might be close to a world record (if true, of course).

OT aside, the system following this one looks interesting as the GoA/EPAC trough weakens and comes onshore as a progressive wave.

Correct...I'm pretty sure the record is 1085 mb in Mongolia.

[goknights]

What does euro show for qpf across iowa?