12/3-12/6 MW/GL snow event?

[snowstormcanuck]

It is. Ranks officially as 19th least snowy winter since 1880. I will say this though...the measuring was very crummy at DTW in both 2003-04 and 2004-05. Id estimate more "true" values for the airport, if measured properly, would be 30" in 2003-04 and 70" in 2004-05, versus the 24.1" and 63.8" that are official. (Imby I had 38" in 2003-04). But most major climate stations have had snowfall measuring issues within the last 15 years or so at one time or another.

The best part of the 2003-04 winter is that from January 4 til February 24th saw a solid, uninteruppted snowcover. Not terribly deep, but enough to do all the winter essentials like sledding and stuff. A case of irony as in many of the winters since, it was the complete oppositte. We werent able to hold a CONTINUOUS snowcover during the heart of winter (remember 2007-08, would lose a nice snowcover for a day or two, then itd come right back, but have to start from scratch). But the snowstorms and snowfall were plentiful. Also, one more thing about 2003-04, it was clearly a northern suburbs winter. The NWS in White Lake had 62.6"!

Speaking of bad winters, what did toronto get and where did it rank for 2009-10? I thought it was in your sig but its not. Dont blame you lol, start a fresh slate for a new season

Yeah, exactly. Fresh board too. I left that sig was over at Eastern.

I finished with 40.8", I think the official airport number was around 44". It was on the low end, but within the range of what I'd call a "normal" winter in terms of total snowfall. But like you said, it was all about January 2004. Cold, constant snow cover, and a nice 12 incher on Jan 26-27 (with a ton more *just* to my south). Outside of that month though, pretty bleh.

[cyclone77]

An interesting question. It is strongly dependent on the strength of the upper level wave and upper level cold front. Clippers are mostly low amplitude upper tropospheric shortwaves interacting with a rather sharp thermal gradient (baroclinic zone). From a standpoint of cyclogenesis, what you have is a "wave" in the upper atmosphere and a tight low level circulation. This results in rapid frontogenesis as the thermal gradient "tightens" with the progression of the low amplitude wave. Frontal banding along the frontal circulation aloft becomes the dominant forcing mechanism (mesoscale) with synoptic forcings generally playing a much smaller role than larger cyclones. These clippers are so challenging to forecast both because of the small scale upper wave, the rapid speed of the wave (low amplitude waves propagate much faster, so timing is a challenge), and small changes in the thermal gradient and placement of the polar front can make huge changes. Look at our snow pack across the northern plains and intermountain west: http://www.nohrsc.no...05_National.jpg

For instance, this data is ingested into the numerical models, and exactly how they model both this data and how much snow will potentially melt can have a large impact on where the thermal contrast develops and where the eventual wave develops. Also, this is a phase event over the Pacific: http://www.atmos.was...1_x_500vor+///3

Note how the weak shortwave phases with the upper low around the Aleutians, deamplifies over the Rockies, then weakly phases again with the polar branch over the Dakotas. There is a lot of variability right there, and depending on how far south the wave takes will influence the strength of the cross barrier flow across the Rockies and subsequent lee troughing and moisture/thermal transport (note the lee trough the models develop after 48 hrs). Getting back to what I said earlier though, with clippers, what generally happens is stronger upper shortwaves develop strong frontogenesis aloft. Because the frontal boundary is tilted over cold air (static stability), this results in qpf that generally ends up farther N. Here is a "model" cold front to help you visualize a typical orientation of a cold front using a vertical cross section:

If the upper level shortwave aloft is weaker, this usually results in stronger frontogenesis in the lower levels closer to the surface, which results in a farther S track. As you can see, clippers are usually quite tough to forecast and I have seen many times where the snow band is off kilter by 50-100 miles within the final 24 hours of the forecast. Small scale errors with how models simulate the development of a clipper grows FAST.

As others have said, I think it is a "wash" from a climo standpoint. If you feel the wave is potentially going to be more intense and or/of greater amplitude, possibly shift the track a tad north. if you feel it will be weaker and/or of less amplitude, shift the track a tad south. This of course does not take into account the placement of the baroclinic zone. if you feel that may be farther N or S, also take that into account when forecasting the track.

Interesting read. Thanks for posting.

[BowMeHunter]

Very nice read and probably explains why I have such a love hate relationship with clippers. No Euro for me tonight....Nice cup of Java and hopefully a nice surprise when I get to the Euro at 4:30 AM for a lot of us.

[JoMo]

An interesting question. It is strongly dependent on the strength of the upper level wave and upper level cold front. Clippers are mostly low amplitude upper tropospheric shortwaves interacting with a rather sharp thermal gradient (baroclinic zone). From a standpoint of cyclogenesis, what you have is a "wave" in the upper atmosphere and a tight low level circulation. This results in rapid frontogenesis as the thermal gradient "tightens" with the progression of the low amplitude wave. Frontal banding along the frontal circulation aloft becomes the dominant forcing mechanism (mesoscale) with synoptic forcings generally playing a much smaller role than larger cyclones. These clippers are so challenging to forecast both because of the small scale upper wave, the rapid speed of the wave (low amplitude waves propagate much faster, so timing is a challenge), and small changes in the thermal gradient and placement of the polar front can make huge changes. Look at our snow pack across the northern plains and intermountain west: http://www.nohrsc.no...05_National.jpg

For instance, this data is ingested into the numerical models, and exactly how they model both this data and how much snow will potentially melt can have a large impact on where the thermal contrast develops and where the eventual wave develops. Also, this is a phase event over the Pacific: http://www.atmos.was...1_x_500vor+///3

Note how the weak shortwave phases with the upper low around the Aleutians, deamplifies over the Rockies, then weakly phases again with the polar branch over the Dakotas. There is a lot of variability right there, and depending on how far south the wave takes will influence the strength of the cross barrier flow across the Rockies and subsequent lee troughing and moisture/thermal transport (note the lee trough the models develop after 48 hrs). Getting back to what I said earlier though, with clippers, what generally happens is stronger upper shortwaves develop strong frontogenesis aloft. Because the frontal boundary is tilted over cold air (static stability), this results in qpf that generally ends up farther N. Here is a "model" cold front to help you visualize a typical orientation of a cold front using a vertical cross section:

If the upper level shortwave aloft is weaker, this usually results in stronger frontogenesis in the lower levels closer to the surface, which results in a farther S track. As you can see, clippers are usually quite tough to forecast and I have seen many times where the snow band is off kilter by 50-100 miles within the final 24 hours of the forecast. Small scale errors with how models simulate the development of a clipper grows FAST.

Wow, that's interesting, thanks. I know down here (SW Missouri), Clippers usually go through dry and the precip is typically off to the NE, farther than modeled.

[baroclinic_instability]

Wow, that's interesting, thanks. I know down here (SW Missouri), Clippers usually go through dry and the precip is typically off to the NE, farther than modeled.

Thanks, I will look into that. An interesting observation. Clippers are less common down there of course being farther south, but I could see that as models sometimes initially place the baroclinic zone too far south early in the model cycle sometimes due to simple air mass modification (lack of snowpack) or to other higher order issues such as poor mountain response (not enough lee troughing) which would result in not enough low level thermal advection early in the model cycle (which would result in a baroclinic zone displaced too far south). I will definitely watch that this winter.

[The_Global_Warmer]

baroclinic_instability-

Since there is great snowpack right now and this clipper will help aid that even further south some. How much impact does the snowpack have on our weather well south of it?

SInce Canada is covered and the Northern US is covered and getting more. will that influence the pattern at all, or is it just effecting local temps.

[baroclinic_instability]

baroclinic_instability-

Since there is great snowpack right now and this clipper will help aid that even further south some. How much impact does the snowpack have on our weather well south of it?

SInce Canada is covered and the Northern US is covered and getting more. will that influence the pattern at all, or is it just effecting local temps.

Indeed it will to a point, but that influence will wane a bit with time with decreasing insolation. Moreover, large scale weather patterns and teleconnections can still drive large scale rossby waves where the local positioning of the snowpack has little to no influence. Possibly CSNavy can chime in since he has more long-range forecasting experience than I do (read his pinned long range discussion).

[Hoosier]

00z Euro looks faster so far.

[Hoosier]

Everybody from MSP to MKE to ORD to LAF is looking pretty decent on the 00z Euro.

[Moneyman]

hr 78 1012 low over western oklahoma. lgt precip over northern plain, starting to enter wis and ill. lgt to mod precip over central and southern mn

hr 84 broad area of 1016 pressure, lgt precip ln,mn,wi,iowa,il,missouri. lgt to mod precip southern mn and central and southern wi

From Tombo.

[Moneyman]

Hour 90:

hr 90 1012 low over western ky, lgt precip over ohio val into great lakes, lgt to mod precip southern wi to ky

Awesome. Wonder how much QPF this spits out?

[Hoosier]

The Euro is beefy.

[The_Global_Warmer]

Indeed it will to a point, but that influence will wane a bit with time with decreasing insolation. Moreover, large scale weather patterns and teleconnections can still drive large scale rossby waves where the local positioning of the snowpack has little to no influence. Possibly CSNavy can chime in since he has more long-range forecasting experience than I do (read his pinned long range discussion).

Thanks, also your blog is fantastic. A laymen can learn for days in there.

[Moneyman]

Hoosier, how much QPF do you think the EURO spits out this run? Sounds like it's a pretty good event.

[Hoosier]

Hoosier, how much QPF do you think the EURO spits out this run? Sounds like it's a pretty good event.

This run would be a high end advisory to warning criteria event from MSP down toward LAF.

[Moneyman]

Awesome. A good trend, hopefully it continues. Even Central WI gets in on the action right?

[daddylonglegs]

6 inches here? possible with the GFS

[csnavywx]

Indeed it will to a point, but that influence will wane a bit with time with decreasing insolation. Moreover, large scale weather patterns and teleconnections can still drive large scale rossby waves where the local positioning of the snowpack has little to no influence. Possibly CSNavy can chime in since he has more long-range forecasting experience than I do (read his pinned long range discussion).

This is the important part. Large scale, powerful systems will generally overwhelm snowpack influences. Low to medium amplitude waves are affected more, as long as the wave is located close enough to the snowpack for it to make a difference. The most common effect is to retard the progress of the warm front and sharpen the surface temperature gradient. This can lead to increased frontal forcing, which increases precipitation, which releases latent heat aloft, decreasing static stability. This creates a positive feedback loop. As direct consequence, precip type forecasting can be a nightmare. I've seen plenty of situations where this resulted in prolonged mixing and/or ice accretion. In fact, there was a similar situation last year where we recieved about 1/2" of unforecasted ice accretion due to this "snowpack process".

But, the track of this clipper probably isn't going to allow it to take advantage of the current snowpack. The current snowcover line runs in a more SW-NE direction, whereas the clipper in question will be crossing that 'barrier' at a perpendicular angle and crossing into a completely snow-free area.

Hope that clarified it a bit, Friv. Off to bed with me!

[Hoosier]

Awesome. A good trend, hopefully it continues. Even Central WI gets in on the action right?

Parts of it do pretty well, yeah.

[baroclinic_instability]

Thanks, also your blog is fantastic. A laymen can learn for days in there.

Yah no problem, definitely give it a read. It was written from more of a met perspective but I try and keep it understandable for laymen as well. Let me know if you have questions.

[baroclinic_instability]

Thanks, also your blog is fantastic. A laymen can learn for days in there.

This is the important part. Large scale, powerful systems will generally overwhelm snowpack influences. Low to medium amplitude waves are affected more, as long as the wave is located close enough to the snowpack for it to make a difference. The most common effect is to retard the progress of the warm front and sharpen the surface temperature gradient. This can lead to increased frontal forcing, which increases precipitation, which releases latent heat aloft, decreasing static stability. This creates a positive feedback loop. As direct consequence, precip type forecasting can be a nightmare. I've seen plenty of situations where this resulted in prolonged mixing and/or ice accretion. In fact, there was a similar situation last year where we recieved about 1/2" of unforecasted ice accretion due to this "snowpack process".

But, the track of this clipper probably isn't going to allow it to take advantage of the current snowpack. The current snowcover line runs in a more SW-NE direction, whereas the clipper in question will be crossing that 'barrier' at a perpendicular angle and crossing into a completely snow-free area.

Hope that clarified it a bit, Friv. Off to bed with me!

Yah, positive and negative feedbacks are key in forecasting, and it is why things can change so rapidly with certain systems frivolous. It is also why chaos theory, investigated by Lorenz in the 60's, plays such a prominent role in meteorology and why we will likely never break past realistic accurate short-term forecasts beyond a week and a half, at least in my lifetime.

[baroclinic_instability]

This is the important part. Large scale, powerful systems will generally overwhelm snowpack influences. Low to medium amplitude waves are affected more, as long as the wave is located close enough to the snowpack for it to make a difference. The most common effect is to retard the progress of the warm front and sharpen the surface temperature gradient. This can lead to increased frontal forcing, which increases precipitation, which releases latent heat aloft, decreasing static stability. This creates a positive feedback loop. As direct consequence, precip type forecasting can be a nightmare. I've seen plenty of situations where this resulted in prolonged mixing and/or ice accretion. In fact, there was a similar situation last year where we recieved about 1/2" of unforecasted ice accretion due to this "snowpack process".

But, the track of this clipper probably isn't going to allow it to take advantage of the current snowpack. The current snowcover line runs in a more SW-NE direction, whereas the clipper in question will be crossing that 'barrier' at a perpendicular angle and crossing into a completely snow-free area.

Hope that clarified it a bit, Friv. Off to bed with me!

I partially disagree with the statement regarding the snowpack in this case as it will still result in a slightly colder cold sector and less modification as the system progresses into the northern plains and frontogenesis ensues once the wave interacts with the warm sector.

[Chicago Storm]

Looks like we're back to those large changes in precip amounts between on/off hour runs. It probably just wanted to screw with the LAF crew too.

[baroclinic_instability]

Looks like we're back to those large changes in precip amounts between on/off hour runs. It probably just wanted to screw with the LAF crew too.

Yeah the NAM is going gangbusters and the SREF guidance took a large shift south. The 6Z NAM's .81" liquid QPF over southern MN is almost laughable, but a decent snow event is getting close to the "likely" category.

[BowMeHunter]

Nice to see the models coming in juicier.. I'd lock the Euro and my 2-3" in faster than Gibbs screaming torch incoming.

[KeenerWx]

Looking better and better for a 1-3" snowfall here in West Lala.

[A-L-E-K]

liking the 6z runs but smart money says 12z comes back to earth. I smell Chicagostorm's dusting call about to bust

[Chicago WX]

Looks like we're back to those large changes in precip amounts between on/off hour runs. It probably just wanted to screw with the LAF crew too.

NAM on steroids. Would be pretty cool to see verify though.

[michsnowfreak]

Needs to move north lol

[LizardMafia]

NAM on steroids. Would be pretty cool to see verify though.

Would be the perfect excuse for staying inside and drinking Bailey's and Coffee all day long..

Though looks like the "better" accumulations would be north..