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

Thundersnow12

By Thundersnow12,
in Central/Western States

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mnchaser

mnchaser

Posted
Posted

No drastic changes in the last 24 hours, Pretty much a general idea where the heaviest snow is expected to fall...Of course each model run is going to differ where the heaviest band sets up..Trying to pin that exact area down RIGHT NOW, are about as good as the odds of picking the winning lotto numbers, no matter who you are!

This should be an interesting hybrid clipper system, definitely something kinda outta the ordinary.

MPX-

WITH ANYWHERE FROM 0.30 TO 0.70 OF LIQUID.

EVEN ON THE CONSERVATIVE SIDE OF SNOW RATIOS...USING A 12:1 WOULD

YIELD HIGH END ADVISORY/LOW END WARNING SNOWFALL. LIKE THE IDEA

OF THE MEDIAN OF THE SREF ENSEMBLES SHOWING A TIGHTER SNOW

GRADIENT WHEN COMPARED TO THE MEAN OF ALL THE MEMBERS. THIS ALSO

HIGHLIGHTS THE HEAVIEST AXIS JUST TO THE SOUTHWEST OF THE TWIN

CITIES. MIXING RATIOS CLOSE TO 3 G/KG IN SOUTHERN MN...ALSO

SUPPORT THE IDEA OF SEEING 6+ INCHES IN MANY AREAS.

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Chicago WX

Chicago WX

Posted
Posted

Seems like the models have peaked...and a weakening trend is underway. In the end, we may be just getting some sloppy seconds here in LAF. [knee jerk reaction] I shouldn't have spoke too soon with my previous post (2-4" IMBY)...T-2" looking more reasonable at the moment.[/knee jerk reaction] arrowheadsmiley.png

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A-L-E-K

A-L-E-K

Posted
Posted

Then again, it's not even onshore yet. Will be interested to see what happens with tonight's 00 and 06z runs.

True and no matter what happens the changes aren't going to be earth shattering. The track seems pretty stable and ammounts will be of the widespread 1-5" variety, pretty much standard clipper business.

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LizardMafia

LizardMafia

Posted
Posted

Seems like the models have peaked...and a weakening trend is underway. In the end, we may be just getting some sloppy seconds here in LAF. [knee jerk reaction] I shouldn't have spoke too soon with my previous post (2-4" IMBY)...T-2" looking more reasonable at the moment.[/knee jerk reaction] arrowheadsmiley.png

Quit swaying back and forth like the models.. :whistle:

At least whatever falls, won't be in the form of rain..

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Tony

Tony

Posted
Posted

Tell me if I am wrong but this system is not your normal clipper as this one starts to develope in the Dakotas and not in Canada so I don't think the models have a true handle on it yet. Also, there could be some gulf moisture being thrown into this system, albeit minor, but enough to add to the totals. As all of you have said earlier, we have to at least wait till the 0Z runs to see what happens with this but so far looks good for our first snowfall.

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baroclinic_instability

baroclinic_instability

Posted
Posted

Tell me if I am wrong but this system is not your normal clipper as this one starts to develope in the Dakotas and not in Canada so I don't think the models have a true handle on it yet. Also, there could be some gulf moisture being thrown into this system, albeit minor, but enough to add to the totals. As all of you have said earlier, we have to at least wait till the 0Z runs to see what happens with this but so far looks good for our first snowfall.

Yeah, a typical "pure" Alberta Clipper is a strong Pacific cyclone that has long occluded over the Pacific, lost its baroclinity with the upper trough shredded by the BC Coastal Range/Alberta Rockies, and re-emerges in the Alberta Plains as a strong surface frontal wave with an associated lower amplitude but intense shortwave/strong jet streak. A typical ALberta Clipper often induces extreme Chinook winds if it is replacing a stagnant low level arctic air mass over Alberta then goes on to develop into a strong low level surface cyclone with a compact surface low and strong cold front and CAA behind the front often with much less moisture. Still, they can be prolific snow makers under the right conditions, and they can be even more prolific blowing snow makers. This system almost isn't a Clipper at all.

This is an image of the thermal gradient at 850 hpa and the typical intensity of a normal Alberta Clipper. MUch stronger and working a much more intense baroclinic zone.

This was one of the shortwaves a couple weeks ago that ejected ahead of the main Thanksgiving storm.

post-999-0-39951600-1291301902.png

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A-L-E-K

A-L-E-K

Posted
Posted

Yeah, a typical "pure" Alberta Clipper is a strong Pacific cyclone that has long occluded over the Pacific, lost its baroclinity with the upper trough shredded by the BC Coastal Range/Alberta Rockies, and re-emerges in the Alberta Plains as a strong surface frontal wave with an associated lower amplitude but intense shortwave/strong jet streak. A typical ALberta Clipper often induces extreme Chinook winds if it is replacing a stagnant low level arctic air mass over Alberta then goes on to develop into a strong low level surface cyclone with a compact surface low and strong cold front and CAA behind the front often with much less moisture. Still, they can be prolific snow makers under the right conditions, and they can be even more prolific blowing snow makers. This system almost isn't a Clipper at all.

This is an image of the thermal gradient at 850 hpa and the typical intensity of a normal Alberta Clipper. MUch stronger and working a much more intense baroclinic zone.

This was one of the shortwaves a couple weeks ago that ejected ahead of the main Thanksgiving storm.

post-999-0-39951600-1291301902.png

Thanks for this.

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weatherbo

weatherbo

Posted
Posted

Bo I know, it's just lame to have 3 rain storms then be missed to the south of all things.

After the months long string of dry/boring weather, I'm actually enjoying the rain, as the fields, lakes, and rivers are being replenished. Plus, a lot of Winter forecasts that favor wetter, and then possibly snowier conditions around here are looking likely. It will happen, it's just a matter of time. Enjoy the weather :)

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baroclinic_instability

baroclinic_instability

Posted
Posted

Thanks for this.

Yeah no problem. Also worth noting is a typical Alberta Clipper is much more strongly influenced by synoptic forcings and is dominated by differential cyclonic vorticity advection aloft above the level of non-divergence and thermal warm air advection in the low levels. There is no positive feedback loop that develops in moist baroclinic waves because low level diabatic heating is very small and height falls on the back of the shortwave (upstream) owing to the edvection of planetary vorticity advection are very small to nil (short wavelength/relatively low amplitude). This will keep propagation speeds fast as the upper wave remains a "wave" and doesn't develop into a full blown closed circulation above the level of non-divergence with strong cyclogenesis remaining in the low levels. Typically they develop during mid-winter and often times they develop "wavetrains" where there is one clipper after another. After going to school at UND and living in MN nearly my whole life, while mostly dry, becuase they are a Polar Jet feature, they are working a strong baroclinic zone with plenty of very cold/arctic air. Models usually struggle mightily with snow production but they almost always seem to spit out light snow near the cyclone center/along the cold front. Strong pressure gradients and very efficient CAA results in efficient wind mixing down to the surface and good blowing snow makers. I personally find Alberta Clippers fascinating.

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HurricaneTracker

HurricaneTracker

Posted
Posted

SREFs say Turtle should see some nice flakage on top the met building in mad town.

SREF_prob_dend_100__f042.gif

If this prog chart hold true for the DGZ, then I am envisioning an event that may be similar to the December 26, 2009 in Northern Illinois, where a "surprise" 12-15" fell when only 1-3" was predicted. Do not underestimate the influence and importance of the dendritic growth zone! I wouldn't be surprised to see widespread 6" amounts (in a very narrow swath) from MSP to ORD.

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baroclinic_instability

baroclinic_instability

Posted
Posted

If this prog chart hold true for the DGZ, then I am envisioning an event that may be similar to the December 26, 2009 in Northern Illinois, where a "surprise" 12-15" fell when only 1-3" was predicted. Do not underestimate the influence and importance of the dendritic growth zone! I wouldn't be surprised to see widespread 6" amounts (in a very narrow swath) from MSP to ORD.

Yeah I agree, and glancing at the 09Z SREF dendritic growth zone, they are still beefy and seem to suggest, without looking at a vertical cross section, of a lot of potential tilting of the upper level cold front through the dendritic growth zone to get 100+ hpa layers that the SREF members are developing. I think the NWS Winter Storm Watch is well warranted. Even taking a low end .40" liquid qpf across southern MN/western WI, looking good for 15-20/1 snow ratios, 6-8" conservative approach, throw in heavier banding and possibly some mild slantwise convection along the deep frontal circulation and could see weird narrow bands 10+.

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Stevo6899

Stevo6899

Posted
Posted

Bo I know, it's just lame to have 3 rain storms then be missed to the south of all things.

I hear ya. Patience and it will come. Minnesota as a whole is getting destroyed so far this year. Northern minny towards duluth almost have 30 inches and with this storm southern minny towards mankato will have 20+. Eastern minnesota is due though.

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