Major Winter Storm/Blizzard Potential for this Weekend

[NWS Forecaster]

All of the operational NCEP and international models seem to be in fair agreement regarding a piece of energy in the desert southwest pushing east with intense cyclogenesis east of the Rockies Saturday through Monday. A polar high pressure system over the Ohio Valley will "drag" cold air south ahead of the system. This will set the stage for a significant warm air advection snow/ice storm Saturday afternoon through Sunday morning anywhere from Nebraska, South Dakota, Iowa, southern Minnesota, Wisconsin, northern Illinois, and Michigan. Very early indications suggest 6 to 12 inches of snow would be possible across these areas during that time frame. Adding to this theory are the strength of southerly 850 mb winds being as strong as 45 to 50 knots ahead of the system and a tight baroclinic zone. Significant overrunning such as this could spell thundersnow in many locations. South of the main snow shield, a significant icing event would be possible across southern Nebraska, southern Iowa, northern Missouri, and central Illinois.

Beyond Sunday morning, most of the heaviest warm air advection snow/ice appears to end across much of the Upper Midwest. By Sunday afternoon however, many models begin to rapidly develop the system as it becomes negatively tilted over Lower Michigan. More significant snow may develop on the backside of the system over Wisconsin, Illinois and western Michigan by Sunday evening.

One thing is for sure, this system will need to be watched over the next few days and I wouldn't be surprised to see Winter Storm Watches being issued by Friday if this scenario pans out.

[Ed Mahmoud]

Interesting, but I'm disappointed that the models, which had hinted at snow a few days ago, for NY, are now strongly suggesting rain or a quick change to rain.


One interesting thing, I was suprised when Minneapolis had a record snow a few years back, and it didn't blow the records for NYC out of the water. I know NYC is much closer to the ocean, but I figured since most systems, even in mid-winter, in NYC, change to rain, that just based on the number of storms, MSP would have more storms to break records with, especially with colder temps and greater fluff factor.

[Ed Mahmoud]

I'll vote in the poll tomorrow when I have perused some models.

[RL3AO]

Interesting, but I'm disappointed that the models, which had hinted at snow a few days ago, for NY, are now strongly suggesting rain or a quick change to rain.


One interesting thing, I was suprised when Minneapolis had a record snow a few years back, and it didn't blow the records for NYC out of the water. I know NYC is much closer to the ocean, but I figured since most systems, even in mid-winter, in NYC, change to rain, that just based on the number of storms, MSP would have more storms to break records with, especially with colder temps and greater fluff factor.

In Minneapolis, and most of Minnesota averages 55-60" of snow per year. Most of that is from ten to fifteen light snows (2 to 4 inches), with only one or two major storms (8+ inches). No storm can get anywhere near the moisture that a serious nor'easter can.

This was Minnesota's worst storm in recent memory. It was a low that formed in the Northern GOM and moved due north, because the Perfect Storm in the Atlantic prevented it from moving east.
http://en.wikipedia.org/wiki/Halloween_Blizzard

[WindRunner]

"Fair agreement" is about all you can call it at this point . . . yes, we have a nice low bomb out over the eastern Rockies and the front range, yes it's nicely fed with Pacific moisture, and yes, the models have been consistent on bringing it eastward and solidly through the 75 degree west mark or so. Other than that, the models have been rather inconsistent on the specifics . . . granted we're just gettinig cloer in than that day 5-7 period, so this is about as good as you can reasonably expect, but I think it's still too early to say anything for sure. There is going to be a ton of snow somewhere and there is going to be a ton of ice somewhere, especially if the warm front that starts developing while the low is in the lower Ohio Valley can get its act together . . . that will most certainly create an interesting scenario with the warm air at 850 not necessarily mixing down in the immediate vicinity of the front. Also being that this system originated with some Pacific moisture, it stays relatively moist throughout its entire life.

The way this system has evolved in the past few runs, I'd definately agree that somewhere in the midwest will be getting around a foot (i.e. possibly S WI/N IL area, maybe IA as well), and maybe even a touch more depending on how quickly the system can connect to some moisture east of the Rockies. There should also be a nasty half-snow, half-ice region somewhere just south of there as well (C MO, C IL, N IN-ish as of the last time I looked).

Further east, the track is still up in the air as the GFS has been bebopping all over the place, though the average trend seems to be towards a deeper and more northerly system, but definitely not to the extent of today's 12z run (however nice that was to look at for me here at ALB). More importantly, the GFS has trended and is now focusing around a solution similar to that of the past two runs of the Euro, which gives me some faith in the GFS's solution. As usual, the Euro is having its problem of overdoing the central pressure of systems, taking our friend noticeably sub-980 as it moves over southern Canada, but that can be accounted for.

It may still be five days out, but it definitely still looks like we have our first major storm of the season on the way.

[Ed Mahmoud]

I still can't vote, because my reading is the storm, while big, comes a bit too far West and Chicago and Milwaukee will see a change to rain at the height of it, cutting accumulations way down. But some nice looking isobar packing and winds. Good heavy snow before, some snow on the end, but the mix/change to rain just cuts accumulations too much.


Now, record setting for severe weather in the Southeast, might be a different story. Right now the GFS shows marginal instability for severe, but my limited experience instability will be higher than now shown, and the wind energy looks good.

But the 0Z GFS and Canadian both suggest an excellent snow storm ruined.

[NWS Forecaster]

I still can't vote, because my reading is the storm, while big, comes a bit too far West and Chicago and Milwaukee will see a change to rain at the height of it, cutting accumulations way down. But some nice looking isobar packing and winds. Good heavy snow before, some snow on the end, but the mix/change to rain just cuts accumulations too much.

I don't know if I would completely agree with that only because the vast majority of the precip with this system is warm air advection variety. When and if the warm sector does get into Chicago and Milwaukee, I think the heaviest precip would have ended anyway. Therefore while there may be some reduced snow/ice accumulations if this does pan out, it won't be more than a few inches and chances for a major snow/ice storm are still very decent.

[Ed Mahmoud]

Well, the last GFS suggests about 7 to 10 inches in Chicago before the change, and maybe a quarter inch liquid after, which shouldn't melt away too much snow, and while the snow will be a little too crunchy for my tastes, as a purist, it should be good for packing.


The bad news is, between the change to rain and when that happens, it should give the sanitation or public works or whoever does snow removal plenty of time to ruin a day off for Catholic school children.


I'm just assuming that Chicagoland Catholic kids loved school days as much as I did growing up in the suburbs of NYC, and my measure of a snowstorm is cancelled school days, the best being the February 1978 snow storm which kept me out of eighth grade for 5 consecutive days!

[NWS Forecaster]

Actually looking at the new 12z GFS soundings indicate more of a sleet/freezing rain scenario after snow to start. Could be talking 4 to 8 inches before the changeover to sleet and freezing rain later Saturday night. Ice accumulations could then reach maybe a 1/4 inch before a changeover to rain Sunday morning. Of course that's one model run and I'd like to see the ECMWF before starting to pinpoint amounts. Typically the ECMWF does better with these major winter systems.

[Ed Mahmoud]

Actually looking at the new 12z GFS soundings indicate more of a sleet/freezing rain scenario after snow to start. Could be talking 4 to 8 inches before the changeover to sleet and freezing rain later Saturday night. Ice accumulations could then reach maybe a 1/4 inch before a changeover to rain Sunday morning. Of course that's one model run and I'd like to see the ECMWF before starting to pinpoint amounts. Typically the ECMWF does better with these major winter systems.

As an amateur, I can't get quite the level of detail you can, but the GFS MOS for ORD I get from AccuWx shows surface temps above freezing before the 850 mb temps do.

First number is surface, then 850, pressure, surf RH, 700 mb RH, 6 hour QPF, 500 mb heights and 1000-500 mb thicknesses. I look at the PSU e-Wall maps first, because of the 540 and 284 thicks and 850 mb temps, winds/pressures (always important on East Coast systems, no matter what the heights and temps, an East wind is a killer on the coast), and then try to fine tune w/ the AccuWx MOS for interesting looking cities.

SAT 18Z 01-DEC -1.6 -4.2 1024 97 100 0.21 563 545
SUN 00Z 02-DEC 1.6 -1.3 1014 96 100 0.78 564 552

[RL3AO]

I know this is in the winter forum, but how big is the risk for severe wx in the southern plains?

[Ed Mahmoud]

I know this is in the winter forum, but how big is the risk for severe wx in the southern plains?

18Z GFS shows some instability and some shear, so t-storms seem possible/likely, but not enough for widespread severe, IMHO.

[Nimbus]

This all depends on whether or not we get a major low pressure redevelopment off the coast.
They still think a coastal low is likely to develop and track up into New Brunswick so this could be a major with high winds, rain changing to snow in northern New England. Probably just be a nuisance storm for the mid atlantic states.

[Ed Mahmoud]

Just curious, how does a professional met get the bolded font nic? Because I noticed NWS Forecaster doesn't have one.



Of course, in my line of work, although I passed the Fundamentals of Engineering exam when I was finishing college, and have worked as an engineer for over a decade, I haven't passed the 'Principles and Practices' exam administered under the supervision of the Texas Board of Professional Engineers, and thus can't call myself a 'professional engineer.'


A PE is a requirement to work in Texas as a consultant, and the Texas Railroad Commission, which oversees oil and gas exploration and production, requires a PEs signature on certain calculations and forms. (We pay a consultant to either perform or check off on our work, when required).

I hear the P&P exam is a bear.

[WindRunner]

Coastal development seems unlikely at this point, especially with the storm looking to put most of the NE US in the warm sector at one point or another.

And (of course) the models continue to flip around . . . 18z GFS was a complete joke of a system - especially for the central Plains and Midwest - in comparison to any of the past 10 runs or so. Looks like we're gonna have to start over with the trend-watching and hope something more stable can develop in the models. As long as the ECMWF is staying consistent, however, I still am liking the route via the southern tips of the Great Lakes and into southern Canada, but with a GFS-like pressure.

[MGC]

Looks like there will be a good amount of moisture to work with. It will all depend on the track of the low. If the low tracks south of Chicago then there could be a pretty good amount of snow there. If it tracks to the north of Chicago it will likely start as snow then change to rain.....MGC

[RL3AO]

It looks like the 0z NAM has come into agreement with moisture in SE MN, S WI, and N IL. Not much for a low though.

[RL3AO]

After seeing the 0z NAM and 0z GFS, I feel very confident of waking up to a solid half-foot of snow on Sunday. Too bad the Metrodome has a roof.

[PurdueWx80]

the GFS has never had two similar runs with this system. it's been all over the board, from a major snow/ice storm in the ohio valley just a few days ago, to the ice and snow being pushed hundreds of miles to the north, and it continues to push everything north tonight. i've relied very little on the GFS over the past few months, especially since the ECMWF has been doing so well.

i think the run-to-run discrepancies mostly have to do with the fact that all of the energy going into this storm is offshore right now, where data sampling is sparse. everything feeding into the developing trough is sliding down the coast, mostly offshore. ugh. the main upper-level disturbance that will kick off the warm advection snows talked about above is the upper-level low spinning to the west of baja. i'm impressed with how much tropical moisture this thing is kicking up at the moment - should produce some flash flooding in the desert southwest, but this will also team up with a wide open gulf to bring copious moisture into the midwest. precipitable water is forecast to be about as high as it gets in winter storms in these parts (near and above 1 inch at times).

anyway, i have to agree with NWS forecaster re: the warm advection precip - most of it, at least here in wisconsin, should fall as snow before mid-level temps warm above freezing. and the gfs is notorious for underforecasting the amount of cooling associated with intense vertical motions. this is not to say that there won't be some signficant icing on the southern edge of the system. i'm just not convinced the cold air will be eroded quite so fast.

an ~80-knot low level jet laden with all that tropical moisture, slamming into a very cold/dense atmosphere spells a major winter storm. i suspect there will be a band of thundersnow with the warm advection precip, as well. the forecast pressure gradient is also getting dangerously close to blizzard-like levels. i have to believe someone will get 12-18" out of this storm, especially if snowfall rates reach 2-4" per hour.

the amount of phasing still remains a huge question, and i don't think we'll know the extent of it until this weekend, to be honest. i wouldn't be at all surprised to see a strong coastal low this weekend/early next week, especially if the leading surface low remains weaker and more upper-level energy lags behind.

i'm surprised to see the NAM come into line so quickly this evening. it's progs will probably shine come friday.

[RL3AO]

Where do you think the most likely area to see that band of 12+ inches? Southern Wisconsin?