se WI/ne IL/nw IN/se MI lake effect snow event

[A-L-E-K]

I wouldn't be surprised if it looks disorganized/crappy on radar much of the time except for that period on Sunday.

Pretty much your standard NE Illinois event I outlined above, diffuse unorganized snow showers and a transient band pivoting into NW IN.

[A-L-E-K]

I agree with your area to watch. I think the placement could be very similar to 1/20/09. I think Aleking got like 4" from that.

I don't even have the foggiest memory of that event, but i'm now 2 miles south of that location, maybe it would be 4.3" now.

[weatherguru]

Pretty much your standard NE Illinois event I outlined above, diffuse unorganized snow showers and a transient band pivoting into NW IN.

That is not pretty. I cant really understand why that is always the case. I always see these scattered crappy snow LES snow-showers. Why cant we just get a fat single band of 30-35dbz LES snow band in all of Lake, Cook and Dupage counties! If GFS shows a QPF of .25+ running down the Lake this means business and not a crappy LES event.

[Hoosier]

I don't even have the foggiest memory of that event, but i'm now 2 miles south of that location, maybe it would be 4.3" now.

Here's a little bit of info:

http://cimss.ssec.wisc.edu/goes/blog/archives/1818

[A-L-E-K]

Well the GFS is showing a nice fat single band of snow stretching down from the Lake into all of far NE IL. It doesent look weak. The band looks

pretty healthy.

hmmm, i'm not seeing what you're seeing here. I see a general signal for a large diffuse area of light lake snow. The GFS is in no way equiped to pick up on a banding feature like that, especially 100hrs out.

[A-L-E-K]

That is not pretty. I cant really understand why that is always the case. I always see these scattered crappy snow LES snow-showers. Why cant we just get a fat single band of 30-35dbz LES snow band in all of Lake, Cook and Dupage counties! If GFS shows a QPF of .25+ running down the Lake this means business and not a crappy LES event.

It's really worth taking the time to read the study on Lake Michigan lake effect snow Hoosier posted on the last page and even it is somewhat limited.

[weatherguru]

It's really worth taking the time to read the study on Lake Michigan lake effect snow Hoosier posted on the last page and even it is somewhat limited.

Do I sound like I am talking out of my behind?

[beavis1729]

I recall that but I thought that was December 29-30.

Yeah, you're probably right.

[A-L-E-K]

Do I sound like I am talking out of my behind?

Nope, it just might help understand why a 60 hr cumulative QPF marker for .25" doesn't neccesarily translate into single fat band into Chicago.

[LizardMafia]

Little snip from the IND AFD this afternoon..

STILL APPEARS A RATHER ROBUST LAKE EFFECT SNOW EVENT OFF LAKE

MICHIGAN POISED TO GET GOING SATURDAY AFTERNOON AND PERSIST POSSIBLY

INTO THE DAY SUNDAY. LOW LEVEL FLOW DURING THE TIMEFRAME WILL BECOME

NORTHERLY WITH THE POTENTIAL FOR SOME OF THESE BANDS TO ROTATE SOUTH

INTO THE FORECAST AREA. WILL MAINTAIN LOW CHANCE POPS INTO SUNDAY AS

A RESULT. POSSIBILITY FOR SOME LIGHT ADDITIONAL ACCUMULATIONS FROM

THE LAKE EFFECT SATURDAY AFTERNOON/NIGHT. ADDITION OF STRONGER

NORTHERLY WINDS WILL LIKELY CAUSE SOME BLOWING OF SNOW AS WELL...AND

COULD VERY WELL EXACERBATE TRAVEL IN SOME LOCATIONS. WILL EMPLOY

MORE DETAIL OVER THE NEXT FEW DAYS.

[KeenerWx]

Nope, it just might help understand why a 60 hr cumulative QPF marker for .25" doesn't neccesarily translate into single fat band into Chicago.

This.

It's usually not worth doing much more than recognizing a potential at this point. This event is out of range for our mesoscale models. Models such as the GFS, Euro, GGEM, etc are really only used to diagnose a potential and to get a wider, overall synoptic picture of what's going on. We won't have much of a clue as to what's really going to happen until Friday/Saturday. And because Lake Effect Snow is so fickle, what happens can sometimes be far from what we expect will happen.

[tornadotony]

That is not pretty. I cant really understand why that is always the case. I always see these scattered crappy snow LES snow-showers. Why cant we just get a fat single band of 30-35dbz LES snow band in all of Lake, Cook and Dupage counties! If GFS shows a QPF of .25+ running down the Lake this means business and not a crappy LES event.

The reason you typically get the crappy looking LES events on that side of the lake is that it's difficult to get the type of temp profiles you need for a good, focused event with a NE wind. That colder air originates more over the Canadian prairie provinces and is advected southward in N or NW flow. Thus, even if you get a favorable fetch for Chicago, you often don't have air that is cold enough to create enough instability for a more organized event.

[A-L-E-K]

The reason you typically get the crappy looking LES events on that side of the lake is that it's difficult to get the type of temp profiles you need for a good, focused event with a NE wind. That colder air originates more over the Canadian prairie provinces and is advected southward in N or NW flow. Thus, even if you get a favorable fetch for Chicago, you often don't have air that is cold enough to create enough instability for a more organized event.

That and we have a hard time maintaining the convergence you seen in northern indiana when you get light NW winds on the western shore and light NE winds on the eastern shore.

[tornadotony]

That and we have a hard time maintaining the convergence you seen in northern indiana when you get light NW winds on the western shore and light NE winds on the eastern shore.

Yes. The frictional forces of land cause wind to turn a bit counterclockwise to the isobars, which with a NE wind at the south end of the lake would actually promote more divergence near the shore. With a northerly flow event, the frictional effects of land act to create convergence over the lake and enhance lift for LES.

[beavis1729]

The reason you typically get the crappy looking LES events on that side of the lake is that it's difficult to get the type of temp profiles you need for a good, focused event with a NE wind. That colder air originates more over the Canadian prairie provinces and is advected southward in N or NW flow. Thus, even if you get a favorable fetch for Chicago, you often don't have air that is cold enough to create enough instability for a more organized event.

Agree. With that said, the upcoming NE IL potential could be a bit interesting, as today's 12z GFS (fwiw) is showing sub-520dm thicknesses in the area. That's some decent cold air aloft. Obviously it's not the only factor...but we could actually have some decent temp profiles with this one. There's also a 1030+ mb high in south-central Canada on the 12z GFS, to help funnel in the NE winds.

I don't understand LE events/synoptics as much as some others...so I could be incorrect in my thinking. Still a long ways out. As Keener mentioned, the best takeaway at this point is that there is potential for a decent NE IL lake-effect event...which is unusual in and of itself.

[weatherguru]

That and we have a hard time maintaining the convergence you seen in northern indiana when you get light NW winds on the western shore and light NE winds on the eastern shore.

Very true. The years I been interested in weather I never thought about that.

[A-L-E-K]

Yes. The frictional forces of land cause wind to turn a bit counterclockwise to the isobars, which with a NE wind at the south end of the lake would actually promote more divergence near the shore. With a northerly flow event, the frictional effects of land act to create convergence over the lake and enhance lift for LES.

Thanks for the more accurate description of the processes involved.

[weatherguru]

LES snowband in Chicago at 60hr on 18z NAM:

http://www.nco.ncep....am_pcp_060l.gif

System snow looks alot furthur north.

[tornadotony]

Just to kind of paint a picture of what I said earlier, I came up with the following map. I don't have exact amounts attached to this map yet, but the lightest area would have a low chance of significant (3"+) accumulation, the Cubbie blue area would be a moderate chance of significant accumulation, and the shaded dark blue is where I think the highest chance of significant accumulations are likely.

[weatherguru]

18z NAM looks way furthur north with the system. I see a more decent LES on this run with a better NE fetch.

[A-L-E-K]

18z NAM looks way furthur north with the system. I see a more decent LES on this run with a better NE fetch.

The system is still down on the gulf then and there is a lot of veering over the lake. We won't get into a favorable setup until it rides up the coast some.

[weatherguru]

The system is still down on the gulf then and there is a lot of veering over the lake. We won't get into a favorable setup until it rides up the coast some.

Yeah at 78hr became discouraged.

[A-L-E-K]

LOT special wx statement for the holidays agrees with Skilling on the potential of light lake effect accumulations.

EDIT: to summarize LOT's thoughts on LE potential = meh

FINALLY...WITH A RE-ENFORCING SURGE OF COLD AIR RUSHING SOUTH THIS

WEEKEND AS THE LOW DEEPENS ACROSS THE EASTERN SEABOARD AND HIGH

PRESSURE BUILDS ACROSS THE NORTHERN PLAINS...EXPECT LAKE EFFECT

MACHINE TO BE SWITCHED ON. THERMAL PROFILES SHOW MARGINAL DELTA-TS

BUT FAVORABLE NORTHERLY FETCH. CLOUD LAYER MEAN FLOW HAS SLIGHT

EASTERLY COMPONENT WHICH COULD SET THE STAGE FOR SNOW SHOWERS ACROSS

THE SOUTHERN METRO AREA IN ILLINOIS. WILL HOLD OFF ON SNOW AMOUNTS

FOR NOW...BUT DOES LOOK LIKE THE EVENT WILL LAST THROUGH THE

WEEKEND.

[Chicago Storm]

12z...

MKE:

ECMWF: 0.03"

GFS: 0.22"

GGEM: 0.01-0.10"

UGN:

ECMWF: 0.06"

GFS: 0.32"

GGEM: About 0.10"

ORD:

ECMWF: 0.06"

GFS: 0.42"

GGEM: About 0.10"

GYY:

ECMWF: 0.09"

GFS: 0.40"

GGEM: 0.25-0.50"

VPZ:

ECMWF: 0.11"

GFS: 0.32"

GGEM: 0.25-0.50"

[weatherguru]

18z GFS would fluff up to 3-6 inches in northern IL with localized 6+ There is a period of 6-10hrs of light to mod sypnotic snow as it showing now on 18z GFS.

[A-L-E-K]

12z...

MKE:

ECMWF: 0.03"

GFS: 0.22"

GGEM: 0.01-0.10"

UGN:

ECMWF: 0.06"

GFS: 0.32"

GGEM: About 0.10"

ORD:

ECMWF: 0.06"

GFS: 0.42"

GGEM: About 0.10"

GYY:

ECMWF: 0.09"

GFS: 0.40"

GGEM: 0.25-0.50"

VPZ:

ECMWF: 0.11"

GFS: 0.32"

GGEM: 0.25-0.50"

I like when you do this, it helps pick out outliers, which in our case is the GFS, especially compared to the consistent ECMWF.

[Stebo]

12z...

MKE:

ECMWF: 0.03"

GFS: 0.22"

GGEM: 0.01-0.10"

UGN:

ECMWF: 0.06"

GFS: 0.32"

GGEM: About 0.10"

ORD:

ECMWF: 0.06"

GFS: 0.42"

GGEM: About 0.10"

GYY:

ECMWF: 0.09"

GFS: 0.40"

GGEM: 0.25-0.50"

VPZ:

ECMWF: 0.11"

GFS: 0.32"

GGEM: 0.25-0.50"

Cough, DTW, Cough

But yeah I think there is a decent shot at some LES off of Lake Huron over a good portion of DTX's area.

[Thundersnow12]

FWIW the 18z runs of both the NAM/GFS continue to trend up in qpf for the synoptic snow before the LES which continues to look interesting.

will be nice when we get into the 48hr timeframe to see what the hi res models do with it.

[Chicago Storm]

I like when you do this, it helps pick out outliers, which in our case is the GFS, especially compared to the consistent ECMWF.

I'll add the NAM starting with the 0z...

Cough, DTW, Cough

But yeah I think there is a decent shot at some LES off of Lake Huron over a good portion of DTX's area.

DTW:

12Z...

ECMWF: 0.03"

GFS: 0.09"

GGEM: 0.01-0.10"

[Chicago Storm]

FWIW the 18z runs of both the NAM/GFS continue to trend up in qpf for the synoptic snow before the LES which continues to look interesting.

will be nice when we get into the 48hr timeframe to see what the hi res models do with it.

Don't get your hopes up.