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December 2016 General Discussion

snowlover2

By snowlover2,
in Lakes/Ohio Valley

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Hoosier

Hoosier

Posted
Posted

LOT dropped temps for Sunday night/Monday morning, now going -20 to -23 in the typically coldest areas and mid/upper teens below zero around here. Yikes.

Seems to me like the surface high has gotten a tad weaker on recent runs, but it could just be noise.    Positioning may be slightly less than perfectly ideal for northern IL.

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beavis1729

beavis1729

Posted
Posted
6 hours ago, Hoosier said:

LOT dropped temps for Sunday night/Monday morning, now going -20 to -23 in the typically coldest areas and mid/upper teens below zero around here. Yikes.

Seems to me like the surface high has gotten a tad weaker on recent runs, but it could just be noise.    Positioning may be slightly less than perfectly ideal for northern IL.

I think the high will still be sufficiently strong (1042-1044 mb)...but I agree that it will not be positioned perfectly.  The center appears to be in central IL overnight Monday, meaning that Chicago metro may see temps freefall on Sunday from about sunset through midnight...then rise slowly after that.  Still a bit too far out to nail down the timing...but I imagine that all areas away from the core UHI will drop lower than -10 for at least a few hours, including ORD.  My point is down to -19 in SW Lake County IL.  

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cyclone77

cyclone77

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Posted

DVN a little more conservative regarding temps compared to the LOT office, keeping temps generally in the -11 to -13 range from central cwa northeast.  We won't be as optimally timed with the ridge axis compared to LOT, but think temps could get quite a bit colder than whats forecast as we plummet beneath the ridge Sun eve.  DVN has mentioned that possibility in their disco though, so later forecasts may bump the lows down some.  I've noticed in the past that these ridge axis can hold on a little longer than modeled, and temps can many times overperform on the west side of the departing axis.  As long as high clouds aren't streaming in overhead of course.  Will be interesting watching the temps tank after sundown as winds go dead calm beneath the axis.  Just need to get another inch or two of fresh/fluffy snow to maximize this potential.

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Jackstraw

Jackstraw

Posted
Posted
49 minutes ago, Hoosier said:

The GGEM is obscene on Monday morning in a band between I-80 and I-70 in Illinois and Indiana...widespread 20-25 below with some isolated colder.  I'm not sure I buy it but that area will probably be a little better positioned under the surface high.

It's on some damn good crack.

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IWXwx

IWXwx

Posted
Posted
5 hours ago, Hoosier said:

Here's something kinda cool.  Some of the coldest temperature anomalies on the planet are progged in WI/IL/IN on Sunday night/Monday morning.

gfs_T2ma_global_10.png

I see what you did there. Seriously, pretty extreme anomalies. The surprising thing to me is how quickly the flow goes zonal and we end up with near normal, quiet weather.

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beavis1729

beavis1729

Posted
Posted

Both the GFS and GGEM show a 1045 mb high over Champaign Sunday evening into early Monday morning. May be a bit too far south to get ideal radiational cooling conditions in N IL, but should still be decent. At this point, I think -10 for ORD, -13 for RFD, and -15 to -20 in the cold spots like Aurora and Rochelle. I hope I bust too high, but the airmass just isn't that impressive. If the high settles in a bit further north than currently progged, it could be a different story.  

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Hoosier

Hoosier

Posted
Posted
15 minutes ago, beavis1729 said:

Both the GFS and GGEM show a 1045 mb high over Champaign Sunday evening into early Monday morning. May be a bit too far south to get ideal radiational cooling conditions in N IL, but should still be decent. At this point, I think -10 for ORD, -13 for RFD, and -15 to -20 in the cold spots like Aurora and Rochelle. I hope I bust too high, but the airmass just isn't that impressive. If the high settles in a bit further north than currently progged, it could be a different story.  

The high seems to have ticked stronger again on recent runs...NAM even has it peaking at 1047 mb.  Placement isn't ideal as has been talked about but maybe some areas in northern IL can still manage to go calm for a prolonged period, at least on a localized basis.  That is something that would probably be difficult for the models to nail down exactly.

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cyclone77

cyclone77

Posted
Posted

FWIW the new GFS is underestimating the cold temps in parts of SD and NE right now.  Pine Ridge SD is already at -29, and Valentine NE at -21.  GFS has both of those areas in the -10 to -15 range.  NAM and RGEM look too cold, although there are a few locations that are as cold as what they show.  NAM/RGEM must be showing optimal radiational cooling potential, which only a few locations have.  Something to watch as the night goes on.

EDIT:  I still think the models are a little too quick to move the western edge of the extreme cold temp potential tomorrow night.  Like I mentioned earlier in the thread, the west edge of the departing ridge axis always seem to outperform the guidance, and in this case the high pressure will actually be strengthening as well.  That should only prolong the max radiational cooling potential further to the west.

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cyclone77

cyclone77

Posted
Posted
2 hours ago, Hoosier said:

I think -15 is definitely within reach here. This is not really a prime radiating location, but it could be worse.

Yeah timing looks really good for you guys.  You won't be having to hope that the western side of the ridge axis hangs on as long as possible like us further west.  

 

This is about as brutal as it gets around here, especially for January.  Updated point now has temps falling to -12 during the day tomorrow...

 

Sunday
Sunny and cold, with a temperature falling to around -12 by 5pm. Wind chill values as low as -30. Northwest wind 5 to 15 mph, with gusts as high as 20 mph.
Sunday Night
Mostly clear, with a low around -17. Wind chill values as low as -30. West wind around 5 mph becoming south after midnight.
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RCNYILWX

RCNYILWX

Posted
Posted

c5ebf78a61fe78c6edb9c62e47e39848.jpg

The 00z Euro has the high in a good location tomorrow at 00z to get winds to quickly decouple and start the free fall. Then by 06z it's showing the high at 1044 mb over roughly IKK. If that's right, that should be close enough to maximize radiational cooling potential, especially with the new snow cover. The raw guidance such as the GFS has been keeping winds up despite showing such extreme cold but the MOS is getting a hint, showing some spots with 1 kt or less of wind. I don't know how to quantify this but in analyzing this pattern, I've been thinking that just being in the envelope of 1040 mb+ pressures should be enough for winds to go light/calm. I wouldn't be surprised if there's still multiple spots calm or light/vrb at 12z. Also, even a few knots shouldn't preclude things going crazy in the classic radiating spots, seeing as ARR got to -12 and RPJ -10 earlier in the week with a much less impressive low level air mass. Also, FWIW, new Euro shows lowest temps occurring after 06z. Will be very interesting to follow this one.

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Hoosier

Hoosier

Posted
Posted

With it looking like almost a slam dunk that ORD will reach/surpass -10F, here's the list of December days of -10F or colder for Chicago. Officially, it has happened 29 times.  Since the official observation site moved to O'Hare in 1980, it has happened 11 times, but those 11 occurrences happened in a total of 3 years -- 1983, 1985, 1989.  That also means that it has been about 27 years since it has happened in December.

 

12/24/1983:  -25

12/24/1872:  -23

12/22/1872:  -21

12/23/1983:  -21

12/23/1872:  -18

12/22/1983:  -18

12/25/1983:  -17

12/29/1880:  -15

12/9/1876:  -14

12/23/1960:  -14

12/19/1983:  -14

12/21/1989:  -14

12/13/1903:  -13

12/28/1924:  -13

12/21/1872:  -12

12/28/1880:  -12

12/15/1901:  -12

12/16/1951:  -12

12/22/1989:  -12

12/19/1884:  -11

12/18/1983:  -11

12/26/1983:  -11

12/25/1985:  -11

12/23/1989:  -11

12/27/1886:  -10

12/26/1892:  -10

12/26/1903:  -10

12/27/1950:  -10

12/31/1967:  -10

 

 

 

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beavis1729

beavis1729

Posted
Posted
33 minutes ago, cyclone77 said:

Hit -11 earlier, which was even colder than forecast.  Still at -9.  DVN hit -13 earlier, and had a wind chill of -37 at one point.  Nasty stuff.

Wow...you're still -9, which is even more impressive since there is some wind and therefore some mixing, keeping temps a bit higher than they could otherwise be. Strange that it's still 5 at ORD, under what I imagine is a similar airmass?? I don't think all of that can be attributed to UHI. I think Chicago metro has had some bad timing so far, as cloud cover held all night, then full sun began right at sunrise. Not that this precludes temps from dropping like a rock beginning late this afternoon...but we'll see. 

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