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January 22-23, 2024 | OV/GL Snow/Ice Threat


Jpfalcon

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I might regret using the RAP for this lol, but just posting this to make a point.  Below are 2 forecast soundings valid at 12z Tue.  One is from Indianapolis, and the other is from far northwest Indiana.

First up, Indianapolis:

2024012203_RAP_033_KIND_winter_ml.thumb.png.fc1718088ecfd8ce5b25af0bb5dfd43e.png

This forecast sounding has a big bulge of warm air aloft, with the warm layer peak temp at about 5C.  Temps near ground are progged below freezing, so it's technically a "freezing rain" sounding, but with that much warm air aloft and such a shallow cold dome underneath, rain would normally have a hard time freezing very well on most objects/surfaces, especially anything that has some intensity.  As has been discussed, the cold ground is another story, so I think even this kind of marginal sounding could allow for continued freezing rain on the ground.

Now here's northwest Indiana, also valid at 12z Tue.

2024012203_RAP_033_41.4-87.34_winter_ml.thumb.png.675ab8b57cd0738c75c8b03c318d9881.png

Here we have a much less pronounced warm layer aloft, with peak warm layer temps around 2C.  With this kind of sounding, it would be much easier for freezing rain to occur on all objects, including of course the cold ground.

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Sorry for big print….From LOT: 

As a result of the colder temperatures, our forecast now
  features dramatically increased (doubled) ice amounts, ranging
  from around 0.05" near Rockford to 0.25 to 0.4" south of I-88,
  highest south of I-80. In fact, it would not be surprising to
  see ice amounts locally hit 0.5" in a narrow band near the
  Kankakee River, as hinted by RRFS/RAP/HRRR guidance. Meanwhile,
  closer to the Wisconsin state line where the warm nose will not
  be as strong (near or just above freezing), a mix of primarily
  sleet and snow is expected with up to 1" of accumulation.
  Somewhere in between (I-88 corridor?), precipitation type may
  remain all sleet. Our forecast snow, sleet, and ice amounts
  tonight may still be too conservative on a region-wide basis,
  but we think we`re nudging them in the right direction (up).
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1/2 the state now under a Winter Weather Advisory (i71 the dividing line, as usual lol). The HRRR and RAP continue to look like the coldest models (12z runs currently updating). I'm more worried about kiddos trying to walk to school on the sidewalks than roads, I think, especially with the temps over freezing today.

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10 minutes ago, BuckeyeGal said:

1/2 the state now under a Winter Weather Advisory (i71 the dividing line, as usual lol). The HRRR and RAP continue to look like the coldest models (12z runs currently updating). I'm more worried about kiddos trying to walk to school on the sidewalks than roads, I think, especially with the temps over freezing today.

Yep, walking surfaces would be a bigger issue. 

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58 minutes ago, BuckeyeGal said:

NAM believes this will be something of a nothing burger save central Illinois/Missouri.

I'm shocked, considering the NAM's cold bias. 

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1 hour ago, RobB said:

For the first time since January 13, the temp is above freezing at the house. 32.3 degrees.

Holding steady at 28 up this way with thickening clouds. Might be able to stay at/below freezing if the sun fails to peek out this afternoon. 

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1 minute ago, MesoscaleBanding said:

Holding steady at 28 up this way with thickening clouds. Might be able to stay at/below freezing if the sun fails to peek out this afternoon. 

35.9 degrees now!

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1 hour ago, MesoscaleBanding said:

Holding steady at 28 up this way with thickening clouds. Might be able to stay at/below freezing if the sun fails to peek out this afternoon. 

Thats what our local guy said. Cloud cover will impact ground temps and they’re watching every degree in temp change 

Schools all over the state are closing right now before it hits 

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Just a tick under 31 here at the moment. Feels warmer than that outside. Perhaps it's just because of the recent arctic outbreak. Temps will probably drop a bit in most areas once precip begins due to dynamic cooling and temps hit wet bulb.

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Nice little precursor to the snow expected tomorrow here today in Southern Ontario. Solid snow bands and the radar looks decent. Bit unexpected for today but I’ll take it. Already around a inch down. Kind of hard to see in the picture but it’s coming down at a good clip.

IMG_0134.thumb.jpeg.d90d61e20ba4baf68140ebc74c4f76df.jpeg

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15 hours ago, Hoosier said:

I might regret using the RAP for this lol, but just posting this to make a point.  Below are 2 forecast soundings valid at 12z Tue.  One is from Indianapolis, and the other is from far northwest Indiana.

First up, Indianapolis:

2024012203_RAP_033_KIND_winter_ml.thumb.png.fc1718088ecfd8ce5b25af0bb5dfd43e.png

This forecast sounding has a big bulge of warm air aloft, with the warm layer peak temp at about 5C.  Temps near ground are progged below freezing, so it's technically a "freezing rain" sounding, but with that much warm air aloft and such a shallow cold dome underneath, rain would normally have a hard time freezing very well on most objects/surfaces, especially anything that has some intensity.  As has been discussed, the cold ground is another story, so I think even this kind of marginal sounding could allow for continued freezing rain on the ground.

Now here's northwest Indiana, also valid at 12z Tue.

2024012203_RAP_033_41.4-87.34_winter_ml.thumb.png.675ab8b57cd0738c75c8b03c318d9881.png

Here we have a much less pronounced warm layer aloft, with peak warm layer temps around 2C.  With this kind of sounding, it would be much easier for freezing rain to occur on all objects, including of course the cold ground.

Great analysis and you are absolutely correct. 

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Very slippery out there. 

Not quite sure how tonight will shake out locally.  Temps are currently right around freezing.  Possible that there is a small dip with loss of daylight or when precip picks up again.  The ground is going to be a disaster regardless, but just not sure the trees and powerlines will accrete as much.  Kind of an odd event in more ways than one.  The winds look to become very light later tonight/overnight, which I can't really recall seeing too much in a bona fide freezing rain event (not talking about freezing drizzle setups).

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Messing around on the INDOT website, many of the highway asphalt temps along and south of Indianapolis are currently above 40.    North of the metro, still 35-36.    Will be interesting to see how those drop off tonight

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