January 17-18 Winter Storm

[Chicago Storm]

11 minutes ago, Hoosier said:

18z NAM is hitting the ice.  But again, gotta take the freezing rain maps with a grain of salt especially when rates are higher.  

Rates will definitely be lower than the last storm system, so that should be a positive.

[nwohweather]

51 minutes ago, IWXwx said:

The 06z GFS was showing something similar, but I don't have a clue.

EDIT: My bad, that's the 12z

I believe it is due to the abnormally dry air off to the east of the low. Typically the cold conveyor belt moistens as it flows under the warm conveyor belt when wrapping around a storm and dries off a bit turning into snow on the backend of a low. This is honestly a perfect CAD example as you can see how as this moves east it drops freezing rain/sleet all over the Apps

[Thundersnow12]

GFS isn't bad here. 3-4" with more west of I-39 

[nwohweather]

5 hours ago, Snowstorms said:

2011-12, 2012-13 and 2015-16 were worse up until now. 

 

2011-12 was a lovely winter in my opinion. It does stink when the snowmobile and ice skates stay in the garage but the weather was beautiful and sunny which was a nice reprieve considering what was on the horizon.

I think 2013-14 was honestly overwhelming, the constant snow and cold just wore you down.  I do like snow, but 86" was too much for me

[cyclone77]

DVN has 100% snow in the point for here.  Interesting.

 

Friday  Snow, mainly after 7am. High near 32. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible.
Friday Night  Snow. Low around 28. Chance of precipitation is 90%.
Saturday  Snow, mainly before 1pm. High near 34. Breezy. Chance of precipitation is 90%.

 

 

 

 

 

[RCNYILWX]

DVN has 100% snow in the point for here.  Interesting.   Friday  Snow, mainly after 7am. High near 32. Chance of precipitation is 90%. New snow accumulation of 1 to 2 inches possible. Friday Night  Snow. Low around 28. Chance of precipitation is 90%.

Saturday  Snow, mainly before 1pm. High near 34. Breezy. Chance of precipitation is 90%.

         

 

 

The reason for that is they still use the first generation top down methodology for p-type derivation, max wet bulb temp aloft. It's fine as a proxy but the modified Bourgoin wet bulb energy method provides better results with less potent warm noses but enough positive energy for full melting and not enough low level negative energy for refreezing. In max Tw aloft, probabilities are set to certain temp thresholds, so anything below 2C aloft has increasingly high snow probs and less sleet, 2-3C has max sleet probs and above 3C has highest ZR probs.  

The work done by my co-workers, who are getting a paper published on modified Bourgoin, has real sounding cases that show the max Tw aloft method causes too much sleet and snow and not enough ZR in a lot of cases. On the other hand, when a fairly potent warm nose is undercut by a pronounced low level cold wedge, that method won't produce enough sleet.  

 

The energy method is the way the agency is going and it's what's being used for experimental probability of weather type grids in the NBM, but they still haven't brought all offices on the same page. So for offices west of GRB, MKX, LOT, ILX, they're still using max wet bulb temp aloft, creating an unfortunate discrepancy. Once confidence increases in the scenario closer in, I'm sure they'll do more to have better interoffice consistency with the weather grids.

 

 

 

 

 

 

 

 

 

[RCNYILWX]

18z Euro and Euro ensemble came back up with snow accums I-80 and north in Illinois.

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[Hoosier]

53 minutes ago, RCNYILWX said:

The reason for that is they still use the first generation top down methodology for p-type derivation, max wet bulb temp aloft. It's fine as a proxy but the modified Bourgoin wet bulb energy method provides better results with less potent warm noses but enough positive energy for full melting and not enough low level negative energy for refreezing. In max Tw aloft, probabilities are set to certain temp thresholds, so anything below 2C aloft has increasingly high snow probs and less sleet, 2-3C has max sleet probs and above 3C has highest ZR probs.  

The work done by my co-workers, who are getting a paper published on modified Bourgoin, has real sounding cases that show the max Tw aloft method causes too much sleet and snow and not enough ZR in a lot of cases. On the other hand, when a fairly potent warm nose is undercut by a pronounced low level cold wedge, that method won't produce enough sleet.  

 

The energy method is the way the agency is going and it's what's being used for experimental probability of weather type grids in the NBM, but they still haven't brought all offices on the same page. So for offices west of GRB, MKX, LOT, ILX, they're still using max wet bulb temp aloft, creating an unfortunate discrepancy. Once confidence increases in the scenario closer in, I'm sure they'll do more to have better interoffice consistency with the weather grids.

 

 

 

 

 

 

 

 

 

The energy methods that you talk about are enlightening... sort of treating it as an integrated value like CAPE is.  I have a question though.  I have no idea where I got this from but a long time ago I read that in situations with a warm layer aloft, having -4C or colder in the cold layer greatly increases the chance for sleet, even if the warm layer aloft is pretty warm.  How well do you think that works? 

[RCNYILWX]

The energy methods that you talk about are enlightening... sort of treating it as an integrated value like CAPE is.  I have a question though.  I have no idea where I got this from but a long time ago I read that in situations with a warm layer aloft, having -4C or colder in the cold layer greatly increases the chance for sleet, even if the warm layer aloft is pretty warm.  How well do you think that works? 

The energy method works on that basis because it is so intuitive and mirrors severe weather forecasting. An integrated value tells you a lot more than a point value, like CAPE and CIN and iterations of both, versus LI, K Index and totals totals. Not that there's no use for more simplistic measurements, but they oversimplify the atmosphere.

-4 to -5 C is definitely a decent rule of thumb or proxy and one I've used before. You'd figure to have that magnitude of cold underlying a warm layer, it would have a decent amount of negative energy.

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[Hoosier]

00z NAM was still fairly bullish on ice.  Certainly some negative factors for getting really big ice amounts in this setup, like duration (maybe only about 3-6 hours tops in a given location) and surface WAA.  But it could still get a little dicey, and it doesn't take much to start causing problems with trees/powerlines when you add some wind, and it should be at least a little breezy with a decent pressure gradient.  

[Radtechwxman]

This storm is certainly not trending in a good way. At least for me. Slower timing which allows temperatures to moderate quite a bit giving a much shorter window of wintry precipitation 

[RogueWaves]

18 minutes ago, Hoosier said:

00z NAM was still fairly bullish on ice.  Certainly some negative factors for getting really big ice amounts in this setup, like duration (maybe only about 3-6 hours tops in a given location) and surface WAA.  But it could still get a little dicey, and it doesn't take much to start causing problems with trees/powerlines when you add some wind, and it should be at least a little breezy with a decent pressure gradient.  

Even tho the window may be a short one, I'm seeing a much greater risk of icy roadways with the much colder sub-freezing temps leading into the event. Unlike the last 2, when it was 50s in the morning before dropping to freezing afterwards. Ofc, that's tricky as well, since the main roads should be getting scraped & treated (with temps rising chem's will be much more effective) thus you'd lean towards secondary roads being more likely to ice up, but they are less likely to be scraped and if snow-covered, it will mitigate any ZR. As you say tho, there's the off surface concerns too. 

[RogueWaves]

14 minutes ago, StormChaser4Life said:

This storm is certainly not trending in a good way. At least for me. Slower timing which allows temperatures to moderate quite a bit giving a much shorter window of wintry precipitation 

Yeah. 0z NAM has SLP way north, tho still keeps me mostly snow/frozen. Not a fan of that look, but WPC actually put most of the Mitt in the Hvy Snow contour with today's release. I'm cautiously hopeful for a 4-ish thump of wetter snow, a period of mix, maybe a not too long window of liquid, followed by a change to backside snow and LEhs>>LES on Sunday (have Snow Likely in my grid for Sunday actually). 

[wegoweather]

Oz GFS with an ORD donut hole.

 

[Hoosier]

3 minutes ago, wegoweather said:

Oz GFS with an ORD donut hole.

 

Strange look... not that the amount has to be wrong but would expect something more uniform.

[RyanDe680]

Resembles that odd dry slot

[ILSNOW]

Oz CMC

I think that it includes sleet and is overdone!!!

 

[UMB WX]

Someone I fear is going to choke on dry air and waste precious qpf.   Tomorrow is the day we hopefully get some improvements and clarity.

[Chinook]

Interesting stat: Toledo OH gets exactly 5.2" (Kuchera ratios) with the 00z GFS and 00z Canadian. With this storm, the borderline of rain/snow is going to be hard to forecast, and may come down to nowcasting, so this consistency means almost nothing at this point.

[Hoosier]

12z run was so bad that this is actually some improvement in southward extent of snow

[cyclone77]

Just now, Hoosier said:

12z run was so bad that this is actually some improvement in southward extent of snow

A high-end event to be sure relative to this year.  Breaching the 1" barrier is equivalent to a warning criteria event in most years.

[Stebo]

22 minutes ago, Hoosier said:

12z run was so bad that this is actually some improvement in southward extent of snow

Yeah so far the models stopped the bleeding tonight at least.

[HillsdaleMIWeather]

If current forecasts pan out, the roads around here are gonna get wrecked. The little bit of rain won't even help for long as they're expecting a flash freeze

[Baum]

looking like a mere 1-2" before changeover. Have to hope for an earlier onset to do better. In most winters this event is barely worth a look given trends. 

[A-L-E-K]

On 1/13/2020 at 9:07 AM, A-L-E-K said:

final call 2.5"

Looking $$$

[ILSNOW]

6z Euro 

[DaveNay]

LOL @ Cook County

 

[Cary67]

30 minutes ago, DaveNay said:

LOL @ Cook County

 

Donut hole moved from Cook to Mchenry Co. 6Z Euro looks like it has a bit of a dry slot pointed toward same area

[SchaumburgStormer]

I know everyone is shocked, but this one is trending crappier for about everyone. 

[Pascy619]

GFS is waaay North. Almost too far north for me here even in WI.