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January 30-February 1 Winter Storm


Hoosier
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1 minute ago, RCNYILWX said:

When the convective allowing nested model seems to be handling things well in a pretty convective setup given such steep lapse rates, if anything can give it more weight than the parent model. Liquid equivalent QPF amounts on the NAM aren't too far off what the consensus has been, I guess we'll have to watch for an earlier weakening of the warm advection burst for far northern areas. If both NAMs came in drier, would have been more concerned.

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Agreed. Though there does appear to be legitimate concerns across Indiana from both. 

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I'm riding a fine line near I74. Models showing a later changeover now here. Hoping precip can arrive later. 3km nam was showing a better deformation band Sun. 
I didn't look closely specifically at your area, but for our far southern areas, without even looking at wet bulb, the 0C line just sneaking in there near southern Ford to me pointed toward evaporative and dynamic cooling doing a lot of work. The winds will be pulling from the departing high, so that'll help from an evaporative cooling sense and support for heavy precip maxes out dynamic cooling. Certainly uncomfortably close down there. Wish I could stay up to diagnose all the 12z guidance with everyone lol, but gotta get some sleep for another busy shift tonight.

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13 minutes ago, McHenrySnow said:

There is definitely an increase in QPF across Missouri across both versions of the NAM and the 3K paints a relative QPF minima over central Indiana. I don't have time to delve into it more deeply than that right now. Just something to watch. 

I think I made a post yesterday about how the GFS run increased precip in central IL(max for the system at the time)  but decreased it across northern IL on one run 

suggesting convection may be robbing some of the moisture transport for at least a little while

perhaps the NAM also is hinting at it now???

time will tell

 

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Those of us in Iowa are wondering what happened to our big snow event that appeared as locked in as any storm could be a few days out.  Nearly all models are either cutting the precip down, warming us up, or both.  Even the HRRR, which nailed the colder, snowier late December storm, has now warmed us up and drops at least a few hours of mix crap here.  The 6-9" snow event has been cut in half.

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I think I made a post yesterday about how the GFS run increased precip in central IL(max for the system at the time)  but decreased it across northern IL on one run 

suggesting convection may be robbing some of the moisture transport for at least a little while

perhaps the NAM also is hinting at it now???

time will tell

 

This storm system is not going to have the same sig/widespread convection further south, as the last storm system did. Also, moisture transport is great. PWATS were actually higher on 12z NAM than previous run as well.

 

So no, there will be no moisture transport issues this time around.

 

 

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13 minutes ago, hawkeye_wx said:

Those of us in Iowa are wondering what happened to our big snow event that appeared as locked in as any storm could be a few days out.  Nearly all models are either cutting the precip down, warming us up, or both.  Even the HRRR, which nailed the colder, snowier late December storm, has now warmed us up and drops at least a few hours of mix crap here.  The 6-9" snow event has been cut in half.

Those of us in places that havent seen a 4+ event all winter are thinking nobody in iowa should be upset.

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8 minutes ago, RCNYILWX said:

I didn't look closely specifically at your area, but for our far southern areas, without even looking at wet bulb, the 0C line just sneaking in there near southern Ford to me pointed toward evaporative and dynamic cooling doing a lot of work. The winds will be pulling from the departing high, so that'll help from an evaporative cooling sense and support for heavy precip maxes out dynamic cooling. Certainly uncomfortably close down there. Wish I could stay up to diagnose all the 12z guidance with everyone lol, but gotta get some sleep for another busy shift tonight.

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I appreciate your input. Even hi resolution cams can struggle with timing of changeover due to dynamic cooling. Earlier timing could be detrimental here during warmer sfc temps. Going to be a very nowcasting situation. 

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27 minutes ago, hawkeye_wx said:

Those of us in Iowa are wondering what happened to our big snow event that appeared as locked in as any storm could be a few days out.  Nearly all models are either cutting the precip down, warming us up, or both.  Even the HRRR, which nailed the colder, snowier late December storm, has now warmed us up and drops at least a few hours of mix crap here.  The 6-9" snow event has been cut in half.

12z HRRR still shows CR getting nearly 8 inches although that will possibly change in the 18z run.  Let's see what the 15z RAP says.  The good news is that with temps at 30-31F, there won't be any notable ice accretion during the 2-3 hour period of ZR before changing to sleet.

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Temperatures are going to be dropping into the upper 20s in the band of heavy snow, at least in northern IL and WI, so I don't see this being as wet as some think. The reason it could be dense and lower ratio has more to due with cloud microphysics and how the smaller or rimed snowflakes are able to compact together.

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Just now, purduewx80 said:

Temperatures are going to be dropping into the upper 20s in the band of heavy snow, at least in northern IL and WI, so I don't see this being as wet as some think. The reason it could be dense and lower ratio has more to due with cloud microphysics and how the smaller or rimed snowflakes are able to compact together.

ratios definitely overperformed locally for the last storm, albeit slightly. But with this much QPF, a minor change is average ratio will add up. 

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Still sticking to my call of 6 inches although it might need to be lowered by an inch if the models keep cutting forecast totals.  However, if CR does indeed get 6 or more inches of snow with this very wet consistency, it's going to be detrimental to the trees, especially with the wind gusts.  HRRR and NAM have temps flirting at freezing during the bulk of the snow.

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5 minutes ago, purduewx80 said:

Temperatures are going to be dropping into the upper 20s in the band of heavy snow, at least in northern IL and WI, so I don't see this being as wet as some think. The reason it could be dense and lower ratio has more to due with cloud microphysics and how the smaller or rimed snowflakes are able to compact together.

It's a tradeoff between raw numbers with the fluffier stuff and I think higher impacts with the wetter stuff. Harder to shovel and it sticks to your car tires and further reduces traction. The first notable accumulating snow we had (the one before Christmas which mostly melted by then) was wet and heavy, and I had to charge the hill out of my apartment building's parking lot about ten times praying my car wouldn't get stuck before I finally made it up to the road. Had the pedal to the metal, front wheels spinning like mad spraying snow everywhere, and moving at maybe 2 MPH.

That, plus spinning out twice this winter on just the thin-packed layer left on secondary roads from snow events days earlier, prompted me to get new tires.

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Temperatures are going to be dropping into the upper 20s in the band of heavy snow, at least in northern IL and WI, so I don't see this being as wet as some think. The reason it could be dense and lower ratio has more to due with cloud microphysics and how the smaller or rimed snowflakes are able to compact together.
On that note, what are your thoughts on blowing/drifting potential? It's a good point about the actual air temperatures. The moisture content of the snow and overall density will be high but maybe it can still be blown around when temps are 28-30 instead of 31-33.

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