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April 5-7 One-Two Punch Snow Systems


Hoosier

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This is really 2 systems in quick succession, and instead of having separate threads or no thread at all, I am combining them here.

As I have been posting about in the April thread, the first system on Thursday-Friday system has some pretty nice mesoscale banding signals... and indeed, the 00z NAM came in fairly hot.  It is looking increasingly possible that a band of accumulating snow occurs near/north of I-80, with still varying solutions on placement.

This system will be followed by another one that tracks farther south on Friday-Saturday with more of an Ohio Valley target.  

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12 minutes ago, Indystorm said:

Bah, humbug.  But seriously, it is fascinating to see how long these winter systems can last into April and the meteorological conditions retarding full blown spring warmth until it finally comes crashing in like a bull in a china shop.

It's a remarkably wintry pattern for the time of year.  We have snow producing systems spanning basically the entire region from north to south.  On a personal level, I hate this chilly weather at this time of year but on a meteorological level, it is interesting to watch.  More sustained spring like weather can only be held back so long.

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The 12Z suite is staying fairly consistent.  Been lucky around here so far, more "Spring" snow than I've had all winter.  It's the day's in between when you know the greener grass is licking at your heels that are torture.

1 minute ago, Hoosier said:

It's a remarkably wintry pattern for the time of year.  We have snow producing systems spanning basically the entire region from north to south.  On a personal level, I hate this chilly weather at this time of year but on a meteorological level, it is interesting to watch.  More sustained spring like weather can only be held back so long.

I agree.  I'm in a right brain left brain quandary right now, not that that's unusual for me lol.  I'm well aware that, particularly in the lower Great Lakes area,  the seasonal changes can vary widely year to year, and it does make it fun from a weather standpoint.  But swings from dismal to snow back to dismal, yeah, bah humbug.  One thing I hope not to see is a transition into the warmer months with stifling prolonged stretches of unbearable 90 degree heat and humidity.  I had enough of that in the south.  I want my late childhood summers of a few days of 80's- 90's, some boomers, followed by a couple days of 60's and 70's.. in July! lol. 

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Some differences in placement of the better band of snow tomorrow.  The 12z NAM is on the northern end but a compromise solution would put the better potential along or even south of I-80... will be interesting to see how LOT handles it.  Gino brought up what the higher end scenario would be in the morning afd.

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2 hours ago, Baum said:

Always love to watch the LOT AFD that follows Izzi's. Banana Split with Jalapeño versus vanilla. In this case the new guy gave us a saltine cracker to munch on. 

The band tomorrow is probably going to be a bit of a nowcast.  Not saying the setups are the same but I have 4/1 fresh in my head with how the models struggled with the magnitude/placement right up until it was snowing.

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Looking at the HRRR/RAP for tomorrow, they are turning the band of precip over to rain toward the end of the run as diurnal warming becomes too much. Here is an example HRRR forecast sounding from directly under the band at 17z.

hrrr_2018040423_018_41.21--89_43.thumb.png.b7ba4472861c993c61ac239deb4251a1.png

The question is, is this right?  I don't think it is... yes, it's April, but it's not easy to get dry adiabatic lapse rates in the near surface layer when precip is occurring. The freezing level is very low on this sounding, so there would be snow surviving to the surface or pretty darn close (like look up and see the flakes above your head close).  I would think these models would come in cooler and show more snow on upcoming runs but we'll see.

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4 minutes ago, Hoosier said:

Looking at the HRRR/RAP for tomorrow, they are turning the band of precip over to rain toward the end of the run as diurnal warming becomes too much. Here is an example HRRR forecast sounding from directly under the band at 17z.

hrrr_2018040423_018_41.21--89_43.thumb.png.b7ba4472861c993c61ac239deb4251a1.png

The question is, is this right?  I don't think it is... yes, it's April, but it's not easy to get dry adiabatic lapse rates in the near surface layer when precip is occurring. The freezing level is very low on this sounding, so there would be snow surviving to the surface or pretty darn close (like look up and see the flakes above your head close).  I would think these models would come in cooler and show more snow on upcoming runs but we'll see.

You're not kidding...I would assume the same though. Could be an interesting little event to see how things end up playing out.

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Models doing a pretty terrible job with tomorrow's little wave.  They've been all over the place with placement and strength.  Wouldn't be surprised if we got a nice burst of wet snow or two, but also wouldn't be surprised to not see a flake.  Temps will be above freezing even in areas where snow is ripping, so it's basically gonna be all for show anyway.

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8 minutes ago, cyclone77 said:

Models doing a pretty terrible job with tomorrow's little wave.  They've been all over the place with placement and strength.  Wouldn't be surprised if we got a nice burst of wet snow or two, but also wouldn't be surprised to not see a flake.  Temps will be above freezing even in areas where snow is ripping, so it's basically gonna be all for show anyway.

Not sure about temps... some models have been hinting at temps dropping to around freezing in the band.  Probably will come down to intensity... if it is indeed well organized with good precip rates, then I'd buy temps slipping down to around freezing.  

 

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Yeah, temps are looking quite marginal for tomorrow. If the band is more intense, then yes temps may be lower but the way its looking now, doesn't seem to be too impressive. You never know though, as hi res models didn't perform well on Easter and it's always hard forecasting snow in April.

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59 minutes ago, CoalCityWxMan said:

Yeah, temps are looking quite marginal for tomorrow. If the band is more intense, then yes temps may be lower but the way its looking now, doesn't seem to be too impressive. You never know though, as hi res models didn't perform well on Easter and it's always hard forecasting snow in April.

I think one or both of us may be in a decent spot tomorrow, assuming this thing actually does something lol.  The model uncertainty at this stage is a bit concerning though.  While the HRRR/RAP are torching the boundary layer, they are cold enough at 925-850 mb so I feel like they will correct down with 2m temps provided that nice banding occurs.   

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3km has temps in the mid 30s here tomorrow afternoon due to influences from snowfall.  HRRR has no snow or rain, and has us pushing 50.  Dry ground, and southerly flow could have temps overachieve if snow/precip doesn't occur.  I could see a scenario where we make a run at the mid 50s and the 3km NAM busts by 20 degrees.

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2 minutes ago, Hoosier said:

This reminds me of a system on 4/1/2002.  I don't know if anyone remembers.  It ripped pretty good for a while where I was.

I remember that one well.  Had a few inches of heavy wet snow fall, with even some thunder.  Meanwhile out in southwest Iowa they warmed into the lower 80s.

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5 minutes ago, cyclone77 said:

I remember that one well.  Had a few inches of heavy wet snow fall, with even some thunder.  Meanwhile out in southwest Iowa they warmed into the lower 80s.

Ha.  It was an obscure reference so I wasn't sure if anyone remembered.  

Here's a radar grab from back then.  

n0r_20020401_2000.png.498bcd755a014ddc0c7159d1b45f805d.png

 

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