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Winter Storm? Jan 18-19th, 2019


cyclone77

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20 minutes ago, SchaumburgStormer said:

Snow wise, yes. But we have stopped the bleeding from a zzzz system. Hopefully keep stepping the right direction 

Looks pretty similar to the 12z for this area.  Would like this system to slow down a little.  Not a big fan of these fast movers for appreciable amounts.  

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Looking at the DSM NWS forecast discussion it would seem they are being quite conservative about central Iowa. They are thinking 3 inches or so maybe 4, but most models I’ve seen are showing 4-7 inches here, with the 18z NAM closer to 8 inches and the GFS at over 6. The argument is that it’ll be columns and not dendrites, but I have a feeling they might change their minds and include us in a Watch tomorrow.

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Just now, ConvectiveIA said:

Looking at the DSM NWS forecast discussion it would seem they are being quite conservative about central Iowa. They are thinking 3 inches or so maybe 4, but most models I’ve seen are showing 4-7 inches here, with the 18z NAM closer to 8 inches and the GFS at over 6. The argument is that it’ll be columns and not dendrites, but I have a feeling they might change their minds and include us in a Watch tomorrow 

A lot of guidance was fairly dry prior to the 18z runs. The grids have 4-6” now, don’t have a problem with that.

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Very happy to see the trends continue, the thing is this could very well be mostly southern stream and still give a great hit to the subforum if it goes neutral to negative tilt. Basically another way to come a great outcome without as much significant phasing. There is more than enough cold air in place on this one.

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7 minutes ago, StormChaser4Life said:

Great points Stebo! Was thinking the same thing. A more NE movement would help though with keeping the deformation band around longer. Has anyone noticed how much models are underestimating the current snowpack we have to?

In my scenario if we want the deformation band to hold into the region longer, we need this to go negative tilted or phase.

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Just now, Stebo said:

In my scenario if we want the deformation band to hold into the region longer, we need this to go negative tilted.

Totally agree. You may have a shot being further east but I may be too west to benefit from it. Depends on if and when that even occurs. 18z runs were certainly more encouraging 

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I think this is a good average starting point for around here. Let's see how things trend as we get some sampling going on Thursday.

DMX:

Quote

Confidence continues to increase in a widespread snowfall across Iowa from Friday into early Saturday. Blustery north to northeast winds are also expected and will likely cause visibility restrictions due to blowing and drifting snow, especially while snow is still falling. Behind this system very cold air is expected to surge into the state, wind chills well below zero expected by Saturday night.

DVN:

Quote

The likelihood of a winter storm impacting the region towards the end of the week is increasing. At this time, snowfall amounts around 4-6 inches will be possible from Friday afternoon through Saturday, with the bulk of the snow falling Friday night. If you have plans to be out and about this weekend, please continue to monitor later forecasts!

 

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dvn.png

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3 minutes ago, mimillman said:

SREF plume continues to come in good. 21z mean at ORD is 7”

Nice jump from previous runs in earlier hours. There's actually a greater number of them above the mean as well.

They also have a period of 1-4"/hr snowfall rates Friday night/Saturday morning. The mean is closer to 1-2"/hr.

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So here are some thoughts on the lake effect potential for western/southern Lake Michigan...

Many times the low level flow allows for lake enhanced snow on the western shore, with this translating eastward into IN and then MI as the low level flow backs westerly and that's that.  In this case, there has been a trend in the past day or two to have the surface high slide east near the US/Canada border instead of more southward into the Plains.  Assuming this doesn't reverse itself on future model runs, the effect that this has is to not shift the flow westerly as much and as quickly.  As a result, there is a growing possibility that once the band establishes itself into NE IL/NW IN, it may tend to hang around the area much of the time.  A plausible scenario is that the band shifts into IN and possibly southwest MI for a time on Sunday, but then actually drifts back west toward the western shore late Sunday into Monday as the low level flow becomes more easterly.  

The lake band looks capable of dropping 6+ where it persists the longest.  I'm talking pure LES and not enhancement.  As has been mentioned, most parameters look good for heavy snow with the main negative being relatively low inversion heights around 5500-6000 feet.  A lot of setups with inversion heights that low are pretty ho hum, but in this case, I believe the other favorable factors (good delta T, long fetch, favorable convergence, good omega/dgz profiles, etc) will help to compensate and produce heavy snow.  I have seen heavy snow rates with similarly low inversion heights... it's just not as easy.  If inversion heights were up around 700 mb or higher, I would feel quite confident in the band being able to produce 3-5" per hour rates given all the other favorable factors.  But we don't have inversion heights like that, and off the top of my head I can't think of an event with these inversion heights that produced such heavy rates, so it's best to temper expectations a bit.  That being said, I think 1-2" per hour rates are quite possible in the heart of the band at maturity. 

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4 minutes ago, Chicago Storm said:

NAM definitely going to be better and probably north.

Southern wave is stronger, neutral tilt trough sooner, more ridging over Midwest/OV and less ridging over Western states earlier.

Fully agree

Would be nice to see this continue at 12z, which is really the beginning of the cycles that matter more from a RAOB perspective. 

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