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One More Shot: Feb 20-21 Event


Tar Heel Snow
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3 minutes ago, Wow said:

QPF slightly less but it's the sfc temps killing the snowfall amts

Yeah it's definitely concerning. It's a storm where dynamics will have the final say. If it snows hard enough low level temps can easily wet bulb to allow accumulations. Could be a situation where the roadways are fine but grassy surfaces get a couple inches depending on where you are. 

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Just now, It's Always Sunny said:

Yeah it's definitely concerning. It's a storm where dynamics will have the final say. If it snows hard enough low level temps can easily wet bulb to allow accumulations. Could be a situation where the roadways are fine but grassy surfaces get a couple inches depending on where you are. 

Thanks, yeah that's been exactly my fear all along. GFS was in and out of there quick too.  It's NAM or nothing at this point for mby.  

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2 minutes ago, SnowNiner said:

Thanks, yeah that's been exactly my fear all along. GFS was in and out of there quick too.  It's NAM or nothing at this point for mby.  

Yeah unfortunately NAM is the outlier but on the bright side of things the fronto band remains aligned in the same location for the most part, just a little less robust on 12Z GFS but nothing I'm too concerned about regarding accumulating snow.

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The transition to snow almost always takes longer than expected.  I don't feel too optimistic on 10" totals around here, even in the sweet spot, wherever that ends up being.  But I do think it will snow for a lot of people.  The most likely scenario in my mind is a similar distribution of precip type, along the lines of what the NAM is showing, but with much lower totals.  South of Raleigh will probably fight mixing issues for a good portion of the storm.  I'd guess a 1-3" gradient across Wake and higher amounts of maybe 3-5" toward the VA border.  The northern and central coastal plain will probably be the best area to see 4-6".  Going to be hard to beat that unless a really intense band sets up and doesn't move.

No doubt things could overperform.  But they usually underperform, in spite of what the models are showing at this lead.

If the HRRR doesn't come around and if the NAM keeps creeping north with the warm layer, and if other models like the GFS continue to warm, then we know that we're tracking toward a lower end event.  This isn't an ideal setup, but it may be just good enough.  Often, just good enough is the same as not very good, so we'll see how this one unfolds.  We need good rates, and hopefully they will occur.

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I'm very encouraged by the HRRR.

The 12z run had far south evolution of the 800mb warm nose. The best I can tell the upstate isn't getting a *push* north of warmer air at 800mb during the storm. It's more like our current 800mb temps are above freezing and the cold air doesn't begin to press until the storm has started.

As such, it's imperative that the 800mb between now and tomorrow morning verify on the cold side of guidance,(like the HRRR is showing).

If you look at the latest run of the HRRr, 15z. It has that 800mb temp at only around freezing for upstate, SC at 1am tonight. Compare this with the 3km NAM sounding which has it at +3C for the same time.

If the HRRR is correct here, I don't expect a push of warmer air at 800mb as the storm comes in, and we may well be around isothermal as the heavy precip moves in tomorrow around 10am.

This is my very weenie take on the situation, and what I am clinging to for the moment.

HRRR on top, NAM on bottom

Screen Shot 2020-02-19 at 12.35.02 PM.png

Screen Shot 2020-02-19 at 12.35.12 PM.png

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3 minutes ago, wncsnow said:

Right now the GFS is the driest model for the majority of the state

 

Just now, BullCityWx said:

That's right where I want it. No one legitimately can convince me the opposite scenario would be the best. 

Agreed, if the global with the worst verification score out of the big 3 is the driest, I'm ok with that.

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Just now, burrel2 said:

Here's the end of the HRRR run at 4am tomorrow morning, at the end of it's run. Notice the 800mb temp has not went up, and the cold/dry air has really funneled in to the lower levels thanks to the NE fetch.

Screen Shot 2020-02-19 at 12.46.10 PM.png

Gonna take a long time to wetbulb if you're starting at 44.

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Just now, SnowDeac said:

Gonna take a long time to wetbulb if you're starting at 44.

I'm not super concerned about the HRR surface temps since it has a known warm bias in that regard.  Also the 3km NAM quickly gets the upstate to 33 when the heavy precip moves in, even with the warm nose up above. FYI, the HRRR may have a cold bias at 800mb for all I know... we will find out.

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I can officially report from the heart of our storm down here in Tyler Texas.....it's VERY rainy.  Now I just need to get into GSO tomorrow night before it beats me there!

Still think this is going to be rate driven lollipops following I40 and HWY 264 out east.  Otherwise its gonna be snow or no with the warm nose.

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What are we thinking temps will realistically be at go-time with this one across the board? Do we think BL temps warming into the 40's are going to be an issue? Models all over the place. Living here most of my life has taught me to usually go on the high end of guidance for an event starting in the afternoon, and low-end of guidance with the event starting in the morning (assuming radiational cooling took place without full cloud cover). I know we will wet bulb but, just from my experience, it usually takes much longer than we expect or models show.

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23 minutes ago, Cold Rain said:

The transition to snow almost always takes longer than expected.  I don't feel too optimistic on 10" totals around here, even in the sweet spot, wherever that ends up being.  But I do think it will snow for a lot of people.  The most likely scenario in my mind is a similar distribution of precip type, along the lines of what the NAM is showing, but with much lower totals.  South of Raleigh will probably fight mixing issues for a good portion of the storm.  I'd guess a 1-3" gradient across Wake and higher amounts of maybe 3-5" toward the VA border.  The northern and central coastal plain will probably be the best area to see 4-6".  Going to be hard to beat that unless a really intense band sets up and doesn't move.

No doubt things could overperform.  But they usually underperform, in spite of what the models are showing at this lead.

If the HRRR doesn't come around and if the NAM keeps creeping north with the warm layer, and if other models like the GFS continue to warm, then we know that we're tracking toward a lower end event.  This isn't an ideal setup, but it may be just good enough.  Often, just good enough is the same as not very good, so we'll see how this one unfolds.  We need good rates, and hopefully they will occur.

This is your storm CR.  If anybody's going to pull off a winter storm in NC it's you guys out east. You may mix with some sleet but I think eastern sections score even with the warm nose. Moisture hangs out with you guys a lot longer than it will for us out west.  That'll give time for the cold to get here IMO. Bask in your coastal!

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22 minutes ago, burrel2 said:

I'm very encouraged by the HRRR.

This is my very weenie take on the situation, and what I am clinging to for the moment.

thank you for your analysis burrel2, some great posts today. I like when you are optimistic! I don't know about you, but the wildlife are very aggressive today...almost like they can sense something. Outside my window, I have seen two sets of geese fighting (maybe mating) and saw a couple hawks, together. Which is very unusual.

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