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Winter Storm 1/6 - 1/8, 2017


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3 minutes ago, Cold Rain said:

Great stuff as always.  Thank you.  Really helps illustrate how all of these processes relate to each other.  Hopefully, we can crash the warm nose east a little sooner than forecast with this one, though that's not seeming like a high probability at present.

Yeah nice write up from Phil....and for my laymen's comments on it, the upper wave at 500mb kind of dictates everything.  In the Jan 2002 storm for example that hit ATL to RDU (a different setup with a very strong diving upper wave/low), the 500mb vort max tracked through S GA into S SC and the 850mb low popped in NE SC.  That's ideal for you and I.  Ideally, both of those features are farther south than they are with this storm.  That keeps all of the elevated warmth out of play and it's a more dynamic storm as the 500mb wave/vort, 850 low, and sfc low are all closer together.  You can see it here - http://mp1.met.psu.edu/~fxg1/NARR/2002/us0103.php 

Of course, there are other types of setups that give us snow...like Jan 1988 which was strong overrunning into a very cold airmass (diff setup)

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2 minutes ago, griteater said:

Yeah nice write up from Phil....and for my laymen's comments on it, the upper wave at 500mb kind of dictates everything.  In the Jan 2002 storm for example that hit ATL to RDU (a different setup with a very strong diving upper wave/low), the 500mb vort max tracked through S GA into S SC and the 850mb low popped in NE SC.  That's ideal for you and I.  Ideally, both of those features are farther south than they are with this storm.  That keeps all of the elevated warmth out of play and it's a more dynamic storm as the 500mb wave/vort, 850 low, and sfc low are all closer together.  You can see it here - http://mp1.met.psu.edu/~fxg1/NARR/2002/us0103.php 

Of course, there are other types of setups that give us snow...like Jan 1988 which was strong overrunning into a very cold airmass (diff setup)

Yeah, that's good stuff.  Seems like lately, most 850 lows go right over the Triangle.  Would love to get a true overrunning event again.  We just don't see those outside of the digital universe anymore.

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1 hour ago, phil882 said:

Careful though... because upstream obs show that the warm nose is actually strongest a little bit above 850-hPa which also is showing up on the forecast HRRR soundings near Raleigh overnight. I fear that a lot of the snow in the Euro Snowfall maps may actually be heavy sleet...

52S5W14.png

This seems pretty typical for NC winter storms. That 750-800 mb layer loves to screw us over.  I've seen it many times in my time following these things.

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6 minutes ago, griteater said:

Yeah nice write up from Phil....and for my laymen's comments on it, the upper wave at 500mb kind of dictates everything.  In the Jan 2002 storm for example that hit ATL to RDU (a different setup with a very strong diving upper wave/low), the 500mb vort max tracked through S GA into S SC and the 850mb low popped in NE SC.  That's ideal for you and I.  Ideally, both of those features are farther south than they are with this storm.  That keeps all of the elevated warmth out of play and it's a more dynamic storm as the 500mb wave/vort, 850 low, and sfc low are all closer together.  You can see it here - http://mp1.met.psu.edu/~fxg1/NARR/2002/us0103.php 

Of course, there are other types of setups that give us snow...like Jan 1988 which was strong overrunning into a very cold airmass (diff setup)

Good point... see in the case of the the Jan 2002 storm you had a lot of upper-level forcing that was running the show (i.e., the 500hPa low was stronger than the sfc vortex) so where the 500-hPa low went, so did the other low-level features in tandem slightly to the south and east (with the exception of the sfc vortex). The surface vortex is a trickier entity to figure out because at the surface there is always a lot of natural baroclinicity offshore (because the gulf stream is so warm, and the land immediately adjacent is typically much colder).

This event is closer in setup to the January 1988 snowstorm which was almost all frontogenesis/overrunning precipitation which featured a broad open 500-hPa wave. 

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2 minutes ago, phil882 said:

Good point... see in the case of the the Jan 2002 storm you had a lot of upper-level forcing that was running the show (i.e., the 500hPa low was stronger than the sfc vortex) so where the 500-hPa low went, so did the other low-level features in tandem slightly to the south and east (with the exception of the sfc vortex). The surface vortex is a trickier entity to figure out because at the surface there is always a lot of natural baroclinicity offshore (because the gulf stream is so warm, and the land immediately adjacent is typically much colder).

This event is closer in setup to the January 1988 snowstorm which was almost all frontogenesis/overrunning precipitation which featured a broad open 500-hPa wave. 

2

29 years to the date of the 88 storm. 

Thanks for the thoughts Phil.

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1 minute ago, Cold Rain said:

Cary's getting HRRRd!  Don't do it man!  I've seen it do that before, only to break your heart with wintry mix.

Yes, I noticed 18z ticked south and east around CLT as well.  This is going to drive me and my family crazy the rest of the night. I don't know why I do this to myself...:wacko::twister:

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Yep. Short term modeling does seem to be coming in a bit colder.  Interested in the next RGEM in a bit.  Plus, this tweet:

Interesting discrepancy b/t RAP/OBS. CAA in obs sounding 50-100hPa deeper than what RAP depicted. Colder 2mT/Td and drier low lvls than fcst

C1gpFt4UUAAssLt.jpg

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1 minute ago, SnowNiner said:

Yes, I noticed 18z ticked south and east around CLT as well.  This is going to drive me and my family crazy the rest of the night. I don't know why I do this to myself...:wacko::twister:

The 18z broadened the transition zone.  Looks like I'm safely in the pink for the whole storm, except for the last half hour or so of flurries.

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1 minute ago, PackGrad05 said:

That last HRRR is still good.  All of wake in purple.  Snow/sleet.

Yeah, bigtime sleet fest.  Should make for a quite night's sleep.

Where is Jet Stream Rider with his analysis maps to tell us how this thing is bombing out or moving farther south or is colder than forecast!?

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