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March 5th Snow Threat


WxUSAF

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   most NCEP models generate multiple output grids from the same model run.   The NAM has 12, 20, 32, 40, and 80 km grids, among others, for example.   Different grids cover different parts of the domain so that a user focused on a specific region doesn't have to download the large full domain files.    Having grids of different resolution are mostly for bandwidth issues - many customers can't download the large, higher-resolution files and grab smaller, coarser grids.   For a global model like the GFS, there is a need for some very coarse grids to have some smaller files available.

 

Why have 2 resolutions for the same model?

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   most NCEP models generate multiple output grids from the same model run.   The NAM has 12, 20, 32, 40, and 80 km grids, among others, for example.   Different grids cover different parts of the domain so that a user focused on a specific region doesn't have to download the large full domain files.    Having grids of different resolution are mostly for bandwidth issues - many customers can't download the large, higher-resolution files and grab smaller, coarser grids.   For a global model like the GFS, there is a need for some very coarse grids to have some smaller files available.

Interesting, thanks!

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most NCEP models generate multiple output grids from the same model run. The NAM has 12, 20, 32, 40, and 80 km grids, among others, for example. Different grids cover different parts of the domain so that a user focused on a specific region doesn't have to download the large full domain files. Having grids of different resolution are mostly for bandwidth issues - many customers can't download the large, higher-resolution files and grab smaller, coarser grids. For a global model like the GFS, there is a need for some very coarse grids to have some smaller files available.

Good point. We run the NAM 12, 40 and 80 in AWIPS.

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I have no need to wait for the Euro. Let's see how many opm messages we can get this week. Later all!

Preview:

Hr 12: oh man the NAM was onto something.

Hr 36: definitely north but also south.

Hr 60: :o

Hr 66: looks a lot like the other models.

Hr 72: but I'm still worried about the NAM.

2:45a: yoda posts the SREF looks intersting, no one reads till 530a.

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Preview:

Hr 12: oh man the NAM was onto something.

Hr 36: definitely north but also south.

Hr 60: :o

Hr 66: looks a lot like the other models.

Hr 72: but I'm still worried about the NAM.

2:45a: yoda posts the SREF looks intersting, no one reads till 530a.

 

problem with the euro is we have no detailed thermal profiles so we have to do some sleuthing to try and deduce if/when we flip.  Hopefully it is wet as hell...

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problem with the euro is we have no detailed thermal profiles so we have to do some sleuthing to try and deduce if/when we flip.  Hopefully it is wet as hell...

Like Winterwxluvr always says, get as much QPF as possible and worry about temps later.

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Preview:

Hr 12: oh man the NAM was onto something.

Hr 36: definitely north but also south.

Hr 60: :o

Hr 66: looks a lot like the other models.

Hr 72: but I'm still worried about the NAM.

2:45a: yoda posts the SREF looks intersting, no one reads till 530a.

 

2:45a: yoda says SREF's are  "juicy".  Then uses that adjective 5,145 times over the course of every model suite in the following 12 hours.

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some of the individ members get DCA close to 2.5" QPF in 72 hr period

 

The 2.5" QPF is storm total fyi

2" is a tough mark in winter.. even with half+ rain it'll be tough to go much north of that imo. not sure the ensembles are hugely useful at this range?

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2:45a: yoda says SREF's are  "juicy".  Then uses that adjective 5,145 times over the course of every model suite in the following 12 hours.

may the euro be with you. time for my annual go to bed as it begins to run ritual. ;)

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2" is a tough mark in winter.. even with half+ rain it'll be tough to go much north of that imo. not sure the ensembles are hugely useful at this range?

 

I am more just using them to see if they agree with the OP; also as another group of possible solutions to look at

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I'd estimate 0.7" falls for many after 6z.  Storm doesn't end until 2-3pm.  Hard to say when we flip to snow.  It is going to be later than 12z run.  I think we go to sleet from far NW to SE from 6z to 10z.  And then we'd obviously flip to snow NW to SE from say 9z to 13z.  I'd say a 3-4 hour period of sleet and then 3-6" of snow.

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Gotta wait for soundings. Old school thicknesses are slow to get snow going. I'm not sure anything before 12z is snow in the cities. Prob sleet before rippage. It's a great run either way.

i think it counts sleet as snow so its probably a 4-6 inch event

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I'd estimate 0.7" falls for many after 6z.  Storm doesn't end until 2-3pm.  Hard to say when we flip to snow.  It is going to be later than 12z run.  I think we go to sleet from far NW to SE from 6z to 10z.  And then we'd obviously flip to snow NW to SE from say 9z to 13z.  I'd say a 3-4 hour period of sleet and then 3-6" of snow.

I think the vigor with which the cold air comes in will allow for less sleet.

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Gotta wait for soundings. Old school thicknesses are slow to get snow going. I'm not sure anything before 12z is snow in the cities. Prob sleet before rippage. It's a great run either way.

 

The globals are all suggesting the same thing.  That we get attacked in the cold sector versus some bootleg heavy rain to a couple hours of snow at the end.

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The globals are all suggesting the same thing. That we get attacked in the cold sector versus some bootleg heavy rain to a couple hours of snow at the end.

I liked that the euro backed off on the heavies from 6-12z and then dropped the hammer. High impact event for sure. Good stuff.

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I think the vigor with which the cold air comes in will allow for less sleet.

 

It's a much better template than our usual rain to snow where the cold air chases after the moisture and tries to catch up.  In this case the moisture is attracted to the cold sector.  I think sleet is the big wildcard.  Hopefully you are right, and it isn't a protracted sleet event.

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