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September Weather Discussion 2019


dryslot
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4 hours ago, CoastalWx said:

Euro has the chance of the first synoptic snow of the season across the NNE mtns, especially the mtns of NW Maine. Low levels may be borderline, but E-NE flow banked against the high terrain may help cool it a tad. Elsewhere, a fascinating temp gradient exists between, say, BOS to DC. Euro has +22C at 850 in the Mid Atlantic. That's just amazing to see. It looks like we'll be in the 40s and 50s with rain Thursday and Friday. Interior likely below 50 one or both days.  

Looks like last night's 18z GFS sniffed it out first.   What a beast of a model.

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On 9/29/2019 at 3:56 PM, OceanStWx said:

 

GTFO with Kuchera ;)

Basically at all NWS offices the forecasters will create grids for temps, PoP, QPF, snow ratio. From that you get Wx grids, and from that you can determine where snow you be output in a snow grid. You can also choose how you want to display it temporally. A one hour grid will produce a more realistic snow fall than a 3 or 6 hour grid that has parameters averaged over that time. 

It is up to the forecaster whether they want to hand draw grids, pick a model of the day, or use some form of a blend. Personally I use a blended approach, and then tweak for things like local effects or forecast position of banding. 

We have grids every hour with thousands of grid points, so we rarely are editing just one gridpoint. Rather we try and lock down the base grids and everything sort of fall out from there (i.e. if your temp, dewpoint, PoP, QPF, snow ratio are good, then your Wx and snowfall should be good too). We could automate a lot of that, but you would lose local knowledge and QC. Like we don't want to blend GFS 2 m temps in a damming scenario, but the computer doesn't know that.

Thank you for that insight! 

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