qpf to snow amount

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Ruth Ebert, modified 8 Years ago.

qpf to snow amount

Youngling Posts: 8 Join Date: 10/29/16 Recent Posts

I have noticed that forecast builder and POWT are producing snow amounts where we do not have qpf. I suspect it has something to do with the hourly pop weighting calculation, and it does happen where we have measurable snow accumulation without measurable qpf, so maybe that is what is expected?

Anyway just to let you know how we are doing things here in GGW, we do hourly pops but 6 hour qpf/snow amount.

Ruth Ann Ebert

WFO glasgow MT

Charles Greif, modified 8 Years ago.

RE: qpf to snow amount

Youngling Posts: 27 Join Date: 9/10/15 Recent Posts

Thanks for the question, Ruth. That seems to be out of step with my understanding of how it should be calculating snow. Let me get with the developer on this and make sure that this behavior is not unexpected. We may need to see some screen shots if you can capture them when this occurs.

Thanks!

Chuck Greif

CRGMAT

Ruth Ebert, modified 8 Years ago.

RE: qpf to snow amount

Youngling Posts: 8 Join Date: 10/29/16 Recent Posts

Here is a quick screen capture that demonstrates what I am seeing.

The image is the snow amount, the contours are the qpf. Note the area highlighted in the red box where the 0.01 qpf contour runs along the border between the 2 pink shades of snow amount. The lighter pink is 0.1", while the dark pink is 0.2" snow accumulation.

Ruth Ann Ebert

WFO Glasgow

Charles Greif, modified 8 Years ago.

RE: qpf to snow amount

Youngling Posts: 27 Join Date: 9/10/15 Recent Posts

Thanks, Ruth! We'll look into this.

Chuck Greif

Charles Greif, modified 8 Years ago.

RE: qpf to snow amount

Youngling Posts: 27 Join Date: 9/10/15 Recent Posts

Ruth, we are wondering if you might be seeing the effects of your QPF not being saved, and therefore not truncated to each hundredth of an inch, before the SnowAmts are created. Also, you also might want to confirm that your office is running the latest version of FB. Thanks!

Ruth Ebert, modified 8 Years ago.

RE: qpf to snow amount

Youngling Posts: 8 Join Date: 10/29/16 Recent Posts

I am pretty sure we are at the latest version of forecast builder and that the qpf grid is saved before the snow amount is run. The general practice is to save grids as we go, but I can run a few tests just to double check.