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Tuesday 1/6/2015 clipper discussion and obs


famartin

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I'm so ready for this, I did a marathon jobsite visit today so I wouldn't have to tomorrow. Partly to avoid the first snowy rush hour but also just to be able to enjoy it. Normally the first area wide snow tends to create greater traffic issues than snowfalls later in the season. Not sure if it has to do with practice or what. Tomorrow might not be bad since it's the morning rush hour which is more about people getting from point A to point B, and since it will be plenty cold tonight it should be a dry powdery snow on cold surfaces. I wonder if PennDOT has some kind of algorithm for conditions based on ground temps, temperature while snowing, rate of snowfall, ratios, type of snowflakes, etc.

I'll be at work so will have to live it vicariously through Ray's Snow ruler cam :)

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I'll be at work so will have to live it vicariously through Ray's Snow ruler cam :)

Hopefully wunderground is good about updating it tomorrow, they can have odd gaps between updates. I'll be watching it mostly thru the device itself, but for your sake

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I'm so ready for this, I did a marathon jobsite visit today so I wouldn't have to tomorrow. Partly to avoid the first snowy rush hour but also just to be able to enjoy it. Normally the first area wide snow tends to create greater traffic issues than snowfalls later in the season. Not sure if it has to do with practice or what. Tomorrow might not be bad since it's the morning rush hour which is more about people getting from point A to point B, and since it will be plenty cold tonight it should be a dry powdery snow on cold surfaces. I wonder if PennDOT has some kind of algorithm for conditions based on ground temps, temperature while snowing, rate of snowfall, ratios, type of snowflakes, etc.

 

Not sure if they have an algorithm themselves, but they do have those variables factored in by their forecasters. I was a road weather forecaster for a couple of years and we had an in-house model that used the user forecasted cloud cover, precip rate, sun angle, temperature, wind, etc. to output recommended snow removal techniques. PennDOT was one of our clients but they seemed to be on the way out as I was leaving last year, I imagine even if they went another vendor they'd be receiving similar forecasts.

 

Sorry for the off topic! As for tomorrow, it is always nice to see that first snowfall.. I am a little concerned about dry air. It's such a quick mover so 1-2 hours of precip not reaching the ground could mean the difference between a nice coating and 2 inches.

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Not sure if they have an algorithm themselves, but they do have those variables factored in by their forecasters. I was a road weather forecaster for a couple of years and we had an in-house model that used the user forecasted cloud cover, precip rate, sun angle, temperature, wind, etc. to output recommended snow removal techniques. PennDOT was one of our clients but they seemed to be on the way out as I was leaving last year, I imagine even if they went another vendor they'd be receiving similar forecasts.

 

Sorry for the off topic! As for tomorrow, it is always nice to see that first snowfall.. I am a little concerned about dry air. It's such a quick mover so 1-2 hours of precip not reaching the ground could mean the difference between a nice coating and 2 inches.

 

Thanks for the reply and the insight. A coating to 2" is a good range. At least there won't be precipitation type issues.

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Still concerned about the dry airmass in place could result in models overdoing qpf.

 

RHs near 30-35% with temps near 20F often don't take long for snow to fall from my experience...also decent RH in the 5K-15K layer on most models, I think it'll reach the ground relatively fast most places.

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RHs near 30-35% with temps near 20F often don't take long for snow to fall from my experience...also decent RH in the 5K-15K layer on most models, I think it'll reach the ground relatively fast most places.

 

It'll depend a lot on what's going on with low level advection.  Most cases I can recall where precip had trouble starting were instances with continuous advection of dry low level air into the area from the northeast. 

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