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Tar Heel Snow

One More Shot: Feb 20-21 Event

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13 minutes ago, DopplerWx said:

wow, on 3km nam charlotte gets rid of the warm nose after hr48 and then we have an all snow sounding if sfc temps cooperate. interesting...

 

3 minutes ago, magpiemaniac said:

When does the northern trend start?   :arrowhead:   But seriously, I need to see some guidance agreement before I’m buying.

These things almost always climb north right.  The fly in the ointment here is that the UKMet and Euro are headstrong on being south...so that flys counter to maybe conventional wisdom

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8 minutes ago, BullCityWx said:

That’s a good point. It crossed my mind today. This is about where the euro was at this point in time as well

IIRC Fishel didn't bite on that one till late as well.

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RAH Afternoon AFD

With the cold front well to the south of the NC/SC border Thursday, 
central NC will remain under the influence of cold high pressure 
ridging southward into the region advecting cold air in from the 
north. This front is expected to remain south of the area as a 
coastal low develops off the SC coast Thursday aft/eve in response 
to an upper level shortwave. The proximity of this low to the NC 
coast and how much/far moisture extends to the NW will be the 
determining factor for how much snow will fall and accumulate. The 
wetter NAM/GFS solutions may be a bit too aggressive with the 
precipitation extending into central NC, while the much drier ECMWF 
solution may be more reasonable. Precipitation should start as rain, 
moving into the south during the aft/eve, which will help cool 
temperatures to the wetbulb values in the 30-32 degree range by 
Thursday night. There will likely be a period of rain mixed with 
snow, with little accumulation expected during that time. The best 
chance for snow accumulation will be if and where there is a 
transition to all snow. Regardless, there will likely be a "sweet 
spot" across eastern NC where snow could accumulate to more than an 
inch or two and a very tight gradient of snow amounts across the 
area. Given the uncertainty, will keep expected snowfall 
accumulations below warning criteria at this time, though still have 
about 1-2 inches in the Coastal Plain. Highs on Thursday will top 
out in the 40s, quickly lowering into the low 30s as rainfall 
occurs. 
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Hi All,

Does anyone know what all factors are included in the "Snow Depth" plots on Pivotal?  Is it based on Kuchera or straight 10:1? Consider compaction? Melting due to ground temps?   Is this plot generally accurate?  

Thanks!

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1 minute ago, Tar Heel Snow said:

For those less educated (like me!) Could you explain what we're looking at here? Thanks!

So if you read from left to right: 

 

Hour valid on the model run/Date/time of day/temp/dew point/wind direction/speed/precip accumulation in those 3 hours. Below that, you have the precip type. The rest of it is not as important to know.

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Rgem is well south. This storm's outcome is still TBD. Here's 1pm Thursday. NAM has snow ripping across the entire state of NC and most of TN at this point.

Screen Shot 2020-02-18 at 3.57.26 PM.png

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8 minutes ago, Tar Heel Snow said:

For those less educated (like me!) Could you explain what we're looking at here? Thanks!

I'm not sure of the location, but would guess that it's close to Durham maybe, but that is a very long duration snow storm  :lol:  

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4 minutes ago, burrel2 said:

Rgem is well south. This storm's outcome is still TBD. Here's 1pm Thursday. NAM has snow ripping across the entire state of NC and most of TN at this point.

Screen Shot 2020-02-18 at 3.57.26 PM.png

This is the 18z CMC, which is a little different from the actual RGEM.. , in the same camp and similar but not the same... the RGEM just started running a little bit ago...

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1 minute ago, buckeyefan1 said:

I'm not sure of the location, but would guess that it's close to Durham maybe, but that is a very long duration snow storm  :lol:  

It snows an inch an hour for 12 hours. I’m sold.

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8 minutes ago, BornAgain13 said:

Not sure how this is going to play out , but Tim Buckley said the High Pressure on the models is being overdone....

Which if true, would mean cold air is being overdone...correct?  Based on the last two very minor events, the high pressures outperformed and gave us some nice snow falling from the skies!

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7 minutes ago, BornAgain13 said:

This is the 18z CMC, which is a little different from the actual RGEM.. , in the same camp and similar but not the same... the RGEM just started running a little bit ago...

Nah this is the Rgem. It's just a webpage where you can get the output a little faster than other sites. I've used it for years. https://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

If you go past 48hrs it reverts to the CMC map.

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Just now, BullCityWx said:

It snows an inch an hour for 12 hours. I’m sold.

:lol:   I bet you are!  The NAM sure is consistent and shows no signs of caving. Could the NAM make it two in a row?  :lol:    

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11 minutes ago, SnowJoMoJo said:

Hi All,

Does anyone know what all factors are included in the "Snow Depth" plots on Pivotal?  Is it based on Kuchera or straight 10:1? Consider compaction? Melting due to ground temps?   Is this plot generally accurate?  

Thanks!

There is a snow melt forecast variable, which I assume accounts for things like ground/air temperature, and that would be incorporated to calculate the snow depth. I also believe it accounts for snow density/compaction. I'm not sure of the overall accuracy. You can see all of the forecast variables here: https://www.nco.ncep.noaa.gov/pmb/products/nam/nam.t00z.bgrdsf00.tm00.shtml

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Just now, NCBlizzard said:

There is a snow melt forecast variable, which I assume accounts for things like ground/air temperature, and that would be incorporated to calculate the snow depth. I also believe it accounts for snow density/compaction. I'm not sure of the overall accuracy. You can see all of the forecast variables here: https://www.nco.ncep.noaa.gov/pmb/products/nam/nam.t00z.bgrdsf00.tm00.shtml

Thanks!

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Sorry for the annoying question (I promise I'll go back to lurking like I have been for the past 9 years).

What's the timeframe for this in the Durham area? I haven't seen it really posted anywhere, and if it has been, I overlooked it and I apolize.

Thank y'all for being so informative and fun to read.

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1 minute ago, burrel2 said:

Nah this is the Rgem. It's just a webpage where you can get the output a little faster than other sites. I've used it for years. https://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

Correct on  RGEM out to hr48, then it flips to the GEM Global after hr48....you can see the resolution change with the pixel size after hr48.  Also, at the bottom, it has Forecast System R for RGEM out to hr48, then it flips to G for Global after hr48

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