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Jan 7 Two-Headed Coastal Obs


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11 minutes ago, ORH_wxman said:

Thanks for the detailed post. I’ve always despised the model snow maps (or clown maps as I call them) and this is another great description of why they stink. They are fun to look at for sure…but they do often cause a lot of confusion and often inflate expectations compared to usual. 
 

Yep, great post.

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1 minute ago, moneypitmike said:

Yeah--this stuff will evaporate/sublimate really quickly.  The cotton candy of snow.

I'm expecting this to compact down to about 4" glacier by the time we get FROPA on Sunday night. It'll prob already be down to 6" or so by tomorrow night even before the brief warmup Sunday.

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6 minutes ago, moneypitmike said:

Yeah--this stuff will evaporate/sublimate really quickly.  The cotton candy of snow.

My deck is south facing, down to 3 inches already. However the yard is still between 6 and 7. I wish it would melt faster on my solar panels. I definitely do not need a glacier forming on those....

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19 minutes ago, STILL N OF PIKE said:

It’s good to see Cape Ann and S CT coast get hit hard . Did the cape get at least advisory snows

The pattern last couple years seems to have really favored (more than climo ) areas away from the SE and E coastal areas , I wonder if the “man cold” pattern coming up will deliver for most all 

about 4" / 4.5" of paste. had trouble accumulating, just kept compacting down

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46 minutes ago, MuddyWx said:

Have about 10" in Beverly on the North Shore. Going at a decent rate right now with large dendrites in that last gasp band, might pick up a quick 1"?

Just about got it!

10.8" Final in Beverly. Nothing like a white, wintry landscape with a lot of fresh pow.. So peaceful out there with the muted sounds and some lingering light snow. Man I love winter

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Reports coming in so far from CoCoRahs represent a pretty uniform 18-20:1 in that band over CT.

Would like to see all the climo sites and take a look back to see what models did well in that regard, a quick look at the GFS and it seems pretty reasonable from the 00Z run last night over CT. The past 6 runs i would say are consistent after 18Z Jan 5th run

Screenshot 2022-01-07 145559.png

gfs_apcpn24_neus_fh24_trend.gif

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6 minutes ago, JC-CT said:

Indeed I have. Sim radar, for the models that have it, will always show a more accurate "in time" look at the storm's forecasted existence. Average precip rate is always lagging the actual storm evolution.

HRRR seems to also have an explicit snow forecast, at least based on the (?) info screen on pivotalweather. Although it seems boilerplate so probably worth confirming. And also very possible that not all model sites use it for their graphics.

Ah! I didn't know that field was available. You are correct.

In the GrADS Data Server, there is a field called, 'asnowsfc.' It looks like the field is obtained via HRRR's LSM (I'll double check later to be sure). You can view it here if you'd like: https://github.com/wrf-model/WRF/blob/master/phys/module_sf_ruclsm.F

The AMS submission is here: https://journals.ametsoc.org/view/journals/wefo/25/1/2009waf2222311_1.xml?rskey=LFzwBc&result=4

To summarize its procedure, the weighted snow density (stepwise multiple linear regression) is first calculated by determining the (frozen) densities of snow, graupel, and sleet (as a function of the lowest atmospheric layer's temperature). The weighted snow density is then used to calculate SLR = (density of water) / (density of frozen). Snowfall is then the product of SWE * SLR. This is all done diagnostically using calls to the mp routine. It's also used to calculate new snowfall accumulation for its snow depth field.

It's a pretty good algorithm actually compared to climatology and Kuchera. Taking the weighted contribution of different hydrometeors is a great method to avoid inflation of snowfall due to mixing. It's a huge advantage to have it calculated between modeled time steps too.

Other modeling systems can incorporate this variable if the RUC LSM is applied. 

 

 

 

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