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Monday Morning FZDZ?


CT Rain

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I studied this a lot my senior year of college at Cornell...and its kind of quirky...especially if you have some evap cooling potential and some upslope. It doesn't take a ton of weird helpers to get some crappy flakes if you have onshore flow.

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I studied this a lot my senior year of college at Cornell...and its kind of quirky...especially if you have some evap cooling potential and some upslope. It doesn't take a ton of weird helpers to get some crappy flakes if you have onshore flow.

The salt nuclei is an interesting topic. good stuff Will, thanks

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Snowing nicely here now... vis likely 1-2 miles.

Look at the temperature difference up here this morning... this is why the eastern side of the mountain here retains snow so much better than the west. Its already low 30s a few miles away on the other side of the mountain, while this side is low 20s. That 4,000ft spine makes for a great divider. We shouldn't take much, if any, of a hit to the snowpack with this event... the fluff on top will just settle out and firm up.

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The salt nuclei is an interesting topic. good stuff Will, thanks

I became really interested in it back in 2002 when I went on an interview to be the NWS BOX intern in summer of '02 in March of 2002 (probably a rare thing now days)....and Dave Vallee grilled me on why the Mar 20, 2002 storm might as end as rain at ORH from straight snow and I gave him the right answer at the time because I knew about snow growth (good thing I was even a weenie back then), but didn't really know it as well as I should.

So I read like 4 papers on it including one from the local NWS BGM (at the time when I was back in Ithaca) and I came across the studies that showed the ice nucleation much more efficient on the shore line with warmer wetbulb temps. In the interior, it was more common to see FZDR with wetbulb temps around -6C than it was closer to the coast when dendrites were more efficient at warmer temps. It was shown that dendrites were almost completely absent once the wetbulb temp wamred about -4C even on the coast.

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I became really interested in it back in 2002 when I went on an interview to be the NWS BOX intern in summer of '02 in March of 2002 (probably a rare thing now days)....and Dave Vallee grilled me on why the Mar 20, 2002 storm might as end as rain at ORH from straight snow and I gave him the right answer at the time because I knew about snow growth (good thing I was even a weenie back then), but didn't really know it as well as I should.

So I read like 4 papers on it including one from the local NWS BGM (at the time when I was back in Ithaca) and I came across the studies that showed the ice nucleation much more efficient on the shore line with warmer wetbulb temps. In the interior, it was more common to see FZDR with wetbulb temps around -6C than it was closer to the coast when dendrites were more efficient at warmer temps. It was shown that dendrites were almost completely absent once the wetbulb temp wamred about -4C even on the coast.

I've seen it so often....It's big with OES too. I've probably come across some of those papers..it was actually after Drag mentioned it way back in the early 2000s that I actually cared enough to read. So many variables go into snow growth.

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I've seen it so often....It's big with OES too. I've probably come across some of those papers..it was actually after Drag mentioned it way back in the early 2000s that I actually cared enough to read. So many variables go into snow growth.

One of the papers I came across back then in 2002 (lol even in the age of internet) was a paper journal...I think it was BAMS or weather journal....it was the 1994 case study in south Weymouth MA where the temp profile supported sleet but OES promoted snow growth below the warm layer so they were getting synoptic sleet at the same time they were getting +SN from mesoscale processes....I think it was shown that the 725mb temps were +2-+3C while 900mb temps were -11C where the max mesoscale lift was occurring.

So places as far north as ASH and MHT were sleeting and NZW (back when they still had obs in 1994) was heavy snow AND ice pellets at the same time. One of the weirdest case studies.

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The nam didn't even have anything near -4C TWs in the moist layer though over FWN at 9z. Maybe it underestimated the cloud tops and they're just high enough for a little nucleation.

I

think its been shown too that even like 70-80% RH above the saturated layer can produce seeder-feeder snow growth...so that has to be looked at too in addition to how accurate the model soundings are. You can get no saturated layer, but if its decently moist above the actual saturated layer, you can still get seeder feeder.

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One of the papers I came across back then in 2002 (lol even in the age of internet) was a paper journal...I think it was BAMS or weather journal....it was the 1994 case study in south Weymouth MA where the temp profile supported sleet but OES promoted snow growth below the warm layer so they were getting synoptic sleet at the same time they were getting +SN from mesoscale processes....I think it was shown that the 725mb temps were +2-+3C while 900mb temps were -11C where the max mesoscale lift was occurring.

So places as far north as ASH and MHT were sleeting and NZW (back when they still had obs in 1994) was heavy snow AND ice pellets at the same time. One of the weirdest case studies.

That's awesome. Talk about an inversion. Too bad they don't report anymore. That area is always on the line for many events.

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I

think its been shown too that even like 70-80% RH above the saturated layer can produce seeder-feeder snow growth...so that has to be looked at too in addition to how accurate the model soundings are. You can get no saturated layer, but if its decently moist above the actual saturated layer, you can still get seeder feeder.

Yeah. I don't have the soundings in front of me on my phone right now, but I think they were exceptionally dry above the moist layer throughout NJ. I'm not doubting the reports...I'm just saying I wouldn't have expected anything other than ZR/R from the soundings I looked at. Cool NZW case study though...I'll have to find that one.
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Yeah. I don't have the soundings in front of me on my phone right now, but I think they were exceptionally dry above the moist layer throughout NJ. I'm not doubting the reports...I'm just saying I wouldn't have expected anything other than ZR/R from the soundings I looked at. Cool NZW case study though...I'll have to find that one.

are you getting the occassional bursts of weenie flakes? man we sure do hold onto cold air here...

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Yeah. I don't have the soundings in front of me on my phone right now, but I think they were exceptionally dry above the moist layer throughout NJ. I'm not doubting the reports...I'm just saying I wouldn't have expected anything other than ZR/R from the soundings I looked at. Cool NZW case study though...I'll have to find that one.

only started to saturate at 900 level, heres sort of what the sounding looked like. many areas of nj jersey saw light snow and flurries thorughtout the night. mine went to freezing drizzle at about 2 am

wvrjbs.gif

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