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OBS only thread winter event Feb 12-early 13 , 2019


wdrag

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22 minutes ago, wdrag said:

Ditto on fine snow here in Wantage. 2.4 at 720P and 20.8F.  the snow means that that there is possibly only a shallow saturated layer of rh with lift in the -8C range causing the fine snow. 

Just measured 2 1/4" here. Was wondering why it was snowing here when everybody else is going the opposite direction. My question to you is, what is rh? 

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8 hours ago, sussexcountyobs said:

Just measured 2 1/4" here. Was wondering why it was snowing here when everybody else is going the opposite direction. My question to you is, what is rh? 

sorry for the delay. RH is relative humidity.  Models are generally very good at forecasting deep layered high humidity precipitation, but are not so good with precip at layers of high humidity below ~3000 feet (example when a dry slot cleans out the high humidity above 3000 feet). In yesterdays case, With still very high humidity trapped below the inversion, and probably a temperature of nearly -8C somewhere in that layer, and just a bit of lift (with the secondary developing near the coast-there was convergence here), fine snow may have been produced because snow generally needs to be generated with ice nuclei in a saturated layer of ~ -8C or colder.  Also, as a side bar...when precip is changed to rain by a warm layer aloft, it can refreeze to ice pellets (sleet), with a temperature of -6C below that above freezing layer, or to ice pellets by a deep layer of sub0C below the above freezing layer. Anyway, hopefully the first part of your message is answered and my reasoning is possibly not the only answer. 

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1.7" max depth of snow and sleet.  Most of it is still there this morning.

Total precip 0.77"

Snow/sleet - 0.37"

Rain - 0.40"

The snow sleet SWE could be a little low.  That's just what collected in the can melted before the phase shift.  4" can isn't the best way to collect snow.

So  half the precip was frozen and half was liquid.  Plenty of it left this morning, plows still moving it around, and the peanut gallery is quiet.

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14 minutes ago, NorthShoreWx said:

1.7" max depth of snow and sleet.  Most of it is still there this morning.

Total precip 0.77"

Snow/sleet - 0.37"

Rain - 0.40"

The snow sleet SWE could be a little low.  That's just what collected in the can melted before the phase shift.  4" can isn't the best way to collect snow.

So  half the precip was frozen and half was liquid.  Plenty of it left this morning, plows still moving it around, and the peanut gallery is quiet.

sleet has staying power!  this was like a lesser version of the VD 2007 event

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14 hours ago, JerseyWx said:

Funny thing is, I measured on it and got 2 inches as well.  Now it's freezing rain.  Glaze on everything.

Sidewalks were terrible this am and  side roads . Temps peaked at midnight at 33 than slowly dropped to a low of 30.8 at 430. What’s odd was the most ice I saw on trees was looking towards riverdale (also butler heights area behind hs )and Bloomingdale . Hills to my west and north  are higher in elevation   (kinnelon and west Milford) had no signs of ice in trees  . I have a decent view of both areas from my street

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5 hours ago, wdrag said:

sorry for the delay. RH is relative humidity.  Models are generally very good at forecasting deep layered high humidity precipitation, but are not so good with precip at layers of high humidity below ~3000 feet (example when a dry slot cleans out the high humidity above 3000 feet). In yesterdays case, With still very high humidity trapped below the inversion, and probably a temperature of nearly -8C somewhere in that layer, and just a bit of lift (with the secondary developing near the coast-there was convergence here), fine snow may have been produced because snow generally needs to be generated with ice nuclei in a saturated layer of ~ -8C or colder.  Also, as a side bar...when precip is changed to rain by a warm layer aloft, it can refreeze to ice pellets (sleet), with a temperature of -6C below that above freezing layer, or to ice pellets by a deep layer of sub0C below the above freezing layer. Anyway, hopefully the first part of your message is answered and my reasoning is possibly not the only answer. 

Walt a Met here a few years ago here  kind of explained the same thing saying the fine snow must have formed right below the warm layer . I’m in butler and had that fine snow as well most of the day . They were needle shaped  when I examined them on my glove. 

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21 minutes ago, rgwp96 said:

Sidewalks were terrible this am and  side roads . Temps peaked at midnight at 33 than slowly dropped to a low of 30.8 at 430. What’s odd was the most ice I saw on trees was looking towards riverdale (also butler heights area behind hs )and Bloomingdale . Hills to my west and north  are higher in elevation   (kinnelon and west Milford) had no signs of ice in trees  . I have a decent view of both areas from my street

Yeah the freezing rain came in last night and put a hard shell over everything.  I can actually see the heights from where I am across town.

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So this morning around 10 when I finally went out it was 2" compacted snow topped with 1" of sleet and .2-.3" clear ice over everything. Areas that were shoveled or blown yesterday after the sleet was mostly over were solid ice but also melted off quickly. There's a fair bit of melting on asphalt but not on anything else, this stuff is locked up solid even though it's 37* out there. At least the ice has pretty much fallen out of the trees now because it was windy for a while this morning. The roads aren't bad but they're narrow.

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3 hours ago, rgwp96 said:

Walt a Met here a few years ago here  kind of explained the same thing saying the fine snow must have formed right below the warm layer . I’m in butler and had that fine snow as well most of the day . They were needle shaped  when I examined them on my glove. 

We had the same fine snow here as well right up until everything changed to rain around 6pm.  I've seen it in just about every sleet event we've ever had.  It probably happens during snowstorms too, but you wouldn't notice it then.

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4 hours ago, LibertyBell said:

1.2 at NYC 0.8 I think at the airports?

 

3 hours ago, Snow88 said:

Only 0.8?

That seems low

 

Actually all 6 reporting stations were between 1.2 and 2.0. Central Park was low on the totem pole this time, a throw back to the zookeepers measurements of winters past.

The park 1.2

LGA 1.5, JFK 1.2 EWR 1.9 Bridgeport 1.3 and Islip 2.0

 

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