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Rain/Thunder and Anafrontal Snow

WeatherGeek2025

By WeatherGeek2025,
in New York City Metro

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  • WeatherGeek2025 changed the title to Rain/Thunder and Anafrontal Snow
RU848789

RU848789

Posted
Posted

As always, accumulation rate = snowfall rate - melting rate, where based on experience (and some deep knowledge of heat transfer and physical chemistry phase changes) I'd guesstimate the melting rate in mid-March is about 0.2-0.3" per hour during the day (say 10 am to 4 pm) with temps around 32F, so with temps in the mid-30s, I'd expect a melting rate around 0.4-0.5"/hr on the colder surfaces, so we'd need snowfall rates around 0.5"+ per hour (0.05" QPF/hr) to see accumulation and rates just don't look to be that high, which is why I don't expect much accumulation.

On the flip side, if we can get a thump of snow for an hour or so with ~1" per hour rates, that can get us ~1/2" of snow on the ground and not everyone realizes this, but once there is snow on the ground, that snow is by definition at 32F (at most), meaning subsequent snowfall is no longer melting at the rates above, which are due to a combination of elevated surface temps and elevated air temps with indirect sunlight - the elevated surface temps are a bigger factor in melting (just look at how much more snow melts as temperature increases with the same insolation level, like we saw over the past couple of weeks after the blizzard) - so I'd expect those melting rates to come down to maybe 0.1-0.2" per hour once there is accumulated snow on the ground.

I've never seen anyone truly quantify these melting rates (maybe someone in some research paper has done it?), so these are at best educated guesses - would love to know what they are under various surface temp/surface type/air temp/insolation factor (vs time of day), etc. If I had gotten a PhD in meteorology instead of chemical eng'g, I could see wanting to have done research on such a thing.

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RU848789

RU848789

Posted
Posted
45 minutes ago, MJO812 said:

No one is saying snowstorm . Its a wave riding along the front as the cold air comes in ( Anafronts)

We have seen plenty of those in the past. No one is saying this will accumulate. I do think it does on colder surfaces if we get good rates but it will most likely be white rain.

Exactly.  This wouldn't be more than a moderate 2-4" snowstorm even with cold temps in Jan, as there's just not enough precip and with the elevated surface temps and higher sun angle this one will be unlikely to put down more than 1" on grassy surfaces anywhere.  

But temps in the 70s and lower 80s yesterday has nothing to do with whether or not we can have a snowstorm the next day.  If it turns cold enough and there's enough snowfall intensity, it'll accumulate easily even at midday.  

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gravitylover

gravitylover

Posted
Posted
7 hours ago, PhiEaglesfan712 said:

No, I'm not the one creating chaos. You're the ones doing it by causing unnecessary panic by saying there's going to be a snowstorm, when you all know it isn't going to happen. When was the last time you saw snow immediately after 80 degree days? Because I can't think of one of the top of my head. And I'm not young, I was born in 1988 and remember the 1993 snowstorm.

Unnecessary panic because we're discussing a backside inch or two? And yes, by definition it would be considered a snow storm. I can think of several accumulating snows after warm spring days, 4/1/97 comes to mind when it was a beautiful spring day and 6 hours later I had 17" on the ground. This obviously isn't like that but it will be a dramatic turn and it will be cool to watch happen. 1988? Back to the sandbox with the shiny toys for you >> 

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Freezing Drizzle

Freezing Drizzle

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Anafronts

A rainy cold front is usually an anafront. Anafronts are the kind of cold front associated with moisture and clouds.

Ana means to ascend. What’s ascending in the case of an anafront? The warm and moist air — it actually rises over the lower leading edge of the cold front and can create clouds and rain behind the actual cold front itself.

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Freezing Drizzle

Freezing Drizzle

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24 minutes ago, NEG NAO said:

Radar is showing snow in Central PA but surface reports as of 10 am have none

RWR from KCTP

I see snow echoes on a line from Hazleton to Harrisburg, but not sure what's falling there.
I've seen snow under rain echoes, and rain under snow echoes. Usually, the snow detection is rather good though.

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Monty

Monty

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According to mPing reports frozen is mixing in along a line from west mil Ford NJ to Easton PA. Surface temps below 40F in Bucks, Hunterdon, Warren, Sussex. Precip all the way back to Harrisburg. Soundings point to a warm layer above 32F just below H7. Looks like a sleety afternoon in n/c NJ

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