January 30, 2019 Snow Squall Observations Thread

[Tatamy]

17 minutes ago, Albedoman said:

MT Holly is dropping the ball IMHO. They overreacted on the winter storm warning two weeks ago, now they are being way too conservative.  Two wrongs do not make it right.  In the LV 6 inches is considered a winter storm warning event in a 12 hour period. Why not a watch issued then?  Why does their map go from 2 inches in Philly to 8 inches in MT Pocono. Err on the safety side for this event This snow will be 180 degree difference from the last storm event as the snow ratios will be much higher as the temps continue to drop as the front has already passed.  Salt will not work on the roads after early Tuesday night. Blowing and drifting will be huge issues which are not even being discussed yet they talk about squalls on Wednesday? What comes with the squalls? I say nasty wind gusts and heavy snow, blowing and drifting. Usually we get squalls when we have bare ground with no snow. When a squall goes through this time, it will be a disaster. The public is not prepared for this in the LV and NJ. Rt 78 will have multiple wrecks. I see it coming. 40 years of weather experience says so.

Based upon the available model outputs the probability of 6”+ snow fall is not high enough to justify a WSW south of the Poconos in the LV.  That is what the NWS is looking at.  Maybe a WWA gets issued later.

[Tatamy]

1 minute ago, NEG NAO said:

I didn't know the LV is now part of the NYC Metro...…..

Who cares where he posts from??  The issue of timely warnings / advisories applies to everybody.

[Albedoman]

My god, when will it end.  Playing with confidence levels and probabilities over snow totals was never the intentions of weather forecasting. This is statistical tool to arrive at a snow total forecast. Forecasting is always intended for the safety of the public.  Keep on playing with your probabilities and confidence levels for snow totals  in order to issue warnings but watch what happens to I-78 between Harrisburg and NYC.  People ignore winter weather advisories plain and simple as they are too young to remember what true travelers advisories were. They do however pay attention to warnings. Why, I do not know.  When the criteria even comes close to six inches, why not err on the safety of the traveling public and those who work outside? Why does it have to be the other way around? Its like the same old scenario, you have to wait until someone gets killed before putting up a traffic signal. I know I am right after doing this for over 40 years before the internet was even around. Its the overall conditions that warrant the warning, not the amount of snow.  Thanks for the rant

[forkyfork]

1 hour ago, purduewx80 said:

12Z NAM quicker w/ the cold air and has good forcing for a quick 1-3" tomorrow evening. Nice lift w/ that fronto band right in the DGZ. We'll see what other guidance shows. There should also be a brief squall with the true Arctic/Polar front midday Wednesday that could be good for an inch given good lapse rates through the DGZ and 500mb jet forcing. 

this is one of the most impressive snow squall soundings i've seen for this area

[NEG NAO]

Just now, forkyfork said:

this is one of the most impressive snow squall soundings i've seen for this area

been a while since I have seen a real snow squall in Northern Middlesex County NJ - one where just like a summer thunderstorm darkens the sky to the west first and then when the squall hits you have white out conditions where if driving you have to pull your car over to the side of the road until it passes and after it does you have an inch or more on the ground after a short period of time.

[Stormlover74]

3 minutes ago, NEG NAO said:

been a while since I have seen a real snow squall in Northern Middlesex County NJ - one where just like a summer thunderstorm darkens the sky to the west first and then when the squall hits you have white out conditions where if driving you have to pull your car over to the side of the road until it passes and after it does you have an inch or more on the ground after a short period of time.

We had one the day after the March 2017 storm. Blasted through Middlesex and intensified over Monmouth county. I was driving through it on the GSP and it was nuts

[purduewx80]

7 minutes ago, forkyfork said:

this is one of the most impressive snow squall soundings i've seen for this area

No doubt. Given the jet moving through, it should have no trouble surviving the mountains and may even get a boost of Atlantic moisture for LI/CT. It's pretty cool to see the tropopause that low, too.

[SnowGoose69]

I still see 2-4 as very possible tomorrow night.  Especially in a belt from Queens/Nassau north up through western CT.  The 1000-850 thicknesses to me just do not argue for much that falls after 23Z to be rain.  The Euro only shows about .07-.10 snow for NYC/Queens but I’m not biting on that low amount being frozen.  Bob and PSU in the MA forum have noticed the same thing on the model profiles for BWI/DCA.  They seem to support snowier solutions that guidance is spiitting out 

[NEG NAO]

5 minutes ago, SnowGoose69 said:

I still see 2-4 as very possible tomorrow night.  Especially in a belt from Queens/Nassau north up through western CT.  The 1000-850 thicknesses to me just do not argue for much that falls after 23Z to be rain.  The Euro only shows about .07-.10 snow for NYC/Queens but I’m not biting on that low amount being frozen.  Bob and PSU in the MA forum have noticed the same thing on the model profiles for BWI/DCA.  They seem to support snowier solutions that guidance is spiitting out 

I agree with the 540 line staying so far south the entire event I would not be surprised if area from North of Freehold NJ at least stay mostly frozen with maybe a brief mix for a while tomorrow afternoon and a general 2 -4 in Central NJ - maybe !

[SnowGoose69]

7 minutes ago, NEG NAO said:

I agree with the 540 line staying so far south the entire event I would not be surprised if area from North of Freehold NJ at least stay mostly frozen with maybe a brief mix for a while tomorrow afternoon and a general 2 -4 in Central NJ - maybe !

This is the sort of setup I’ve brought up before that models have a tendency to miss in this area.  They usually either underdo the QPF or are too warm.   Recently I think 12-14–10 had this occur.  It wasn’t exactly the same setup as this but it was that same general weak surface reflection or low forming and moving NNW into SNE and there’s a corridor of precip running NNW-SSE back behind it over NYC-CT-LI with a slight negative tilt in the trof.  I believe the 2010 event dumped as much as 5 inches in Suffolk and the forecast was nothing.   

[RU848789]

2 hours ago, SnowGoose69 said:

I still see 2-4 as very possible tomorrow night.  Especially in a belt from Queens/Nassau north up through western CT.  The 1000-850 thicknesses to me just do not argue for much that falls after 23Z to be rain.  The Euro only shows about .07-.10 snow for NYC/Queens but I’m not biting on that low amount being frozen.  Bob and PSU in the MA forum have noticed the same thing on the model profiles for BWI/DCA.  They seem to support snowier solutions that guidance is spiitting out 

I know you know this stuff way better than I do, but I'm thinking the same way.  When I look at the 12Z Euro on weather.us, the 850 mbar temps are below -1C for the entire event for all of CNJ/NNJ/NYC (NJ coast just touches 0C in the late afternoon) and are below -2C from 6 pm onward when 90% of the precip falls for these locations - however, surface temps are mid/upper 30s at 6 pm, so I could see rain for a few hours, but they drop to 33-34F for most by 8 pm when about half of the total of 0.3-0.4" QPF has fallen, leaving 0.15-0.20" of QPF to likely fall as snow (don't think it'll melt before hitting the ground and might not be rain except even earlier - although accumulating on 34-36F surfaces early on will be tough, except it will be at night), while the Euro only shows about 1/2" of snow for most of that area.  I'm thinking more like 1-2" and maybe even 2-3" under these conditions.  

[LongBeachSurfFreak]

3 minutes ago, RU848789 said:

I know you know this stuff way better than I do, but I'm thinking the same way.  When I look at the 12Z Euro on weather.us, the 850 mbar temps are below -1C for the entire event for all of CNJ/NNJ/NYC (NJ coast just touches 0C in the late afternoon) and are below -2C from 6 pm onward when 90% of the precip falls for these locations - however, surface temps are mid/upper 30s at 6 pm, so I could see rain for a few hours, but they drop to 33-34F for most by 8 pm when about half of the total of 0.3-0.4" QPF has fallen, leaving 0.15-0.20" of QPF to likely fall as snow (don't think it'll melt before hitting the ground and might not be rain except even earlier - although accumulating on 34-36F surfaces early on will be tough, except it will be at night), while the Euro only shows about 1/2" of snow for most of that area.  I'm thinking more like 1-2" and maybe even 2-3" under these conditions.  

It’s been plenty cold so surfaces that tend to retain cold shouldn’t have a problem accumulating. 

[SnowGoose69]

24 minutes ago, RU848789 said:

I know you know this stuff way better than I do, but I'm thinking the same way.  When I look at the 12Z Euro on weather.us, the 850 mbar temps are below -1C for the entire event for all of CNJ/NNJ/NYC (NJ coast just touches 0C in the late afternoon) and are below -2C from 6 pm onward when 90% of the precip falls for these locations - however, surface temps are mid/upper 30s at 6 pm, so I could see rain for a few hours, but they drop to 33-34F for most by 8 pm when about half of the total of 0.3-0.4" QPF has fallen, leaving 0.15-0.20" of QPF to likely fall as snow (don't think it'll melt before hitting the ground and might not be rain except even earlier - although accumulating on 34-36F surfaces early on will be tough, except it will be at night), while the Euro only shows about 1/2" of snow for most of that area.  I'm thinking more like 1-2" and maybe even 2-3" under these conditions.  

The Euro 1000-850 thickness at 00Z is 131.  You’ll snow about 9 out of 10 with that 

[RU848789]

46 minutes ago, LongBeachSurfFreak said:

It’s been plenty cold so surfaces that tend to retain cold shouldn’t have a problem accumulating. 

Yes, but it'll be in the upper 30s during the day for the 95 corridor, which will warm immediate surfaces up above 32F over several hours (but it'll be cloudy and the sun angle is still low. so not as much as it could be above 32F) and there will be at least some rain to start, so it's quite possible the first 0.5" of snow after the changeover will be lost to melting.  The changeover being after sunset will also help.  

29 minutes ago, SnowGoose69 said:

The Euro 1000-850 thickness at 00Z is 131.  You’ll snow about 9 out of 10 with that 

I've never taken the time to learn about thicknesses at various levels in the column and impact on snow - any chance you can provide 1-2 sentences explaining what is meant by your statement (other than the obvious that you think that means snow at 00Z and after)?  Or a link to something that does?  Thanks!

[Ericjcrash]

Might be primed for a mini NAMing.

[NorthShoreWx]

3 hours ago, SnowGoose69 said:

This is the sort of setup I’ve brought up before that models have a tendency to miss in this area.  They usually either underdo the QPF or are too warm.   Recently I think 12-14–10 had this occur.  It wasn’t exactly the same setup as this but it was that same general weak surface reflection or low forming and moving NNW into SNE and there’s a corridor of precip running NNW-SSE back behind it over NYC-CT-LI with a slight negative tilt in the trof.  I believe the 2010 event dumped as much as 5 inches in Suffolk and the forecast was nothing.   

Mostly 1 - 3" on LI on  12/10/14 (and also in Bronx and Westchester), but what happened on 3/31/2014?  That was the day we had 5" with 0" forecast. 

 

Also there were a couple of good blinding mid-day snow squalls on February 26 and again on February 27, 2014.  This one blew through shortly after noon on the 2/26/14:

[NorthShoreWx]

24 minutes ago, RU848789 said:

Yes, but it'll be in the upper 30s during the day for the 95 corridor, which will warm immediate surfaces up above 32F over several hours (but it'll be cloudy and the sun angle is still low. so not as much as it could be above 32F) and there will be at least some rain to start, so it's quite possible the first 0.5" of snow after the changeover will be lost to melting.  The changeover being after sunset will also help.  

I've never taken the time to learn about thicknesses at various levels in the column and impact on snow - any chance you can provide 1-2 sentences explaining what is meant by your statement (other than the obvious that you think that means snow at 00Z and after)?  Or a link to something that does?  Thanks!

An average 850mb - 1000mb thickness of about 135 decameters (1350 meters) is cold enough on average to snow, but averages don't matter.  If its very cold at 850 and very warm below 950, it's gonna rain.  At 131dm thickness, it's a colder layer (on average), as SG alluded to.

Basically, warm air takes up more space, so the colder it is the less the thickness of the layer.

[Ericjcrash]

NAM continues to be unenthusiastic, 3K is nice for NNJ though.

[sussexcountyobs]

WWA up now for NW NJ. 3-6" of snow.

[ForestHillWx]

I'm in Perth amboy for a scene investigation...it's 30 degrees. Ground is cold. You never know what tomorrow night could bring. 

[hazwoper]

Mt Holly's thoughts.  WWA posted for most of their area

Mt Holly's 

[Ericjcrash]

GFS cut back for mostly everyone. Eastern HV does better.

[NJwx85]

My call. Good luck to all.

[RU848789]

23 minutes ago, Ericjcrash said:

GFS cut back for mostly everyone. Eastern HV does better.

It cut back for some and is more for some, especially in CNJ and NNJ near 95 and SE of there.  Maps below...

 

[RU848789]

2 hours ago, NorthShoreWx said:

An average 850mb - 1000mb thickness of about 135 decameters (1350 meters) is cold enough on average to snow, but averages don't matter.  If its very cold at 850 and very warm below 950, it's gonna rain.  At 131dm thickness, it's a colder layer (on average), as SG alluded to.

Basically, warm air takes up more space, so the colder it is the less the thickness of the layer.

 

Gotcha, thanks, although being a chem engineer, this makes me just want to do a total heat balance on the entire column, lol, to figure out exactly where the snowflake heats up enough to melt.  If the temp is 28F at 5000 feet and then 30F at 2500 feet and then 32F at 500 feet and then 34F at the surface, one would need to know the velocity of an average snowflake to figure out the total time it spends above 32F (and how far above 32F), as well as to determine how quickly it warms up during its descent  I'm guessing what @SnowGoose69 was hinting at with the 131 dm "thickness" being colder than normal for 0-5000 feet in the column is that perhaps only the last few hundred feet would be above 32F if the surface is at 33-34F, meaning the flakes might not melt in that short time.  Whereas if the surface is 33-34F, but the last 2000 feet of that are all above 32F, then melting is much more likely.  

This is cool stuff and not hard to put into a model, one would think, but one would need to know the profile of the column over time at far more granular points than just 850, 925 and the surface, in order to really do an accurate heat balance.  Damn, this would've been fun to do when I was younger - think I've forgotten most of the equations, lol.  

[MJO812]

Para gfs has 2-3 inches for the city with more inland.

[RU848789]

2 minutes ago, Snow88 said:

Para gfs has 2-3 inches for the city with more inland.

Probably best model run yet for most, especially for most of CNJ/NNJ and NYC (particularly anywhere near 95).  This is what happens if we don't see a very delayed changeover for 95 on eastward, as many have been speculating...

[NycStormChaser]

5 minutes ago, RU848789 said:

Probably best model run yet for most, especially for most of CNJ/NNJ and NYC (particularly anywhere near 95).  This is what happens if we don't see a very delayed changeover for 95 on eastward, as many have been speculating...

Why do people bother with the GFS at this range? We need to look at the meso models. 

[NorthShoreWx]

34 minutes ago, RU848789 said:

 

Gotcha, thanks, although being a chem engineer, this makes me just want to do a total heat balance on the entire column, lol, to figure out exactly where the snowflake heats up enough to melt.  If the temp is 28F at 5000 feet and then 30F at 2500 feet and then 32F at 500 feet and then 34F at the surface, one would need to know the velocity of an average snowflake to figure out the total time it spends above 32F (and how far above 32F), as well as to determine how quickly it warms up during its descent  I'm guessing what @SnowGoose69 was hinting at with the 131 dm "thickness" being colder than normal for 0-5000 feet in the column is that perhaps only the last few hundred feet would be above 32F if the surface is at 33-34F, meaning the flakes might not melt in that short time.  Whereas if the surface is 33-34F, but the last 2000 feet of that are all above 32F, then melting is much more likely.  

This is cool stuff and not hard to put into a model, one would think, but one would need to know the profile of the column over time at far more granular points than just 850, 925 and the surface, in order to really do an accurate heat balance.  Damn, this would've been fun to do when I was younger - think I've forgotten most of the equations, lol.  

Those calculations are built into the models, but the data in, starting point and model resolution introduce sources of error.  Here is what today's 18z 3k NAM forecast sounding looks like for my area at 4PM tomorrow.  Freezing level is at about 930mb and everything above that is cold enough.  Below 930mb the temp rises from 0C to 3C with most of that rise done by 950, hence plenty of time for the snow to melt on the way down.  The problem is with the S to SE boundary layer winds.  in subsequent hours the model shows the temperature warming a little more at the surface while 850 stays below freezing on more of a southwest wind.  This run shows it getting cold enough to snow here after 10PM, but not much precip around at that time.

[Ericjcrash]

14 minutes ago, RU848789 said:

Probably best model run yet for most, especially for most of CNJ/NNJ and NYC (particularly anywhere near 95).  This is what happens if we don't see a very delayed changeover for 95 on eastward, as many have been speculating...

Lol at the weenie NYC snow hole. 

Fv3 definitely an uptick at 18z as were the RGEM and HDRPS, granted they went from nothing to not much.