HIGH IMPACT Stormy Christmas (EVE and morning) 12/24-25/20 6P-10A

[wdrag]

Follow NWS on flooding.  No one on here has said massive flooding.  

Flooding is possible, a few streams maybe but major??  My guess is very little if any because of shorter duration of R+/big warmth and fast cool down to near freezing Friday.

 

I think clearing drainage basins, especially where more than 8 inches on the ground right now is a good idea, just to reduce any possible coding of water in those areas.  Must be done SAFELY, if at all. Thanks.

[bluewave]

7 hours ago, psv88 said:

Upton mentioned the flooding potential too. @bluewave has been on this for a week. Posters such as @JoshSnow and @jfklganyc owe him an apology. 
 

good work as always Walt, thank you

I am not sure why my original post was quoted so many times. All that I said is that the interior areas with the deepest snowpack would have to watch the shorter term forecasts for flooding potential. I didn’t go into  any specifics since it was based on the longer range Euro.This is very similar to the BGM AFD.  I also mentioned that the coastal sections would have time to gradually melt their smaller snowpack over the next several days before the storm arrives.

2 inch rainfall totals are not out of the question for those
enhanced higher terrain locations. Combined rain and snowmelt
could result in significant runoff and thus potential for
flooding will need to be monitored closely. Finally, weight of
old snow and new rain on rooftops where heaviest recent snow
occurred, could lead to problems.

[cleetussnow]

6 hours ago, JoshSnow said:

Binghamton will most likely rain for an hour and than turn to heavy snow so I’m not sure how Binghamton will get any flooding from this!

Binghamton will have a glacier until May.  

[bluewave]

It’s been a big year for squall lines. This could be one of the most intense low topped squall lines that we have seen on Christmas. I wonder what the annual record number is for all types of squall lines in the region?

 

[Brian5671]

4 minutes ago, bluewave said:

It’s been a big year for squall lines. This could be one of the most intense low topped squall lines that we have seen on Christmas. I wonder what the annual record number is for all types of squall lines in the region?

 

Just this fall we've had 4 or 5 of them....

[Roger Smith]

I think something like this happened in 1965 (I was in NJ for Christmas and New Years that year) and then it was close to 70 deg again on New Years eve. Only reason for mentioning the analogy is that you had that memorable snowstorm in late January of 1966. That was on a similar track (NNE) a bit further east than the event being discussed here. That was more or less a mild winter with the one big event. 

[qg_omega]

looks pretty standard low top line of convection, very typical in this new regime

[Santa Claus]

46 minutes ago, bluewave said:

It’s been a big year for squall lines. This could be one of the most intense low topped squall lines that we have seen on Christmas. I wonder what the annual record number is for all types of squall lines in the region?

 

great point.  we've had some ragers this year.

this one though, if it pans out as depicted, looks like something special.  it's coming in as a straight line top to bottom, almost no bowing, and runs the length of much of the eastern seaboard.  can't remember anything like that ever happening in recent memory.  the low its attached to isn't really showing a comma head of precip, it's like there's just a big wall of fury coming in at a right angle.

question since i don't know where to find soundings for upcoming events: is there a TOR threat with the screaming S flow and what i assume is some directional shear as you climb through the air?  i feel like events with strong southerly flow tend to be decent TOR threats for us.

[White Gorilla]

26 minutes ago, Will - Rutgers said:

great point.  we've had some ragers this year.

this one though, if it pans out as depicted, looks like something special.  it's coming in as a straight line top to bottom, almost no bowing, and runs the length of much of the eastern seaboard.  can't remember anything like that ever happening in recent memory.  the low its attached to isn't really showing a comma head of precip, it's like there's just a big wall of fury coming in at a right angle.

question since i don't know where to find soundings for upcoming events: is there a TOR threat with the screaming S flow and what i assume is some directional shear as you climb through the air?  i feel like events with strong southerly flow tend to be decent TOR threats for us.

I can't believe we are talking TOR a week after a major winter storm.  This is just insane. 

[LoboLeader1]

[Santa Claus]

1 hour ago, White Gorilla said:

I can't believe we are talking TOR a week after a major winter storm.  This is just insane. 

i'm just asking a question, have no idea if that's even remotely feasible in this setup.  NWS doesn't mention TOR at all.

[MJO812]

Yikes

[Stormlover74]

An additional concern is the windy conditions that will develop. GFS forecast soundings show 65 to 75 kt winds at 950 mb by Thursday night. Given the inversion that is likely to develop with the snow pack keeping the lower levels cold, it will be difficult to mix these higher winds to the surface. However, Wind Advisory level winds (gust of 46 to 57 mph) seems plausible. 
The strongest winds should occur overnight, with the core of the strongest winds along
the coast. This will be fine tuned as we get closer to the event

[White Gorilla]

21 minutes ago, Stormlover74 said:

An additional concern is the windy conditions that will develop. GFS forecast soundings show 65 to 75 kt winds at 950 mb by Thursday night. Given the inversion that is likely to develop with the snow pack keeping the lower levels cold, it will be difficult to mix these higher winds to the surface. However, Wind Advisory level winds (gust of 46 to 57 mph) seems plausible. 
The strongest winds should occur overnight, with the core of the strongest winds along
the coast. This will be fine tuned as we get closer to the event

Last thing the public needs is widespread power outages right on Christmas morning.  What a way to add more misery on an already stressful and distressing holiday time for so many in this year that just needs to freaking end.  

[MJO812]

Gfs 

[Cfa]

Might not be any snowpack here by Thursday at the rate it’s melting.

[WEATHER53]

What are temps over next 24 hours after frontal passage?

Thanks 

[SnoSki14]

If we get to 60F+ plus the squall line then those 60-80mph gusts will mix down. 

Correct forecast is very conservative because they assume the inversion will hold however how many times how temps gone over forecast in the warm sector during these cases. 

Snow pack is also rapidly dwindling south of I-78. 

[wdrag]

Saw some of the previous posts and agree...

Topic edit at 522AM Tuesday the 22nd: Changed the title to WILL be accompanied by damaging wind LI, and restricted the period of accumulative snow to the interior. I think the wind damage potential is the largest threat from this rapidly deepening 980s surface low moving northward up the front into NYS predawn Christmas. SVR's possible (in my mind likely, even if no lightning) for HSLC heavy showers.The R#/wind profile combo on the NAM and even GFS tells me 45kt+ gusts all the major airports in and near NYC sometime between 10P/24 and 5A/25 . This is further supported by multiple models 80KT+ 850MB winds over LI, in some cases around 90-95kt. From my looking at Richardson (R)# and wind grab, this has the most favorable potential in my past 3 months of examining to realize downward transfer 50-65KT from the lowest 25 to 50 MB of the boundary layer. Whether an isothermal sounding in the lowest part of the boundary layer, or even a slightly inverted sounding can diminish-mute the potential, I don't know. What I do think, is that a lot of folks could wake up with lights out Christmas morning across LI, and possibly NJ/CT.  Flooding potential to me looks the same as it did yesterday-previous days, all a matter of qpf, snowmelt combo to prompt a few rivers into minor or eventually moderate flood stage, even as temps plummet from 60ish near midnight Christmas morning, to near freezing by ~ Noon Friday. Please follow NWS closely on flood potential-they have more tools than I. Snowfall, accumulation less than 1 inch probably restricted in our forum counties only I84 high terrain northwestward. I'll copy this to the last page of this topic and add a couple of wind profiles there.  The future posts will look at FOUS BL winds, which I think will exceed 34kt at LGA and BOS around 06z and 12z/25 respectively. IF not, then I'm a little too severe on my wind expectations.  Also, I'll be adding shorter term wind gust potential graphics, especially Wednesday onward. 

I added the 00z/22 GEFS chance of 60+MPH gusts for 06z/25.  I think pretty impressive for the the coasts-LI. I also added the LGA 06z/22 NAM time section. Note how close to the surface the 50kt winds at LGA Christmas evening-overnight. In my mind, to avoid damage, we'll need a stronger inversion or a weaker system and less wind aloft in future model cycles.  (corrected many typos at 822A-my apology-was too much of a hurry)

[Brian5671]

9 hours ago, Cfa said:

Might not be any snowpack here by Thursday at the rate it’s melting.

yep alot of it will go today and tomorrow with temps in the low 40's and sun today at least

[MJO812]

The low keeps shifting west for Christmas and slower. Disgusting weather for Christmas.

[LibertyBell]

4 hours ago, wdrag said:

Saw some of the previous posts and agree...

Topic edit at 522AM Tuesday the 22nd: Changed the title to WILL be accompanied by damaging wind LI, and restricted the period of accumulative snow to the interior. I think the wind damage potential is the largest threat from this rapidly deepening 980s surface low moving northward up the front into NYS predawn Christmas. SVR's possible (in my mind likely, even if no lightning) for HSLC heavy showers.The R#/wind profile combo on the NAM and even GFS tells me 45kt+ gusts all the major airports in and near NYC sometime between 10P/24 and 5A/25 . This is further supported by multiple models 80KT+ 850MB winds over LI, in some cases around 90-95kt. From my looking at Richardson (R)# and wind grab, this has the most favorable potential in my past 3 months of examining to realize downward transfer 50-65KT from the lowest 25 to 50 MB of the boundary layer. Whether an isothermal sounding in the lowest part of the boundary layer, or even a slightly inverted sounding can diminish-mute the potential, I don't know. What I do think, is that a lot of folks could wake up with lights out Christmas morning across LI, and possibly NJ/CT.  Flooding potential to me looks the same as it did yesterday-previous days, all a matter of qpf, snowmelt combo to prompt a few rivers into minor or eventually moderate flood stage, even as temps plummet from 60ish near midnight Christmas morning, to near freezing by ~ Noon Friday. Please follow NWS closely on flood potential-they have more tools than I. Snowfall, accumulation less than 1 inch probably restricted in our forum counties only I84 high terrain northwestward. I'll copy this to the last page of this topic and add a couple of wind profiles there.  The future posts will look at FOUS BL winds, which I think will exceed 34kt at LGA and BOS around 06z and 12z/25 respectively. IF not, then I'm a little too severe on my wind expectations.  Also, I'll be adding shorter term wind gust potential graphics, especially Wednesday onward. 

I added the 00z/22 GEFS chance of 60+MPH gusts for 06z/25.  I think pretty impressive for the the coasts-LI. I also added the LGA 06z/22 NAM time section. Note how close to the surface the 50kt winds at LGA Christmas evening-overnight. In my mind, to avoid damage, we'll need a stronger inversion or a weaker system and less wind aloft in future model cycles.  (corrected many typos at 822A-my apology-was too much of a hurry)

Walt, I'm going to be in NEPA for this and it looks like that area will also see 60 mph gusts, especially at 2000 ft where I'll be.  

[LibertyBell]

10 hours ago, MJO812 said:

Gfs 

63 mph winds where I'll be for the holidays too.

[Juliancolton]

2 hours ago, Brian5671 said:

yep alot of it will go today and tomorrow with temps in the low 40's and sun today at least

My pack really took it on the nose yesterday. Down to a ripe 5-6".

[bluewave]

Widespread 60-70 mph gusts on the 12z NAM and GFS.

[lee59]

I was curious how they determine if Christmas day is a white Christmas or not. This year it is possible there could be snow on the ground at midnight but not at noon Christmas Day. I was wondering how they make the official determination.

[lee59]

20 minutes ago, lee59 said:

I was curious how they determine if Christmas day is a white Christmas or not. This year it is possible there could be snow on the ground at midnight but not at noon Christmas Day. I was wondering how they make the official determination.

For anyone interested I did read that the NWS says a White Christmas is having 1 inch of snow on the ground Christmas morning. Could be an interesting call this Christmas.

[Stormlover74]

Just now, lee59 said:

For anyone interested I did read that the NWS says a White Christmas is having 1 inch of snow on the ground Christmas morning. Could be an interesting call this Christmas.

Seems unlikely at central park

[LibertyBell]

33 minutes ago, bluewave said:

On track for our windiest Christmas on record. NAM has widespread 60-70 mph gusts sway from the coast. Areas closest the coast come in with 70-75 mph gusts.

 

hey Chris, could you also post E PA as I'll be there for the holidays I see 65-69....will the hilltops be seeing higher winds?  And is that 74 hurricane force gusts for JFK? wow

 

[Brian5671]

1 hour ago, lee59 said:

For anyone interested I did read that the NWS says a White Christmas is having 1 inch of snow on the ground Christmas morning. Could be an interesting call this Christmas.

I think it's long gone in most places on this subforum by 6am.  Temps will be in the upper 50's with heavy rain