Extreme Cold, Snow & Sleet: SECS 1/24 - 1/26

[jm1220]

Just now, CentralNJSnowman said:

Would be cool if Mt Holly’s maps didn’t show way more snow than their discussion implies

I’m sure they’ll adjust further today. Hopefully the models are done with the warm shifts but the confluence needs to hold as long as it can. 

[Voyager]

1 hour ago, SnoSki14 said:

Once it gets under 48hrs we'll pay attention. Even so it still has the 6-8" front end dump before any changeover. That's pretty much the floor with this. 

Yup. Right or wrong, we're getting to the time where I pay more attention to the mesos over the globals.

[MJO812]

What a mess it will be outside if we get 6 plus inches of snow and some sleet.

[weathermedic]

Good AM discussion out of OKX

The overall synoptic picture into early next week continues to
sharpen. At the surface, arctic high pressure slides east from
the Great Lakes into the Northeast this weekend. Meanwhile, low
pressure develops and tracks through the South before
redeveloping off Cape Hatteras, passing near or just inside the
40N/70W benchmark into Monday.

Aiding the potential for snowfall, an arctic air mass settles
in ahead of the storm. 925 mb temps look to fall toward -20C or
below on Saturday, with surface temperatures progged in the
teens during the afternoon, setting up one of the coldest days
in several years. This will allow snow to fall everywhere at the
onset, which looks to develop rather quickly either very late
Saturday night, or more likely Sunday morning around or after
daybreak. Periods of heavy snow then appear likely late Sunday
morning through the afternoon via the strong frontogenetic and
thermal forcing aided by an anticyclonic upper jet to the north.
Snowfall rates in this period likely eclipse 1 in/hr at times,
perhaps closer to 2 in/hr. Given the cold air mass in place
initially, SLRs start out on the higher side (15-18:1) at onset,
gradually falling back toward 10:1 or lower along the coast by
late afternoon as the mid levels warm. With guidance having
adjusted to a closer to the coast surface low, the proximity
introduces the possibility of enough warm air intrusion around
800 mb for the snow to mix with or change to sleet Sunday
evening. Best chances for this are along the coast, including
Long Island and NYC metro. Lower confidence in this occurring
going north, with all snow still the most likely solution into
the Lower Hudson Valley and Southern Connecticut. Freezing rain
or drizzle also cannot be ruled out, though significant icing
appears unlikely.

As the coastal system deepens and lifts north and east into Monday,
the boundary cools once again, and any wintry mix likely tapers
as snow showers or flurries into late Monday morning or afternoon.
Any additional accumulation is likely light.

Forecast snowfall totals have decreased slightly along the
coast. This is due to the increased potential for mixing as the
warmer air aloft works in. It should be emphasized though the
heaviest and steadiest precipitation is expected Sunday morning
into early evening, with the bulk of snow accumulation
occurring prior to any potential changeover. With QPF progged
over an inch, areas that remain all snow should be able to yield
double digit snowfall. The question becomes how much warm air
is able to work in and force a changeover to sleet, cutting down
snow totals. All said, still expecting a widespread 8 to 14
inches across the region, with localized amounts perhaps
approaching a foot and a half where best banding sets up and
ptype remains all snow. Greatest likelihood for this is across
the interior.

We remain just over 48 hours from event onset, so opted for no
headline changes with this update. It appears likely warnings will
be warranted for all areas later today or tonight, dependent on
no significant deviations in forecast thought.

Continue to monitor the forecast on what is increasingly likely
to be a major winter storm with significant disruption to travel
and daily life early next week.

[BoulderWX]

The NWS actually added an inch to my WSW - 12-17. Not sure what they’re looking at. 

[ILoveWinter]

The NAM is not infallible when it comes to being the most aggressive with warm noses but agree that it could verify. 

I do wonder why in this instance it is the most aggressive - is it because it tracks the primary further north vs the other models? Does it show a stronger primary?
 

[donsutherland1]

Latest NWS probabilistic estimate of 6" or more snow for New York City: 90%

Islip was at 81% and Newark was at 88%.

[jm1220]

23 minutes ago, MJO812 said:

What a mess it will be outside if we get 6 plus inches of snow and some sleet.

Oh yeah. Sleet has more bang for its buck-doesn't pile up like snow obviously but will thicken up the snowpack and be a huge pain to move. After 3/14/17 the snow/ice piles were crazy. I remember the Feb 2007 storm in central PA with 10-11" of thick snow/sleet that hardened up into cement. A week from now even though we shave a few snow inches off for sleet I doubt people will be complaining if they like snowpack staying around like me. 

[psv88]

Models look great! Nice to see icon and RGEM snowier 

[BoulderWX]

Just now, psv88 said:

Models look great! Nice to see icon and RGEM snowier 

NAM should give pause. I hate the model but I think it’s very good at detecting warm noses. 

[SnoSki14]

2 minutes ago, jm1220 said:

Oh yeah. Sleet has more bang for its buck-doesn't pile up like snow obviously but will thicken up the snowpack and be a huge pain to move. After 3/14/17 the snow/ice piles were crazy. I remember the Feb 2007 storm in central PA with 10-11" of thick snow/sleet that hardened up into cement. A week from now even though we shave a few snow inches off for sleet I doubt people will be complaining if they like snowpack staying around like me. 

We might set some modern snow pack longevity records with no warm ups in sight after the storm. That glacier will last a very long time 

[NJwx85]

2 minutes ago, jm1220 said:

Oh yeah. Sleet has more bang for its buck-doesn't pile up like snow obviously but will thicken up the snowpack and be a huge pain to move. After 3/14/17 the snow/ice piles were crazy. I remember the Feb 2007 storm in central PA with 10-11" of thick snow/sleet that hardened up into cement. A week from now even though we shave a few snow inches off for sleet I doubt people will be complaining if they like snowpack staying around like me. 

The piles of black and yellow snow in Brooklyn are going to look great next week.

[lee59]

NYC has a chance to break their record of longest stretch of below 32 temperatures.

[jm1220]

1 minute ago, NJwx85 said:

The piles of black and yellow snow in Brooklyn are going to look great next week.

Good thing I don't have to commute there. 

[Stormlover74]

2 minutes ago, BoulderWX said:

NAM should give pause. I hate the model but I think it’s very good at detecting warm noses. 

It can overdo it. We're flipping regardless but hopefully can get a bigger front end thump like the other models have. Problem is we still have 48 hours to go

[jm1220]

2 minutes ago, SnoSki14 said:

We might set some modern snow pack longevity records with no warm ups in sight after the storm. That glacier will last a very long time 

Yep, it will be hard as granite. The snowpack will contain the same water as anywhere else since we aren't transitioning to rain or going above freezing-it will just be denser near the coast. 

[Stormlover74]

This is starting to remind me of that storm in Dec 2013 where we went from teens and snow over to sleet. It was a smaller storm but I remember the crazy temperature differential with like 13 in Sussex and 44 and rain in AC

[jdj5211]

Steven’s thoughts….




.

[nycwinter]

snow and sleet will stick around for awhile with high temps next week in the 20's and lows in the low teens at night.

[East of the Parkway]

9 minutes ago, jdj5211 said:

Steven’s thoughts….




.

I've been a 4 my whole life

[MJO812]

7 minutes ago, nycwinter said:

snow and sleet will stick around for awhile with high temps next week in the 20's and lows in the low teens at night.

And possible another storm next weekend 

[kat5hurricane]

There will still be a nice thump of snow but IMO the bigger story is becoming the sleet. 6-10" of snow with a ton of sleet on top is going to be create big problems in the coming days with the very cold week coming up and it icing up even further.

[NorthShoreWx]

I'm pretty confident it will taint, but I think the somewhat weak consensus in this thread is overestimating the magnitude of it. 

I looked at model soundings last night that showed the warmest part of the column at about -2C at my location aligned with a p-type map where we were deep into the purple.  Gives me more confidence in the NWS sticking to their guns.  The 3rd party p-type maps are often bizarre.

I'm eager to see NAM soundings once most of the storm gets within 60 hours.

[snowman19]

17 minutes ago, Stormlover74 said:

This is starting to remind me of that storm in Dec 2013 where we went from teens and snow over to sleet. It was a smaller storm but I remember the crazy temperature differential with like 13 in Sussex and 44 and rain in AC

That storm was one of the NAM’s shining moments (there aren’t very many). I remember everyone discounted it because, well it’s the NAM. But it nailed the midlevel warm nose perfectly and early. Even the other mesos didn’t pick up on it until it was almost happening and the globals completely missed it. These types of setups are the only reason why, IMO, the NWS shouldn’t totally retire the NAM. It’s literally the only thing it’s good at

[winterwarlock]

19 minutes ago, SnoSki14 said:

We might set some modern snow pack longevity records with no warm ups in sight after the storm. That glacier will last a very long time 

It will never top the  January 94 ? Snow ice pack

[mob1]

Sleet at least adds up and makes the snowpack last, we want to avoid rain though (NAM shows a bit at the tail end for southern parts of the city). 

 

Just need the NAM 30-40 miles south and I honestly don't care if we flip to sleet a bit earlier than modeled. 

[EastonSN+]

1 hour ago, snowman19 said:

There is still a big front end thump of snow before the mix to sleet, that’s locked in. Getting back to the NAM, Binghamton NWS is expecting a possible turn to sleet all the way up into Northeast PA in their new disco this morning: 

“Models continue their jog northward for our winter storm Sunday into Monday. No major changes at this time, with still a significant snowstorm expected for the area with a widespread 10"+ with locally higher amounts possibly over 20". The finer scale models will be coming into play over the next 24 hours. It should be noted that the NAM and CMCreg are showing strong SE flow at H850. The NAM is notorious for doing very well forecasting the warm layers aloft and this will be something to monitor as we get closer. This warm layer aloft may not cause mixing per say, but it may significantly change snow ratios Sunday night across NEPA and possibly into the Southern Tier and this would produce lower snow totals in these areas if it comes to fruition. Also, mixing is not noted in our forecast at this time, however, a future change could be warranted if this trend north continues any further and this would also hinder snowfall totals across the southern forecast area some.”

You are right. However in the last storm it showed sleet to CT and we never turned to sleep. Its great but not always perfect.

[jm1220]

7 minutes ago, NorthShoreWx said:

I'm pretty confident it will taint, but I think the somewhat weak consensus in this thread is overestimating the magnitude of it. 

I looked at model soundings last night that showed the warmest part of the column at about -2C at my location aligned with a p-type map where we were deep into the purple.  Gives me more confidence in the NWS sticking to their guns.  The 3rd party p-type maps are often bizarre.

I'm eager to see NAM soundings once most of the storm gets within 60 hours.

If we have heavy rates we can overcome shallow layers a bit above freezing-we might get rimed flakes etc but it's when the rates are reduced and we get dry holes in the precip that the warm air can become more established. And sometimes there are sneaky warm layers that aren't captured well in the soundings. Seems like the warm layer that can flip us over would be around 750mb from what I've seen. In any case it will still snow a lot and hopefully by the time the sleet gets here we're about to shut it off anyway. That's a potent high pressure dome all that Gulf moisture is slamming into and it will take a while to warm it up. The dryslot will also be a consideration if we have a strong 700mb low tracking into Lake Erie. Dry air will pivot around the SE side of it. 

[jdj5211]

We’ve also seen plenty of times when the NAM shows 30+ amounts 48 hours before a storm and those locations end up with 6-12. Like most storms, likely going to be a nowcast situation with some hopefully pleasant surprises.


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[kat5hurricane]

53 minutes ago, BoulderWX said:

The NWS actually added an inch to my WSW - 12-17. Not sure what they’re looking at. 

They're going to adjust that downwards almost certainly I'd think, they've already started the process of lowering totals with the new update. I can't see a widespread 12+ outside of the NW burbs