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

[MANDA]

Just now, SACRUS said:

Based on most guidance going to see intense rate of snowfall from roughly 11am through 4pm along and north of a TTN to Sandy Hook to Montauk line from SW to NE.  The bulk of the snow is going to fall during those roughly 5 hours.

[nycsnow]

Just now, jm1220 said:

Looks lame/warm again like 12z. Hopefully tonight 0z we resolve this one way or another, if not we watch the radar in the morning to see how the snow advances in. That’s really the difference maker here. 

Shouldn’t we be putting less thought into these models and focusing more and meso

[nycsnow]

The gfs snow map don’t even make sense?? It’s not like there wasn’t snow or precip falling over the metro 

[wthrmn654]

As one of the NWS mets just told me, in regards to the nam. 

 

That degree of warming aloft might not be wrong. European seems slower to bring it in though. See what I wrote above about snow falling down south in some places where sleet was expected, don't know if that idea will work out east of the Appalachians as dynamic cooling from strong lift when the heavier snow falls here could delay any change to sleet and keep it farther south

[SnoSki14]

2 minutes ago, Winterweatherlover said:

GFS went from the coldest/snowiest model all week to now one of the warmest models.

Which should tell how of crappy it really is.

Also crazy how SNE could score 2'+ amounts with this when they thought it was gonna be suppressed 

[psv88]

I don’t see orient getting 12” and the city 3” in this setup 

[jm1220]

1 minute ago, nycsnow said:

Shouldn’t we be putting less thought into these models and focusing more and meso

Starting to get to that point but I’d say tonight we pay more attention. In any event we’ve seen the HRRR gradually getting warmer although still impressive at 18z. 

[MJO812]

2 minutes ago, nycsnow said:

The gfs snow map don’t even make sense?? It’s not like there wasn’t snow or precip falling over the metro 

It has a weird dryslot 

[nycsnow]

1 minute ago, jm1220 said:

Starting to get to that point but I’d say tonight we pay more attention. In any event we’ve seen the HRRR gradually getting warmer although still impressive at 18z. 

I mean I’m sure hrrrrr will fluctuate run to run but it’s been pretty locked in. Nam and gfs by far have been moving around the most of any suite  

[danstorm]

This is BARELY sleet (GFS sounding near me) and likely snow/sleet… with heavy rates it’s probably snow 

This is not the kind of storm that flips to sleet and done, that’s why I think my 8” call here may be low… I had 4/5 inches after mixing with sleet in Mar 2017 and this could be similar 

[jm1220]

Just now, SnoSki14 said:

Which should tell how of crappy it really is.

Also crazy how SNE could score 2'+ amounts with this when they thought it was gonna be suppressed 

The nature of this storm is pretty clear that New England would get nailed a few days ago. It was pretty clear to everyone this wouldn’t end up a VA/Mid Atlantic snowstorm. Retreating high, retreating confluence, trough in the west and SE ridging=SWFE that favors I-90, Boston over to Albany and S NY. The initial high pressure/overrunning gives people like us down to DC a fighting chance but the best is along I-90. I-84 should do very well too. 

[wthrmn654]

5 minutes ago, psv88 said:

I don’t see orient getting 12” and the city 3” in this setup 

Don't forget orient is farthest north versus the city or the island but yeah that is wonky 

[binbisso]

5 minutes ago, psv88 said:

I don’t see orient getting 12” and the city 3” in this setup 

Or dc 7" Philly 6" and nyc 3.5". Gfs should be retired

[EasternLI]

I think this is closer to reality from that run

 

[wthrmn654]

1 minute ago, EasternLI said:

I think this is closer to reality from that run

 

Yeah, where long island or cap cod doesn't even exist.  

[NJwx85]

4 minutes ago, danstorm said:

This is BARELY sleet (GFS sounding near me) and likely snow/sleet… with heavy rates it’s probably snow 

This is not the kind of storm that flips to sleet and done, that’s why I think my 8” call here may be low… I had 4/5 inches after mixing with sleet in Mar 2017 and this could be similar 

Couldn’t agree more. I think the heavier rates will help to overcome the borderline mid level warming. The charge to sleet probably only happens once a majority of the precip has already fallen, sometime after 02-03z.

[Prue11]

NOAA has me getting up to 32 degrees tomorrow for a high. 

[donsutherland1]

Prior to the warming of the mid-levels tomorrow afternoon, soundings showed a strongly saturated dendritic growth zone (DGZ) between –12°C and –17°C. That is almost ideal for producing large, fluffy dendritic flakes. There was also strong lift and high saturation supporting very efficient snow growth and high snow-liquid ratios, especially in areas with stronger banding. In short, for 3-4 hours there could be snowfall rates of 1" per hour and perhaps 2" per hour at times. That's when most of the snow will fall in and around New York City. The visibility could fall under one-quarter mile during the periods of heaviest snow. Thundersnow seems unlikely in most of the area as there isn't a convective signature in the soundings. 

It is these dynamics, not 10:1 snow-liquid ratio maps that tell the story of what continues to look to be a significant snowfall in and around New York City. On account of the system's dynamics ahead of the changeover to sleet and the storm's forecast QPF, I have little reason to deviate from my thinking based on today's 12z and early 18z guidance. 

Through early portion of the 18z cycle, it appeared that even as differences persisted among the guidance, the models were slowly moving toward a consensus with the exception of the 18z GFS. As 100% of individual EPS ensemble members from the 0z and 12z cycles had 6" or more snow, the 18z GFS's < 4" figure is not within the realistic range of possibilities. The strong dynamics noted earlier also suggest that the GFS's solution is unlikely.

Overall, a reasonable low-case snowfall for New York City remains 5". A reasonable high case is 12". 

New York City and nearby areas remain in line for 6"-12" of snow and sleet. Areas to the south and east of New York City could see 4"-8" amounts (even farther south beyond the New York City area, places like Atlantic City should see 3"-6"). General 12"-18" amounts are likely well north and west of New York City, most likely in parts of northeastern Pennsylvania (Pike County, Lackawanna County), Orange County, Dutchess County, Sussex County into at least the northern half of Connecticut.   

For perspective, the last time New York City saw a 6" or greater snowfall was January 28-29, 2022 when 8.3" fell from a rapidly deepening blizzard that buried parts of Long Island into southern New England under two feet of snow. Its last 10" or above snowfall occurred during the long-duration January 31-February 3, 2021 snowstorm when 17.4" accumulated. 

Up in southern New England, Boston appears on track to see 14"-20" of snow. If so, that would be that city's biggest snowsorm since the January 28-29, 2022 blizzard, which dumped 23.8" of snow. 

[NJwx85]

1 minute ago, wthrmn654 said:

Yeah, where long island or cap cod doesn't even exist.  

cap cod sounds like an elegant fish dish.

[SACRUS]

 

21z rap

snow between 2 - 5 am sunday

 

 

 

 

 

 

 

[NorthShoreWx]

1 hour ago, Rjay said:

19 and sleet lol

 

I'm not sure everything melts in that melt layer.  50mb is enough, but it looks like no more than 1⁰C.  OTOH, I'm not sure how much is even falling into that layer.  I'm thinking that's a mix, including some fairy crappy snowflakes from below 775mb.

[NJwx85]

Just now, SACRUS said:

 

21z rap

snow between 2 - 5 am sunday

 

 

 

 

 

 

 

Most of what falls before sunrise is probably virga.

[EasternLI]

Just now, wthrmn654 said:

Yeah, where long island or cap cod doesn't even exist.  

Well the GFS doesn't see us as important enough to include in the country so we have to extrapolate.

[jm1220]

3 minutes ago, binbisso said:

Or dc 7" Philly 6" and nyc 3.5". Gfs should be retired

It has crappy resolution which results in the weird snow map outcome but it doesn't have a heavy consolidated snow shield like the RGEM group does. Has an inch per hour maybe which is moderate snow. 

[wthrmn654]

Upton

 

Snow will quickly develop from south to north across the area Sunday
morning as the region lies underneath an intense polar jet streak
lifting into southeast Canada. The snow will fall into arctic air
with surface temperatures only in the low to mid teens. This is a
bit unusual for the area as most snow events over the Tri-State
occur with temperatures in the 20s or low 30s. The snow will quickly
accumulate as the intensity picks up through the morning. Mid level
thermal forcing will increase over the area, especially heading into
the afternoon. The 850-700 mb frontogenesis is impressive and the
overall deep layer of vertical velocities over the area strongly
support heavy snow over the region in the afternoon. Only a slight
increase in temperatures is expected in the afternoon, except the
southern half of the area where temperatures rise into the mid 20s.

As the warming in the mid levels continues, the chance for a mix
with sleet near the coast increase sometime in the afternoon. Latest
model trends this morning have a stronger warm layer with the
coastal low development being a bit closer to the coast. This may
allow for the mix of sleet to be a bit earlier than previously
expected, beginning first as mainly snow mixed with sleet as early
as 1-3 PM but becoming more of a primary period of sleet thereafter
along the coast into Sunday evening. It needs to be emphasized that
the overall impacts will not change and significant snow will occur
before any wintry mix. There is a possibility the heavy snowfall
rates will be able to hold back the warm nose just enough or create
an isothermal layer on the 0C isotherm to prolong heavy snow for
even just an hour two. Given the expected heavy snowfall rates of 1-
2" per hour (or possibly higher), even just an hour or two of mainly
snow rather than sleet can result in a 2-5" difference in snow
accumulation prior to the transition to sleet. Additionally, a few
lightning strikes cannot be ruled out in the heaviest bands with the
impressive dynamics aloft and deep moisture being lifted over the
low level arctic air.

The strong mid level frontogenesis lifts northeast between 00-06z
Monday and this should serve to gradually reduce precip rates. There
may also be drying aloft, which will start to reduce snowfall rates
where it remains all snow. The southern half of the area should see
a wintry mix of sleet, potentially mixed with snow if the warm nose
is not as deep. There is also a chance for some light freezing rain,
mainly for Long Island and the NYC metro as the drying aloft occurs,
cutting off snow growth along with the thinning of the depth of the
low level cold air. This may also be dependent on how close the low
pressure ends up to Long Island. The consensus of the modeling keeps
the low just south and east of Long Island, but if it were to end up
closer to the shore, some parts of eastern Long Island could briefly
rise above freezing with light plain rain briefly possible.

The system starts pulling away from the area late Sunday night into
Monday morning. Some bands of light snow may return as the trailing
upper trough approaches and the thermal profiles become colder
heading into Monday. Probabilities for precip decrease significantly
Monday afternoon and there is potential anything that falls may just
be flurries.

Overall, snowfall totals were adjusted slightly downward, mainly for
the coast with increasing potential for sleet and an earlier timing
of the mixing cutting down a bit on total accumulations. Long Island,
the NYC Metro, and NE NJ are expected to see 8-12" total, but this
may be in the form of 6-9" of snow and 1-2" of sleet. For more
inland areas, total accumulations of 12-15" are expected consisting
of primarily snow with less than an inch of sleet.

As noted above, snowfall rates of 1-2 inches per hour are expected
in the afternoon and early evening. Winds will pick up in the
afternoon and evening, especially near the coast and could create
near white-out conditions/near blizzard conditions with winds
gusting 30 to 40 mph at times, especially for coastal Long Island
and coastal Connecticut. A mix or change to sleet will reduce this
potential as visibilities would not be as low.

[NJwx85]

1 minute ago, NorthShoreWx said:

I'm not sure everything melts in that melt layer.  50mb is enough, but it looks like no more than 1⁰C.  OTOH, I'm not sure how much is even falling into that layer.  I'm thinking that's a mix, including some fairy crappy snowflakes from below 775mb.

I think the bigger issue is that the mid level warning will hurt rates quite a bit. Some areas might start off at 12 or 15 to 1 and go down to half that by sunset.

[SACRUS]

RAP has mixing around 3pm

 

[Roger Smith]

Would you expect a zone of enhanced amounts extending west from Long Island Sound across Bronx and Yonkers into n NJ? Looking at the synoptics model and real time I would expect that enhanced zone to be oriented almost E-W, possibly 260 deg? Also that can generate thunder-snow within squall cells. 

[nycsnow]

2 minutes ago, SACRUS said:

RAP has mixing around 3pm

 

Pretty similar keeps it just below Long Island for a while

[Picard]

How fast does everything overcome dry air?  Surface dews are still well below 0 over much of the storms path.