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

[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.

[EastonSN+]

[CPcantmeasuresnow]

7 minutes ago, Prue11 said:

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

How long have you lived on the Delmarva?

[NJwx85]

3 minutes ago, SACRUS said:

RAP has mixing around 3pm

 

To be fair that only shows mixing in the Southern third of the forum and barely at that.

[nycsnow]

Regardless what happens. Gotta give the RAP credit. Hasn’t wavered Lol you’d think they put same maps out just change times 

[Jt17]

RAP has mixing around 3pm
 

Hmm I think it doesn't make it to nyc here - in fact stays south for 8 more hours.


.

[NJwx85]

1 minute ago, Picard said:

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

Everyone should be ripping by 9am.

[nycsnow]

[nycsnow]

10:1 still a foot plus as well on RAP

[mikeysed]

The RAP is cold bias. 

[EastonSN+]

GFS was snowier West and east. Just a small punch of sleet lol. 

[Snowlover11]

Gfs ticked ever so slightly south, not much but a tickle of a nickel smudge. Snow axis is a little weird though.

[nycsnow]

1 minute ago, mikeysed said:

The RAP is cold bias. 

Also a dry bias… so warm it up a bit give us more precip we still do good lol 

[nycsnow]

[Jt17]

Ukie a little better.


.

[wxman]

Just now, Jt17 said:

Ukie a little better.


.

Essentially all snow like it was at 12z.  

[EastonSN+]

1 minute ago, Snowlover11 said:

Gfs ticked ever so slightly south, not much but a tickle of a nickel smudge. Snow axis is a little weird though.

Yeah I just did the comparison the GFS was about 20 miles south and colder. Just that SMALL warm punch lol.

[SACRUS]

 

UKIE

 

[nycsnow]

Ukie great and locked in for days 

[SnoSki14]

I suspect we'll be fighting off sleet for a while as long as precip comes down heavily. 

[NorthShoreWx]

1 hour ago, ILoveWinter said:

Most people don't follow the models as closely as us weenies and probably don't know that CPK tends to under measure snow! Seems like a nice arbitrage opportunity here lol.

Seems like a lawsuit generator if there is a ridiculous measurement reported by the conservancy.

[nycsnow]

1 minute ago, SnoSki14 said:

I suspect we'll be fighting off sleet for a while as long as precip comes down heavily. 

Do you think it can be one of those instances where despite what models show it goes back and forth depending on rates ?

[JBG]

2 hours ago, Winterweatherlover said:

It is but it mainly only helps places between 84 and 287 this run, would need another 30 mile tick to mean much for NYC metro.

There's warm and there's warm. IP is better than ZR.

[wthrmn654]

Sister in Tennessee says about 1 inch of snow and now is sleeting, forecast hasn't really changed much at all for her temperature is 23 down there right now

[nycsnow]