February 27-28, 2023 | NE/Mid-Atl Winter Storm

[MaineJay]

GYX 

Quote

With low pressure gaining strength over the Midwest Monday and
then occluding overnight into Tuesday, this aforementioned PWAT
gradient is displaced northward towards southern New England by
Tuesday morning. This is expected to bring greater QPF and
longer duration of precipitation than the weekend systems, but
there are a lot of moving parts that will impact mainly precip
amounts and thus impacts.

As the parent low occludes over Michigan, secondary low forms
off the Mid-Atlantic coast which initially will help spread snow
into southern NH and ME Monday. With both systems lodged within
the same jet axis, movement should be roughly in unison. But,
LLJ increases more rapidly with the developing sfc low off the
New England coast than w/ stacked low over the Great Lakes. This
may offer a quicker departure into the open Atlantic, reducing
max lift duration and bringing a lull to precip rates between
the departing sfc low and slower, broad stacked low to the west.

This would have implications on potential snowfall totals in
the region, with a downtick noted in evening EPS probs. There
will still be a connection via inverted trough between these
features, so complete precip shutoff is unlikely for now. But,
should ridging continue to strengthen to the west, this
eventually lifts the stacked low north vs. bringing it across
New England.

The period after this mid-week system is quite varied in
ensembles and global models, but the pattern remains active
along with a bit of a warm up into late next week.

&&

 

[MaineJay]

Ukie, as had been the case this winter, unfortunately erroneously often, appears the coldest looking at snowfall distribution.  So grains of salt. 

  It's a more "spread the wealth" outcome. Some of this in northern NE/NY is from previous systems.

[TLChip]

I can hope right? Trying to leave my feelings back in January still 😅

[HVSNOWSTORM]

Looking like a nice solid 3-6/4-8" event for most of NY into SNE at least. Best of season if so for some.

[HVSNOWSTORM]

Pa looks to get the screw job on this one unfortunately. Most the area is too close to the low cutting into the lakes.

[TheRex]

I just closed the books from the last storm and noticed this thread for late Feb.  Hopefully this will be the system that gives snow to those that have been screwed all winter.

BTV's forecast discussion.  I bolded the areas that sounded like someone from our forum could have written those sentences: this system is tricky to forecast and how this winter has unfolded.  Even meteorologists don't like less snowy winters.

Quote

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 347 AM EST Friday...Our next system arrives late Monday night
into Tues associated with elongated double barrel low pres structure
with shear apart 700 to 500mb s/w energy. These systems are always
tricky in terms of placement of highest qpf/snowfall, as many times
best precip splits our cwa either to the north and west associated
with the initial s/w energy/sfc low pres, while secondary maximum
occurs to our south and east associated with developing coastal
system and our cwa is left in a relative minimum. The general idea
of likely to cat pops lifting from southwest to northeast acrs our
cwa on Monday night into Tues looks reasonable associated with
initial surge of mid lvl moisture/lift. Given southeast 850mb winds
of 35 to 45 knots, would expect some downslope shadowing along the
western slopes, which is showing up in the GFS qpf. Also, have
started to note a sharp cutoff in deep moisture lifting quickly from
sw to ne acrs our cwa on Tues aftn/evening associated with potential
dry slot, which wl need to be watched, as ridging builds. Given how
this winter has unfolded my initial thoughts would be mainly an
advisory level type event with maybe low end warning for se upslope
areas of the southern/central Greens. Plenty of time for system to
evolve and become better sampled in the days ahead. I would
anticipate guidance to become better locked on a solution this
weekend, along with the finer details of wind speeds/direction and
potential impacts on precip fields. Otherwise, temps wl run near
normal for early to mid week with highs mid 20s to mid 30s and lows
mainly in the mid teens to mid 20s.

 

[JDClapper]

12 hours ago, PA road DAWG said:

Man, idk what is is, but i find it so hard for me to get excited for these type of systems.  Front end snow thump to mix and rain.  

This also doesnt inspire excitement. Its always nice to see things coming into the short rangers hours so you can really get a feel for the precip shield. The globals make storms look so enormous, when it is usually a 4-8 hour event.

[MaineJay]

Could be a neat little Nor-Lun like meso feature passing through somewhere between @Wayuphereand myself with the wave that immediately precedes this thread.  May be just a tad too far SE to be impactful.

  The wave will determine the downstream flow, so it's strength and positioning do play a role for the "main event".

 

 

[MaineJay]

SREF 850mb 0°C spaghetti plot.

 

[StretchCT]

Post on snow maps. Playing around in Accupro they have different ways of producing snow maps. This is based on the 0z GFS run for CT as I'm focused on the southern cutoff point for snowfall and how sharp it is.  The regional map made it look like there was a 20 mile or so distance between 6" and 0"

 

So I looked at it closer up and it is tight.  But used Kuchera.... and now LI is in the mix?

So I went to the hi res, which only has model depth and 10:1

And I'll leave my favorite for last.  Same model has 0-12" for Long Island.

For those wondering about "Cobb Method"

Spoiler

Snow/Liquid Ratio The snow/liquid ratio (SLR) is computed using the 2011 Cobb-Waldsteicher method. 1 We compute the SLR for each member of the SREF by looking at the debiased sounding2 for layers with sufficient moisture (>90% RH with respect to ice) and rising vertical motion (negative omega). If these conditions are met for at least 11 of the 21 SREF members, then we will produce a probabilistic SLR forecast. The spread of the probabilistic SLR forecast is calculated from the standard deviation of the SLR member forecasts. Box-and-whisker plots are then generated from these probabilities. SLR can be computed regardless of whether or not it is cold enough to snow. As a result, it can produce some unrealistic values. We constrain the SLR for each ensemble member to be no more than 30-to-1. Once the standard deviation is used to create the probabilistic SLR, some probability levels can be less than zero. We set any probabilistic SLR values that are less.

https://www.weather.gov/media/mdl/SLR.pdf

And a thesis from Josh Barnwell... if you really want to nerd out.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1013&context=geoscidiss#:~:text=The Cobb method algorithm incorporates,layer of a cloud column.

 

Edited February 24, 2023 by StretchCT

[StretchCT]

Speaking of Josh - here's a indepth look at snow forecasting and it's difficulties

https://www.weather.gov/media/ohx/PDF/Weather101Snow.pdf

 

[Brodozer1]

a true snow event and this place is slow what happened to the days of 300 pages 

[StretchCT]

UKIE has a nice consistent trend fwiw

[StretchCT]

12 minutes ago, Brodozer1 said:

a true snow event and this place is slow what happened to the days of 300 pages 

If the GFS looked like the UKIE we'd have more involvement. But with half of the region getting little to no snow and that half holding the most members, it's gonna be quiet unless it changes

[StretchCT]

CMC looks better than GFS

[StretchCT]

WPC

[telejunkie]

While the cut-off energy for this system is basically on-shore now...the wave that will eventually push it east doesn't come in until Sunday-ish. Feel like things could shift between now and then despite a relatively stable, and consistent handle from models.

[StretchCT]

Haven't seen this in the 4 day forecast in probably a year.  Snow. Just snow.  Chance 100%.

[StretchCT]

Mixed trends on Euro

Euro drying up

R/S lines aren't too different, actually a bit further south today.

[HVSNOWSTORM]

6 hours ago, MaineJay said:

Ukie, as had been the case this winter, unfortunately erroneously often, appears the coldest looking at snowfall distribution.  So grains of salt. 

  It's a more "spread the wealth" outcome. Some of this in northern NE/NY is from previous systems.

It now looks like the Euro so I'd say it might actually get this one. Although I'd agree it's had a rough season for sure.

[JDClapper]

Wpc update just before noon.

[JDClapper]

12z EPS with a big move towards higher probs of measurable white in central PA. Not saying I believe it, but here it is.

[HVSNOWSTORM]

18z Euro snow

[TheComet]

4 hours ago, HVSNOWSTORM said:

18z Euro snow

This is not meant to sound as wish casting, but I’ve found euro/Canadian are better at picking out local features like elevation in this type of scenarios. The gfs/NAM, not so much.

[HVSNOWSTORM]

0z Euro