February 2nd: Light Snow Event

Alex if the 12z NAM verifies verbatim we’d all be 2-4” easy.

Big if though

syosnow94 wrote:Alex if the 12z NAM verifies verbatim we’d all be 2-4” easy.  

Big if though

Yupp, i strongly dislike changeover events (wet ground, NW winds cause downsloping and erode the precip, etc), however this event has strong jet energy moving over our area which could mitigate those factors (NAM is showing this), so we will really have to nowcast. But regardless, a flash freeze will occur. Ground will not dry by the time the cold air crashes in obviously.

aiannone wrote:

syosnow94 wrote:Alex if the 12z NAM verifies verbatim we’d all be 2-4” easy.  

Big if though

Yupp, i strongly dislike changeover events (wet ground, NW winds cause downsloping and erode the precip, etc), however this event has strong jet energy moving over our area which could mitigate those factors (NAM is showing this), so we will really have to nowcast. But regardless, a flash freeze will occur. Ground will not dry by the time the cold air crashes in obviously.

12k and 3k NAM both show a nice hit

Hi-Res:

It looks like a 1 to 3 inch event in my eyes. There may be pockets of towns who see 3"+ if precip rates intensify.

Frank_Wx wrote:It looks like a 1 to 3 inch event in my eyes. There may be pockets of towns who see 3"+ if precip rates intensify.

Concur

aiannone wrote:Hi-Res:

Is the 850 freezing line visible on this map and if so, could someone please point it out for me?

And more directly, is coastal NJ in as bad a shape as it looks based on the 32 line?

(Edit: OK, now that I looked at the title of the map after my post, I should rephrase the 1st question to: Can someone point it out for me please?)

(2nd Edit: Wait a minute, is the 32 the 850 freezing line? I thought that was the surface level freezing line. I'm confused...again. Ha ha. This is a rather humbling foray!)

Thank you Sroc...so, I guess the cold air isn't much of a issue.

I'm with Scott on this one, and have been. I like an enhancement of the precip field, but dissimilarly to the most recent event, I like this enhancement from east-central PA eastward, and from the approximate latitude of 295 northward. I think 1-3" would be a good call, as Frank had also stated. Intensifying mid-level energy in response to a change in the trough's axial tilt combined with a quick moving but potent jet max with the region defined above located in the overlap of forcings will allow the precip field to expand seemingly out of nowhere as, and after the low-level cold gets in.

SENJsnowman wrote:Thank you Sroc...so, I guess the cold air isn't much of a issue.

At least it wouldnt be for this model run verbatim.

rb924119 wrote:I'm with Scott on this one, and have been. I like an enhancement of the precip field, but dissimilarly to the most recent event, I like this enhancement from east-central PA eastward, and from the approximate latitude of 295 northward. I think 1-3" would be a good call, as Frank had also stated. Intensifying mid-level energy in response to a change in the trough's axial tilt combined with a quick moving but potent jet max with the region defined above located in the overlap of forcings will allow the precip field to expand seemingly out of nowhere as, and after the low-level cold gets in.

GFS not as enthused, but I think the NAM is better at picking up on the several important factors you are pointing out here

Scott, Rb great points made here.
This is a anafront passage with a vigorous jets streak that will help enhance this on the backside.
1" for NW NJ to 3" out towards where else LI.
Should be a fun commute tomorrow morning.
Hi Res Models way to go here.

amugs wrote:Scott, Rb great points made here.
This is a anafront passage with a vigorous jets streak that will help enhance this on the backside.
1" for NW NJ to 3" out towards where else LI.
Should be a fun commute tomorrow morning.
Hi Res Models way to go here.

I'm worried about the a.m. too, rain going into a deep freeze will bring icing on the roads with the snow, not going to be fun for sure.

AND here is the euro - my god this model has been wonky at best!
Cold Press at work

Euro is a solid 1-3".
Mike (Math23x7) did you see those maps?

While probably a low chance, I wouldnt be surprised if a WWA is issued for NYC east at the afternoon update. Although there may only be 1-3", it will coincide with the morning commute so they may want to raise extra attention beyond a Special Weather Statement

Here's NWS take on the two upcoming events,and even touching on a 3rd event tues-wed:


.NEAR TERM /THROUGH TONIGHT/...
Updated temperatures/dewpoints and winds with this afternoon
update to reflect current conditions.

Otherwise, broad longwave trough over the lower 48 will sharpen
over the next 24 hours as a mid level shortwave over the
central Plains strengthens and moves towards the Mid Atlantic
states. At the sfc, a cold front will approach from the west.
The combination of frontal forcing, the exit region of a
150-160kt upper jet and mid level frontogenesis will contribute
to the blossoming of pcpn early this evening and continuing
overnight.

The first half of the day will be cloudy but should be dry with
the local area warm sectored. May start to see pcpn in the form
of rain move into areas well NW of NYC this afternoon, but the
better chances will hold off until the front and better upper
dynamics move closer to the region. Pcpn ahead of the front will
be in liquid form but it also lags behind as the exit region of
the upper level jet moves over the area late tonight. Most
model guidance indicate QPF between 1/10 and 1/3 of an inch,
highest amounts east, except for the SREF mean which is around
1/4 of an inch higher. This is interesting because the upper jet
is weaker as is the mid level frontogenesis. So stronger
dynamics don`t appear to be the reason for the higher values.
It`s progression is a bit slower which could be the contributing
factor.

The tricky part of the forecast is how quickly the column cools
for the rain to change over to snow and the subsequent
accumulation amounts. GFS soundings look more reasonable given
the scenario with changeover occurring around 07z in NW zones,
09z in the NYC metro area and 10-11z in southern CT and Long
Island. Since the changeover is anticipated to be late, only
expect light snow accumulations, generally less than an inch at
most locations, although can`t rule out a few 1-2" accumulations
especially across SE CT and eastern LI.

&&

.SHORT TERM /FRIDAY/...
Any lingering pcpn will end during Fri morning with
strengthening NW winds from strong CAA. Winds of 15-25mph with
30-35mph gusts will be common during the day. Highs will only be
a few degrees higher than tonights lows, generally mid to upper
20s, possibly lower 30s in the NYC metro area.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Zonal flow aloft Friday night and Saturday, with no significant
shortwaves embedded in the flow, should allow for dry conditions
both periods. Temperatures will be very cold for this time of year.
Lows Friday night should generally be from around 5 to 15 above,
with wind chills from 5 below to around 5 above (around 0 to 5 above
in NYC). Highs on Saturday should be around 10 degrees below normal:
mainly from the mid 20s to around 30.

SW flow sets up aloft Saturday night, with low level warm advection
bringing some spotty light snow to mainly the NW 1/2 of the CWA late
Saturday night. A 700-500 hPa shortwave coupled with increasing
isentropic ascent will produce more widespread precipitation on
Sunday, especially in the afternoon. A 700-500 hPa trough then
approaches Sunday night then lifts to the NE on Monday. This will
help drive the intensification of a coastal low of the Mid Atlantic
Coast Sunday night. This coastal low tracks SE of Long Island, but
probably inside the 40N/70W benchmark Sunday night, before lifting
NE on Monday. There is some uncertainty on this timing, with some
suggestion that things might occur 6 hours or so faster than
current forecast.

In terms of sensible weather Sunday-Monday morning. Will see
precipitation change from snow to a wintry mix across the interior
and from snow to rain elsewhere. There are then differences in how
quickly low level cold air returns Sunday night. For now keep
transitions back to all snow across mainly far northern portions of
interior zones Sunday night, with a wintry mix possible across the
remainder of the northern/far western zones - with NYC/Long
Island/Coastal SE CT staying all rain. Precipitation ends on Monday
morning, as snow across interior zones/coastal SW CT zones. A wintry
mix over E NE NJ/into NYC and as plain rain over Long Island/coastal
SE CT. For now to early to specify amounts, but there is some
potential for an advisory level to possibly a warning level snowfall
across mainly northern interior zones from Sunday into Monday
morning. Will address this potential in the HWO.

Zonal flow with no shortwaves of note should allow for Monday night
to be dry.

Low level warm advection sets up on Tuesday. For now appears that
most precipitation should be limited to the N/NW of the region,
except for maybe some light snow over far W Orange County.

Continuing low level warm advection and the passing of a strong low
level jet (40-50 KT) should bring some snow to most of the area
Tuesday night, with potential for some rain to mix in across
NYC/southern Long Island. An approaching 700-500 hPa trough
Wednesday should sharpen low level flow more towards the S-SW - so
low level warm advection should be sufficient to turn all
precipitation to rain. For now there is too much uncertainty to
gage how much, if any snow ends up accumulating Tuesday night and
Wednesday.

GreyBeard if this forecast verifies it will be like a series of hard punches to the gut. Give me 60 on Christmas instead of this for gods sake

Welp the 18z NAM just gave the finger to the NWS and strongly supports our collective thinking that a nearly board-wide 1-3" event is in store for tonight. Happy thoughts, Syo, happy thoughts!!

Actually looks better aloft than its 12z predecessor.

rb924119 wrote:Welp the 18z NAM just gave the finger to the NWS and strongly supports our collective thinking that a nearly board-wide 1-3" event is in store for tonight. Happy thoughts, Syo, happy thoughts!!

And since they are model huggers, they might actually adjust the forecast

syosnow94 wrote:GreyBeard if this forecast verifies it will be like a series of hard punches to the gut.  Give me 60 on Christmas instead of this for gods sake

I agree sysos, however as many have stated, the NWS tends to lean more to the conservative side, which is hopefully what will happen. I was hoping for a repeat of the cold we had back in early Jan.Something the main guys on the forum are still bullish about. Time will tell I guess.

GreyBeard wrote:

syosnow94 wrote:GreyBeard if this forecast verifies it will be like a series of hard punches to the gut.  Give me 60 on Christmas instead of this for gods sake

I agree sysos, however as many have stated, the NWS tends to lean more to the conservative side, which is hopefully what will happen. I was hoping for a repeat of the cold we had back in early Jan.Something the main guys on the forum are still bullish about. Time will tell I guess.

Rb and aianonne filled in the blanks while I was responding to you lol.

Soundings show a changeover around 6am is in NNJ and cold air driving in just before this. If so it could be a treacherous commute manana. No one is really talking about this on SM etc.

Upton looking like they are ticking up amounts for tn, and also went colder for the coast sunday night lol

New Update:
As the front pushes eastward overnight, temperatures will drop
rapidly resulting in the rain becoming a wintry mix across the
entire area before changing to all snow. The changeover is expected
to occur around 1 to 3 am across areas northwest of the NYC metro
area, around 3 to 4 am across NYC metro area and 4 to 5 am across
Connecticut and Long Island. Snowfall accumulations should be
between 1 to 2 inches but, can`t rule out some locations seeing up
to 3 inches if any heavier snow bands develop or if the rain change
over to snow is an hour earlier than expected.