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OBS/Totals for 12/26-27 Storm


jm1220
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Just now, SnowGoose69 said:

Long Island is probably still fine.  Not sure about Queens Brooklyn Bronx or NYC though unless that line stops like the 12/3Km NAM showed 

To be honest the precip shield over NJ looks like crap to me with all the holes that are perfect for letting the mid level warm air catch up. The short range models seem to consolidate and fill this in soon, hope they’re right. Sorry to all those guys getting sleet and now we know-we can’t dismiss the NAM when it shows lousy QPF and surging mid level warmth. 

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3 minutes ago, SnowGoose69 said:

Long Island is probably still fine.  Not sure about Queens Brooklyn Bronx or NYC though unless that line stops like the 12/3Km NAM showed 

I know it's still early in the storm but agree leaning lower end of totals for the five boroughs and even lower Westchester. The banding upper westchester through LI seems to be creating a lot of subsidence. 

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2 minutes ago, jm1220 said:

To be honest the precip shield over NJ looks like crap to me with all the holes that are perfect for letting the mid level warm air catch up. The short range models seem to consolidate and fill this in soon, hope they’re right. Sorry to all those guys getting sleet and now we know-we can’t dismiss the NAM when it shows lousy QPF and surging mid level warmth. 

100% spot on.

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12 minutes ago, Rjay said:

National Weather Service Mount Holly NJ

621 PM EST Fri Dec 26 2025

 

.SYNOPSIS...

Low pressure approaches from the west and passes through the

region tonight before departing Saturday morning. High pressure

then passes through the region Saturday afternoon through Sunday

afternoon. A strong low pressure then rides through the Great

Lakes Sunday night into Monday, dragging a strong cold front

through our region. High pressure thereafter, though passing

cold fronts may bring small chances of snow through the rest of

the week.

 

&&

 

.NEAR TERM /THROUGH SATURDAY/...

620 PM update...

Well, that changed quickly. The models that were surging in the

warm air aloft (NAM in particular) seem to have mostly had a

handle on things, at least across our CWA, with most areas

already changed to freezing rain and sleet. Have made a

significant cut to snowfall totals, which necessitated dropping

the warnings for Monroe, Warren, Middlesex and Monmouth

counties. That having been said, we are now starting to get

anxious about ice accumulation, since several more hours of

freezing rain may put some areas in the game for ice storm

warning criteria (1/4 inch). Made some upward adjustments in the

ice forecast and will watch obs closely over the next few

hours.

 

2 PM discussion...

No significant changes were made to the forecast as everything

appears on track taking into account most recent observations

and guidance

 

Winter Storm Warnings remain in place for Monmouth, Middlesex,

Somerset, Warren, Morris, and Sussex County in NJ, and Monroe

County in PA with Winter Weather Advisories all the way down to

South Jersey and Northern Delmarva, though the Advisories on the

southern extent are more for ice than snow.

 

The overarching theme still remains as in impactful winter

storm moves in this afternoon and evening. The key threat will

be widespread travel disruptions during the evening and heading

into the overnight hours.

 

The setup for this storm is an area of low pressure currently

near Western Pennsylvania diving toward the Mid-Atlantic and

moving offshore by Saturday morning. Cold air is firmly

entrenched at the surface as a Canadian high pressure system has

locked in a cold air damming pattern across the Mid Atlantic.

As the surface low digs through the Mid Atlantic it will bring a

widespread mix of wintry precipitation across our forecast

area.

 

Warm air advection in the mid levels will promote lift through

the afternoon and lead to an advancing precipitation shield

moving into western areas by 3 PM or so. Generally, guidance is

showing this leading edge starting out as snow for most areas

with predominantly sleet starting to mix in as a low level warm

nose starts pushing into the region. There still is some

considerable spread in the guidance at this point with respect

to the strength of the warm nose and the extent it pushes

northward. Ensemble soundings in DESI suggest that the warm

noise will push close to I-78 but stays just south. The only

guidance that pushes the warm air further north is the NAM and

it certainly can`t be discounted given the historical record

when it comes to boundary layer temps in previous winter storms

across the Mid Atlantic. However, it does not appear to be

initializing well compared to upstream observations, so while

not discounting entirely, it would be surprising if that

solution pans out.

 

Further south across the Philly Metro area, the ensemble

guidance confirms deterministic guidance with a modest 0.5-1.5C

warm noise setting up over the southern portion of the forecast

area.

 

What all this means is that in areas north of I-78, we`ll

likely see mostly snow throughout the event. From roughly Philly

to I-78, we`ll see a widespread mix of snow and sleet generally

favoring sleet as there`s warm air starting the melting process

aloft, and for areas south and east of Philly it will be mostly

a rain event.

 

As for specific totals, the challenge in addition to ptype is

the presence of a good 850mb deformation band expected to

develop as a result of strong 700mb fgen. This points to the

development of a mesoscale band that sets up somewhere between

I78 and the Catskills. Within that band, we`ll see orographic

lift and snowfall rates of 1- 2" an hour. Ensemble guidance

suggests that the band will most likely be pushing through

between 7-11pm but could arrive as early as 5pm.

 

This leads to snowfall totals in the warned area ranging from

4-6 for the lower elevations and southern portion of the

warning, with amounts in the 6-10 range in the northern portion.

Highest confidence to see those higher totals are in northern

Sussex and Morris County as well in local higher elevation

spots. All of this remains subject to the warm nose staying

south however so the failure mode for this forecast is somewhat

high. Regardless if some spots in the warning do not reach the

6" criteria, the presence of inch an hour snow rates in the

night time rush hour on a Friday suggest high potential for

travel disruptions over the holiday weekend.

 

Looking further south, its really all about how strong the warm

nose is. Soundings and guidance have honed in on the idea that

for most of this area, its going to be predominately a sleet

storm. Current forecast has about 2 to 5" south of I-78 to about

I-195 in NJ and from Monroe County south to the Allentown area

in PA. No changes to the Winter Weather Advisory in this area.

 

Around the Philly metro area out to about Reading and points

south in PA and into South Jersey, generally a coating to 2

inches of snow/sleet are expected. Areas along and west of the

I-95 corridor also see some light icing, up to a 0.05" or so,

though higher amounts over a tenth and up to two tenths are

anticipated over portions of Chester and Berks County (thank

cold air damming for that). Thinking the stronger dynamics and

colder air is more off to the north, limiting snow totals with a

brief period of snow and a prolonged period of sleet. While

less snow is expected, it will be quite messy with the

combination of snow, sleet, and freezing rain. Winter Weather

Advisory remains in effect for this area.

 

Going further south to far South Jersey, and northern Delmarva

there is increased confidence in potential for icing. Low-level

cold air will struggle to be removed as warm-air advection at

the surface is not particularly strong. The result will be a

period of freezing rain and a Winter Weather Advisory for icing

rather than snow in Salem/Cumberland County in NJ, New Castle

County in DE, and Kent County in DE. HREF Probability is around

60-80% to see measurable ice accumulation in these spots

tonight. While there will be some snow at onset, significant

accumulations are unexpected, with amounts only up to an inch.

 

For the South Jersey coast and lower Delmarva, this will

primarily be a rain event. While some flakes are possible at

onset, a quick change to rain is expected.

 

Precipitation tapers off Saturday morning as temperatures

struggle to warm into the 30s. For areas with a fresh snowpack

anticipate sub freezing max temps while areas further south

should be able to warm into mid to upper 30s

Wow

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1 minute ago, Dark Star said:

Changed to sleet here in Garwood, central Union County NJ.  Tell me its because of the light precipitation and not that the atmosphere is warming at upper levels...

I mean doesn't the fact it's sleeting mean there's some mid-level warmth in there?

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Lets not go nuts congratulating the NAM guys, i mean christ this is just a big a bust in the other direction. The warm mid levels were def underestimated by some models. But claiming the nam nailed anything in this subforum is probably luck, because wtf is this nonsense lol

IMG_4460.png

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Just now, BxEngine said:

Lets not go nuts congratulating the NAM guys, i mean christ this is just a big a bust in the other direction. The warm mid levels were def underestimated by some models. But claiming the nam nailed anything in this subforum is probably luck, because wtf is this nonsense lol

IMG_4460.png

Mount Holly said congrats NAM

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1 minute ago, BxEngine said:

Lets not go nuts congratulating the NAM guys, i mean christ this is just a big a bust in the other direction. The warm mid levels were def underestimated by some models. But claiming the nam nailed anything in this subforum is probably luck, because wtf is this nonsense lol

IMG_4460.png

That counts slwet..post pivitol

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