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
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