Overnight:
A chance of snow. Cloudy, with a low around 28. East wind around 5 mph. Chance of precipitation is 30%. Little or no snow accumulation expected.
Tuesday:
A chance of snow before 7am, then sleet between 7am and noon, then rain. Cloudy, with a high near 34. East wind 5 to 10 mph. Chance of precipitation is 90%. Little or no snow accumulation expected. Little or no ice accumulation expected.
Tuesday Night:
A chance of rain before 1am. Cloudy, with a low around 31. Northwest wind 5 to 10 mph. Chance of precipitation is 30%. Little or no ice accumulation expected.
Wednesday:
Partly sunny, with a high near 40. Northwest wind around 10 mph.
Wednesday Night:
Mostly cloudy, with a low around 24. Northwest wind 10 to 15 mph.
Thursday:
Mostly sunny, with a high near 31.
Thursday Night:
Mostly clear, with a low around 18.
Friday:
Mostly sunny, with a high near 28.
AREA FORECAST DISCUSSION
National Weather Service Mount Holly NJ
400 AM EST Tue Jan 26 2021
Weather Synopsis:
Weakening low pressure will move into the Northeast and Mid-Atlantic
regions later today before moving offshore tonight. Low pressure
develops near the Carolinas later Wednesday and rapidly intensifies
as it tracks out to sea through Thursday. High pressure builds into
our region Friday night and Saturday, then a storm system is
forecast to arrive later Sunday and Monday.
Near Term:
THROUGH TONIGHT -
A mid level short wave trough was located over Iowa and vicinity
early this morning. The feature will progress to the east passing
over the Great Lakes and moving toward northern New England late
tonight. Weakening surface low pressure is forecast to move from
Ohio early this morning to western New York tonight. A secondary
surface low is expected to slide off the Virginia coast today.
The latest observational and model trends regarding the
precipitation are suggesting that little will fall in our region
early this morning. The dry air in place should continue to prevent
any light precipitation that develops overhead from reaching the
ground in most spots.
The precipitation moving across southern Virginia early this morning
will likely remain to our south. We will need to wait for the
precipitation in the upper Ohio River Valley to reach us during the
mid to late morning. It is expected to blossom a bit as it
approaches in the developing isentropic lift. Our best chance for
precipitation is from late this morning into this evening. Lingering
light precipitation is anticipated for tonight and it should come to
an end gradually from southwest to northeast.
We have not made a great deal of change to the precipitation type
forecast. However, with the later arrival of the precipitation, the
potential for a light ice accumulation has diminished in southern
New Jersey, and in the city of Philadelphia. We will remove
Philadelphia, and the New Jersey counties of Salem, Gloucester,
Camden, Burlington and Middlesex from the Winter Weather Advisory.
We have made only modest adjustments to our ice forecast at this
point. The expected mid level drying may be a bit slower than
previously thought, so the snow may persist a little longer in the
Poconos and in far northern New Jersey. We have increased snow
totals there with some locations in the higher terrain expected to
receive 2 to 3 inches of snow.
Short Term:
WEDNESDAY THROUGH THURSDAY NIGHT -
It gets milder for Wednesday then much colder air begins to
overspread our area for Thursday.
A very active flow regime continues with a closed low traversing
southern Canada Wednesday into Thursday. Meanwhile, southern stream
energy sliding across the Ohio Valley region Wednesday shifts due
eastward and emerges off the Mid-Atlantic coast Wednesday night into
early Thursday. A closed low in the vicinity of the Canadian
Maritimes along with the southern stream energy not phasing with the
northern stream results in a surface low well to our south tracking
right out to sea. Given the blocking Canadian Maritimes closed low
and a lack of phasing, the surface low cannot turn up the coast. As
a result, the precipitation shield is forecast to pretty much bypass
our region to the south and east Wednesday night into Thursday. We
still cannot rule out some northern edge light snow reaching into
our far southern zones, therefore kept some 20-30 PoPs in for now.
Prior to the above, a weak low off the southern New England coast
may pivot southward with a weak surface trough extending
northwestward from it and near our northern and eastern zones for a
time Wednesday. Some guidance wants to produce a little light
snow/rain shower activity with this along the coast, but overall it
looks disorganized and therefore held off on adding a mention for
this. However, there could be a little light snow or freezing
drizzle across the far northern areas early Wednesday with lingering
low-level moisture as the weak system aloft translates offshore.
Otherwise, clouds should break for some sunshine Wednesday.
As an ocean storm rapidly intensifies Wednesday night and Thursday,
strong high pressure will be building into the Ohio Valley. This
places our region within a tight pressure gradient. The combination
of strengthening cold air advection will result in efficient mixing
especially later Wednesday night and particularly on Thursday. The
forecast soundings continue to show winds mixing down to the surface
to be about 30 knots, therefore increased the wind and wind gusts
especially for Thursday. Temperatures on Thursday should only rise
into the 30s across the area (upper 20s in the higher elevations),
and with gusty winds the wind chill values will be in the 20s and
teens (single digits in the higher elevations). The winds should
settle some Thursday night, however a lingering breeze will drive
wind chill values down into the single digits across the area (below
zero in the higher elevations).
Long Term:
FRIDAY THROUGH MONDAY -
Summary...Potent ocean storm results in very cold and windy
conditions Friday into Saturday, then a storm system Sunday into
Monday may bring a wintry mix.
Synoptic Overview...An active flow regime with a robust northern
stream closed low traversing the Northeast Friday, then this system
gradually lifts out Saturday and Saturday night. An amplifying upper-
level trough in the Plains and Midwest Sunday shifts eastward and
may close off as it nears the upper Ohio Valley Sunday night.
Meanwhile, a ridge in front of this trough results in strong high
pressure across portions of eastern Canada. The entire trough slides
eastward and moves across the East Coast early next week, with
surface low pressure tracking up the Ohio Valley then a secondary
low developing over the Carolinas which tracks northeastward Sunday
through Monday.
For Friday and Saturday...The Canadian closed low is forecast to
dive across the Northeast Friday with robust cold air advection
occurring. This will also maintain a tight pressure gradient and
efficient mixing within a strong wind field. As a result, Friday
will be very cold with a gusty wind and very drier air as dew points
will be in the teens and single digits. The entire area should
struggle to get above freezing Friday. There should be some lake
effect activity which may try to reach into the Poconos, however the
flow may become more northerly and therefore limit this activity to
much closer to the eastern Great Lakes. The winds then subside
Friday night and Saturday as high pressure slides across our area
and gradually weakens. The cold air advection weakens Friday night
and Saturday, with some improvement in the temperature department
Saturday but still on the cold side. The next in a series of systems
then slides across the U.S. through Saturday night approaching our
area near daybreak Sunday. Cold and dry high pressure still sitting
over our area should tend to hold back the incoming warm air
advection driven precipitation.
For Sunday and Monday...An amplifying upper-level trough which may
end up closing off shifts east from the Midwest to Ohio Valley. This
feature will drive surface low pressure up the Ohio Valley, however
strong short wave energy rotating through the base of the trough
along with strong high pressure wedging southward east of the
Appalachians results in a secondary surface low development in the
Carolinas. The evolution of these features will be key to our
sensible weather, especially given a cold and dry air mass gradually
departing over our area. In addition, surface high pressure wedging
southward from eastern Canada if strong enough may keep colder air
locked in longer as precipitation overruns it. The track of the
surface low will also determine how much low-level warming can
occur. As of now, the signals in the model guidance suggests a snow
to a wintry mix across much of the region to even some rain across
portions of the area. The timing and other details are far less
certain, therefore kept PoPs in the chance range with a general
rain/snow mention.
Click for full NWS PHI Office Area Forecast Discussion
