Area forecast discussion
National Weather Service Mount Holly New Jersey
924 PM EST Wednesday Dec 11 2013
a reinforcing cold front from the Great Lakes will move through
overnight. High pressure will then build across the northeast
Friday into Saturday and move northeast into the Canadian
Maritimes by Sunday. A low pressure system from the southwest will
move east over the lower Mississippi Valley Saturday before
turning northeast where it will strengthen off the middle Atlantic
coast Sunday. This storm will then quickly move into the Canadian
Maritimes by Monday allowing high pressure to build into the area.
A possible quick clipper system on Tuesday will be followed by
high pressure which will begin to push in again Wednesday.
Near term /until 6 am Thursday morning/...
estf update dropped temperatures a bit over the next couple of
hours based on current conditions. Overnight some cloudiness along
with an expected increase of winds makes temperature adjustments
slightly less confident. We did lower them a bit to make them
flow from current readings. We added some flurries west based on
observations in western PA. The latest hrrr and rap dont seem to
impressed by it, but snow that is reaching the ground (even if its
not going to be at .01 west/e) is slightly greater than their
A mainly dry cold front and associated short wave/vorticity impulse
are expected to cross the area overnight tonight. This should
bring an increase in cloud cover to much of the area overnight,
and with a limited amount of moisture, a few isolated snow
showers/flurries are possible across our northern and western
areas. Any snow that does fall should be relatively light,
although a coating is possible, mainly for our highest elevations.
It will continue to remain cold, especially with the snow cover
across the area. Winds may increase toward daybreak behind the
frontal boundary, which combined with the winds will create low
wind chill temperatures. Wind chills should drop to the single
digits to low teens for most areas, with some minus single digits
across our higher elevations.
Short term /6 am Thursday morning through 6 PM Thursday/...
a dry, cold, breezy day is expected for Thursday. The
aforementioned cold front will push offshore early in the morning,
while high pressure begins to push in from the west. This will
allow west-northwesterly winds to increase across the area.
Meanwhile, thicknesses will lower across the area as a trough
aloft swings across the area. This will keep temperatures quite
cold, and with the breezy winds, wind chills will remain low for
the day. Wind chills will generally be in the teens, with some
single digits possible, mainly for higher elevations. No
precipitation is expected as drier air aloft moves across the
area, although an increase in cloud cover is possible during the
Long term /Thursday night through Wednesday/...
the large-scale pattern for the extended period continues to
feature a long-wave trough over the central/eastern U.S. With shortwave
features moving through it. Temperatures will be below normal and
precipitation will be mostly lacking expcept for the weekend storm system
discussed below. In general the wpc guidance was follow for
populating the longer-term grids.
The closed low currently off the southern cal coast is forecast to be
ejected eastward across the southwestern U.S. On Friday...with both the kicker
and kick-ee continuing eastward across the central and eastern U.S. On Sat
and Sunday. Models generally incdc that low/middle level warm
advection, upward vertical velocity and near-Sat relative humidity will arrive over the forecast
area early on Sat morning. Model quantitative precipitation forecast hangs back a bit and may be too
slow. Have introduced chance probability of precipitation in the grids prior to 12z on Sat.
At that time temperatures at the surface and aloft should be cold enough for
Warm advection will increase during the day Saturday and the precipitation
should turn over to rain for areas mainly S/east of phl. Warm
advection above the surface will continue Sat night but sub-freezing air
at the surface may be hard to dislodge Sat night for areas north/west of phl.
Thus a mixed bag of precipitation is likely for those areas. A few inches
of snow/ice accumulation is possible as the surface low moves northeastward off
the middle-Atlantic coast and deepens. Also there is the potential
for fronto-general to play havoc with snow amounts as it did last Sunday.
Most precipitation is expected to be over by Sunday morning although the
lastest European model (ecmwf) indicates it may hold on through part of the day. Forecast
grids have chance probability of precipitation with rain shower- southeast light snow shower norhtwest.
A fast moving clipper system across the Great Lakes on Tuesday could bring
a chance of light snow to northern areas Tuesday or Tuesday night. Otherwise high
pressure will provide fair weather with moderating temperatures through the middle of
Aviation /02z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR conditions expected through the period. High level clouds early
tonight, before lower clouds move in overnight with a dry frontal
passage, but still VFR. Additional cloud cover is possible Thursday,
but should remain VFR.
Gusty winds this afternoon will drop off overnight, before becoming
gusty again on Thursday behind the frontal passage.
Friday...VFR conds with west wind around 10 miles per hour.
Saturday and Sunday...conds deteriorating to IFR on Saturday with
mixed precipitation types and fog. East winds around 10 miles per hour on Sat will
shift to northwest 15 to 20 miles per hour on Sunday as the storm moves offshore.
Conds should improve to VFR again by Sunday afternoon.
Monday...VFR conds with light winds.
the Small Craft Advisory for the northern waters
remains in effect although winds have dropped off below advisory
levels for now. The winds will increase later this evening into
the overnight hours and continue into Thursday. A Small Craft
Advisory has been issued or the remainder of the waters, including
the Delaware Bay. Winds are expected to increase overnight behind
the frontal boundary, and continue into Thursday.
Friday...Small Craft Advisory conditions may continue through
early morning but winds and seas should subside below Small Craft Advisory by
Saturday and Sunday...a storm is forecast to develop off of our
coast late Saturday into Sunday then move toward the Canadian
Maritimes. At least a Small Craft Advisory will likely be needed
in northwest winds behind the storm from Sunday evening into Monday.
Monday...winds and seas should subside as high pressure moves over
Marine...Small Craft Advisory until 7 am EST Friday for anz452>455.
Small Craft Advisory until 7 am EST Friday for anz450-451.
Small Craft Advisory from 5 am to 6 PM EST Thursday for anz430-