Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
639 am EST Thursday Dec 5 2013
a weak warm front will lift north of the area today. A frontal
boundary is expected to move across th East Coast Thursday night
into Friday morning and move to our south over the weekend. High
pressure will briefly build across the northeast Saturday night into
Sunday. An area of low pressure will develop across the lower
Mississippi River valley, then strengthen as it moves northward into
the Great Lakes Sunday night. This will lift another frontal system
across our region Monday. A couple of weak clipper systems may skirt
across the northern tier of the country next week before high
pressure builds across the region late in the week.
Near term /until 6 PM this evening/...
a dense fog advisory has been issued for much of the area through
the morning. Visibilities have continued to drop below one-half
mile over an ever widening area. Conditions will be slow to
improve since surface winds will be light much of the morning.
Low pressure will be moving across the upper Great Lakes and Ontario
Canada today. The attached warm front will be crossing the area. Low
clouds/drizzle and light rain are expected this morning and then
some improvement this afternoon as the southern parts of the area get
into the warm sector. Areas to the far north may remain in the
frontal zone into the afternoon with a continuation of low
clouds/light rain there. Temperatures today will be well above
normal with low/middle 60s central/south and middle to upper 50s north.
Short term /6 PM this evening through 6 am Friday/...
the warm front will have lifted north of the area by tonight. A cold
front will move into the western areas after midnight and cross through
the rest of the region by around dawn. Mostly likely or categorical
probability of precipitation for showers will be across the area. Probability of precipitation across the southern
Delaware-Maryland-Virginia will remain in the chance range for now. It will remain mild
overnight before temperatures drop behind the front. The colder air
will arrive across the western areas by dawn before spreading east.
Winds will shift from SW to northwest behind the front. Overall precipitation through
12z Sat will total .10 across the del valley and closer to .50 in
the southern Poconos.
Long term /Friday through Wednesday/...
an active weather pattern for a good portion of the long term
forecast with a break possible toward the end.
The beginning of the long term period starts off with a frontal
boundary that will be moving off the East Coast early Friday
morning. The front will slowly push offshore, but there will still
remain quite a bit of moisture lagging behind the front as South
West flow aloft will keep a good moisture influx across the area.
There may be a brief break in precipitation Friday morning as one
short wave/vorticity impulse slides to our north, before another
round of precipitation begins later during the day into Friday
night as a second short wave/vorticity impulse approaches and
passes through the area. Precipitation will likely start out as rain
as temperatures will be fairly warm early in the day, before
changing over to a wintry mix by Friday evening and overnight. In
fact, the high temperatures will likely occur early in the day as
temperatures are expected to drop during the day. There should be
enough of a cold surge behind the front to allow all precipitation
to change over to a rain/sleet or snow/sleet mixture. There is the
possibility for some freezing rain to occur, mainly for our far
Saturday into Saturday night may end up being dry for most areas as
the front will have pushed to our south and high pressure begins to
briefly build to our north. Drier air is expected to build across
the area and there will not be much of any vorticity impulses to
help create any shower activity. The only exception is our southern
areas where there may be some showers early Saturday morning as the
last of the precipitation pushes southward.
The high pressure lifts into the northeast on Sunday, which will
allow a warm front to begin lifting into the area late Sunday into
Sunday night as an area of low pressure moves into the Great Lakes
region. As the low continues to lift into southeast Canada on
Monday, it will drag a cold front across our area. Several short
waves/vorticity impulses are expected to affect the area during this
period which will allow periods of precipitation to occur through
the time frame. With cold air in place, this precipitation will
possibly start out as a wintry mixture for Sunday into Sunday night,
before possibly changing to rain Monday as warmer air moves in. Our
northern zones could hold on the the wintry mixture longer into
Monday morning as cold air could get dammed up before the warm surge
pushes through. The precipitation should begin to dissipate Monday
night into Tuesday as the frontal boundary pushes farther offshore.
There still will be a small chance however until the front and it's
moisture completely pull away.
Drier weather is currently expected for Wednesday as high pressure
begins to build into the area from the west. A weak clipper system
may skirt to our north on Wednesday, but is not expected to affect
Aviation /12z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
The onshore flow and a warm front crossing the region today do not
fare well for great flying conditions. IFR ceilings and lower visibilities in
fog are already fairly widespread across the area. Conditions may
improve for awhile this afternoon...especially south where VFR may
return for several hours (low confid). Winds will veer from east/southeast
early today to srly this afternoon...then to SW tonight. A cold
front will move through tonight and winds will go wrly/nwrly behind
it. Improvement in conditions will arrive behind the front very late
Friday-Friday night...VFR possible early, becoming MVFR/IFR with
periods of rain by afternoon/evening, possible changing to wintry
mix overnight Friday. Gusty winds 15-20 knots possible.
Saturday-Saturday night...mostly VFR. Gusty winds 15-20 knots possible.
Sunday-Monday night...MVFR/IFR probable with rain/wintry mix
Sunday into Monday. Possible improvement Monday night.
high pressure will remain well offshore today and tonight. Low
pressure will be winding up over the Great Lakes heading for
Ontario. The pressure gradient over the waters slowly improves
today...behind the departing warm front. It appears the low-end Small Craft Advisory
gusts will be over the waters tonight and then the seas will be up
close to 5 feet by late tonight and into Friday. Therefore...we will
raise the Small Craft Advisory flag for tonight and carry it on into Friday. Scattered showers
today and a better chance for showers tonight as a cold front
approaches. Patchy fog expected on the waters today with the higher
dew points arriving over the chilly waters.
Friday-Monday...Small Craft Advisory, or near advisory, conditions
are possible through the period as seas may remain near 4-6 feet and
winds could gust 20-25 knots.
PA...dense fog advisory until 11 am EST this morning for paz054-055-
New Jersey...dense fog advisory until 11 am EST this morning for njz013>024-
Delaware...dense fog advisory until 11 am EST this morning for dez001>004.
Maryland...dense fog advisory until 11 am EST this morning for mdz008-012-
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EST Friday