Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
638 PM EST Tuesday Dec 1 2015
a warm front will lift through our region overnight. A cold front
will then move through our region late Wednesday, as low pressure
intensifies to our northeast Thursday into Thursday night. High
pressure builds over our region on Friday and continues through the
weekend into next Monday. Another storm system approaches the region
Near term /until 6 am Wednesday morning/...
a rather moist airmass remains across the area ahead of an incoming
warm front. The dew points are increasing well into the 50s across
portions of the southern zones, and this is where more fog seems to
be developing so far especially as the flow diminishes some.
Otherwise, some fog is expected through the overnight with probably
the higher terrain and the southern areas having the better chance of
patchy dense fog occurring. As of now, we are not anticipating
widespread dense fog to develop.
We are mostly between short waves now with the next one scheduled to
arrive after about 06z. As the lift has waned, we may see drizzle as
opposed to rain. To keep it simple as we are anticipating times of
light rain or drizzle, we kept probability of precipitation mostly in the categorical range
and carried periods of rain and drizzle. The temperatures may not
change much through the overnight from where they are this evening.
The hourly grids were adjusted based on the latest observations
which included higher dew points for many areas. The lamp/lav
guidance was blended in to help assist.
Short term /6 am Wednesday morning through 6 PM Wednesday/...
Wednesday will continue to be a cloudy, rainy day across the area.
As one short wave/vorticity impulse lifts out of the area during the
early morning, another will be right on its tail later in the
morning into the afternoon. There could be a break in the rainfall
during the early to middle morning hours, but rainfall is expected to
develop again and move into the area by late morning into the
afternoon. A cold front will be making its way toward the area
during the day, so this could help focus the precipitation and lead
to a period of more moderate rainfall during the day, especially for
eastern Pennsylvania and northern New Jersey where rainfall amounts
of 0.50-1.00 inches could be possible. Southern New Jersey and
Delaware-Maryland-Virginia could see 0.25-0.75 inches. The good thing is the rainfall
should fall over a fairly prolonged period, so we do not expect any
flooding problems, although there could be ponding on roadways
and poor drainage areas.
Long term /Wednesday night through Tuesday/...
a cold front will approach from the west on Wednesday evening while
low pressure starts to develop over our region. Precipitation
continues into Wednesday evening, ending as the front moves
through. The low pressure area will intensify as it moves toward
New England resulting in strong northwest flow for Thursday into
High pressure builds into the region on Friday and continues through
the weekend into next Monday. Temperatures will be close to seasonable
norms. No precipitation is expected in this time frame.
A storm system will approach from the west on Tuesday, bringing the
next chance of precipitation to the region.
Generally used full model blend for this time period. Used wpc
probability of precipitation for day 7 forecast timeframe.
Aviation /00z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
Tonight...IFR/LIFR ceilings, however some terminals may improve to
MVFR for a time this evening. Periods of rain and drizzle will
continue, which will reduce the visibilities into the MVFR/IFR
range. Some fog will also reduce the visibilities. Easterly winds 4-
8 knots, becoming light and variable or locally light southerly.
Wednesday...IFR/LIFR conditions /visibilities at or below 1sm
possible in the morning with fog/ continue with rain/drizzle
potentially becoming more showery in the afternoon as a cold front
arrives. Some of the rain could be moderate to heavy at times. South
or southeast winds 4-8 knots turning southwesterly later in the
Wednesday night...starting as IFR with low ceilings and rain, but
by late Wednesday night conditions should become VFR. Abrupt shift
to westerly winds possible with the cold front on Wednesday night.
Thursday through Sunday...mostly VFR conditions expected.
Small Craft Advisory remains in effect for the Atlantic coastal
waters. The southern half will continue with their end time of 5 am
Wednesday as seas should be below 5 feet by that time. The northern
half was extended through 9 am Wednesday as seas may linger there a
little longer. Winds should lower this evening, but since there
remains some gusts around 25 knots, we will not convert to hazardous
seas yet. There should be a long enough period during the day
Wednesday when seas will be below 5 feet, so we will not extend it
through the day.
Wednesday night through Thursday night...behind the cold front
that will push through Wednesday night, wind gusts of 25 to 30 knots
are expected on the Bay and the ocean waters. 12z gefs ensemble
suggests slightly increased risk of 35 knot gusts. Held off on
gale watch with this package, but will need to be monitored.
Through this period waves up to 6 feet are expected on the ocean
waters and up to 5 feet on the Lower Bay. Winds and seas should
slowly subside Thursday night.
Friday through Sunday...winds and seas should stay below Small Craft Advisory
Marine...Small Craft Advisory until 5 am EST Wednesday for anz452>455.
Small Craft Advisory until 9 am EST Wednesday for anz450-451.