Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
804 PM EDT Wednesday Oct 22 2014
an area of low pressure offshore will continue to strengthen as it
slowly tracks northeastward overnight. This storm system should
be off the New England coast later Thursday into Friday, then move
into Nova Scotia Friday night. High pressure is forecast to build
toward our area from the southwest Friday and Saturday, then a
cold front is expected to move through Saturday night. High
pressure builds in for later Sunday and Monday before shifting
Near term /until 6 am Thursday morning/...
the middle level low was centered over the waters off Delaware-Maryland-Virginia this
evening. It should lift northeastward to the waters off New
Jersey and Long Island toward morning. Meanwhile, the surface low
was centered about 150 miles off the Delaware coast. That feature
is expected to drift about 50 miles to the east during the course
of the night.
It will remain overcast and chilly in our region overnight. Low
temperatures are anticipated to be mainly in the 40s. The wind
should back from the north to the northwest at speeds around 10 to
15 miles per hour with gusts into the 20s.
Rain rotating around the coastal system will maintain a northeast
to southwest orientation in our region overnight. Sometimes the
rain will come down a little heavier than at other times, but most
of this precipitation is still expected to lift north of our area
during the late overnight perioe. Rainfall amounts over the entire
County Warning Area should be in the quarter to half inch range, with lesser
amounts possible in the southern poconoes...and western Berks County.
Short term /6 am Thursday morning through 6 PM Thursday/...
the middle level low and the surface low are forecast to move toward
the waters off Cape Cod on Thursday. The precipitation associated
with the coastal system will begin to lift northeastward, as well.
We are expecting the rain to become showery and end gradually from
southwest to northeast on Thursday.
The sky should remain cloudy with a northwest wind in the 10 to 20
miles per hour range with gusts of 20 to 30 miles per hour. The clouds and the northwest
flow will likely keep temperatures from getting above the 50s on
Long term /Thursday night through Wednesday/...
model consensus through the first couple days of the extended is
pretty good, but once you get past Saturday a much larger spread is
seen. We will, however, be transitioning from troughiness to degrees
of ridging through the extended, starting by early next week. For
the most part we maintain a relatively dry longterm from Saturday
Onward as ridging begins to build to our south-southwest.
Friday...upper level low continues to spin and pull away to our
northeast with just some lingering backside showers possible across our
northern zones. The overall trend on Friday is for drying as the
strong pressure gradient and northwest winds remain in place.
Temperatures should be able to rebound back in the low to middle-60s
with less cloud cover than previous days and the lack of showers.
Saturday and Sunday...high pressure builds to our south Saturday,
however a strong short wave diving southeastward from the Great
Lakes will dig another upper-level trough across the northeast later
Saturday into Sunday. This will toss a cold front across our area
Saturday night but still unsure if we will see a dry passage with
this system. Thinking that the atmosphere will not have much time to
modify ahead of the front and how much influence the energy will
have as it comes in on the heels of the once cut-off low. With the
limited amount of moisture expected it should result in a generally
dry frontal passage. The associated surface low looks to intensify
as is exits New England, which means a tightening pressure gradient
down into the middle Atlantic Sunday. As a result, a breezy day may
occur as mixing deepens. High pressure then starts to build in
Monday - Wednesday...an upper-level ridge slides toward the east
allowing high pressure to build across our area Monday before
shifting offshore Tuesday. This is expected to result in warming
conditions, especially as warm air advection develops Tuesday ahead of the next
cold front. No major changes were made for this time frame, with
just some blending in of the new 12z wpc guidance.
Aviation /00z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Generally, MVFR ceilings are anticipated through tonight in our
region. Periods of rain are expected, with some breaks in between.
The ceilings are forecast to lift gradually into the VFR category
from southwest to northeast on Thursday. The rain is anticipated to
become more showery and it should end at our taf sites by middle to
The wind shifted from north to northwest after sunset, and a
northwest flow is expected overnight and Thursday. Sustained
speeds are expected to be around 10 to 15 knots with gusts into
the 20s or higher on Thursday.
Friday...VFR. Continued northwest winds with gusts around 20 knots.
Some lingering showers possible north of Abe. Medium confidence,
lower on showers.
Saturday - Sunday...VFR. Winds shift to the west-southwest. Dry cold
front passage expected late Saturday night. Medium confidence.
the Gale Warning continues until 600 PM Thursday for our ocean
waters and for the lower part of Delaware Bay. The circulation
around the slow moving low off the coast should maintain a north
to northwest wind over our waters with gusts of 35 to 40 knots
anticipated. A Small Craft Advisory remains in place for the upper
part of Delaware Bay. Gusts there should peak around 30 knots.
Friday - Saturday morning...Small Craft Advisory conditions persist, once the gales
come down, as the coastal low pressure continues to move northeast
though the pressure gradient should be relaxing by Friday night.
Northwest winds around 15 to 20 knots. Medium confidence.
Saturday...sub-sca. Westerly winds around 15 knots. Medium
Sunday...period of Small Craft Advisory possible behind a passing cold front. Medium
Monday...sub-sca. Medium confidence.
tides are running high due to a combination of the storm off the
coast and the approaching new moon. High tides occur this evening
before midnight along the ocean, then again on Thursday morning along
the ocean around noon. Tommorrow/S high tide has the higher
astronomical contribution, but by that time there should be a
well-established northwest wind. Right now the only flooding we/re
expecting would be isolated minor flooding below our established
thresholds needed for an advisory. However...we will be keeping an
eye on the situation and issue any additional statements if
Marine...Gale Warning until 6 PM EDT Thursday for anz431-450>455.
Small Craft Advisory until 6 PM EDT Thursday for anz430.