Scientific Forecaster Discussion
fxus61 kphi 060913
Area forecast discussion
National Weather Service Mount Holly New Jersey
413 am EST Fri Dec 6 2019
a weak cold front will move across the East Coast today. High
pressure will build across the mid Atlantic and northeast states
Saturday and Saturday night, before shifting offshore on
Sunday. A warm front is expected to lift northward across the
area on Monday, followed by a cold front Tuesday into Tuesday
night. High pressure builds back across the mid Atlantic region
Thursday into Thursday night, before shifting offshore through
Near term /until 6 PM this evening/...
potent trough that brought some lake-effect precipitation all
the way to the northern County Warning Area on Thursday is finally moving off
the coast early this morning. Descent on the upstream side along
with nocturnal decoupling (aided by an approaching surface
ridge) has aided in the dissipation of lower clouds, with
temperatures falling quickly the past few hours. However, the
lower clouds will return this morning as the next northwest-flow
shortwave trough digs southeastward into the northeast. An
attendant surface low will migrate eastward through New York
today, with a southwestward- extending cold front approaching
the area this afternoon. Though this system is fairly moisture-
starved, do expect a few showers to develop along and in advance
of the front today via fairly Stout large-scale lift. Best
chances look to be during the afternoon. Precipitation amounts
will be quite light, and temperatures will be warm enough for
rain, except possibly the Poconos and vicinity.
With warm advection in advance of the approaching system,
temperatures should be a little warmer today, though this will
be tempered by increasing/lowering cloud cover. Generally have
Max temps about 5 degrees warmer than thursday's values. Winds
will diurnally swing upward this afternoon, aided by an
increasing surface pressure gradient as the low to our north
makes its closest approach to the County Warning Area. A few gusts of 20 to 25
mph or so can be expected this afternoon.
Short term /6 PM this evening through 6 am Saturday/...
the aforementioned cold front will move through the area this
evening, switching winds to northwest (perhaps gusting for a bit
around the time of frontal passage). Showers (scattered and
light in nature) may occur near the time of frontal passage,
with best chances along/southeast of the urban corridor given
anticipated location of the front. The front should move
offshore around/after 06z with skies rapidly clearing upstream.
Though winds should diminish somewhat overnight, they will
probably remain elevated enough to prevent ideal radiational
cooling conditions. As such, kept temperatures fairly close to
consensus and continuity, which are not too different than the
readings being observed this morning.
Long term /Saturday through Thursday/...
quiet weather begins the long term period over the weekend,
then unsettled weather returns for the beginning of next week,
then quiet weather returns for the end of next week.
High pressure builds across the area later in the day Saturday
then centers itself across the region Saturday night, before
shifting offshore on Sunday. This will keep dry weather in the
forecast Saturday through Sunday. Winds may be a little gusty at
times Saturday morning, as well as during the day Sunday, but
gusts should remain mostly 15 to 20 mph, with occasional High
Peak gusts around 25 mph.
As we move into Sunday night, a warm front is expected to be
lifting north toward the area, then lift across and through the
area during the day Monday. At the same time, there will be
multiple short wave/vorticity impulses moving across the area
starting late Sunday night and continuing through Monday night,
even once the warm front lifts through the area. With enhanced
moisture across the area, this is expected to lead to several
possible periods of enhanced rainfall chances across the area
through Monday night. If any precipitation starts early enough
Sunday night while temperatures a cold enough, a brief wintry
mix may be possible for portions of northeast Pennsylvania and
northern New Jersey before changing to all rain.
Then as we move into Tuesday, a cold front is expected to move
across the area later during the day into the evening. This will
lead to another period of enhanced rainfall chances, especially
during the afternoon and evening. Precipitable water values will likely exceed
1.00 inches and approach 1.25-1.50 inches Monday-Tuesday, so
there could be period of moderate to heavy rainfall at times.
The cold front will have moved offshore by Wednesday morning,
then our area will be under the influence of strong northwest
flow. Wind gusts are expected to increase to at least 20 to 30
mph with occasional higher gusts around 35 mph possible. Lake
effect snow showers will likely be ongoing through the day to
our north across New York and northern Pennsylvania where the
steepest lapse rates and enhanced moisture will be located. The
low-mid level flow will likely keep the showers to our north,
but there is still a slight chance if the flow turns a little
more south some lake effect showers could make it down into our
The chance for showers cuts off by Thursday as high pressure
builds across the area, so dry weather is expected for Thursday
into Thursday night.
Aviation /09z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Rest of tonight...VFR with mid/high cloudiness increasing.
Winds light west or southwest. High confidence.
Friday...mainly VFR with a lengthy period of cigs around 5000
feet. Cannot rule out a passing shower during the day, but any
impacts would be minimal. Winds west or southwest around 10 kt
with perhaps a few gusts to 20 kt or so. Moderate confidence.
Friday night...VFR with any cigs rapidly dissipating overnight.
Northwest winds 5 to 10 kt, perhaps a little stronger in the
evening. High confidence.
Saturday-Sunday...VFR conditions expected. Northwest winds
Saturday shift to the northeast Saturday night, then southeast
and south on Sunday. Winds may gust around 15-20 knots at times
Saturday and Sunday. --High confidence.
Sunday night...conditions may lower to MVFR later in the
overnight ahead of a lifting warm front. South winds may shift
to southeast late in the night. --Moderate confidence.
Monday-Tuesday...an extended period of MVFR and IFR conditions
likely as periods of rain move across the area. Southeast winds
early Monday become southwest once a warm front lifts across the
area Monday. Winds shift to the northwest behind a cold front
later Tuesday into Tuesday night. --Moderate confidence.
have allowed the Small Craft Advisory for the Atlantic waters
to expire early this morning, but this will be short-lived.
After a lull in winds that should last much of the morning,
expecting south to southwest winds to increase rapidly around
midday, with advisory conditions expected to return on the
Atlantic waters this afternoon. It is not out of the question
that gales are observed, but the regime is not climatologically
favorable for gales (harder to reach in pre-frontal southwest
flow versus Post-frontal northwest flow) and model soundings are
fairly marginal both in terms of magnitudes of gusts and
duration. As a result, issued another Small Craft Advisory
beginning at noon today. A cold front will move through the
waters this evening/tonight, switching winds to northwest. This
may be the best timing for a few gusts to reach marginal gales,
but confidence is too low to issue a warning at this time. Winds
should diminish slowly late in the night, so the advisory
expiration time is 6 am Saturday.
For Delaware Bay, expecting mostly sub-advisory winds today
(though a few gusts to 25 kt or so may occur this afternoon).
However, as the front moves through this evening, expecting a
few hours of marginal advisory conditions with the switch to
northwest wind directions and favorable channeling effects.
Therefore, issued a Small Craft Advisory for lower Delaware Bay
from 9 PM this evening to 6 am Saturday.
Seas may approach 5 feet late this afternoon into this evening
near the time of frontal passage.
Cannot rule out a few showers near the front late this
afternoon into this evening. These showers may be accompanied by
Saturday-Sunday night...conditions are expected to be below
Small Craft Advisory levels.
Monday-Tuesday...Small Craft Advisory conditions likely as
winds and seas increase as a warm front lifts across the area
Monday, then a cold front moves across the area Tuesday.
Marine...Small Craft Advisory from noon today to 6 am EST Saturday for
Small Craft Advisory from 9 PM this evening to 6 am EST
Saturday for anz431.