Scientific Forecaster Discussion
fxus61 kphi 231428
Area forecast discussion
National Weather Service Mount Holly New Jersey
1028 am EDT Wed Oct 23 2019
high pressure builds in from the west today, moves overhead on
Thursday before moving out to sea on Friday. A cold front passes
through the region Friday night, then low pressure affects the area
over the weekend and into the start of next week.
Near term /until 6 PM this evening/...
surface high pressure builds across the southeastern states
today with it gradually extending more toward our area late in
the day. The cyclonic flow aloft will gradually become more
zonal by the end of the day, however give surface low pressure
near northern New England and the southern surface high
pressure, a tight pressure gradient will be over our area today.
This combined with the leftover cold air advection will result
in deeper vertical mixing through the day, especially as the
boundary layer warms through the morning hours. The forecast
soundings show 20-25 knots of wind mixing down, therefore peak
wind gusts should be around 25 mph. The winds however should
start to diminish quickly closer to the evening. Plenty of
drying of the atmosphere today, therefore lots of sunshine
expected although there could be a touch of inland stratocumulus
development for a time. Despite the cold air advection
especially this morning, west to northwesterly flow along with a
well mixed boundary layer and downsloping flow into the coastal
plain will yield warmer temperatures. We went with a mostly
MOS/continuity blend for the high temperatures.
Short term /6 PM this evening through 6 am Thursday/...
as the flow aloft backs to more southwesterly in the east,
surface high pressure builds right over our area during tonight.
This results in a relaxing of the pressure gradient and winds
should quickly decouple in nearly all areas this evening. A
system sliding through the Great Lakes region overnight may try
to toss a little high clouds our way. A mainly clear night along
with light to calm winds and low dew points will result in good
radiational cooling conditions. Temperatures in many places
should quickly drop this evening. For the low temperatures, we
used a MOS/continuity blend then went a little lower in the
typically colder locals (i.E. The New Jersey Pine barrens, far
northwest New Jersey and into the poconos).
Long term /Thursday through Tuesday/...
high pressure over the area moves offshore on Friday. Sunny and
tranquil conditions will be in place on Thursday, and then
clouds build into the region on Friday ahead of an approaching
cold front. The cold front passes through the region Friday
night, and some showers are possible across the northern zones.
Will cap pops at slight chance for areas north of I-195, but
latest guidance seems to be fairly dry in terms of precip. Weak
high pressure passes to the north late Friday night through
Going into the weekend, the front becomes nearly stationary
over the mid-Atlantic. A closed 500 mb low with several strong
shortwaves will move through the southern plans, and surface low
pressure will develop along the stationary boundary. This
boundary begins to return north as a warm front late Saturday,
and some overrunning precip will develop out ahead of the
boundary and will move into far southwest zones by Saturday
Low pressure then tracks from the lower Mississippi Valley,
through the Great Lakes and Ohio Valley, and into eastern Canada
Saturday night through Sunday night. There are some differences
between the 00z GFS and the 00z European model (ecmwf) in terms of timing and
placement of the low, but the general consensus is for likely
pops Saturday night and Sunday.
Low pressure moves offshore Sunday night, and a cold front
moves through the region behind the departing low.
From there, some weak waves of low pressure may affect the area
early in the new week. 00z CMC is mainly dry, as well as the
00z GFS. But there is some upper level energy that could touch
off some isolated showers both days.
Aviation /15z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today...VFR. West-northwest winds 4-8 knots increasing to 10-15
knots with gusts 20-25 knots through this morning, then
diminishing some after 20z. High confidence.
Tonight..VFR. Winds quickly becoming light and variable to
calm. High confidence.
Thursday through Friday...VFR with mostly sky clear conditions on
Thursday, and then thickening and lowering clouds during the day
Friday. Light SW winds.
Friday night...mainly VFR, but MVFR possible in -shra at
krdg/kabe. Winds shift to the northwest less than 10 kt.
Saturday...VFR initially, then clouds thicken and lower during
the day. North winds less than 10 kt, veering to the east late in the
Saturday night through Sunday...increasing chances for rain and
associated sub-VFR conditions. However, forecast confidence is
low during this time.
the west-northwest surge behind a cold front looked to be on
the weaker side, even on Delaware Bay. Increasing mixing for a
time today should elevated the winds especially nearshore with
gusts around 25 knots at times. The Small Craft Advisory was
trimmed back to 16z/12pm for Delaware Bay and the Delaware
Atlantic coastal waters as the better gust potential looks to be
this morning and seas subside with an offshore wind. The
advisory for the New Jersey Atlantic coastal waters continues
through today with increasing wind gusts to 25 knots and seas
around 5 feet. The conditions are then below advisory criteria
Thursday through Saturday...winds and seas should stay below
Small Craft Advisory criteria.
Saturday night through Sunday...low pressure with increasing
winds and seas likely to affect the waters but confidence is low
on the details including wind direction as the track and timing
of the low remains uncertain. That said, increasing chances for
at least Small Craft Advisory conditions.
Marine...Small Craft Advisory until 7 PM EDT this evening for
Small Craft Advisory until noon EDT today for anz430-431-454-