Scientific Forecaster Discussion
fxus61 kphi 191338
Area forecast discussion
National Weather Service Mount Holly New Jersey
938 am EDT Thu Jul 19 2018
high pressure will build across the region today before moving
offshore on Friday. A low pressure system will move up the coast on
Saturday. Another low pressure system will remain nearly stationary
over the Midwest, affecting our area through the middle of next
Near term /until 6 PM this evening/...
surface high pressure was centered over the northeast and mid-
Atlantic states this morning. This high will gradually build
eastward but continue to influence our weather through the
remainder of the day.
A light north-NE wind will continue into the afternoon. However, a
sea-breeze is expected to move inland across the coastal plain
this afternoon, resulting in a wind shift from the east-southeast behind
the boundary. Minor updates were made with the 930 am estf to
highlight this effects of the sea breeze.
High temperatures will generally be in the lower to mid 80s this
afternoon. The humidity should be low, especially for mid Summer
standards, with dewpoints mainly in the 50s.
Short term /6 PM this evening through 6 am Friday/...
the center of high pressure is expected to pass off the New England
coast tonight. However, will will continue to experience dry weather
under a mostly clear sky.
A light and variable wind is forecast for tonight with low
temperatures mainly in the upper 50s and lower 60s.
Long term /Friday through Wednesday/...
Friday and Friday night...high pressure slides offshore early Friday
and this looks to be the last of the more pleasant days in this
forecast. Very little moisture will be across the region through
much of Friday and we should have mostly sunny skies across the
region through the day. High temperatures will feel comfortable and
in the low to mid 80s (mid to upper 70s across the higher elevations
of the southern poconos).
As we head into Friday night, we will start to see some clouds
moving into the area in response to a developing coastal low to our
south. Some showers may start to edge their way into parts of our
area, mainly southern Delaware and Maryland. Meanwhile, a strong
upper level trough and strong surface low will start to push
southeastward from the upper Midwest towards the Ohio Valley.
Saturday and Saturday night...the coastal low will start to make its
way up the coast on Saturday. The models continue to have
differences with respect to timing, strength, and speed of the low
as it moves up the coast but the solutions look much closer than did
on last nights model runs. One of the biggest discrepancies is just
how much precipitation will fall through Saturday. All the guidance
suggests some pretty decent rainfall, especially near the track of
the low, but with the exact track uncertain, it is hard to pinpoint
just which areas may see the most rain fall. Should the low track
right along/closer to the coast, we would expect to see fairly poor
conditions across the region on Saturday. A slightly further
offshore track will mean some areas may see a decent Saturday,
albeit a cloudy/overcast one.
Meanwhile, the upper level trough/closed low and strong surface low
begin to settle in over the Midwest.
Sunday through Wednesday...not much change is noted as the upper low
digs down deeper and into the Tennessee Valley. The associated
surface low makes little progress as it continues to sit and spin
over the Midwest, largely due to the strengthening surface high
building over the Atlantic Ocean. The models show the surface low
moving to the west southwest as the Atlantic high continues to
strengthen. Unfortunately, the upper trough doesn't break apart as
easily as the surface low and we will remain in an unsettled pattern
through at least the midweek period.
As the low spins, a warm front looks to be pushed northward into our
area on Sunday. With a deep southerly flow in place, we will
continue to see moisture rise across the region with pwats running
very high (ranging from 1.5 to 2+ inches across the area). Hard to
pinpoint exactly where the heaviest rain will fall at this point but
heavy, flooding rain will be likely in any storms that develop
through this period and will need to be monitored as the forecast
For the most part through this period, the warmer air at 850mb
remains suppressed to the south and west. While we will still see
temperatures rise into the mid to upper 80s, we should be able to
avoid temperatures reaching well into the 90s and the excessive heat
that comes along with it when humidity rises. Apparent temperatures
will likely start reach into the low to mid 90s but should remain
below heat advisory criteria. However, with all of the moisture
across the region, it will remain rather humid outside (on top of
being mostly cloudy).
Aviation /14z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today...VFR with a mostly clear sky. North wind 3 to 7 knots
becoming variable in the afternoon. Sea and Bay breeze fronts are
forecast to reach kacy, kmiv and kilg with the wind becoming
southeasterly at those locations in the afternoon.
Tonight...VFR with a mostly clear sky. Light and variable wind.
Friday...mainly VFR conditions expected. Southeast winds around 10
knots or less. High confidence.
Friday night through Sunday...periods of MVFR/IFR as showers and
thunderstorms overspread the region. East to southeast winds around
8 to 12 knots on Saturday, becoming more southerly on Sunday.
Monday...periods of MVFR/IFR as showers and thunderstorms overspread
the region. South winds around 10 to 15 knots with gusts up to 20 to
25 knots, especially closer to the coast.
high pressure is expected to influence the coastal waters of New
Jersey and Delaware for today and tonight.
A north wind around 10 knots this morning should become southeast to
south 5 to 10 knots for this afternoon into tonight.
Wave heights on our ocean waters should favor the 2 to 3 foot range.
Waves on Delaware Bay are anticipated to be 2 feet or less.
Friday...sub-Small Craft Advisory conditions expected.
Saturday...increasing east to northeast winds. Gusts may near 25
knots at times during the afternoon/evening. Seas will build through
the day and may exceed 5 feet Saturday evening. A Small Craft
Advisory may be needed for Saturday evening.
Sunday through Monday...southeast winds around 10 to 20 knots. Gusts
around 25 knots on Monday. Seas will remain elevated above 5 feet
through Monday. A Small Craft Advisory will likely be needed.
A light onshore flow and a medium period swell should result in a
low risk for the development of dangerous rip currents for