Area Forecast Discussion
Issued by NWS Mt. Holly, NJ-- Remove Highlighting --
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FXUS61 KPHI 271440
Area Forecast Discussion
National Weather Service Mount Holly NJ
1040 AM EDT WED JUL 27 2016
A weak front will stall to our south today into Thursday. A few
waves of low pressure developing along this boundary will result
in periods of showers and thunderstorms late in the week into
early next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Mid morning surface analysis shows a zonally oriented stationary
front located near the southern tip of NJ, extending back to the
west across central DE and eastern MD. Differential heating owing
to strong heating and sunshine on the cool, northern side of the
boundary and increasing cloud cover along and south of the
boundary, frontolysis is expected. There will still be some weak
wind convergence along the axis of the pressure trough, which
could provide enough lift for convective development during peak
heating this afternoon. Made some minor tweaks the PoP/Weather
grids based on the latest hi-res model guidance. Isolated to
widely scattered showers and storms are expected in Delmarva and
the coastal plain in far southern NJ, where the greatest low-
level lift and instability will forecast to reside.
Forecast high temperatures are in the lower 90s across a majority
of the region. Readings should not get out of the 80s in the
elevated terrain of the Poconos and northwestern New Jersey. Also,
a developing sea breeze should keep temperatures from rising above
the 80s along the immediate coast. Dew point readings are expected
to be mainly in the 60s in eastern Pennsylvania and New Jersey and
in the lower 70s in much of Delaware and northeastern Maryland.
Heat index values will likely be near or only slightly above the
air temperatures where dew points are in the 60s. Heat index
values are forecast to reach the upper 90s in much of Delaware and
northeastern Maryland due to the expectation of higher dew points
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
The frontal boundary should remain to our south for tonight. We
will keep a slight chance of showers and thunderstorms in the
forecast for our southern counties. Otherwise, the sky should be
in the mostly clear to partly cloudy range.
The wind is expected to be light and variable and temperatures
should fall back into the 60s in our northern counties and into
the 70s in the south.
.LONG TERM /THURSDAY THROUGH TUESDAY/...
The chance for showers and thunderstorms will be on the increase
through Friday with a weak front in the area, potential waves of
low pressure along the boundary, and surging precipitable water
values. At this point it appears the highest chances will occur
during Friday as a stronger in a series of hard to time impulses
moves west to east across the region. The threat for severe
weather will be highest farther south during Thursday as
instability is limited for the northern areas. The latest SPC
outlook highlights a Marginal Risk across southern NJ, MD and DE.
A Marginal Risk will expand across NJ Friday however, expect the
potential for heavy rainfall/flooding to be a potential threat as
well. During Friday the precipitable water is projected to range
from 2 to 2.3 inches, which is above the 90th percentile for this
time of year. The precipitable water will remain around 1.5 to 2
inches during Saturday while the swath of higher values will be
displaced offshore in the wake of the aforementioned impulse.
Regardless, with a couple waves of low pressure expected along the
boundary unsettled weather will persist into the first part of
Max temperatures will be warmest during Thursday with afternoon
heat indices of 96 to 99. Otherwise, increasing cloud cover and
convection will limit max temperatures Friday through early next
week. Low temperatures each night will be a category above normal
through Saturday night, then near normal for the remainder of the
.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
VFR conditions are expected through the TAF period under a mostly
clear sky. The wind is forecast to be 8 knots or less. The
direction may favor the northeast to east for a time this morning
before switching to the southwest and south during the afternoon.
The direction is anticipated to be variable for tonight.
Thursday through Sunday...Mainly VFR conditions are expected.
However, the potential for shra/tsra Thursday through Sunday will
support tempo MVFR/IFR conditions at times.
The wind direction is forecast to veer from the north this
morning to the south for this afternoon into tonight. Wind speeds
will be generally 10 knots or less.
The ocean will be like a mill pond (in the words of our former
marine report relay Mrs. Cook) with wave heights of 2 feet or
less. Waves should be 1 foot or less on Delaware Bay.
Thursday through Sunday...Light and variable flow under a weak
pressure gradient early Thursday will become southerly around 10
knots with lower pressure across PA and weak high pressure farther
offshore. The pattern becomes a little more complex by Friday
night as low pressure may evolve near Delmarva. The low is
projected to move northeast during Saturday across the offshore
waters. The passage of the low would support light east winds
Friday that would back to a north-northeast direction and increase
a notch Saturday morning prior to lifting away later in the day. A
weak pressure gradient during Sunday would result in light onshore
flow. Seas of 2 ft or less are expected during Thursday with a
combination of a minimal southerly wind wave and minor southeast
swell. Multiple higher frequency wave components are likely during
Saturday given the shifting winds with a dominant easterly wind
wave taking hold. Seas will subside some during Sunday. Advisory
criteria is not expected to be met at this time.
There is a low risk for the development of dangerous rip currents
for today due to the relatively light wind and tranquil seas.
The probably risk for the development of dangerous rip currents
on Thursday is also low.