Scientific Forecaster Discussion
fxus61 kphi 280756
Area forecast discussion
National Weather Service Mount Holly New Jersey
356 am EDT Mon may 28 2018
Near term /until 6 PM this evening/...
a challenging forecast for today, but first a synoptic overview. An
upper-level trough across the northeast is forecast to retreat some
through today. This will result in some height rises from the
southwest. Meanwhile at the surface, high pressure wedged down into
the northern mid-Atlantic is forecast to weaken and shift eastward
as the trough lifts out some.
A shallow marine layer remains entrenched across our area, resulting
in a wealth of low clouds and some fog. While some drizzle may
certainly be around to start, a few lingering showers cannot be
ruled out early this morning mainly south and east of Philadelphia
as a short wave exits. As the surface high gradually weakens and
therefore allowing The Wedge of shallow cool air to weaken, low
clouds should lift some especially west of the fall line where a bit
more entrainment of drier air and subsidence works in. The forecast
soundings overall suggest the layer of low clouds is fairly shallow,
therefore enough heating from above should work on this enough to
hopefully allow for some breaks of sunshine to develop especially
this afternoon. There is a low-level inversion present due to some
warming being maintained just above the lingering marine layer,
however a frontal zone to our south and west is forecast to start
working northeastward as a warm front by late in the day. We should
remain on the cooler side of this front though, and how warm it gets
will depend on just how much sunshine is able to develop. For now,
leaned closer to the cooler guidance although the surface winds
should begin shifting to a more south or southwest direction this
afternoon. The warmest temperatures as forecast for portions of
eastern Pennsylvania and northern New Jersey.
Some additional showers are possible mainly across the far southern
areas through the early afternoon as the aforementioned boundary is
nearby. The bulk of any renewed convection though looks to reside
farther to our south, therefore kept pops on the lower side.
Short term /6 PM this evening through 6 am Tuesday/...
as an upper-level trough slides across the Canadian Maritimes
tonight, surface low pressure will accompany it. A trailing weak
cold front is forecast to approach our area toward daybreak from the
north, with high pressure centered near Hudson Bay Canada building
east-southeastward. There is some low-level warm air advection in
advance of this weak cold front, however weak flow will allow for a
lack of mixing. The forecast soundings show a low-level inversion
remaining in place or even strengthening, and with low-level
moisture pooling beneath it there looks to be low clouds either
redeveloping or expanding. The moisture may also manifest itself
into fog, which could be locally dense especially in the coastal
plain and also the higher elevations as surface dew points rise
some. As of now, we are not anticipating widespread dense fog.
Our region should be dry tonight, outside of perhaps a little
drizzle in the presence of low clouds and fog. Some showers should
accompany the cold front to our northwest, however these should
generally dissipate before reaching our area. Low temperatures are
mostly a multi-model blend with continuity.
Long term /Tuesday through Sunday/...
Tuesday... a backdoor cold front will pass through New England
on Tuesday. The southern tail of this front will move into the
northern mid-Atlantic region during the afternoon, but will be
rather diffuse by the time it reaches over eastern PA and New Jersey.
Low-level convergence to focus convection along the boundary
appears to be rather questionable. Even with strong daytime
heating and modest instability during peak heating, it may be
difficult to overcome a capping inversion near 800 mb in place
without a better defined source of lift. Accordingly, chances
for storms were capped at 20 percent and confined to the higher
terrain north/west of the fall line. Tuesday will be the warmest day
this week with highs in the mid and upper 80s. Some locations in
east PA and interior New Jersey may reach 90f while the New Jersey and Delaware beaches
will continue to be 10-15 degrees cooler than inland locations.
Tuesday night...high pressure builds southward into New England.
This will cause the backdoor cold front to surge to the south-
southwest across the region. A few showers may develop during
the night as low-level convergence enhances along the boundary
but less instability and deep-layer moisture than yesterday, do
not anticipate a heavy rainfall/flash flooding event like we
say with yesterday's backdoor fropa.
Wednesday...high pressure builds southward into the Gulf of
Maine. The forecast for Wednesday has trended drier with the
high center shifting closer to our region, helping to keep the
deep tropical moisture and precip associated from what will be
the remnants of subtropical storm Alberto south and southwest of
our region. It's still a bit too close of a call to rule out
isolated showers or sprinkles across the southern/western fringe
of our County Warning Area Wednesday afternoon and night. Easterly flow around
the high will allow the marine layer to advect inland, resulting
in cloudy and cool conditions (highs in the 60s toward the
coast and 70s inland) for most of the region.
Thursday through Sunday...a potentially very unsettled, wet pattern
evolves late in the week as the remnants of subtropical storm
Alberto and an upstream mid-latitude trough merge in vicinity of the
Great Lakes. Models then show this system evolving into a cutoff low
in association with the development of an Omega-like blocking
pattern farther upstream. This could allow the low to drift
southward across the eastern U.S., Prolonging unsettled weather into
next weekend. Hydro concerns could be renewed but the extent of the
heavy rain and flood risk will depend on how the pattern evolves,
including the track of the low. All of this is highly uncertain at
this point due to the poor agreement evident among the global models
and due to the low predictability skill in these types of complex
Aviation /08z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Today...IFR ceilings gradually improve to MVFR later this morning
and afternoon. The ceilings should improve to VFR or marginal VFR,
near and north/west of phl and especially at Abe and ridge. Local MVFR
visibility possible through early this morning due to fog. The
timing of the improvements though is of lower confidence. East-
northeast winds 4-8 knots becoming light and variable through
midday, then turning light southerly this afternoon.
Tonight...ceilings lower to IFR, possibly locally LIFR, due to low
clouds once again. MVFR/IFR visibilities should develop mainly after
04z due to fog, and this may be more pronounced at miv and Acy where
LIFR visibility is possible toward daybreak. Light and variable
winds, or light southerly.
Tuesday...lingering MVFR cigs at the beginning of the day should
improve from north to S during the morning. Generally VFR for the
afternoon but there is potential for isolated showers/storms and
brief/localized restrictions during the afternoon at Abe and
ridge. Light/variable winds may acquire a S-southeast direction by
Tuesday night and Wednesday...low clouds are favored to develop
from NE to SW across the region behind a backdoor cold front
late Tuesday night into Wednesday morning. Cigs will most
likely be in MVFR range but there is some potential for IFR
cigs. Overall, forecast confidence is low. East winds 5-15 kt
expected behind the front.
Wednesday night through Friday...sub-VFR with showers possible.
A slight chance of thunderstorms Thursday and Friday. Southeast winds
5-10 kt through Thursday, becoming SW Friday.
the Small Craft Advisory for the New Jersey Atlantic coastal waters
has been cancelled, as seas continue to subside. The northeasterly
wind is expected to diminish some more through the morning, then
become east-southeast to south-southeast during the afternoon hours
and continue tonight. Areas of fog are expected to develop tonight,
and this may become dense. Otherwise, the conditions are anticipated
to be below Small Craft Advisory criteria through tonight.
Tuesday through Friday...winds and seas generally below Small Craft Advisory
levels. However, a medium-period easterly swell is forecast to
build toward the coast midweek and could allow seas to briefly
reach 5 ft late Wednesday and/or early Thursday.
For today into this evening, a lingering northeast wind this morning
is forecast to become more southerly this afternoon. The wind speeds
are anticipated to be on the lighter side, however elevated seas at
least this morning combined with the full moon tomorrow should
result in a moderate risk for the development of dangerous rip
currents along the Monmouth and Ocean County beaches. For the rest
of the New Jersey and Delaware coasts, a low risk for the
development of dangerous rip currents is forecast.
Remember, a low risk of rip currents does not mean no risk!
Life threatening rip currents often still occur near jetties,
reefs, and piers. The vast majority of rip current victims swam
at unguarded beaches. Always swim in the presence of a
the Sandy Hook nos tide gauge (sdhn4) remains out of service.
Corms is addressing the problem. There is currently no estimated
time for a return to service.