Scientific Forecaster Discussion
fxus61 kphi 260117
Area forecast discussion
National Weather Service Mount Holly New Jersey
917 PM EDT sun Aug 25 2019
surface high pressure over Quebec will continue to drift
eastward and weaken through the middle portion of the week.
Meanwhile, an amplified shortwave trough will eject into the
Great Lakes region by Thursday, drawing a surface low across the
northern tier and a cold front through the mid-Atlantic. A weak
ridge of high pressure will build into the region behind this
front before another front approaches the area by next weekend.
Near term /until 6 am Monday morning/...
forecast mainly on track, so will keep forecast as-is, only will
adjust hourly grids based on the latest surface obs.
Otherwise, the dominant feature through Monday will be the high
centered over Quebec and northern New England. With high
pressure to the north, the winds for our region will stay
persistent northeasterly through tonight and Monday.
Because this is not a favorable direction for large diurnal
temperature swings, especially now with warm ocean temperatures
in place, lows tonight will likely only be 10 to 15 degrees
below the day time highs on the coastal plains - generally in
the lower to mid 60s. North and west of the fall line which is
less likely to see a significant influence of the marine layer
overnight, lows will be in the 50s.
Short term /6 am Monday morning through 6 PM Monday/...
Monday looks like a similar story to Sunday. The persistent
onshore flow continues, which will likely result in mostly
cloudy conditions on the coastal plains thanks in large part to
the warm ocean temperatures. Highs should once again be in the
70s across most of the area. As for precipitation, much like
this morning, we could see isolated showers, generally right
along the coast especially in the morning.
Long term /Monday night through Sunday/...
high pressure will continue to drift across southeast Canada
into the Canadian maritime provinces through Wednesday, leading
to continued onshore, cool flow Tuesday. A warm front will begin
to push northward, leading to showers and thunderstorms by the
afternoon. Temperatures will remain slightly below normal with
cloud cover lingering for the most part.
Temperatures will return to normal with a returning chance for
rainfall as a surface low migrates across Ontario. As this low
moves toward the area, a cold front will progress eastward
across the Great Lakes. This will bring rainfall to the area
most of the day Wednesday with 0.5-1.5 inches of rain possible.
Guidance suggests the front will pass through the mid-Atlantic
sometime Wednesday night.
Thursday through Saturday looks much nicer with seasonable
highs in the low to mid 80s and dry conditions. A front to our
northwest and a stalled front to our south will try to nudge
their way toward our region, however, they will likely interfere
with each other, leading to overall nice condition across our
By Sunday, another shortwave perturbation will drift across
southern Canada, leading to cyclogenesis and the formation of a
surface low across southeast Canada. A cold front will also move
southeast with this system, approaching our area by Sunday
according to the latest guidance. There still exists a great
deal of discrepancy regarding the timing of this with the GFS
suggesting a much quicker and drier scenario, with the front
turning more zonal and dissipating by Sunday. In terms of high
temperatures and rainfall amounts, it is still too distant to
tell for sure.
Aviation /01z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Tonight...mostly VFR conditions. Northeasterly winds should drop
below 10 kt and may shift more easterly through the overnight
Monday...mostly VFR conditions. We could see some temporary
MVFR ceilings, especially from the Delaware valley eastward
between 12 and 18z, but confidence is too low to include in the
tafs at this time. Northeasterly winds of 5 to 15 kt are once
again expected, with gusts near 20 kt possible, especially for
kmiv and kacy.
Tuesday... mostly VFR with northeast winds 5 to 10 knots and
gusts to 15 knots.
Wednesday...MVFR possible with showers and thunderstorms. Light
and variable winds up to 5 knots.
Thursday...VFR with northwesterly winds 5 to 10 knots.
Friday...VFR with southwesterly winds 5 to 10 knots.
strong northeasterly winds will continue through the day
tomorrow, so expect Small Craft Advisory to continue at least
through the day on Monday, especially for the Atlantic coastal
Tuesday...sub-sca conditions expected with northeast winds
gusting to 20 knots and seas generally below 5 feet. Seas may
reach or exceed 5 feet for the southern Atlantic zones, however.
Wednesday...seas 2 to 4 feet. Easterly winds 10 to 15 knots.
Thursday...seas 1 to 3 feet. Northwest winds up to 10 knots.
Friday...seas 1 to 3 feet. Westerly winds turning southerly 10
to 15 knots.
onshore flow and rough surf, with wave heights near or above 5
ft, will continue on Monday. Therefore, expect high risk for
the formation of dangerous rip currents again on Monday. The
elevated rip current risk may also continue into Tuesday.
a brisk northeast wind is forecast to continue along the coasts
of New Jersey and Delaware through late Monday. The wind is
expected to become east with speeds slowly diminishing on Monday
night and Tuesday.
The onshore flow may result in spotty minor tidal flooding
around the times of the late afternoon/evening high tide on
Monday and Tuesday. However, the minor flooding is not
anticipated to be widespread enough to warrant an advisory at
The base level of the early morning high tides are considerably
lower than those of the late afternoon/evening high tides, so
no issues are expected early in the day on Monday or Tuesday.
Once we get past the early week's onshore flow, we will begin
to experience particularly high astronomical tides associated
with the upcoming new moon phase. As a result, there is another
potential for at least some spotty minor tidal flooding from
late this week into the Holiday weekend.
the WSR-88D at Dover, Delaware (kdox), is out of service at this
time. The time when it will return is presently unknown.
New Jersey...high rip current risk through Monday evening for njz014-
Delaware...high rip current risk through Monday evening for dez004.
Marine...Small Craft Advisory until 8 PM EDT Monday for anz430-431-