Scientific Forecaster Discussion
fxus61 kphi 262336
Area forecast discussion
National Weather Service Mount Holly New Jersey
736 PM EDT Wed Apr 26 2017
a weakening coastal low near Long Island will move slowly
northeast overnight. A cold front will move across the area late
Thursday night and early Friday morning before another cold
front crosses Saturday night. A warm front is then expected to
lift north across the area Sunday night, followed by another
cold front Monday night. High pressure is then expected for the
middle of next week.
Near term /until 6 am Thursday morning/...
as the coastal low drifts out to sea, some clearing was taking
place over eastern Pennsylvania early this evening. The back
edge of the clouds should continue to erode a bit more during
the balance of the evening. However, a fair amount of low level
moisture will remain in the wake of the low. As a result, we
expect low clouds and fog to develop late tonight at those
location where clearing has taken place. The lingering clouds
near the coast should lower, as well.
The wind is forecast to remain light and variable. Minimum
temperatures should favor the lower and middle 50s in Delaware,
northeastern Maryland, eastern Pennsylvania and New Jersey.
Short term /6 am Thursday morning through 6 PM Thursday/...
mostly cloudy to start...but all model tsections fcst a much
brighter and warmer day... with a decent amount of afternoon
sunshine so have used the 12z/26 GFS/NAM MOS blend for the fcst
basis. Fcst temps are 7 to 13f above normal. Max T at phl may
reach 82 or 83.
Long term /Thursday night through Wednesday/...
a cold front associated with low pressure moving north through
eastern Canada is expected to cross the region Thursday night,
then move off the coast Friday morning. Mainly scattered showers
are expected at this time, primarily from midnight through 6 or
7 am. A southerly flow aloft will maintain low temperatures in
the mid to upper 40s and high temperatures in the upper 70s to
low 80s, above normal for this time of year. The daytime hours
on Friday will feature mainly dry weather has high pressure
briefly builds into the region.
By Friday night, another frontal boundary is forecast to begin
approaching the area from the northwest as it crosses
Pennsylvania and New York. The front will sag south through the
area during the day Saturday, bringing with it some additional
shower activity, then stall to our south Saturday night into
Sunday. The subsequent onshore flow will cool temperatures down
to the 60s north and low 70s south on Sunday,but with mainly dry
conditions. This front is then expected to lift back north as a
warm front Sunday night into Monday morning, with an increasing
chance of showers as the day wears on with the approach of a
cold front from the west late in the day. Showers and
thunderstorms may accompany this front...especially later Monday
night into Tuesday morning. Instability in the warm sector
ahead of this front could even produce shower and thunderstorm
activity as early as Monday afternoon. High temperatures in the
70s are expected on Monday.
The front will move offshore by Tuesday morning, but a
secondary surface trough may move across the area during the
day. With a short wave/vorticity Max moving across the area
during the day, there could be some isolated showers across
northeastern Pennsylvania and northern New Jersey. Cooler
temperatures are expected through mid week, with lows generally
in the 50s and highs in the 70s.
Aviation /00z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
MVFR ceilings (around 1500 to 2000 feet) should linger over
kttn, kacy and kmiv this evening. Meanwhile, some clearing is
expected to take place at kpne, kphl and kilg, and krdg and kabe
will likely remain mostly clear.
However, lingering low level moisture is expected to result in
the development of additional low clouds and perhaps some fog
after 0600z. We are not confident where the prevailing issue
will be low clouds and where it will be both fog and low clouds.
For the time being, we have forecast conditions on the cusp of
MVFR and IFR since it could go either way.
We are anticipating that conditions will improve through MVFR
late on Thursday morning into the VFR category for Thursday
A light and variable wind overnight is forecast to settle into
the southeast and south on Thursday with speeds increasing to 5
to 10 knots.
Thursday night...generally VFR. A chance of showers overnight
which could temporarily reduce conditions to MVFR.
Friday...VFR conditions expected.
Friday night...VFR early. Patchy fog and low ceilings may develop
Saturday...becoming VFR during the morning, then a chance of
showers during the afternoon. Conditions may temporarily be
reduced with any showers.
Saturday night-Monday...low clouds and fog may develop
overnight Saturday and continue into Sunday leading to reduced
conditions. There will also be a chance of showers.
the Small Craft Advisory hazardous seas continues through
Thursday. Waves (virtually all se swell at 10-11 seconds) are
currently around 7 ft and will gradually subside through
Thursday. How much marine fog develops the next day or so.?
unsure...so fcst the fog conservatively for now.
Thursday night...Small Craft Advisory for hazardous seas
through Thursday night.
Friday...winds expected to remain below advisory levels, but
seas may remain elevated to advisory levels.
Friday night-Monday...winds are expected to remain below
advisory levels. Seas may approach 5 feet at times, but mostly
remain around 4 feet.
the positive tidal departures continued to trend downward
slowly early this evening. As a result, we anticipate nothing
more than some spotty minor tidal flooding with this evening's
high tide in coastal areas of New Jersey and Delaware. The
flooding will not be impactful enough to warrant the issuance of
a coastal flood advisory.
presuming our forecast temps these last 5 days of April are
accurate, we are assured of a top 3 warmest April on record in
much of our forecast area. Sunday is the critical day for
determining record or not.
Below: April projected within the top April avg temps, the
normal for April and the period of record (por).
Phl normal 54.0 por 1874
Abe normal 49.9 por 1922
56.6 projecting record
Acy normal 51.7 por 1874
57.2 projecting record
Marine...Small Craft Advisory for hazardous seas until 6 am EDT Friday