Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
852 PM EDT sun may 3 2015
high pressure will build farther offshore of the East Coast through
Monday, before a cold front moves across the area on Tuesday into
Tuesday night. The cold front is forecast to stall south of the area
through the end of the week with high pressure nosing its way
southward across the area through Friday. The high builds offshore
over the weekend, with return flow developing across the area.
Near term /until 6 am Monday morning/...
another quiet evening across the area. The daytime cumulus has
dissipated across the area. A few patches of ac will move across
the region overnight. Winds across the del valley have turned southeast
behind the sea breeze...but that should diminish shortly. Few
changes needed to the grids for the overnight.
Short term /6 am Monday morning through 6 PM Monday/...
a warm day is in store for our County Warning Area with many places possibly
having the warmest day of 2015 so far. Last couple of days as
indication, big diurnal swings as surface temperatures are doing 12-13c
above predicted 925s and around 18c above above predicted 850s.
Looks like stat guidance is picking up on this trend. Under
more normal antecedent conditions philly might just make 80f.
The slow canopy developing of the trees is likely also assisting.
Forecast soundings are showing slightly more cumulus based moisture
than today, so maybe more flattish appearing cumulus around by
Monday afternoon. Their bases may very well be 7-8k, we dont see
that too often around here.
The gradient between the approaching front and the departing
high is predicted to start tightening during the afternoon. GFS
925mb winds likely too high again, regardless even going with the
more conservative WRF-nmm mixing to a higher level will likely
generate wind gusts 20 to 25 miles per hour by afternoon. The southwest
gradient will also fight the advancement of any sea breeze
front more than the last two days in spite of even higher
Long term /Monday night through Sunday/...
a cold front is forecast to move across the area Tuesday into
Tuesday night, and slowly sag southward into Wednesday. Precipitable water values
will increase to around 1.0-1.5 inches as the front sags across the
area, and with an increase in moisture and warm temperatures, there
is some instability forecast. Cape values approaching 500-1000 j/kg,
slightly negative Li values, and total total values near 50. So as
the front moves through the area, scattered showers are expected,
along with isolated thunderstorms. The front should slowly move
across the area into Tuesday night, but may have a hard time pushing
south of the area through the early part of Wednesday. While showers
may linger into at least early Wednesday, thunderstorm activity will
likely diminish with the loss of daytime heating/instability
As the front slowly passes south of the area Wednesday, it is
forecast to stall out to our south through the remainder of the
week, and may end up washing out to our south. With the front to our
south, high pressure from the north will nose its way into the area
through the end of the week. This should keep the weather dry
through Friday, and with slight ridging building aloft, temperatures
are forecast to remain above normal through the end of the week.
Wednesday may be the coolest day with a north/northeast flow across
the area which may bring in cooler air and keep cloud cover in as
The dry weather should remain through Friday night, but isolated
showers may return for Saturday and Sunday as return flow develops
as high pressure builds offshore and the front to our south may lift
back north of the area. Across the area, increasing moisture and
daytime instability across the area which could lead to a slight
chance of showers, especially across the western half of the area.
Aviation /01z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
00z tafs were VFR.
Tonight...clear skies and winds becoming light and variable.
Air mass again is quite clean and we are not anticipating any
fog at the terminals.
Monday...a southwest wind will develop in the morning and
should average close to 10 knots. Some gustiness is likely
as the day progress, more likely in the afternoon. The predicted
moisture at the cumulus level is slightly more than today, so
maybe a few more high based (looks around 7k again) cumulus clouds
Tuesday-Tuesday night...generally VFR with showers/thunderstorms
possible. Temporary lower conditions possible with
showers/thunderstorms. Southwest wind gusts around 20 knots Tuesday.
Wednesday...MVFR ceilings possibly developing with showers.
Wednesday night-Friday...improving conditions to VFR overnight
Wednesday and continuing through Friday.
sub Small Craft Advisory conditions are expected through Monday
day. Longer period swells continue to slowly subside this afternoon.
We should get another up the Delaware Bay wind increase
later this afternoon and evening but peak below Small Craft
On Monday, a general southwest gradient will prevail with overall
lighter winds farther offshore due to less efficient mixing. In
Delaware Bay and along the immediate coast, there should be more
gustiness, but we are expecting gusts to peak around 20 knots.
Overall gustier in the afternoon than morning.
Monday night-Friday...sub Small Craft Advisory conditions expected.
However, winds may gust around 20 knots and seas approach 4 feet
through the period. Frontal boundary is expected to move south of
the waters late Tuesday and remain south of the area through the end
of the week.
after coordinating with the state forestry services and collaborating
with neighboring offices, we have issued a Fire Weather
Watch for Pennsylvania and New Jersey for Monday afternoon and
Dew points have mixed downward more than stat guidance has been
indicating today. We were rather conservative with afternoon dew
points Monday and predicted rh(s) reach 25 to 30 percent.
Wouldn't be surprised if some lower 20 rh(s) occur. It has been
obviously dry. The least certain element is the wind. The gradient
is predicted to increase during the afternoon with a general
greater chance across northern parts of the watch area.
Because of lighter winds and generally higher wind criteria,
Delaware-Maryland-Virginia was not included in this watch.
PA...Fire Weather Watch from Monday afternoon through Monday
evening for paz054-055-060>062-070-071-101>106.
New Jersey...Fire Weather Watch from Monday afternoon through Monday
evening for njz001-007>010-012-013-015>023-027.