Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
908 PM EDT Thursday Jul 30 2015
a weak cold front will move through our region tonight, then stall
to our south and east on Friday. The next weak cold front should
cross our area late Saturday, before stalling offshore Sunday. A
few weak waves of low pressure may track along this front Monday,
while high pressure moves in from the west. A stronger cold front
is expected to arrive Tuesday, then stall nearby Wednesday.
Near term /until 6 am Friday morning/...
cold front has pushed past Mount Pocono and should be moving into
Berks Colorado and Lehigh Valley within one to two hours. It should
slowly push through the remainder of the area overnight. With dry
air advection expected behind the front, clearing is expected for
tonight. Temperatures are forecast to drop into the 60s at most
locations with a southwest wind shifting to the northwest. Wind
speeds should be 10 miles per hour or less.
Patchy fog is possible over northern and central New Jersey through
midnight where there were higher rain totals and the front may be
a bit slower to arrive. Then, near dawn, there may be some more
patchy radiation fog in the Lehigh Valley and Berks Colorado which had
the highest rain totals in the area earlier.
Short term /6 am Friday morning through 6 PM Friday/...
dry air will build into our region from the northwest and west for
Friday. Dew point readings are anticipated to drop into the 50s at
most locations, so it will be noticeably less humid than today. Even
with the passage of the front, conditions will be quite warm on
Friday. Maximum temperatures will be around 90 degrees except in the
elevated terrain. A northwest to west wind at 6 to 12 miles per hour is
Long term /Friday night through Thursday/...
A closed middle-level low over hudson's Bay will maintain a trough
in the east Continental U.S. And a general cyclonic flow aloft through the
period. There is some model disagreement regarding shortwave energy
entering the Great Lakes region on Sunday...and to what extent
the trough amplifies as a result. There has been little run-to-
run operational model consistency in this regard...thus relied
on the gefs/ecens ensemble means. The main implication is with
regard to the placement of an offshore front on Monday-Tuesday and the
timing of a another cold frontal passage on Tue-Wed.
A weak cold frontal passage is expected on Saturday night...W/
the best chance for rain showers/thunderstorms and rain northwest of I-95. This front will stall
just offshore through Tuesday and may even wash out. As aformentioned
shortwave energy enters the east Continental U.S. Trough... this will turn the
flow more meridional...W/ tropical moisture moving north. The bulk
of this moisture should remain offshore.
The next chance of rain showers/thunderstorms and rain will be with another cold frontal passage
currently timed in the late Tuesday/early Wednesday period. Overall...
early trends /d+5 to d+7/ indicate this front will stall near
the New Jersey coast and wash out. There are no indications of a big
change in the synoptic pattern through d+7...so this solution is
plausible...especially if the middle-level flow parallels the
front as currently indicated. Above normal temperatures
expected through the period.
Saturday...thunderstorms are possible over the Lehigh Valley and
Poconos late Sat afternoon/early evening...but moisture may be limited...
so coverage is questionable as well as how far south/east these
storms progress. An approaching shortwave trough will lead to steep
middle-level lapse rates...while a weak cold front pools low level
moisture...and provides a source of lift. Ml cape is modeled
around 1 kj...while bulk shear approaches 40 knots. Both of these
factors are most favorable over the Lehigh Valley and Poconos.
There is the potential for gusty winds...with model soundings
exhibiting an inverted-v profile near the surface...as well as
a healthy d-cape approaching 1.4 kj. Small hail is also possible
as wbz values fall blw 10 kft in the afternoon....as well as h50
temperatures around -12c. Otherwise...a partly to mostly sunny Saturday
Sun...shortwave ridging aloft west/ high pressure briefly moving in behind
departing cold front. This will promote a mostly sunny and dry
day. The gradient may relax enough for a sea-breeze to develop
along portions of the coast.
Monday...shra/tsra are possible Monday afternoon as shortwave impulse skirts by
to the north and a Lee trough sets up west of I-95. Moisture is
limited...and probability of precipitation were focused over the northern half of the
County Warning Area...closer to the better dynamics. The best chance of thunder is
also over this area...W/ more favorable convective parameters.
The aforementioned plume of tropical moisture but may be close
enough for increased cloudiness near the coastline on Monday.
Tuesday through Thursday...there remains above average uncertainty during
this time frame. The best chance of rain showers/thunderstorms and rain will be west/ the
cold frontal passage late Tuesday/early Wednesday. If the front stalls...
rain showers/thunderstorms and rain are possible through Thursday.
Aviation /01z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Mosly VFR conditions are anticipated. However, patchy light
radiation fog is possible around kttn, krdg, kabe, kacy and kmiv
overnight. Despite drier air moving into the region, areas around
krdg and kabe will likely still have very wet ground setting the
stage for radiation fog. Kttn, kmiv, and kacy though they did not
have as much rain earlier, will see the drier air later, thus
are starting with low dew point depressions. Any fog that does
develop should dissipate shortly after sunrise, if not sooner.
A southwest wind around 5 to 10 knots this evening is forecast to
shift to the northwest overnight. Wind speeds may drop below 5 knots
at some locations for a time overnight.
Sat and Sat night...mainly VFR...with MVFR possible Sat evening and
early Sat night in rain showers/thunderstorms and rain mainly confined to Abe and ttn.
Sun...VFR conditions expected.
Monday and Tuesday...mainly VFR...W/ MVFR possible in shra/tsra...
especially on Tuesday.
a cold front from the northwest is forecast to pass across the
coastal waters of New Jersey and Delaware tonight. With the
front, the wind is forecast to shift to the northwest for late
tonight and Friday morning at speeds of 10 to 15 knots. Wind
speeds will likely decrease on Friday afternoon as air
temperatures begin to exceed the water temperatures and
atmospheric mixing is reduced.
Wave heights on our ocean waters should favor the 2 to 4 foot range.
Waves on Delaware Bay are expected to be 2 feet or less.
Friday through Tuesday...a brief period of Small Craft Advisory winds and seas are
possible Sat night and Sun morning with a cold frontal passage.
Otherwise...sub-sca conditions expected for the remainder of the