Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
927 PM EDT Monday Jul 25 2016
a cold front will approach from the west and move through the region
early Tuesday morning, before stalling near or just to the south of
our area. This front will gradually lift north by the end of the
week with areas of low pressure developing along this boundary.
Near term /through Tuesday/...
the remaining severe watch was lowered a little while ago. Any
remaining thunderstorms across the area are not expected to be severe. The
front will remain across the Delaware-Maryland-Virginia overnight and scattered showers
will continue for the next few hours. Probability of precipitation generally decrease
through the night. Patchy fog is possible overnight. Slow clearing
from northwest possible late.
Short term /Tuesday night/...
the cold front is expected to slow down as it moves southward
through the Delmarva early Tuesday morning. There is still
uncertainty regarding how quickly the front pushes southward. Fronts
tend to get hung up in the Delmarva this time of year and in this
pattern with zonal steering flow aloft. Added a chance for showers
and storms during the afternoon hours across the southern half of Delaware
and adjacent eastern Maryland with the front likely nearby.
Unfortunately, we won't get much of a break from the heat tomorrow
as Post-frontal cold air advection progged to be minimal. Forecast highs are in the
low to mid 90s across most of the area (except cooler in the higher
terrain of northeast PA/northwest New Jersey and along the coast). However,
it will be noticeably less humid across eastern PA and
central/northern New Jersey with dewpoints in the upper 50s and lower 60s.
Farther south, where the front gets hung up, dewpoints will still be
in the upper 60s and lower 70s. Afternoon heat indices should peak
near 100f in the Delmarva.
Long term /Wednesday through Monday/...
the medium range models are in good agreement keeping high pwat
air just to our south as a sfc boundary stalls in the southern
portion of the forecast area. Higher humidity values and a slight
chance for storms will continue near the Delmarva. Heat index
values in the mid 90s are still expected from Philadelphia
In response to an approaching shortwave, heights build on Thursday
and 1000-850mb thicknesses increase resulting in temps climbing a
couple of degrees warmer compared to Wednesday, with heat index
values in the mid to upper 90s. As higher pwat air returns...and
shortwave energy moves through the region...widely scattered to
scattered storms also return Thursday.
The European model (ecmwf)/GFS/Canadian models are coming into better agreement
developing a broad upper trof over the eastern U.S. Into the
weekend...bringing temperatures down closer to normal values for late
July/early August. With pwat values still 1.5-2.0" through
Monday, and weak shortwaves moving through the upper trof
axis, daily afternoon and evening showers and storms will be
possible through the remainder of the long term period.
Aviation /02z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Overnight...behind the evening showers and storms, winds will
shift more to the west, slightly northwest, but remain under 10
knots. Patchy fog will develop in the more prone areas as winds go
light and skies largely clear.
Tuesday...patchy fog early, clearing by around 15z. Then VFR
conditions expected for the remainder of the day. Westerly winds
around 10 to 12 knots through the afternoon.
Tuesday night through Friday...mainly VFR conditions expected.
Scattered showers and thunderstorms Thursday and Friday, with
MVFR/IFR conditions possible at times.
winds and seas will be just below Small Craft Advisory criteria
through tomorrow. South wind gusts to 20 knots will continue to
occur through this evening. Seas will increase from 2 to 3 feet to
4 feet in our coastal waters. Stronger thunderstorms developing on
land this afternoon could threaten the waters this evening.
Locally strong winds and higher seas are possible with these
Tuesday night through Friday...sub-advisory conditions are
expected to continue on the area waters through much of the week.
Expect higher winds and waves in and near scattered showers and
thunderstorms that become more likely at the end of the week.
Rip currents...a moderate risk for rip currents continues through
the night. Tuesday through the most of the week: with the
Atlantic Basin continuing quiet tropically, unless we get a strong
onshore flow...rc risk this coming week should be generally low.
Tstms and pockets of chilly upwelling water may the greater
concerns. There is some sign of colder upwelling along the coasts
as of 3 PM EDT, the temp at phl was 96 which has tied the record
high for this date. Abe was 95, also tying a record high, and ilg
was 96. This also has tied the record for this date.
The last time the temperature reached or exceeded 98f at phl was
three years ago on July 18, 2013. The last 100-degree day at phl
occurred four years ago on July 18, 2012.
Record high temperatures for today through Thursday are below.
Site 25th 26th 27th 28th
---- ---- ---- ---- ----
Phl... 96-1899 101-1892 101-1940 100-1941
Abe... 95-1999 98-1940 98-1955 97-1949
Acy... 99-2010 96-2011 99-2005 98-1999
Ilg... 96-1987 99-1894 100-1894 101-1894
Ttn... 97-1999 99-1892 100-1894 101-1894
Ged... 99-2010 97-2012 98-2005 99-1949
Ridge... 96-1999 99-1940 98-1955 99-1941
Mpo... 90-1999 89-1949 91-1955 93-1949