Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
940 PM EDT Thursday Aug 21 2014
weak low pressure will cross the region tonight through Friday
night and then move off the coast Saturday. High pressure will
build across the area this weekend and remain in control of the
weather into next week. A cold front will approach the area next
Near term /until 6 am Friday morning/...
convection extended from the Lehigh Valley up into northern New
Jersey. The showers and thunderstorms were continuing to
regenerate along remnant boundaries and the dissipation process
should be rather slow from this point Onward, especially with a
middle level short wave trough approaching from the northwest. We
will forecast categorical or likely precipitation for our northern
counties until around midnight, then we will lower the
probabilities into the chance category for the late night period.
The scattered showers around upper Chesapeake Bay and northern
Delaware should be slow to dissipate, as well. The showers are
expected to drift eastward during the night and the area may
expand a bit. As a result, we have the mention of scattered
showers for our central and southern counties.
Temperatures are expected to drop into the 60s overnight with a
light south to east wind.
Short term /6 am Friday morning through 6 PM Friday/...
1000j of MLCAPE and slightly stronger 0-6km bulk shear cues
interest in convection Friday afternoon. Sref has decent probs for
showers...especially east PA...S New Jersey and the Delaware-Maryland-Virginia. For now have
played the shower and thunderstorm risk conservatively and maintained the
330 am Thursday forecast probability of precipitation for Friday...about 10 percent below the
12z/21 GFS/NAM MOS blend.
It will be slightly cooler as the flow turns more easterly as the
surface low consolidates to the S of the Delaware-Maryland-Virginia.
Forecast basis: temperatures/dews/winds are a 50 50 blend of the 12z/21
Long term /Friday night through Thursday/...
the area will continue to be under the influence of the weak
upper low and surface low Thursday night and into Friday. Scattered showers and a
few thunderstorms will be across most areas Thursday evening and then diminish
overnight...a couple leftover showers will develop Sat mostly
across the Delaware-Maryland-Virginia...southeast PA and southern New Jersey. Chance for showers are only
in the chance range however. A few downpours are still possible Thursday
night with the higher precipitable waters still across the southern areas. Lows Thursday
night will mostly be in the low 60s across the north and middle/upper
60s elsewhere. Highs Sat in the upper 70s/low 80s south and low to
middle 70s north. Drier air will continue to push in from north to
An upper ridge builds up to the west of the area this weekend and
then rotates across the area early next week. Surface high pressure
will move slowly in tandem with the upper high. This will produce
a period of dry weather for our region. Probability of precipitation for Sat night through
next wen night are sub-15pct range for the entire area.
Temperatures will be a few degrees below normal sun/Mon...near
normal Tuesday...and then a bit above normal Wed/Thu. Humidity levels
will be comfortable through much of the period...but will trend up
toward the middle of next week.
Aviation /02z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Showers are anticipated for tonight. Scattered thunderstorms are
expected for this evening from around kabe and kttn northward.
Prevailing conditions should continue to lower into the MVFR range
for late tonight and Friday morning. Some spots could fall to IFR
depending upon the extent of any stratus and fog development along
with additional shower activity. Mainly VFR conditions are
expected to return for Friday afternoon and there is a chance of
showers and thunderstorms at that time.
The wind should back from the south and southeast to the east
during the taf period. Speeds are expected to be mainly less than
Friday night through Sat...mostly VFR but scattered showers may bring lower
Sat night through Tuesday...VFR expected.
sub-Small Craft Advisory conditions expected through Friday with
seas 3 feet or less and south to southeast winds 5 to 10 knots
becoming easterly Friday.
We've not seen any new mareps this week from mariners in our easy
use (internet and/or smart phone) link
www.Weather.Gov/phi/marobsform this has been derived for the
mariner to easily Post information instantly to the National Weather Service for use in our
Thursday night through Friday night...sub Small Craft Advisory conditions with scattered showers.
Sat and Sat night...low end Small Craft Advisory conditions expected on the ocean.
Sun through Tuesday...sub-sca conditions with fair weather.