Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
929 PM EDT Tuesday Jul 22 2014
high pressure will continue to move eastward tonight allowing for a
better return flow tomorrow ahead of a potent cold front. The front
should move through later on Wednesday into Thursday morning. High
pressure will fill in behind the departing front through the first
half of the weekend before a complex system approaches Sunday
spilling into the new work week.
Near term /until 6 am Wednesday morning/...
dew point temperatures remain in the middle to upper 60s across the
region and with the continued southerly surface flow expect dew
points to increase slightly through the overnight. As a result,
there may be patchy low clouds, fog and haze toward morning.
Minimum temperatures should range from the middle 60s to the lower
Short term /6 am Wednesday morning through 6 PM Wednesday/...
the guidance has been fairly consistent during the past several days
regarding the forecast for Wednesday. Temperatures at the 850 hpa
level are forecast to rise around 18c or 19c, so maximum
temperatures mainly in the lower 90s continue to seem reasonable.
Dew point readings should be right around 70 resulting in maximum
heat index values in the middle and upper 90s. The wind is
anticipated to favor the south on the coastal plain and the
southwest inland at speeds around 10 miles per hour.
Instability will be on the increase through the morning and early
afternoon with mixed layer cape values expected to rise around 2500
j/kg in areas along and to the northwest of the Interstate 95
corridor. A bit of a middle level cap may prevent much activity from
developing during the early to middle afternoon. However, a line of
thunderstorms should develop ahead of a cold front approaching from
the northwest. The convection will likely move into our northwestern
counties by late afternoon and it should reach the Interstate 95
corridor during the early evening. The Storm Prediction Center
continues to suggest that the greatest threat of severe weather
ahead of the front will be up in New England. However, a few strong
storms and isolated severe weather remain possible in our area.
Long term /Wednesday night through Tuesday/...
cold front should be at our doorstep at the start of the longterm
period though as the case during the Summer, it will not a quick passage.
Upper level support with the right entrance region of the jet
overhead and deeper troughing nudging in from the west combined with
precipitable waters nearing 2 inches, again, could produce heavy rain with any of
the storms. Shear values will be rather robust, around 25
knots...better the further north you go, so organized convection
seems plausible and the storms will be moving. With the deepening
trough expected overhead on Thursday, the front should be slow to
clear the region so we keep chance to likely probability of precipitation in across the
southern zones through most of the afternoon...could be long in The
The base of the trough begins to flatten out by Friday, though not
entirely becoming zonal. This yields slightly below normal
temperatures and decreased chances for convection given a drier
airmass in place. Still a bit uncertain about the Saturday evening
timeframe as some of the operational guidance swings a piece energy
through the base of the trough which could touch off a couple
stray/isolated showers...better east than west with better moisture
pooling and seabreeze interaction.
Ridging builds into the west sending stronger shortwaves of energy
into the trough overhead allowing for another bout of deeper
troughing. Expect unsettled weather through the remainder of the
longterm as a series of embedded waves pushes through aloft touching
off showers and thunderstorms.
Aviation /01z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
For the 00z tafs...VFR conditions are anticipated through at least
06z. Increasing low level moisture in the southerly flow may
result in the development of some low clouds, haze and fog for
late tonight into early Wednesday morning. At this point, expect
mostly MVFR reductions in visibility and ceilings. The exception
is at krdg which looks to have a slightly deeper saturated
boundary layer. Thus, at krdg, IFR visibilities will be possible at
times, primarily between 08 and 12z.
VFR conditions are expected from middle morning on Wednesday into the
middle afternoon hours. However, thunderstorms out ahead of a cold
front approaching from the northwest should impact our region
after 21z, and for much of the Delaware valley and points further
east, storms may not arrive until after 00z.
A southerly wind around 6 knots or less is expected tonight. A
southwest to south wind around 10 knots is anticipated for
Wednesday night and Thursday...MVFR and IFR conditions at times in
showers and thunderstorms. Patchy fog Thursday morning.
Thursday night through Saturday...mainly VFR.
Sunday...sub-VFR possible in scattered showers and thunderstorms.
patchy fog is possible early Wednesday morning primarily for the
High pressure off the coast and a cold front approaching from the
northwest should maintain a southerly flow over the coastal waters
of New Jersey and Delaware for tonight and Wednesday. Wind speeds
will favor the 5 to 15 knot range.
Wave heights on our ocean waters should be 2 to 4 feet. Waves on
Delaware Bay are expected to be 2 feet or less.
There is a chance of thunderstorms late on Wednesday.
Thursday through Sunday...high pressure overhead will keep seas and
winds below Small Craft Advisory criteria.