Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
926 PM EDT Thursday Jul 24 2014
surface high pressure will continue to move into the region through
tomorrow before moving offshore on Saturday. A warm front crosses
the region late on Saturday while the parent low pressure system
moves through the Great Lakes. The attendant cold front swings
through late on Sunday into Monday followed by another high pressure
Near term /until 6 am Friday morning/...
for the 930 PM EDT update...sea breeze did recently arrive at
kacy. As such, there is a moist pool right along the coast. Do not
expect this to last long as the sea breeze should dissipate over
the next few hours. Otherwise...no major changes as the forecast
looks on track.
Previous near term discussion...the GFS initialization looked
slightly better than the WRF-nmmb at most levels, but the op run
looks a bit on the warm side vs the gefs and op WRF-nmmb. Through
the short term, we will Iron the differences.
The 500mb trough axis has still to move entirely through our County Warning Area.
Precipitation along the WV/Virginia border will come close to our southern County Warning Area and we
maintained a low chance of showers there into early this evening.
Otherwise the batch of cold air advection cumulus (odd to type that in july) dont look
widespread or destined to get trapped underneath the developing
subsidence inversion. Once the cirrus from the convection move
through, the second half of the night should be clearer. Dont see
how the WRF-nmmb hanging on solution will come to fruition,
especially geographically where the model has it (the less likely
Another dry air mass with pleasant sleeping conditions. Maybe
someone will have to close the windows in our far northwestern County Warning Area because
its too cool outside? Min temperatures are a NAM/GFS MOS blend. Record low
temperatures appear safe with ridge (52 in 1903) and Abe (51 in 1963) the
most likely climate sites to come close.
Short term /6 am Friday morning through 6 PM Friday/...
with the trough axis through and a more zonal flow aloft, not
expecting too many fair weather cumulus clouds or any other clouds
on Friday. The surface high will be near/over our County Warning Area. With less of
an offshore flow and higher temps, sea and Bay breeze fronts should
form faster. Maximum temperatures are about 10-11c above the model blend
combined 925mb predicted temperatures. This is close again to a NAM and GFS
Long term /Friday night through Thursday/...
overall the medium range guidance shows a good consensus with the
middle-level features through early next work week. The trough currently
across the East Coast flattens with time before a very strong
shortwave dives out of the upper mid-west. This wave will carve out
a much deeper trough by the end of the of the weekend across the
eastern U.S. Beyond Tuesday guidance begins to separate with respect
to the timing of the trough retrograding.
Saturday...over the past several days the guidance has become
murkier and murkier with the possibility of showers during the
afternoon/evening hours. Today is no different though it should be
noted that a majority of the operational suites really pump up
surface dewpoints, some into the low-70s. The flow aloft looks
slightly less zonal than the past couple of runs, with an embedded
weak shortwave, across the board and the ensemble guidance keeps the
noise directly overhead our region...less confidence. One would
think that it would take a bit longer than 24 hours to completely
modify the airmass from the 50s to the 70s and with warming
temperatures we should have a better cap in place, plus better
mixing. All that being said, we keep the slight chance probability of precipitation in place
with daytime highs reaching into the upper-80s.
Sunday - Monday...stronger piece of middle-level energy dives out of the
Upper Middle-west early Sunday morning and begins to carve a more
defined trough across the eastern U.S. Multiple waves embedded
within the mean southwesterly flow aloft swing through, timing of
the waves is still uncertain but getting better, touching off
showers and thunderstorms...very unsettled pattern expected. Periods
of heavy rain is possible with upper level jet dynamics aiding in
large scale ascent and the approach of surface cold front late
Sunday night, tied to a surface low pressure in southern Quebec. No
matter how you Dice it, unsettled weather prevails. Temperatures
should end up being at or slightly above normal.
Tuesday - Thursday...drying trend should continue across a majority of the
region, but with the middle-level trough/cold pool aloft, and the
slightest hint of instability around, isolated showers are possible
on Tuesday...better further north. The chances for showers decreases
each afternoon thereafter. Temperatures should end up being below
normal for late July standards.
Aviation /01z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
For the 00z tafs...VFR conditions expected through out the taf
period. Few if any clouds expected. Sea breeze at kacy now should
dissipate in the next few hours.
On Friday a VFR day with just few middle level cumulus. A sea breeze
front should form again and with higher temperatures faster, make its way
to kacy by 18z and kmiv a few hours later. Less confident that it
will make it to kphl or kilg later in the afternoon, so not
included in this taf.
Saturday...mainly VFR. Isolated showers possible
west...confidence is low on showers. Gusty southwest winds
Sunday - Monday...sub-VFR conditions expected in areas of showers and
no marine headlines through the short term. The flow behind a weak
sea breeze front is going to cause some variable wind directions
into this evening before the north to northwest flow resumes. A more
pronounced sea and Bay breeze are expected to form on Friday
afternoon with a slightly stronger onshore and up the Delaware Bay
Saturday...high pressure overhead will keep seas and winds below Small Craft Advisory
Sunday...sub-sca expected with scattered showers and thunderstorms.
Monday...seas may build to Small Craft Advisory levels under a strengthening
southwest surface flow.
Tuesday...sub-sca conditions expected.