Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
927 am EDT Tuesday Jul 29 2014
weak high pressure will filter in today and Wednesday pushing the
previous cold front further offshore. Eventually the aforementioned
high pressure merges with the western Atlantic high pressure system
late this week. Meanwhile...the old cold front will be lurking just
off the coast as a stationary front. This front begins to back
towards the region this weekend.
Near term /until 6 PM this evening/...
no big changes to the forecast today. The only changes made was to
hourly temperature/dewpoint grids and to increase sky cover slightly.
Will continue to see cold and dry air advection through the day
in the wake of the cold front. Mav and met came in a bit lower for
highs than the previous run, now keeping much of the region in the
70s. Given that most sites topped out in the lower 80s yesterday,
and today should be even a few degrees lower, have followed this
trend with the forecast. Should see some cumulus development, but
with the dry low levels, do not expect any precipitation today
despite the middle and upper level trough remaining west of the
Short term /6 PM this evening through 6 am Wednesday/...
clearing skies, light winds, and dry air will set the stage for
prime radiational cooling conditions across the region. Thus expect
lows to range from the upper 40s in the Poconos to the lower 60s
near the coast and in the urban corridor. For many of our climate
sites, this is near record lows.
Long term /Wednesday through Monday/...
hemispherically the operational envelope seems pretty much in line
with one another through Saturday before diverting. The anomalous
East Coast trough remains the dominate feature/driving force
through the end of the work week. Thereafter, the stronger trough
begins to break down with its closed low opening up and moving off
towards the north and east over the weekend. A much more broad
based trough remains overhead through the end of the period.
Wednesday - Thursday...expecting mostly dry days across the region
outside the possibilities of isolated instability showers across the
northern portions of the County Warning Area. Cold pool interaction with a few
passing shortwaves may be enough to get airmass showers to occur,
though the better chance looks to occur to Thursday, still slight
chance, with mor moisture in the column compared to Wednesday.
Temperatures look to remain below normal, though depending on how
much sunshine we receive on Thursday we could come close.
Friday...transitional day with the looks of an inverted trough
sitting off the Atlantic coast...the old baroclinic zone that pushed
through on Monday. Onshore flow to the east and southeasterly flow inland,
around the departing surface ridge, help to advect in slightly
cooler temperatures but Atlantic moisture. Upslope flow combined
with some heating, weak surface convergence, may be enough to
generate scattered showers and thunderstorms across the interior
zones with better stability closer to the coast. Temperatures should
end up being below normal...again.
Saturday - Sunday...lots of uncertainty at this juncture in terms of
the inverted trough's placement and surface low, along the
front/trough, track. The 00z suite, outside of the Euro, seems
reasonable with keeping a majority of the convective activity to our
south and just offshore on Saturday...Sunday is a different story.
Gefs is showing decent chances for afternoon showers and
thunderstorms that bisect the region...ec ensembles have something
similar. The latest 00z ec came in much much wetter Saturday and
Sunday compared to the other medium range guidance, and without
seeing the ensembles uncertain how much stock to put into its
solution at this time. The GFS anc ggem have the surface low
pressure along the front moving through, ec has it 24 hours earlier
on Saturday...something to continue to watch.
Monday...slight drying trend expected on Monday though not entirely
void of any showers with cold air still aloft with a few more
shortwaves shearing across overhead. More moisture and heat advects
in and could push temperatures back to normal.
Aviation /13z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
VFR conditions are expected through the taf period. Scattered to broken
cumulus clouds around 050 are possible through the day time hours,
but otherwise expect few clouds.
Northwesterly winds will shift to westerly between 15 and 18z and
generally remain westerly through the rest of the taf period. The
one exception is at kacy where a sea breeze could arrive between 18
and 21z...shifting winds to southeasterly. After 00z...expect winds
to become light...generally 5kt or less at all taf sites.
Wednesday - Thursday...mostly VFR. Isolated shower or thunderstorm
possible mainly north of phl.
Friday - Saturday...mostly VFR. Widely scattered showers and
thunderstorms possible each day, though confidence is low on
development. Patchy IFR fog or stratus is possible Friday night.
expect winds and seas to remain below Small Craft Advisory today
and tonight with winds generally staying below 15 knots and seas
between 2 and 3 feet.
Wednesday - Saturday...sub-sca conditions expected. Scattered
showers and thunderstorms possible each afternoon with better
chances Friday and Saturday.