Scientific Forecaster Discussion
fxus61 kphi 141619
Area forecast discussion
National Weather Service Mount Holly New Jersey
issued by National Weather Service Baltimore Maryland/Washington District of Columbia
1119 am EST Thu Nov 14 2019
a ridge of high pressure stretching down along the mid-Atlantic
coastline today will nudge eastward over the Atlantic through
tonight. A cold front will move through late Friday, then high
pressure builds into our area from the northwest and north later
Saturday and Sunday before shifting into the Canadian
Maritimes. A coastal low develops off the southeast Friday
night and slowly moves northeastward over the weekend and
remaining well off of our coasts, then another storm may develop
off the Carolina coast Tuesday and take a similar track through
Near term /rest of today/...
surface high pressure stretches across the region this morning,
with its center anchored along the New England coast. Water
vapor imagery this morning depicting decent mid to upper level
moisture, translating into partly sunny to mostly cloudy skies.
Temperatures are rising into the mid to upper 30s across Maryland/Delaware
and southern NJ, while starting to near and crack the freezing
mark over northern New Jersey and the Poconos.
For the remainder of the day, will continue to see ample mid to
high level clouds thanks to the upper jet and shortwave energy
traversing overhead. With a surface ridge in place, dry
conditions expected under a weak warm air advection regime. Highs this
afternoon will top out mainly in the 40s, nearing 50 across the
Eastern Shore of Maryland/de, while the Poconos hold in the middle 30s.
Short term /tonight through Friday night/...
upper trough digging through the Midwest and moving into the
eastern Seaboard will begin to cut off a closed upper low over
the Mississippi and Tennessee valleys. Out ahead of that upper
low, surface low pressure begins to develop off the southeast
U.S. Coast. A frontal boundary develops along the eastern
Seaboard, and the low will begin to lift along that boundary
well after midnight tonight.
In terms of sensible weather, conditions should be dry for most
of the night, but clouds across the northern zones will move
offshore, and clouds will move into the southern portions of the
forecast area associated with the approach of the surface low
approaching the mid- Atlantic.
After midnight and into the pre-dawn hours of Friday, some
precip will develop off the southeast New Jersey coast and into
Delmarva. Precip should be mostly rain mainly south and east of
the garden state parkway and across most of southern Delaware
and the southern portion of the Eastern Shore of Maryland. Going
a bit inland, however, it may be hard for the cold air at the
surface to scour out, so precip may fall as a period of snow or
a wintry mix west of the garden state parkway to the I-95
corridor. Minimal amounts of quantitative precipitation forecast expected, and pops will be
capped at slight chance to maybe low chance. Not expecting
accumulating snow, so no products will be issued.
Long term /Saturday through Wednesday/...
summary...the air mass moderates some Friday ahead of a cold
front, then colder again Saturday into Sunday. Milder air should
overtake our area early next week, however strengthening
onshore flow may temper or delay the warming at least some.
Synoptic overview...a closed low slides across eastern Canada and
the northeast Friday into Saturday, while a southern stream closed
low reaches the southeast coast Saturday morning. The latter shifts
eastward during Saturday and Sunday taking surface low pressure with
it. A strong surface high moving across New England should wedge
southwestward into the mid-Atlantic slowing the initial forward
motion of the ocean storm. The storm tracks northeastward through
early next week and makes its way well off the mid-Atlantic coast.
Lots of energy dropping into the plains and Gulf Coast regions
should carve out a large trough during early next week. Strong short
wave energy into the base of this trough may develop another ocean
storm off the Carolina coast near Tuesday before it also takes a
similar track to the northeast. The surface high may be more removed
for this second storm, therefore if the overall trough amplifies
fast enough the surface low could be pulled closer to the coast.
This becomes less certain especially the details this far out,
however some model guidance is showing a potentially strong surface
low off our coasts in the later Tuesday through Wednesday time
For Friday...a potent closed low dropping southeastward from Hudson
Bay Canada Friday will carve out a trough into the northeast. This
will drive a mainly dry cold front across our area late Friday,
however some warm air advection ahead of it will help boost
afternoon temperatures to around 50 for many. Meanwhile, energy
diving across the southern states closes off as is nears the
southeast coast. This will induce surface low pressure development
along a lingering baroclinic zone just off the southeast coast. As
this occurs, strong high pressure is forecast to build eastward from
near the Great Lakes region and should help to keep a developing
area of rain well to our south. In addition, the low-level flow
turns north to northeast Friday night and increases some and given
the aforementioned surface high much drier air should be advecting
southward into our area.
For Saturday and Sunday...the model guidance remains in good overall
agreement with the large scale features. Southern stream energy
results in an ocean storm off the southeast coast, which then tracks
northeastward through Sunday night. While the bulk of this system
should remain far enough offshore to keep much of the precipitation
out of our area, some mainly light rain cannot be ruled out
especially later Sunday closer to the coast. Given strong surface
high pressure slowly shifting away from New England, it may provide
enough subsidence to keep the associated ocean storm rain shield
just south and east of our area. However, the presence of the
surface high and the offshore surface low will result in a tight
pressure gradient, and therefore a gusty northeasterly wind is
expected especially closer to the coast. Following a cold front
Friday night, the surface high initially building by to our north
will result in a north to northeast surface wind and bring in colder
and noticeably drier air. Saturday should feature more sunshine due
to the greater influence from the surface high, then clouds increase
Sunday as the storm tracks east of the Carolinas. The pops start to
increase up the coast during Sunday and expand inland some Sunday
night, however this is less certain given the offshore track of the
storm and much drier air still holding on especially inland (pops no
higher than low end chance). The low-level dry air will eventually
start to erode some late Sunday especially closer to the coast.
For Monday through Wednesday...the evolution of the upper air
pattern is an amplified one, however the details are less certain.
As one low pressure slides by well offshore to start Monday, the
flow aloft amplifies to our west with a potentially significant
trough shifting eastward through mid week. The timing of the
embedded short waves will be crucial as at least the 00z European model (ecmwf) looks
to phase things which results in a stronger trough in the east and
therefore a much stronger surface low off the northern mid-Atlantic
coast Wednesday. Some other guidance however keeps things separate
and therefore a weaker surface low that tracks farther offshore.
There is some potential given the scope of the incoming trough, and
given the details are less certain this far out in time we therefore
generally blended the 00z wpc guidance in with continuity.
Aviation /16z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today...VFR conditions expected with a scattered-broken deck at or above 25kft,
with light southwesterly breezes at 10 knots or less. High
Tonight...mostly VFR. Winds become lgt/vrb. After 06z, sub-VFR
conditions possible in rain at kacy, and a rain/snow mix at kmiv.
Friday and Saturday...VFR. Light and variable winds becoming west-
northwest 5-10 knots during Friday then turning north Friday night
10-15 knots before shifting from the northeast with gusts to around
25 knots Saturday (strongest mainly at acy). Moderate confidence.
Sunday and Monday...VFR ceilings, with MVFR ceilings possible
especially closer to the coast with a chance of some rain. Northeast
winds 10-15 knots with gusts to around 25 knots (strongest mainly at
Acy and miv). The winds should diminish some Monday. Low
surface high pressure and a weak gradient will yield sub Small Craft Advisory
conditions through tonight. Expect southwesterly winds around 10
knots, becoming westerly overnight. Seas 2 to 3 feet.
Friday and Saturday...the conditions are anticipated to be below
Small Craft Advisory criteria during the day Friday, then winds
become northerly Friday night and increase. Gale force gusts are
quite possible later Friday night through Saturday night. Seas will
become rough. A gale watch has been issued for all areas except for
upper Delaware Bay late Friday night through Saturday night.
Sunday and Monday...periods of northeast gale force wind gusts are
quite possible along with rough seas. The winds however should
diminish some on Monday.
here are the record low temperatures for today:
Climate sitenov 14
allentown17 in 1986
Atlantic city15 in 1986
atl. City Marina 23 in 1874
georgetown22 in 1986, 1950
Mount Pocono 5 in 1905
philadelphia19 in 1986
reading16 in 1986
Trenton 20 in 1905, 2019
Wilmington 20 in 1986, 1911
Marine...gale watch from late Friday night through late Saturday night