Scientific Forecaster Discussion
fxus61 kokx 080542
Area forecast discussion
National Weather Service New York New York
1242 am EST sun Dec 8 2019
high pressure will settle over the area tonight, then pass east
on Sunday. A warm front will approach on Monday and lift north
Monday night. A cold front will approach on Tuesday and pass
east Tuesday night into Wednesday. Arctic high pressure will
then follow later in the week. Another storm system may impact
the area next weekend.
Near term /until 6 am this morning/...
high pressure settles across the are overnight, this will
result favorable conditions for strong radiational cooling.
Lows by morning will fall well down into the lower teens across
the interior, particularly where snowpack lingers, as well as
The Pine Barrens region of Li. Otherwise, lows generally in the
upper teens to lower 20s coast, mid 20's city.
Short term /6 am this morning through 6 PM Monday/...
weak shortwave ridging moves over and east of the region
Sunday, with deep SW flow developing Sunday night into Monday
ahead of a developing large central Continental U.S. Trough.
At the surface, high pressure slides offshore Sunday, with
developing return flow Sunday night. Another dry day on Sunday,
with increasing high clouds filtering in with SW aloft flow.
Highs generally upper 30s to lower 40s, but still a few degrees
Thickening and lowering high and mid clouds Sunday night and
increasing south-southeast flow. Potential for stratus and light shower
activity developing overnight into early Monday morning. Temps
remain fairly stable or rise along the coast Sunday night in
Developing low pressure across the Central Plains Sunday night,
will lift NE into the Great Lakes Monday. Meanwhile a weak wave
of low pressure off the southeast US coast, lifts north up the coast
in between departing high and approaching frontal system. This
feature then moves over or just southeast of Li on Monday. Deep layered
lift (left front of 150+ kt ulj and nose of developing 50-60kt
llj) and convergence of a sub-tropical Pacific and Atlantic moisture
feed (+2-3 std pwats and elevated weak instability) will
present potential for period of moderate to heavy rain, with
embedded thunder, Monday morning into afternoon. Some spread in
exact track of the wave, lending to uncertainty in how far west
this heavy activity gets, with highest likelihood across Li and
CT. A swath of 1/2 to 1 inches of rain possible in 6 hr period
with this activity. In addition, potential for 20 to 30 mph
sustained and gusts to 40 mph for Li and southeast CT Monday afternoon
if low level jet tracks overhead.
This wave and its trailing trough, with axis of heavy rain,
move east Monday evening, but still bands of shower activity
expected to linger into Tuesday night ahead of next shortwave
and pre- frontal trough.
Long term /Monday night through Saturday/...
with digging large upper trough, passing shortwave, upper and lower
jet energy aiding lift, rain initially will be heavy, then taper off
to light rain, and even scatter as coverage lowers late at night
into Tuesday morning. The area will be warm sectored during that
time, and lowering of pops has been captured in database. Will ramp
up pops once again as the cold front approaches Tuesday afternoon.
Looks like the GFS is a quicker outlier with frontal movement east.
As another shortwave rotates around the back side of the upper
trough in central Canada, there are indications that rain moves just
east, with additional rain/precip shield tracking northeast on the
back side of the front Tuesday night into Wednesday due to upper
level support. Assuming that does indeed occur, colder air will move
in behind the front which will result in a transition from rain to
snow, mix in between. This could result in light snow accumulations
later Tuesday night into Wednesday, northwest to southeast.
The upper trough weakens as it pivots east, and sfc high pressure
builds in from the west late Wed, Wed night and Thursday. This will
be the period of dry, but cold weather. Could be looking at the
coldest air of the season, with temps struggling to reach or exceed
freezing Thursday after a cold start to the day.
Shortwave ridging moves east Thu night, with sfc high moving north
and east of the area. Easterly flow then sets up, with dry
conditions likely lingering into Friday. Thereafter, model spread
grows, with latest run of the operational GFS quicker with southern
shortwave's movement east, which steers a sfc low out of the Gulf of
Mexico and off the southeast coast later Friday and Friday night, whereas
Canadian and European model (ecmwf) are much slower with these features. Eventually,
precip should move back in from the south by Saturday, but big
difference in the upper level pattern are noted in the global
models, with GFS phased with northern stream shortwave and southern
stream. Canadian and European model (ecmwf) look much different (lack of phasing
between the two), so plenty of time to Iron out these details as the
event draws near.
Mild temperatures Monday night into Tuesday, well above normal, fall
below normal Wednesday night through Thursday night. Temps will
moderate late in the week, and a model blend followed which is close
to wpc numbers.
Aviation /06z Sunday through Thursday/...
VFR. High pressure settles over the terminals overnight, then
passes offshore in the afternoon.
Light northerly to variable winds overnight becomes S-southeast by
late morning and increase to around 10 kt with gusts 15-20kt
by early afternoon.
MVFR conditions begin late in the taf period with lowered ceilings
entering the region ahead of potential showers.
Outlook for 06z Monday through Thursday...
Sunday night...MVFR developing late with chance of rain.
Monday...rain becoming widespread. S g20-25kt, mainly at the
coastal terminals, with a chance of low level wind shear Monday into Monday night.
Slight chance thunder Monday afternoon.
Tuesday...MVFR or lower in showers, possibly ending as a period of
snow late at night. SW gusts around 20 kt possible.
Wednesday...chance of rain or snow and MVFR in the morning. West-northwest
sub Small Craft Advisory conditions tonight through Sunday as high pressure
moves across the waters. A strengthening southerly flow may
bring marginal Small Craft Advisory conditions to the ocean waters Sunday night,
with higher likelihood for a period of Small Craft Advisory for all waters Monday
afternoon/evening, and potentially a period of gales for ocean
waters and eastern Li sound and bays. Seas should build to 8 to
12 ft by late Monday as well.
Southerly winds will approach gale force Monday night over the ocean
waters, with solid Small Craft Advisory conditions elsewhere. These winds diminish as
a cold front approaches Tuesday. The winds shift to the west/northwest
behind the front Tuesday night and Wednesday, remaining gusty
through Thursday as high pressure approaches from the west.
Rough seas will slowly subside through the mid week period.
a significant long duration rainfall event is expected from
late Sunday night into Wed. Event total quantitative precipitation forecast likely to range from
Heaviest rain will be Monday into Monday night, with 1 to 2
inches of rain likely during this period. The long duration of
the event should preclude widespread flooding. Nuisance/poor
drainage flooding is the most likely outcome.
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) is still
operating at reduced power.