Scientific Forecaster Discussion
fxus61 kokx 071221
Area forecast discussion
National Weather Service New York New York
721 am EST Sat Dec 7 2019
high pressure will build from the west today, 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 then approach on Tuesday and pass through Tuesday night
into Wednesday. Arctic high pressure will then follow later in
Near term /until 6 PM this evening/...
looking at a mostly sunny and cooler day, with diminishing northwest
winds as high pressure builds from the west and the pressure
With the change in air mass, have stuck closer to MOS numbers
than otherwise might have been the case judging from mav/ecs
performance yesterday. Have thus fcst high temps today near 40
NYC Metro/Long Island and mid/upper 30s north/west.
Short term /6 PM this evening through 6 PM Sunday/...
clear skies and light winds tonight under building high
pressure should lead to a cold night. Lows in the 20s in and
just outside NYC, teens most elsewhere, and some single digit
lows may be possible in the interior valleys well northwest of the city
and in the Long Island Pine barrens.
Developing return flow on Sunday as the high shifts east should
allow slight moderation in temps, with lower 40s NYC Metro/Long
Island/coastal CT and upper 30s elsewhere.
Long term /Sunday night through Friday/...
somewhat complex scenario shaping up for early week as an
amplifying long wave trough develops over the lower 48. First, a
warm front riding up the coast, and accompanied by a shortwave
trough embedded in the deep layer SW flow east of the amplifying
longwave trough, should bring a round of moderate to locally
heavy rain on Mon. Think European model (ecmwf) is more correct than the GFS
with its axis of heavier rain falling more squarely over the
area rather than to the east, via enhanced lift beneath a
coupled low level convergence/upper level divergence couplet.
Wind forecast tricky as there will be both a strong low level jet present
and low level inversion to prevent stronger winds from reaching
the sfc except perhaps in heavier precip accompanying warm fropa
late day or early evening. Have mentioned slight chance thunder
mainly for the Metro area and Long Island with models showing
some elevated instability and tt nearing 50.
Once we get into the warm sector, precip chances should diminish
going into overnight Mon night into Tue morning, then increase
with cold fropa Tue night. This second round of steady precip
will likely be anafrontal in nature given, lagging behind cold
fropa given the lagging mid level trough and anticyclonic upper
level jet streak approaching from the west. In this scenario,
precip should change to a period of snow from late Tue night
into Wed especially north/west, as colder air pours in,
especially north/west of NYC where a couple of inches
accumulation appears likely, and lesser amts toward the coast.
The slower/wetter European model (ecmwf) cold fropa suggests a possible worst
case of advy level snowfall inland, and maybe an inch or two for
NYC Metro and the coast.
Very cold air will settle in Wednesday night and Thursday, with
temps likely remain below freezing. A slight warmup is expected
by Friday as high pressure passes east.
Aviation /12z Saturday through Wednesday/...
VFR. High pressure builds in from the west through tonight, then
passes offshore on Sunday.
Northwest winds (mainly right of 310 magnetic) around 10 kt today, then
becoming light and variable overnight. There could be a few
g15-18kt at the eastern terminals this morning into this afternoon.
Outlook for 12z Sunday through Wednesday...
Sunday night and Monday...MVFR or lower with a chance of showers
after midnight, becoming widespread Monday afternoon. S g20-25kt,
mainly at the coastal terminals, with a chance of low level wind shear Monday
into Monday night.
Tuesday...MVFR or lower in showers, possibly ending as a period of
snow late at night.
Wednesday...chance of rain or snow in the morning. West-northwest g20-25kt
winds and seas will subside today as as high pressure builds in
from the west. The high builds overheard by Sunday morning and
then offshore during the day. A strengthening southerly flow may
bring marginal Small Craft Advisory conditions to the ocean waters Sunday night.
Thereafter, a prolonged period of Small Craft Advisory conditions is forecast on the
ocean waters due to a persistent southerly flow and building seas as
a cold front approaches from the west, passing through the waters
Tuesday night. There is a chance of gales Monday afternoon into
Monday night, however, there is uncertainty as a strong inversion
sets up across the waters, limiting the high wind potential.
Marginal Small Craft Advisory conditions are possible elsewhere.
Post-frontal Small Craft Advisory conditions in the west-northwest flow are possible Wednesday.
a significant long duration rainfall event is expected from late
Sunday night into Wed. Event total quantitative precipitation forecast likely to range from
1.5-2.0 inches, perhaps 2-3 inches if wetter guidance ends up
being more correct. There will be some lulls in the
precipitation, but the rain could be heavy at times Monday and
Monday night, and again later Tuesday. 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.