Scientific Forecaster Discussion
fxus61 kokx 151503
Area forecast discussion
National Weather Service New York New York
1003 am EST sun Dec 15 2019
high pressure builds in from the west today as low pressure
continues to track well to the north. High pressure briefly
builds over the region tonight, then drifts offshore Monday.
A low pressure system impacts the region Monday through
Tuesday, departing to the northeast Tuesday night. High
pressure builds into the region on Wednesday and remains over
the area through the end of the week.
Near term /through tonight/...
forecast on track with just a few minor adjustments to reflect
latest observations. With the cyclonic flow remaining across
the northeast clouds have begun to move back into the western
zones. So increased cloud cover through this morning, as drying
should begin this afternoon with the ridge building. Also
adjusted dew points and temperatures, which were running higher
The deep upper closed low that affected to the region Saturday
will continue to track through eastern Canada as the flow across
the area becomes zonal. Snow streamers were coming off the
eastern Great Lakes in the strong west flow. The flurries should
remain west of the region, however, would not be too surprised
if a few made it into the lower Hudson Valley. Meanwhile the
next shortwave to affect the region will be amplifying into the
intermountain southwest. With a zonal, progressive flow, this
shortwave will quickly translate eastward. However, there
remains uncertainty as to the timing of this system.
Meanwhile weak surface ridging builds into the area today as the
developing surface low tracks through the Southern Plains and
into the lower Mississippi Valley. With a strong pressure
gradient between the departing low to the north and high
pressure to the west, strong and gusty westerly winds are
expected. These winds and gusts will diminish early this evening
as the surface high builds into the area. The high will be over
the area through tonight, with the center of the high shifting
off the mid Atlantic coast toward morning. The high will keep
the frontal system suppressed to the south with precipitation
remaining to the southwest of the area 12z Monday.
Short term /Monday/...
while the guidance has come into a little better agreement with
the shortwave tracking toward the area, there still remains
uncertainty with the track of the low. The latest trend has
been a shift a little farther to the south. And later guidance
may continue this trend or even shift the low back to the north.
The uncertainty will have impacts to the timing and type of
precipitation across the forecast area.
With the latest trends have held off the timing of the
precipitation as the high shows weak signals of damming,
keeping cold air across the northern tier. So, will have likely
probabilities after 18z and only across the far southern zones
with low end chance probabilities reaching much of the area by
later Monday afternoon.
With cold air in place precipitation will be in the form of
light snow. And then with warmer air moving in along the coast,
especially aloft, a mix of rain, snow, and sleet will be
possible late day. There may even be pockets of light freezing
rain across northeastern New Jersey and into northern portions
of New York City.
Long term /Monday night through Saturday/...
storm system Monday night through Tuesday.
Timing and placement differences remain with the track of the
low through Tuesday night with the GFS a little quicker and
farther north than the European model (ecmwf). Thus confidence is on the low end
with precipitation types across the region. And the NAM was
showing colder lower levels as a warm layer moves in aloft, with
a strengthening warm frontal boundary. So, used a blend for
precipitation types Monday night through Tuesday. With the
possibility of colder surface air remaining Monday night into
Tuesday, there may be more freezing rain closer to the coast
than currently forecast. While inland may be predominately
The low will be tracking well east of the area Tuesday night
with the precipitation quickly ending. Drying conditions are
expected by later Tuesday night as the low deepens and
accelerates northeast to eventually southeast of Nova Scotia by
For the rest of the long term, high pressure starts to build
back into the region on Wednesday and will remain over the area
through the end of the week. Expect dry conditions with
temperatures below normal. Low pressure may impact the area over
Aviation /15z Sunday through Thursday/...
strong low pressure tracks north through eastern Canada today,
with weak high pressure building into the region tonight. A weak
area of low pressure approaches the region Monday.
VFR through Monday 12z.
Main concern will be gusty west winds, sustained 20-25ktg30-35kt
today, with an isolated peak gusts to 40 kt possible. Winds and
gusts gradually subside through the evening push, diminishing
Outlook for 12z Monday through Thursday...
Monday...MVFR/IFR conds in light snow/wintry mix becoming likely
for NYC/mj Metro terminals in the afternoon.
Monday night...IFR or lower likely. NYC metros and coastal
terminals, wintry mix gradually changing to plain rain late.
Kewr/kteb/kbdr could see freezing rain linger into early Tue
morning push. Khpn/kswf wintry mix, including freezing rain.
Tuesday...IFR or lower conds. Wintry mix, possibly changing back to
all snow at kswf before ending. Rain at NYC/New Jersey Metro and
coastal terminals, possibly changing to wintry mix before ending
late. North gusts to 20kt developing Tue afternoon.
Tuesday night...VFR. Northwest winds g20kt NYC metros/kisp mainly eve.
Wednesday...VFR. Northwest winds g25kt mainly afternoon.
no changes to the winds and seas at this time.
Gale force wind gusts today, subsiding this evening, and
falling below Small Craft Advisory by late tonight. Ocean seas will be a bit
slower to respond with residual S/se swells, but should fall
below Small Craft Advisory from W to E through Monday morning.
Sub-Small Craft Advisory condition expected through Tuesday morning, with Small Craft Advisory
conditions becoming increasingly likely late Tuesday, and then
likely all waters Tuesday night through Thursday. Potential for
a period of gale conditions on the ocean waters Wednesday night
with passage of an Arctic front.
remaining flooding concerns are for the larger Stem rivers in
CT with a combination of the recent rainfall and melting snow
to the north.
Another significant precipitation event is likely Monday
through Tuesday, with liquid equivalent quantitative precipitation forecast of 0.5 to 1.25
inches possible. There is uncertainty in this amount given
uncertainty in the track of the low and frontal positions.
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) is still
operating at reduced power.
Marine...Gale Warning until 7 PM EST this evening for anz335-338-345.
Gale Warning until 10 PM EST this evening for anz330-340-350-