Scientific Forecaster Discussion
fxus61 kokx 191808
Area forecast discussion
National Weather Service New York New York
108 PM EST Fri Jan 19 2018
high pressure will build to the south through Saturday, while
low pressure passes well to the north on Saturday. A back door
cold front will pass through Sunday night, then return north as
a warm front on Monday ahead of a strong frontal system for
Monday night into Tuesday. High pressure will return for mid
Near term /until 6 PM this evening/...
back edge of clouds progressing across NYC Metro and coastal
locations with skies clearing from northwest to southeast this afternoon.
Temps will be 5-10 degrees warmer than those of yesterday, with
highs mostly in the upper 30s and lower 40s. West-southwest winds may
occasionally gusts up to 20 mph.
Short term /6 PM this evening through 6 PM Saturday/...
zonal flow will prevail aloft between a flat trough passing to
the north and ridging along the southeast coast. After one more cold
night inland with lows in the teens/20s, and lower 30s for NYC
Metro and most of Long Island, downslope flow/warm air advection will result in
a mild day, with high temps in the upper 40s and lower 50s. It
will however be brisk, as a tightening pressure gradient between
low pressure passing east across Quebec and high pressure along
the southeast coast generates west to west-southwest winds gusting up to 35 mph in
NYC and across Long Island, and 25-30 mph most elsewhere to the
Long term /Saturday night through Thursday/...
zonal upper flow through the weekend, with confluence of Pacific
and polar jet to the north of the region, and southern stream
energy tracking through the deep south. Continued return flow
around southern high pressure Sat night into Sunday will allow
for dry and unseasonably mild conditions under a Pacific air
mass, with high temps in the lower and mid 40s on Sunday.
A vigorous polar shortwave moving through southeastern Canada
Sunday night will likely have a back door cold front pushing
through the region, bringing in a more seasonable Canadian
maritime air mass for Monday.
Meanwhile, models in good agreement with the relatively tranquil
pattern being interrupted early next week by the Pacific
energy coming into the western states today. This Pacific
shortwave will amplify through the SW states, and eventually
phase with subtropical jet energy. The resultant deep closed
low is then expected to gradually track NE across the Central
Plains and mid Mississippi Valley Sunday into Mon, before
approaching the northeast by Tuesday as it begins phasing with
northern stream energy. There are still some timing/amplitude
differences with this energy, which is manifesting in
timing/track differences of a resultant frontal system as it
tracks toward the region Monday night into Tuesday. This model
spread should decrease over the next 24 hrs as Pacific energy
comes onshore, but subtle model differences may continue
through Sunday until the subtropical and Pacific energy phase.
Regardless, there has a been consistent model-to-model and run-
to-run signal for a quick moving moderate to heavy rain event
for Monday night into Tuesday, in response to strong deep
layer lift (region under of nose of 65-70 kt low level jet and left front
quad of a 100+ kt jet streak in difluent upper flow) of a
subtropical moisture plume with precipitable water +2 to + 3 Standard deviations
above normal over the region, focused ahead of the cold front
and a surface wave. Before that, still appears there is
potential for a light wintry mix north/northwest of NYC Metro Monday
morning as a warm front moves north with increasing Theta-E
The frontal system pushes through on Tuesday, with breezy
conditions and cold air advection in its wake, returning dry and more
seasonable temps for Wed/Thu.
Aviation /18z Friday through Wednesday/...
high pressure remains centered to the southwest of the region
VFR through the taf period.
West-southwest winds may briefly strengthen to 10-14 kt this
afternoon with an occasional gust to 18 kt. Otherwise, west flow
gradually backs to SW by this evening. Winds aloft (around 2kft)
increase tonight, resulting in some low level wind shear. Have
included a period overnight into Saturday morning for this.
Surface wind gusts should develop Saturday morning, with gusts
to around 25kt.
... Metro enhanced aviation weather support...
Detailed information, including hourly taf wind component forecasts,
can be found at: http:/www.Weather.Gov/zny/n90
Kjfk taf comments: occasional gusts to 18 kt possible this
Klga taf comments: occasional gusts to 18 kt possible this
Kewr taf comments: occasional gusts to 18 kt possible this
Kteb taf comments: occasional gusts to 18 kt possible this
Khpn taf comments: occasional gusts to 18 kt possible this afternoon.
Kisp taf comments: occasional gusts to 18 kt possible this afternoon.
Outlook for 12z Saturday through Wednesday...
Saturday...VFR. West-southwest winds g20-25kt.
Monday...chance of MVFR or lower in -shra. S winds g20kt late day.
Tuesday...IFR in rain. Low level wind shear. S winds g25kt morning, west winds g30-
Wednesday...VFR. Gusty west winds.
could see a stray west-southwest gust up to 25 kt on the ocean waters
Winds should ramp up tonight into Sat as the pressure gradient
tightens between low pressure passing across Quebec, and high
pressure along the southeast coast, with lack of a sfc-based
temperature inversion allowing for wind gusts to increase to
Small Craft Advisory levels tonight, and to minimal gale force daytime Sat on the
ocean waters east of Fire Island Inlet. These conditions should
quickly abate Sat evening, with just some elevated seas
lasting til midnight on the ern ocean waters.
Sub Small Craft Advisory conditions expected Sunday and Monday. Winds and ocean
seas expected to increase to Small Craft Advisory levels late Monday night into
Tuesday ahead of approaching cold front. Small Craft Advisory conditions likely
continue on west/northwest flow and caa flow Tuesday night through
Wednesday, with potential for a period of gale conds.
a frontal system passing through late Monday night into Tuesday has
the potential to bring around inch of rain. No significant
hydrologic issues are anticipated at this time.
NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) is off the
air for an extended period of time.
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EST
Saturday for anz355.
Gale watch from Saturday morning through Saturday afternoon
Small Craft Advisory from 6 PM this evening to 6 am EST
Saturday for anz350-353.