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fxus61 kokx 171143 
afdokx

Area forecast discussion
National Weather Service New York New York
643 am EST Fri Nov 17 2017

Synopsis...
low pressure over southeast Canada will move east today, while
high pressure builds in from the west. Strengthening low
pressure moving northeast across the lower Great Lakes on
Saturday will then send a warm front across the area followed
by a cold frontal passage late Saturday night into Sunday
morning. High pressure builds to the south on Monday. Another
frontal system will move through Tuesday night into Wednesday.
High pressure follows for late week.

&&

Near term /until 6 PM this evening/...
secondary shot of cold advection with the passage of the upper
trough this morning has allowed northwest gusts to ramp back up to
around 30 kt, or 35 mph. These should be the peak will gradually
subside through the day.

Upper low departs across eastern Canada today with building
heights aloft as surface high pressure builds in from the west.

It will be an unseasonably cool day across the area with highs
in the mid to upper 40s. Stayed closer to 2m model temperatures,
versus the warmer MOS guidance.

&&

Short term /6 PM this evening through 6 PM Saturday/...
ridging both aloft and at the surface moves through the area
tonight with diminishing winds. Overnight lows will generally
be in the 20s, but in the 30s closer to the coast and the NYC
Metro.

A progressive upper flow will feature another amplifying upper
trough approaching the Great Lakes and Ohio Valley states on
Saturday. Preference was to go with a deeper, more consolidated
surface low tracking across the Midwest and into the lower Great
Lakes by Saturday evening. This combined with high pressure
moving off the East Coast will result in strengthening southerly
winds and gradually deepening moisture. Much of Saturday though
should be dry with the exception of western portions of the
lower Hudson Valley and NE NJ, as warm advection ahead of the
system encounters a pronounced dry layer in the low and mid
levels. The uncertainty lies in how quickly these layers moisten
ahead of a strengthening SW low-level jet. Rain could move in
faster should this process occur more quickly.

Highs will top out in the lower to mid 50s on Saturday, which
is closer to seasonable levels.

&&

Long term /Saturday night through Thursday/...
strong warm advection will dominate the early portion of Saturday
night as a potent short wave and attendant cold front approach from
the west. Given a significant low level mass response to the
intensifying upper system, the primary uncertainty at this point
lies within how much wind can mix to the surface prior to the
frontal passage. Naefs suggests low-level jet speeds significantly
stronger than normal for this time of year - in the 90-98th
percentile from 850-700 mb. At 925 mb, 50-60kt winds will overspread
eastern portions of the forecast area - primarily eastern Long
Island and Connecticut. Questions remain on how much will be able to
mix to the surface, though given the antecedent dry air mass, there
may be a favorable time prior to saturation where these stronger
gusts may mix to the surface. As such, if confidence increases there
is potential for at least a Wind Advisory to begin as early as
Saturday night.

Temperatures Saturday night depend on how quickly the front moves
through, though timing is currently more towards morning, so expect
that in general with the exception of perhaps up towards Orange
County, that temperatures will be above normal. The front moves
through Sunday morning from west to east, bringing a brief period of
moderate to heavy showers and possibly an isolated thunderstorm.
Significant cold advection follows with strong, gusty winds in its
wake. Although the previously mentioned low-level jet will have
moved east of the area, flow following the deepening, but exiting
low will remain strong, with advisory level west-northwest winds
possible into Monday night. High temperatures will be somewhat mild,
but will likely cool through the afternoon as cold advection
continues, falling back to climatological normals Sunday night.
Winds will remain strong enough between the exiting low and high
pressure developing to the south to prevent lows from falling too
far below normals, though if winds decrease faster than forecast,
primarily across the lower Hudson Valley, then lows could fall well
below freezing.

By Monday, winds will remain strong and gusty, though to a lesser
extent than Sunday. Given the strong west-northwest flow and a
surface trough moving through, there could be enough low-level
moisture and instability to support a quick passing shower, or
perhaps a snow shower in the lower Hudson Valley. Otherwise, dry and
seasonable conditions can be expected through Tuesday as high
pressure passes to the south.

Less confidence exists for mid-week as another front approaches the
area, with Euro and gefs suggesting at least light precipitation
closer to the coast in a brief period of warm advection. As such,
left at least slight chance to chance pops in the forecast. Dry
conditions follow for the remainder of the week in building high
pressure.

&&

Aviation /12z Friday through Tuesday/...
high pressure builds to the west through the day.

VFR forecast through the taf period.

West-west-northwest wind gust to 25-30 knots will become more frequent through the
morning push, before gradually subsiding from west to east this afternoon.
Occasional peak gusts to 35 knots are possible through this morning.
Winds will likely veer right of 310 magnetic for the morning push,
and then waver around or back to the left of 310 magnetic in
the afternoon. Winds diminish overnight.

Outlook for 12z Saturday through Tuesday...
Saturday...MVFR or lower conditions possible by the afternoon and
becoming likely towards evening. Showers at night S-SW winds g25-
35kt.
Sunday...conditions improve to VFR with showers ending. Northwest winds
g30-40kt.
Monday...VFR. Northwest g20-25kt.
Tuesday...VFR. SW g20kt.

New York 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 may be higher than forecast
today.

The afternoon kjfk haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Klga taf comments: occasional gusts may be higher than forecast
today.

The afternoon klga haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Kewr taf comments: occasional gusts may be higher than forecast
today.

The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.

Kteb taf comments: occasional gusts may be higher than forecast
today.

Khpn taf comments: occasional gusts may be higher than forecast
today.

Kisp taf comments: occasional gusts may be higher than forecast
today.

Outlook for 06z Saturday through Tuesday...
late tonight...VFR.
Saturday...MVFR or lower conditions possible by the afternoon and
becoming likely towards evening. Showers at night S-SW winds g25-
35kt.
Sunday...conditions improve to VFR with showers ending. West-northwest
winds g30-40kt.
Monday...VFR. West g20-25kt.
Tuesday...VFR. SW g20kt.

&&

Marine...
marginal gales are possible this morning, otherwise Small Craft Advisory
conditions will end from west to east through this evening as
high pressure builds in from the west.

A gale watch has been issued for the ocean waters starting
Saturday afternoon as deepening low pressure tracks into the
lower Great Lakes and high pressure retreats over the western
Atlantic.

Given a strong low-level jet developing prior to the cold
frontal passage Saturday night, it is possible that gale to
storm force winds will mix down to the ocean waters and possibly
the eastern sound. Gales will likely continue into Sunday night
following the cold frontal passage. Expect at least Small Craft Advisory- level
conditions thereafter in gusty west-northwest flow, slowly subsiding
through mid-week as high pressure moves south of the waters.

&&

Hydrology...
a band of moderate to locally heavy showers with a strong cold
frontal passage late Sat night should cause no more than
local nuisance impacts.

&&

Tides/coastal flooding...
storm surge guidance with a strong cold frontal passage may to be on
the low side given the strength of southerly winds expected Sat
night, and possibly into Sunday morning if the frontal passage
continues to trend more slowly. Typically though, S/SW winds are not
conducive to building surge.

There is a low probability of a surge of 1-2 ft, which if occurred
would result in minor coastal flooding with either of the two high
tide cycles late Sat into Sunday morning along the South Shore back
bays of Long Island, and along western Long Island Sound. The most
susceptible area to minor coastal impacts with this system may be
eastern portions of the Great South Bay and Moriches Bay, due to the
SW flow.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 1 PM EST this afternoon for anz335-
338.
Small Craft Advisory until 6 PM EST this evening for anz330-
340-345-353-355.
Gale watch from Saturday afternoon through Sunday afternoon
for anz350-353-355.
Small Craft Advisory until 10 PM EST this evening for anz350.

&&

$$
Synopsis...MD/dw
near term...dw
short term...dw

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