46°F
Crown Heights Area, Poughkeepsie, NY, USA
UpdatedNov-17-2017 14:08 
 

NOAA UPTON/NYC Forecast Discussion

568
FXUS61 KOKX 171825
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
125 PM EST Fri Nov 17 2017

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

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Wind gusts are trending down a little as the upper level trough
axis has pushed farther east of the region, taking the better
cold air advection with it. Heights are building aloft in
response as surface high pressure builds in from the west.
Clouds are decreasing with the subsidence of this high so sunny
conditions are forecast.

Wind gusts of mainly now 20-25 KTS are expected to diminish
going into this evening.

It will be a cool day especially considering the wind, making
for apparent temperatures a few degrees cooler than actual
temperatures, with highs near the mid and upper 40s for most
locations.

&&

.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 FRIDAY/...
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 /18Z FRIDAY THROUGH WEDNESDAY/...
High pressure gradually builds south of the region tonight and
then offshore towards early Saturday. Then, a developing low
pressure system from the west approaches the area. VFR is
forecast through early Saturday with high confidence. VFR is
then expected to continue through Saturday but chances of MVFR
will increase by late day with rain showers approaching so as a
result, the confidence in the category forecast will lower
Saturday afternoon into Saturday night.

Winds starting to subside with gusts mostly 20-25KT,
occasionally a few KTS higher but high confidence of gusts
continuing through the remainder of this afternoon. Winds
diminish tonight and then become more southerly Saturday with
speeds picking up again by late Saturday morning into early
Saturday afternoon.

Wind direction this afternoon is mostly 300-320 magnetic. Wind
direction becomes more variable tonight. Wind direction forecast
has moderate confidence with observed directions occasionally
varying 20-30 degrees from forecast.

     NY 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: Gust end time could be 1-2 hours off from
TAF.

The afternoon KJFK haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KLGA TAF Comments: Gust end time could be 1-2 hours off from
TAF.

The afternoon KLGA haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KEWR TAF Comments: Gust end time could be 1-2 hours off from
TAF.

The afternoon KEWR haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.

KTEB TAF Comments: Gust end time could be 1-2 hours off from
TAF.

KHPN TAF Comments: Gust end time could be 1-2 hours off from
TAF.

KISP TAF Comments: Gust end time could be 1-2 hours off from
TAF.

.OUTLOOK FOR 18Z SATURDAY THROUGH TUESDAY...
.Saturday...MVFR or lower conditions become a greater
possibility from the rest of the afternoon and becoming likely
in the evening and thereafter. Showers at night. LLWS of SW flow
40-50KT at 2kft. S-SW winds G25-35KT and occasionally higher
especially in any heavier rain.
.Sunday...Conditions gradually improve to VFR with showers
ending. NW winds G30-40KT. Gusts diminish after early Sunday
evening, more in the 20-25KT range.
.Monday...Mainly VFR. W-NW G20-25KT. Gusts diminish gradually
at night.
.Tuesday...Mainly VFR. MVFR possible late Tuesday night with
showers. SW G15-20KT.
.Wednesday...MVFR possible with showers. W G15-20KT.

&&

.MARINE...
SCA conditions will end from west to east through this evening
as high pressure builds 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 SCA-level
conditions thereafter in gusty WNW flow, slowly subsiding
through mid week as high pressure passes to the south.

&&

.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.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 3 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...Goodman/DW
SHORT TERM...DW
LONG TERM...MD
AVIATION...JM
MARINE...MD/Goodman/DW
HYDROLOGY...MD/DW
TIDES/COASTAL FLOODING...

NWS OKX Office Area Forecast Discussion