Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kokx 241541 
afdokx

Area forecast discussion
National Weather Service New York New York
1141 am EDT Wed may 24 2017

Synopsis...
a low pressure system tracks southeast of Long Island this
morning with high pressure briefly building in this afternoon
and evening. A slow moving low pressure system affects the area
Thursday into Friday before weak high pressure returns again for
Saturday. Another frontal system will then impact the area for
the latter half of the Holiday weekend.

&&

Near term /until 6 PM this evening/...
sprinkles will end by 18z and clouds will thin as breaks develop
as the sfc low southeast of Long Island moves further offshore.

Otherwise...in combination with mostly cloudy skies, onshore
winds will keep temperatures a few degrees below climatological
normals.

&&

Short term /6 PM this evening through 6 PM Thursday/...
continued cloud cover ahead of the broad upper low to the west
will keep temperatures overnight closer to normal. Rainfall will
increase from southwest to northeast by morning as the upper low
and a slowly deepening surface low move into the area. An
extended period of southwest flow will continue to advect Gulf
moisture northward, leading to possibly moderate rain at times
through the day. As the warm front lifts through the area by
afternoon, elevated instability may support a slight chance of
thunderstorms, though no severe weather is expected at this
time.

As the surface low deepens, the tightening pressure gradient
will lead to strengthening onshore flow, which will keep
temperatures well below normal and also lead to coastal impacts
with above normal tides. See tides/coastal flooding for
associated impacts.

&&

Long term /Thursday night through Tuesday/...
an unsettled weather pattern continues through this period as an
upper low lifts out of the northeast on Friday, while another
another drops into the Midwest and Great Lakes states over the
weekend. Upper level ridging between the two systems briefly
builds across the area for the first half of the weekend.

Models are in good overall agreement in taking surface low
pressure over the mid Atlantic states Thursday night south and
east of the area and then into the Gulf of Maine on Friday.
Showers and isolated thunderstorms Thursday night will taper off
on Friday with lingering clouds and showers through much of the
day as deep-layered cyclonic flow remains across the region
behind the departing low.

Conditions will then briefly dry out Friday night into Saturday
as both ridging aloft and at the surface translates east across
the area. Things get a little more tricky heading in Sunday as
another frontal system approaches the area. There are
differences amongst the global models, in particular with the
European model (ecmwf) and ggem, as both more aggressive with a frontal wave
ejecting east out ahead of the main frontal system. However, the
00z European model (ecmwf) has trended toward the GFS, with a late day warm
frontal passage on Sunday, followed by a weak cold frontal
passage late Monday. There remains some uncertainty with the
timing of warm advection rainfall Sunday into Sunday night. It
could possibly hold off until late in the day. Scattered
convection is then forecast for Memorial Day along and ahead of
the cold front. Conditions briefly dry out Monday night into
Tuesday before the upper trough and another cold front approach
Tuesday night.

Temperatures during the period will be near seasonable levels.

&&

Aviation /16z Wednesday through Sunday/...
weak high pressure briefly builds this afternoon. Another,
deeper, low pressure system then approaches from the west late
tonight and Thursday.

VFR conditions are expected through 06z although some patches of
MVFR are possible mainly across Long Island through 17z. Ceilings
will gradually fall below VFR late after 06z tonight as the
next low pressure system approaches. Conditions fall to IFR or
less in rain towards 12z.

Light north-northeast-NE winds this morning become NE-east-northeast around 10 kt this
afternoon. Winds then become easterly late in the day into this
evening.

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: patches of MVFR through 16-17z. Winds will
be north-northeast-NE into the early afternoon with veering to the east this
afternoon. Southeast winds 110-140 possible this evening.

Klga taf comments: winds may veer to the east-northeast-east this afternoon
with a slow chance for southeast winds this evening.

Kewr taf comments: winds may veer to the east-northeast-east this afternoon
with a slow chance for southeast winds this evening.

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

Kteb taf comments: winds may veer to the east-northeast-east this afternoon
with a slow chance for southeast winds this evening.

Khpn taf comments: no unscheduled amendments expected.

Kisp taf comments: patches of MVFR through 16-17z. Winds could
veer to the east-southeast-southeast this afternoon.

Outlook for 12z Thursday through Sunday...
Thursday-Friday night...MVFR, IFR possible. Slight chance of
thunderstorms Thursday with east winds g20kt.
Saturday...VFR.
Sunday...MVFR/IFR developing.

&&

Marine...
cancelled the Small Craft Advisory through today for the Atlantic
Ocean coastal waters based on observations and near term forecast
trends.

Otherwise...the pressure gradient will gradually increase this
afternoon as an area of low pressure moves offshore.

Marginal northwest Small Craft Advisory winds and seas will develop by 6 PM. A second
area of developing low pressure to the southwest will maintain
an easterly flow and allow seas to remain elevated on the ocean
through Thursday.

Low pressure passes off the New England coast Friday. Ocean
seas of 5 to 7 ft remain through Friday, then diminish to less
than 5 ft for Saturday and the remainder of the weekend.

&&

Hydrology...
0.50" to 1.50" of rain is currently forecast from today through
the day on Friday. Higher amounts are possible in any
thunderstorms that develop on Thursday. Minor urban and small
stream flooding is possible Thursday due to antecedent wet
conditions.

Another round of light to moderate rainfall is possible for
Sunday into Monday.

&&

Tides/coastal flooding...
there is an increasing threat for successive rounds of minor
coastal flooding tonight through Thursday night, with the
greatest threat for widespread minor and potentially moderate
coastal flooding during the nighttime cycles. This is due to a
slow moving low pressure system approaching the region, and
with less than 1/2 ft of surge needed in many places to reach
minor flood thresholds and 1 to 2 ft for moderate.

&&

Okx watches/warnings/advisories...
CT...none.
New York...coastal flood advisory from 6 PM to 10 PM EDT this evening for
nyz075-178-179.
New Jersey...none.
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EDT
Thursday for anz350-353-355.

&&

$$
Synopsis...Maryland
near term...gc/MD/dw
short term...Maryland
long term...dw

National Weather Service Glossary of Abbreviations