Scientific Forecaster Discussion
fxus61 kokx 241746
Area forecast discussion
National Weather Service New York New York
146 PM EDT Wed may 24 2017
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/...
clouds have thinned and broken up across the area. This should
last until 22z or 6 PM.
Weak sea breezes will continue to develop with day time aftn
Winds blowing from the Atlantic Ocean will place a hold on day
time maxes, with the highest temps west and north of NYC.
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
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
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
Temperatures during the period will be near seasonable levels.
Aviation /18z Wednesday through Sunday/...
weak high pressure this afternoon will be followed by the
approach of another low pressure system late tonight into
NE-east winds this afternoon around 10-15 kt, strongest near the
coast. East-southeast flow has already developed along the CT coast and
could also develop across city terminals and Long Island this
afternoon and evening. Flow briefly weakens overnight before
increasing out of the east-NE early Thursday morning. Gusts 20-25
kt expected Thursday morning.
VFR conditions through this evening with conditions gradually
lowering to MVFR late tonight and then IFR Thursday morning as
rain develops. IFR continues Thursday morning with potential for
LIFR as well. An isolated thunderstorm is also possible Thursday
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: uncertainty with timing of wind veering to
the east-southeast. NE flow may hang on a few hours longer than indicated
in taf. There is a chance wind veers to the southeast this evening.
Klga taf comments: NE flow may hang on a few hours longer than
indicated in taf. There is a chance wind veers to the southeast this
Kewr taf comments: NE flow may hang on a few hours longer than
indicated in taf.
Kteb taf comments: NE flow may hang on a few hours longer than
indicated in taf.
Khpn taf comments: no unscheduled amendments expected.
Kisp taf comments: patches of MVFR possible through 19z. Winds
could veer more to the southeast this afternoon/evening than indicated
Outlook for 18z Thursday through Monday...
Thursday-Thursday night...LIFR/IFR in rain through Thursday
night. Chance of thunderstorms Thursday afternoon. East-northeast gusts up
to 20 kt possible Thursday afternoon.
Friday...MVFR/IFR possible. Chance of showers.
Sunday-Monday...MVFR/IFR possible in showers.
cancelled the Small Craft Advisory through today for the Atlantic
Ocean coastal waters based on observations and near term forecast
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
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.
0.50" to 1.50" of rain is forecast from afternoon midnight 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
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 Thursday night high tide cycle.
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
New York...coastal flood advisory from 6 PM to 10 PM EDT this evening for
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EDT
Thursday for anz350-353-355.