Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 280228

Area Forecast Discussion
National Weather Service New York NY
1028 PM EDT Sat May 27 2017

High pressure will remain fairly stationary to the east of the
region through Sunday Night...retreating northeast on Monday. A
frontal system will approach the region Sunday Night and cross
the area Monday. A series of weak fronts or troughs of low
pressure will follow through the end of the week.


Forecast is on track with only minor changes made to reflect
current conditions. Any showers have for the most part ended
across the area. Can`t rule out an isolated shower across NYC
metro and points NW through around midnight with a separate
northern stream shortwave/jet streak digging into eastern New
England, but not enough confidence to put it in the forecast.

Otherwise...Weak upper ridging builds into the region
overnight...with surface high strengthening to the east of New
England. This will have a Canadian maritime airmass taking hold
of the region.

Combination of low-level onshore flow and nocturnal cooling will
likely result in stratus development overnight into Sun morning.
Models are signaling potential for some patchy fog and/or drizzle
developing late tonight...although confidence is low as
saturation doesn`t appear to be sufficient. Temps should remain
near seasonable in the 50s.


Upper ridge axis moves across the region Sunday...with a deep
upper low sinking south into the upper Mississippi River Valley
through Sunday Night. Ahead of it southern stream
energy/moisture expected to ride into the region Sunday
Night...preceding approaching northern stream shortwave energy.

Canadian maritime airmass will be entrenched on Sunday...with
any morning stratus likely slowly to erode into the afternoon.
The stable low-level airmass should keep the region dry on
Sunday...with temps running below seasonable in onshore flow
and and with cloud cover.

Developing diffluent flow aloft...approaching shortwave
energies and jet streak...combined with an increasingly moist
S/SW flow ahead of an approaching frontal system will result in
increasing likelihood for rain late Sunday Night. Model spread
exists in timing and intensity of rainfall...which is likely
related to model handling of convectively induced vort/shortwave
energy originating over the Mid-Mississippi and Tennessee River
valleys and riding into the region and associated
moisture/instability influx. Should see some better agreement
on these details Sunday.


Global models are in decent agreement with the overall H5 pattern
through the period. However...there are timing differences from mid
week on with regards to pieces of upper level energy moving across
the area.

Cutoff low pres over southern Ontario will slowly track ewd through
the week although maintain it`s hold on the weather pattern across
the area. Mid level shortwave trough moves through the area on Mon.
The NAM is the strongest with the upper level energy associated with
it and thus strongest at the sfc with highest QPF as well.
Differences appear to be associated to the convection over the
midwest today which is where this system is originating from.
Hopefully next 24 hours will converge better. At any rate...Mon
looks like a wet day with rain becoming widespread during the
morning. Elevated instability present could trigger some tstms. See
hydro section for info on totals and impacts.

Weak ridging builds in Mon night with rain ending as the shortwave
trough exits to the NE. A weakening cold front approaching from the
west on Tue could trigger a few showers/tstms during the aftn and
into the evening as it moves into the area. Chc showers may linger
through the night.

The closed upper level low remaining over SE Canada will send rounds
of upper level energy through the area through the end of the week.
Have maintained schc to low chc pops at times through the period but
will need to be fine tuned as the week progresses.

Temps will be above normal levels during the daytime with the
exception of Monday when they will be near to slightly below normal
with clouds and rain.


Weak high pressure remains over the terminals thru Sunday.

VFR to start, however a period of MVFR with stratus will
develop overnight between 07Z and 10Z. Lowering to IFR cigs
possible between 09Z-13Z, but not confident enough to include in
TAFS at this point. Light SE flow tonight. VFR cigs return mid-
morning Sunday.

.Sunday night...Late night MVFR with chc shra/IFR.
.Monday...MVFR conds likely and IFR conds possible. Showers
likely and chance of tstms.
.Tuesday-Wednesday...Mainly VFR. Chance of showers/tstms mainly
NW of the NYC metro terminals.


Tranquil through Sunday night as ocean swells gradually subside
and winds remain light. SE winds increase to 15-20 kt late
Sunday Night into Mon with possible gusts up to 25 kt on the
ocean waters...which could lead to seas reaching 5 ft.

Otherwise...tranquil conds are expected through the remainder of
the forecast period.


Total rainfall amounts on Monday could range from 1/4 to 3/4
inches...with the potential for 1 to 1 1/2 inches if a stronger
solution verifies. No significant widespread hydrologic impacts
are expected attm through at least the middle of next week.


The combination of high astronomical tides and southerly swell
will keep water levels within striking distance of minor coastal
flood benchmarks for the night time high tide cycles into
Monday Night.

Widespread minor coastal flooding is expected for the high tide
cycle tonight along the south shore bays of
Brooklyn/Queens/Nassau, also for the shores of
Westchester/Fairfield along western Long Island Sound. A coastal
flood advisory continues. Brief and localized minor coastal
possible for the remainder of the western LI Sound...lower NY/NJ
harbor and SW Suffolk.

Tides lower for Sun Night high tide...but surge likely increases
a bit with strengthening SE flow. The net result...looks to be
potential for additional widespread minor coastal flooding for
the southern bays of Western LI...with localized and brief minor
flooding for the remainder of areas that have been affected
over the last several days.


CT...Coastal Flood Advisory until 3 AM EDT Sunday for CTZ009.
NY...Coastal Flood Advisory until 3 AM EDT Sunday for NYZ071.
     Coastal Flood Advisory until 2 AM EDT Sunday for NYZ075-178-
     Coastal Flood Advisory from 10 PM Sunday to 3 AM EDT Monday
     for NYZ179.


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