Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 281037
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
637 AM EDT Sun May 28 2017

.SYNOPSIS...
High pressure gradually retreats to the northeast as a series of
weak lows track to the south of Long Island through Tuesday. A
weak cold front approaches from the west Tuesday night, then
crosses the area Wednesday. High pressure then builds in to the
south and southwest through Thursday night. A cold front
approaches on Friday then slowly crosses the area Friday night
and Saturday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Made minor changes this update to reflect the latest trends in
observations and guidance. The forecast appears on track.

A deep layered northern stream ridge builds over the area today.
However, with abundant low level moisture being trapped under
the associated subsidence inversion, should see more clouds than
sun over the area. This coupled with onshore flow, should
result in temperatures being towards the cooler end of guidance.
This is consistent with a blend of ECS/MET guidance, NAM and
ECMWF 2-meter temperatures and a mix down from 975-925 hPa per
BUFKIT soundings. Highs should be around 5-10 degrees below
normal.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
The northern stream ridging slides offshore tonight, delaying
the onset of light rain (in response to increasing isentropic
lift) until mainly after midnight.

A northern stream shortwave pushes through the area Monday.
Along with it are some fairly steep mid level lapse rates,
reflected with showalters progged down to around -2 and possibly
as low as -4. This should be sufficient to turn the character of
the precipitation to more convective driven, so have gone with
showers with embedded thunderstorms. Noting showalters of -2 to
-4, cannot rule out some locally strong storms. With wetbulb
zero heights of 8000-9000 ft, small hail is a possibility.
There is also a very small chance of an isolated sever storm,
with the main threat hail of 1+" in diameter.

Precipitation should taper off from SW to NE this
afternoon/early this evening as the shortwave trough lifts to
the NE.

Lows tonight should be near normal and highs Monday around 10
degrees below normal.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
A closed low will slowly track from SW Ontario/N Great Lakes
Monday night to pres over southern Ontario will slowly track to
near the Quebec Ontario Boarder by Thursday morning. There will
be shortwaves rotating around this rather broad closed low, that
could trigger some isolated to scattered showers from time to
time through Wednesday night, with the best chance over
northern zones.

The models then differ on how fast/far the closed low works to
the east Thursday-Saturday, in part because they differ on how
it is re-enforced from the west. As a result, the forecast from
Thursday on is of at best low-moderate confidence in the
details.

For now it appears that Thursday and Thursday night should be
dry, with the region potentially in between main spokes of the
closed low. The next spoke then influences our weather Friday
or Saturday, so have just slight chance pops for now until the
timing of the system can be better refined.

Temperatures start out near normal Monday night and Tuesday,
should be above normal Wednesday, then near normal again
Thursday-Saturday.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
High pressure will remain fairly stationary to the east through
tonight. A frontal system will begin to approach late Sunday
night.

BKN-OVC higher-based clouds persist north and east of the NYC
metro terminals. Meanwhile a narrow band of low stratus with IFR
cigs has developed from central NJ into western Long Island and
Westchester, including KJFK/KLGA/KHPN. This band not expected to
expand much further, so KEWR/KTEB/KISP/KBDR should remain
unaffected.

Light flow should become SE 8-12 kt by afternoon, then diminish
again tonight.

Will have to watch along the coast for development of low clouds
in the onshore flow tonight. Meanwhile some light rain with
MVFR conds could reach the NYC metro terminals just before 06Z.

.OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY...
.Late tonight...MVFR conds developing from west to east, with
light rain especially from NYC metro on west. IFR conds possible
along the coast.
.Monday...Showers likely and chance of tstms. IFR conds
possible.
.Monday night...Still a chance of showers/tstms early from
KBDR/KISP east with MVFR or lower conds, otherwise VFR.
.Tuesday...Chance of showers and possibly a tstm with brief with
MVFR or lower conds in the afternoon/evening.
.Wednesday...Mainly VFR. Chance of showers/tstms mainly NW of
the NYC metro terminals.
.Thursday...VFR.

&&

.MARINE...
Made minor changes this update to reflect the latest trends in
observations and guidance. The forecast appears on track.

In the near term, will be watching the ocean waters mainly west of
Moriches Inlet for development of any fog before daybreak and
lasting into the morning. So far nothing has developed, but given
the moist onshore low level flow, cannot rule out the possibility.

An SCA may be needed for the ocean waters late tonight into the
daytime hours on Monday. Increasing SE flow looks to peak at
20G25kt Monday morning, with max seas per WaveWatch and buoy
wind/wave climatology 5, maybe 6 ft, with the higher conditions
and longer duration more likely to be out east during the
daytime hours on Monday.

Otherwise, sub-small craft advisory conditions are expected
through Thu night.

&&

.HYDROLOGY...
Dry today.

Total rainfall amounts tonight and Monday could range from
around 1/3 to 1/2 of an inch, with locally higher amounts
possible in areas experiencing strong convection Monday. In
areas that do experience strong convection, there is the
potential for at least localized ponding of water on roadways.

No significant widespread hydrologic impacts are then expected
at this time from Monday night through at least Thursday night.

&&

.TIDES/COASTAL FLOODING...
While astronomical tides are a little lower for the high tide
cycle tonight, surge will likely increase a bit with
strengthening SE flow. As a result, a Coastal Flood Advisory is
in effect for the south shore bays of Brooklyn, Queens, and
Nassau, where widespread minor and locally moderate coastal
flooding are expected. Elsewhere, brief/localized minor flooding
is possible along the shores of Westchester/Fairfield western
Long Island Sound, and along the Kill Van Kull and Arthur Kill
around Staten Island and adjacent portions of NJ. Additional
minor flooding may occur with the high tide cycle Monday night
in the areas that have been affected over the last several days.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Coastal Flood Advisory from 10 PM this evening to 3 AM EDT
     Monday for NYZ179.
NJ...None.
MARINE...None.

&&

$$


SYNOPSIS...Maloit
NEAR TERM...Maloit
SHORT TERM...Maloit
LONG TERM...Maloit/24
AVIATION...Goodman
MARINE...Goodman/24
HYDROLOGY...Maloit/24
TIDES/COASTAL FLOODING...



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