Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 211632
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1232 PM EDT SAT MAY 21 2016

.SYNOPSIS...
Low pres near Cape Hatteras will track south of Long Island
tonight...and east of Cape Cod Sunday. An upper level system will
then spin over the northeastern united states for the beginning
of next week. As the system exits Wednesday...a warming trend
will commence.

&&

.NEAR TERM /THROUGH SUNDAY/...
Rain to the west looks to have a hard time moving east this
afternoon per latest HRRR. Maintained earlier fcst to reduce
rainfall amts thru tngt based on the 3z SREF and 6z data. No other
major changes.

Upr lvl low tracking across the Ohio valley based on water vapor.
Moisture feed extended into the Gulf of Mexico...but there was not
a subtropical tap evident. Msas now indicates low pressure over
Ohio, with secondary developing near Cape Hatteras as expected.

Conceptual model dictates this broad area of low pres will
consolidate into a cstl low as the upr lvl energy reaches the ern
seaboard. All of the models support this idea. There are some
differences...notably the NAM is farther n than just about
everything. As a result...the fcst is weighted heavily towards the
SREF and GFS.

This keeps the best rain chances and heaviest amts confined to
the srn portions of the cwa. Timing mainly aft 18z...and possibly
later...thru tngt...ending early Sun.

Shwrs develop Sun aftn...especially w of the Hudson...as the upr
trof approaches and subsidence in the wake of the low decreases.

Updated temps this morning based on latest obs, and hourly mos
guidance going forward in time. Temps raised in spots as a result.

With clouds and possible rain, temps in the 40s and 50s tonight.
Sunday should see high`s in the 60s across the region.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
The upr low cuts off Mon and spins over the ern seaboard thru Tue
before being ushered into the Maritimes by a building ridge. Cannot
be certain wrt to the exact placement of the meandering low this far
out...but confidence in steepening lapse rates and cyclonic flow
aloft is sufficient to include sct shwrs Mon and Tue. Despite
minuscule cape...temps blw freezing in the unstable zone so cannot
rule out an isold tstm and possible pea size hail. Went close to the
superblend for temps which was very similar to the previous official
fcst.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
A warm up appears on track Wed thru Fri. Temps at h85 will more
than double from what we will have on today`s 12z raob. With a wly
component to the flow...went close to the mex as the superblend
seems to be weighting the recent s shore cold bias too heavily.
Otherwise...with the building ridge...Wed and Thu look dry attm.
Thereafter the cwa gets into the nwrn periphery of the ridge which
would be conducive to tstm development. Included slgt chances in
the fcst for Fri.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR into this afternoon as high pressure remains over the
terminals. MVFR ceilings with light rain mainly after 00Z Sunday
as low pressure deepens along the Carolina coast. There is a low
chance that visibilities become MVFR in the rain and possibly fog.
There is also a low chance of brief IFR ceilings late tonight.
Confidence is low that this will occur.

By 12Z Sunday the low is expected to be southeast of Montauk
Point. There is still some uncertainty as to the track the low
will take and this will have an impact on wind speeds and
directions, along with ceilings and chances for rain.

.OUTLOOK FOR 12z Sunday through Wednesday...
.Sunday...MVFR with conditions improving as steady rain ends.
showers possible the remainder of the day.
.Sunday Night-Tuesday...VFR. However, a few showers will be
possible from time to time with local MVFR conditions.
.Wednesday...VFR.

&&

.MARINE...
Sub small craft conditions are expected today as high pressure over
the waters retreats into the Atlantic. A coastal low developing
along the Carolina coast will track to the northeast tonight
through Sunday. There is some uncertainty as to the track of the
low. If the low tracks farther north, small craft gusts would
become possible across most of the forecast waters.

At this time with the current expected track small craft gusts will
be developing on the ocean waters this evening...and possibly late
this afternoon. Small craft gusts then remain through most of
Sunday.

In addition...seas on the ocean waters build to small craft levels
tonight and remain into Sunday. There is a chance seas remain at
small craft levels Sunday night into Monday as swells continue from
the departing low to the east of the waters.

Conditions then improve late Monday night into Tuesday, with all
waters below SCA levels through the middle of next week.

&&

.HYDROLOGY...
Around 1/2 inch of rain is possible srn and ern portions of Long
Island late this afternoon and tngt...with lesser amts as you go
n and w. Generally expect the heaviest axis stays just s of the
island. Replaced the wpc qpf with the 3z sref data thru tngt...as
it seems to better represent pcpn associated with the expected
track of the low based on the 00z and 6z data.

Shwrs Sun thru Tue will bring potentially a few tenths at a time
where they do occur.

&&

.TIDES/COASTAL FLOODING...
Water levels could approach minimal flood thresholds on the south
shore back bays of Nassau County with the higher of the two high
tide cycles on Sunday.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory from 6 PM this evening to 6 PM EDT Sunday
     for ANZ350-353-355.

&&

$$
SYNOPSIS...JMC
NEAR TERM...JMC/PW
SHORT TERM...JMC
LONG TERM...JMC
AVIATION...JP
MARINE...MET/PW
HYDROLOGY...JMC
TIDES/COASTAL FLOODING...



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