Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 270556

Area Forecast Discussion
National Weather Service New York NY
156 AM EDT Fri Apr 27 2018

High pressure builds in briefly tonight, before a quick moving
low pressure system moves through on Friday. A cold front will
approach on Saturday and pass through late Saturday into
Saturday night, followed by a series of upper level disturbances
Sunday into Monday. High pressure will return for the middle of
next week.


The forecast is mainly on track with only minor adjustments made
to some hourly forecast elements this evening.

An upper low slides slides NE from Northern New England into
the Canadian Maritimes tonight, while a southern upper low lifts
towards the region. At the surface, high pressure briefly
builds in overnight, only to give way to the approaching
southern low.

Mild night tonight, (50s in the NYC/NJ metro and 40`s
elsewhere) with increasing and thickening high and mid cloud
cover ahead of approaching low pressure overnight, although
rain is expected to hold off till after daybreak.


Models in good agreement with the southern upper low opening up
and lifting up the E US coastal plain tonight, and through the
region Friday. At the surface, associated low pressure lifts
northeast towards the region on Friday, and then to the
northeast Friday Night.

This is a progressive system, with a quick hit of moderate rain
(1/4 to 1/2 inch, locally 3/4-1 inch) Friday morning into early
afternoon, coincident with shortwave/llj lift. Still some
uncertainty on where the axis of the heaviest rain will be,
dependent of placement of warm front. In addition, some weak
instability may allow for isolated convection and heavy
downpours, particularly across LI/SE CT.

Best lift/moisture axis pushes NE through the afternoon, but
lingering stratus/drizzle and a few showers are likely into the
evening with deep SW flow aloft ahead of northern stream trough
digging into the Great Lakes. In fact, stratus/fog could
maintain/develop in the evening and linger through the overnight
with moist low-levels and weak flow.

Temps on Friday will be a few degrees below seasonable due to
the rain and cloud cover, and near seasonable Friday night.


Fog will gradually burn off Sat morning as weak sfc ridging
briefly moves across. Then as a digging upper trough carves out
a closed low over the Great Lakes region, a leading cold front
will move across from late day into the evening, bringing
scattered showers.

The upper low will move slowly across New England Sunday into
Monday, with a cooler air mass in place and chances for
isolated/scattered showers as a cold pool aloft swings across,
and cyclonic flow/transient shortwaves rotating around the upper
low provide lift. Isolated thunder and/or small hail might not
be out of the question given the forecast strength of the cold
pool (H5 temps as low as -28C to -30C). Temps on Sunday should
get no higher than the 50s, and while forecast highs on Mon are
in the upper 50s/lower 60s, temps could very well remain in the
50s on Mon as well if the upper low pulls out more slowly than

A warming trend does appear certain for mid to late week as the
upper low pulls out and is replaced by deep layer ridging that
should eventually park off the Mid Atlantic and Southeast coasts
Wed into Thu. Temps on Tue are a little uncertain, and will
depend on how quickly the upper low pulls out--if slower they
may remain in the 60s across the board, for now will forecast
70-75 away from south facing coasts. But then as the high
becomes established off the coast and transports warmer air
northward, late week looks warm, with highs in the lower 80s on
Wed and mid 80s on Thu per warmer MOS guidance.


Low pressure along the Carolina coast tracks northward overnight
and passes along the coast today. Weak low pressure will remain
across the northeast late today and Friday night.

VFR through the overnight and into early this morning. Then
conditions lower to MVFR as light rain develops, then lowers to
IFR around 16Z with light to moderate rain. An isolated
thunderstorm will be possible during the day. Rain ends late in
the day. Stratus and fog remain with conditions likely lowering
to LIFR and possibly to VLIFR.

There is low confidence in the wind forecast, and will be
dependent on the track of the low across the terminals. As of
now, east to northeast winds less than 10 KT are possible during
Friday. Otherwise winds will be light and variable.

.Late Friday night...IFR to LIFR with stratus and fog.
.Saturday...SW winds G15-20KT in the afternoon, and into the early
evening. Areas of stratus and fog early with MVFR/IFR. MVFR
remains possible during the day and at night with a chance of
.Sunday...MVFR possible in showers mainly in the morning, then VFR
with WNW-W winds G15-20KT by afternoon and into early evening.
.Monday-Tuesday...VFR. W-NW winds G15-20KT Monday.


Diminishing winds tonight as high pressure briefly builds,
however seas remain elevated and a SCA remains posted on the
ocean waters. Marginal SE SCA winds are possible Friday with a
quick moving low pressure system, mainly eastern waters Friday
aft/eve on the eastern flank of low pressure.

Lingering 5-ft ocean swells should last into Sat and possibly Sat
evening. SCA conds may also be possible on the ocean waters Sunday
nigh/Monday morning in NW flow behind a departing cold front.


1/4 to 1/2 inch of rain likely, with locally 3/4 to 1 inch possible,
Friday with a quick moving low. No hydrologic issues anticipated.

No hydrologic impacts are anticipated Sat-Wed.


Water levels will approach minor flood thresholds along the
western Great South Bay and western LI Sound waters with the
Friday night high tide cycle. This in response to SE swells and
ESE winds ahead of low pressure today. Water levels will be near
minor flood thresholds once again Saturday Night.

Tidal departures of 1 to 1 1/2 ft are need for minor flooding,
however, at this time, water levels are expected to stay below
minor flood thresholds.


NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) remains off
the air.


MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ350-353-


LONG TERM...Goodman
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