Area Forecast Discussion
Issued by NWS Upton, NY
FXUS61 KOKX 301811
Area Forecast Discussion
National Weather Service New York NY
211 PM EDT Sun Apr 30 2017
High pressure building into New England slowly moves east of the
area through tonight. A warm front moves northward through the
area tomorrow morning, followed by a cold front moving in from
the west Monday night and passing through the area by Tuesday
morning. High pressure builds in briefly for the middle of the
week. An area of low pressure will bring unsettled weather for
the end of the week into the weekend.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
While a mainly dry forecast today, there is still plenty to
talk about due to the marine influence across our area, which is
pronounced in the spring time.
Following a back door cold frontal passage this morning, the
cold air was slow to filter in, also being aided by winds
coming off waters around 50. Coastal locations topped out in
the lower 60s early and have now fallen off some 5 to 10
degrees the last couple of hours, into the lower 50s. Interior
locations will continue to creep upwards another degree or two.
Over the next couple of hours though, as winds veer to the E-SE.
most locations will fall back into the low and mid 50s.
Additionally, a gusty low-level easterly jet, aided by the
cooler marine air, produced winds up to 35 mph along the coast.
This winds will abate over the next couple of hours.
Any warm advection showers over interior CT will end by early
A surface high will continue to build into New England beneath
a building upper high.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Continued onshore flow will lead to low-level saturation, with
increasing chances for light drizzle through the evening and
into Monday night, particularly as warm advection strengthens
ahead of the returning/modified cold front. Low temperatures
will be closer to climatological normals. The warm front is
expected to move north of the area by morning/early afternoon
with brief clearing possible behind the front. Meanwhile, the
upper high off the southeast coast will gradually shift eastward
ahead of a closed upper low. At this time, there is no clear
signal for a pre- frontal trough, though there is a possibility
of a convectively induced vorticity maximum moving through the
area ahead of the main upper trough that may be sufficient
enough to produce isolated afternoon thunderstorms, primarily
north and west of the city. Afternoon highs largely depend on
how quickly the warm front moves through and how much clearing
can occur following its departure, though highs will likely be
much warmer than Sunday.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
The cold front moves through from west to east Monday night,
with rain and isolated thunderstorms clearing the area by
Tuesday morning. Low temperatures will be mild amidst cloud
cover and south flow, generally 5 to 10 degrees above
climatological normals. Flow becomes more westerly following the
frontal passage for Tuesday, and despite cold advection the
westerly component will be favorable for downslope warming which
may keep high temperatures a few degrees above guidance. Expect
above normal highs for Tuesday. By Wednesday, a subtle upper
trough and attendant cold front pass through the area by
afternoon/evening, with a reinforcement of cold advection and
temperatures closer to or slightly below normal. By late week,
upper difluence ahead of a developing system across the central
US will support moisture advection along the east coast and the
intensification of a surface low across the Southeast that will
gradually traverse northeastward into the region, leading to a
period of unsettled weather into the weekend.
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
High pressure remains centered off the New England coast,
extending into New Jersey. The high begins to drift offshore
late this afternoon and tonight. A warm front will approach
from the southwest late tonight and move through sometime
VFR, with clouds lowering through this afternoon, becoming MVFR
23Z or soon after. IFR conditions are likely by late evening,
03Z to 04Z, with fog and drizzle developing. IFR conditions
will develop later at KSWF and KGON, after 07Z. Conditions
improve Monday morning into the afternoon, with MVFR ceilings.
Gusty east to southeast wind are the main issue this afternoon
and evening. Winds become more southeasterly, and gusty, as the
high built into the terminals. Winds are now expected to remain
from the southeast until late tonight, then possibly briefly
become east to northeast and light, or light and variable as
the warm front approaches. With the warm front passage Monday
morning, winds shift to the south. Timing of the frontal passage
is uncertain at this time, and will likely move through the
inland terminals before the coastal terminals, and farther
.OUTLOOK FOR 18Z MONDAY THROUGH FRIDAY...
.Monday afternoon ...MVFR. There is a possibility that ceilings
become VFR briefly.
.Monday night...Conditions lowering back to IFR to LIFR as showers
develop with a chance of thunderstorms. LLWS possible.
.Tuesday-Wednesday night...Showers ending Tuesday morning, becoming
.Thursday-Friday...MVFR or lower conditions with rain.
A moderate pressure gradient over the waters through Monday
morning will result in winds of 15 to 20 KT. The pressure
gradient increases Monday afternoon with gusts up to 25 KT.
A persistent onshore flow will build seas to 5-6 ft over
southern portions of the coastal ocean zones on Monday as well.
The winds increase on Monday night, with solid Small Craft
conditions on the coastal ocean waters. As a result, have issued an
SCA for the coastal ocean waters for Monday and Monday night. On the
non-ocean waters Monday night, gusts to small craft levels possible,
but given limited mixing, confidence is not high enough to warrant
headlines at this time.
From Tuesday into Tuesday night, all waters likely will experience
SCA conditions with gusts of 25-30 KT.
The pressure gradient relaxes to light to moderate again by
Wednesday, and remains so through Thursday, limiting winds to 15 kt
or less. SCA level seas should linger on the coastal ocean waters
into Wednesday, then possibly return again by late Thursday ahead of
the next storm system.
No hydrologic impacts are expected through the forecast period.
MARINE...Small Craft Advisory from 6 AM Monday to 6 AM EDT Tuesday for