Area Forecast Discussion
Issued by NWS Upton, NY
FXUS61 KOKX 252002
Area Forecast Discussion
National Weather Service New York NY
402 PM EDT Sat Mar 25 2017
High pressure over New England will gradually slide east
through the weekend...keeping a cold front to our south through
Sunday...and then returning as a warm front Sunday night into
Monday. Another frontal system approaches on Tuesday and moves
across Tuesday night into Wednesday. High pressure returns
Thursday ahead of the next front on Friday.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Northern stream trough moves east of the Canadian Maritimes
tonight...with shortwave ridging building towards the region.
Spotty light rain shower or sprinkle activity along the coastal
plain should slowly sink south through the late afternoon/early eve.
Upper jet streak induced shower activity across central NY/New
England late this afternoon will approach northern portions of the
Tri- State late today into early this evening. It is likely to
weaken as jet forcing moves east...with scattered
showers and sprinkles early tonight.
Low level cold air damming...under a mild w/sw flow aloft...should
strengthen a low-level inversion over the area. This will be a
favorable set up for stratus tonight...but low-levels appear too dry
for any fog or drizzle under a ne flow. Spotty shower activity may
develop late tonight into Sunday morning across W/SW zones as mid-
level flow turns southerly with zone of theta-e advection.
There is a low probability for spotty freezing rain across far
interior zones late tonight/early Sun Morning...particularly Hudson
and CT river valleys...due to cold air drainage.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
Models in good agreement with Central Plains closed low lifting
into the Mid Mississippi river valley tonight into
Sunday...with shortwave upper ridging moving across the area.
At the surface...New England high pressure gradually shifts to
the coast by late in the day.
A swath of scattered shower activity possible to work north
across the region during the day Sunday coincident with an
elevated warm front and corresponding zone of theta e advection.
Any shower activity should be light due to the weak forcing.
Increasing potential for shower activity late Sunday into
Sunday Evening from sw to ne...as lead shortwave energy
approaches around the closed low to the west and moisture
increases in deepening sw flow. Warm front will slowly approach
from the south Sunday night...supporting drizzle and fog in
addition to any shower activity.
Closed low opens up and crosses to the north on Monday...with
warm front likely struggling to lift north of the area as low
pressure tracks ne through Southern Ontario. The warm front
could stall over the area with potential for a weak low
pressure wave moving along it. The exact location of the warm
front/surface low will determine where the heaviest rain axis
will occur on Monday...but a wet day expected. There are some
hints of weak elevated instability across NW zones...so cant
rule out an embedded tstm on Monday in this area as shortwave
energy pivots through. Rain should taper off from w to e late
Monday into Monday Evening as weak low moves off to the east.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
A weak cold front washes out as it shifts into the region from the
NW during Monday night. Probably no showers in association with this
feature as lift weakens, however during the evening there could be
some lingering showers primarily over eastern sections in
association with an exiting shortwave. Clouds will keep overnight
lows above normal.
Models are split regarding the strength and track of a low pressure
wave that could bring the forecast area some rain on Tuesday,
primarily in the afternoon. A cold front would then pass through
late at night with the chance of more rain. PoPs are capped at
chance for now. High temps on Tuesday will be above normal, and if
more sunshine occurs than currently forecast, some inland locations
west of the city could reach 70 degrees.
Wednesday and Thursday look to be dry with high pressure building
in. Cold air advection appears to be delayed enough to the point
where highs on Wednesday end up above normal, then near-normal for
Thursday. Friday could be completely dry as well, but perhaps some
rainfall sneaks into the western zones by the end of the day. High
temps again near normal. Global models then disagree with the track
of an area of low pressure that could bring rainfall on Saturday.
Have capped PoPs at 40% for now.
.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
A cold front will become stationary to the south tonight. High
pressure will build in tonight, then weaken on Sunday as a warm
Bands of light rain or sprinkles passing by this afternoon not
having any impact on flight category. MVFR cigs to the north
have however already reached KSWF, and should spread southward
late today into this evening. A brief period of IFR cigs
possible at KHPN this evening. After that, cigs should gradually
improve to VFR from NE-SW after midnight, as drier air with the
building high to the north moves in.
Flight cat Sunday morning uncertain. Started off VFR, then
lowered to MVFR after about 13Z-14Z with light rain moving in
well in advance of the warm front.
Winds have turned mostly N-NE around 10 kt, but sea breeze along
the south shore of Long Island could cause winds at KJFK to
become more easterly for a couple of hours toward evening.
Speeds should pick up a little late tonight, then direction
become more easterly after daybreak Sunday, with a few gusts
G15-18KT possible at the coastal/NYC metro terminals.
.OUTLOOK FOR 18Z SUNDAY THROUGH WEDNESDAY...
.Sunday...MVFR with light rain, possibly becoming IFR toward
.Sunday night...Lowering to IFR/LIFR with light
rain/drizzle/fog ahead of an approaching warm front.
.Monday...IFR/LIFR to start. Conds could improve to MVFR or VFR
by late morning or afternoon if the warm front moves through.
.Monday night-Tue night...IFR likely, LIFR possible with low
.Wednesday...VFR. NW winds G20-25KT, possibly stronger.
Ocean seas east of Fire Island Inlet will continue to run 4 to
5 feet due to a southerly swell into this evening. Northeast
flow strengthens overnight through Sunday between high pressure
to the north and the cold front to the south/low pressure to the
west. Marginal SCA gusts are possible on the ocean waters
late tonight and becoming on Sunday into Sunday Night. The
resultant easterly fetch should allow for ocean seas to build
to 4 to 7 ft Sunday into Sunday night. Winds are expected to
weaken and veer se on Monday as a warm front works into the
waters...but e/se swells will likely keep seas at SCA levels.
Ocean seas may still be up to 5 ft Monday night due to a lingering
swell. Otherwise, sub-sca conditions are expected across all waters
through at least Wednesday, however there is a chance that the swell
could still linger and bring seas to 5 ft on the ocean waters at
times during this period. Winds then increase and become more gusty
by Wednesday night with chance of 25 kt gusts mainly on the ocean
Measurable rain chances gradually increase late Sunday through
Monday, with around a half inch to an inch accumulation overall.
No hydrologic concerns are anticipated with any periods of rain that
occur within the forecast period.
A persistent easterly flow may bring water levels close to minor
thresholds across the most vulnerable Western Great South bay
and Western LI Sound locales for the Sunday Night and Monday
Morning high tide.
As astronomical tides rise through the week...water levels may
flirt with minor levels in the most vulnerable spots during high
MARINE...Small Craft Advisory from 2 AM Sunday to 8 AM EDT Monday for
Small Craft Advisory for hazardous seas until 2 AM EDT Sunday