Hempstead, New York Weather Forecast Discussion

517
FXUS61 KOKX 062232
AFDOKX
Area Forecast Discussion
National Weather Service New York NY
632 PM EDT Sat Sep 6 2025
.SYNOPSIS...
A cold front will pass through the area this evening, exiting
far eastern Long Island and southeast Connecticut by early
Sunday morning. The front moves farther out into the Atlantic
Sunday. High pressure building in late Sunday into Monday will
pass east of New England on Tuesday, allowing an offshore wave
of low pressure to pass nearby Tuesday night into Wednesday. A
cold front will approach on Thursday and pass through Thursday
night, followed by Canadian high pressure Friday into Saturday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Severe thunderstorms are no longer a threat across the forecast
area this evening. The cold front has pushed as far east as
interior SW CT and back into the NYC metro. The airmass has been
largely worked over from the earlier convection, however, showers
will continue this evening, mainly across LI and southern CT.
Any thunderstorms will be isolated and primarily offshore.
After midnight, expect post-frontal rain to develop behind the
front due to upper jet dynamics and strong mid level frontogenesis.
This area will initially develop north and west of NYC, but gradually
translates east overnight.
Lows will drop into the upper 50s to lower 60s. Winds become
more northerly tonight.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
For Sunday, right rear quad of upper level jet remains near the
region, supporting synoptic lift. Despite the cold front being
southeast of the region, there will be enough moisture for rain
to remain across the region, especially early and especially
along the coast. The forecast has trended higher with rain for
Sunday compared to previously forecast. Forecast high temperatures
only in the upper 60s to lower 70s for Sunday.
Favorable lift area from upper jet shifts northeast of the
region Sunday night. Upper levels still have a trough across the
region but at the surface, high pressure will begin to build in
from the west. Drier conditions expected along with a decrease
in clouds. This will allow for more radiational cooling, with
forecast lows ranging from the mid 40s to upper 50s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
The period will start off with a longwave trough lifting across
eastern Canada on Monday, with confluence to its rear supporting
high pressure building over over the area through Mon, then passing
E of Tue. Heights aloft then rise along the coast into Tuesday as
the northern stream trough departs, while a shortwave trough along
the Southeast coast lifts northeastward along the periphery of the
offshore ridge. This wave should bring a chance of showers mainly to
Long Island and SE CT from late Tue night into Wed. As the longwave
trough becomes re-established over ern Canada later in the week,
this should send a dry cold front through Thu into Thu night, with
high pressure building from the NW in its wake.
Temps will be mostly a little below normal, with highs in the 70s
and lows mostly from near 60s in NYC to the mid 40s and 50s
elsewhere. The exception to this will be on Thu between passage of
the offshore wave and approach of the cold front, with highs in the
upper 70s/lower 80s, a little above normal.
&&
.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
A cold front gradually moves through the area this afternoon through
Sunday morning. High pressure builds in Sunday night.
A line of showers and thunderstorms is moving slowly east across the
forecast area, affecting the metro terminals as of 20-22Z. This line
will continue to move east through the afternoon and evening
affecting the other more eastern terminals towards 20Z to around
22Z. IFR to MVFR conditions are possible in any
showers/thunderstorms. After about 22Z-23Z lingering the threat for
thunder diminishes for the metro terminals, but an isolated
thunderstorm is still possible through 00-01Z. The line is expected
to weaken as it pushes east, so as it reaches KGON, the chance for
thunder is lower but still possible, so PROB30 added for this
possibility. Wind gusts associated with any thunderstorms diminish
as the line moves east this evening.
Southerly flow continues today at 10 kt to 15 kt, with gusts 20 to
30 kt. As the front approaches later in the day and early evening
look for a wind shift, especially in any thunderstorms to the NW.
Additionally, gusts of 30 to 40 kt (or higher if storms become
severe - generally across NE NJ and Lower Hudson Valley) are
possible with any thunderstorms and added gusts of 30 to 35 kt
within the TEMPO groups for the +TSRA. Otherwise, with the boundary
settling nearby the winds likely go variable in direction late in
the TAF period for the city terminals this evening.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
There remains some uncertainty with the timing of the arrival of
showers and thunderstorms this afternoon with amendments becoming
increasingly likely late in the day and into the evening.
Gusts of 30 to 40 kt are possible with any of the stronger
thunderstorms today. If storms become severe gusts around 50 kt are
possible. Higher chances for severe are with KEWR and KTEB.
Start time of wind gusts may be off an hour or two.
.OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY...
Sunday night: VFR.
Monday and Tuesday: VFR.
Wednesday: Potential for MVFR in -SHRA.
Thursday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
SCA has expired across the ocean waters, but there could be a
few gusts up to 25 kt, mainly east of Fire Island Inlet. Winds
and lower tonight with sub- SCA conditions expected for the
remainder of the weekend. Higher winds and seas within and near
thunderstorms, but thunderstorms should become less coverage by
mid to late this evening and even less overnight into early
Sunday.
The sub-SCA conditions continue Monday and Monday night with
high pressure in control.
The pressure gradient will tighten Tue into Wed as an offshore wave
of low pressure passes by. E flow around 15 kt on Tue should
increase to NE 15-20 kt late Tue night into Wed, building ocean seas
to 5-6 ft from Tue night into Wed. There could also be a few gusts
up to 25 kt on the ocean late Tue night into Wed morning. Gusts/seas
on the non ocean waters should remain below 25 kt and 5 ft.
&&
.HYDROLOGY...
There is no longer an isolated flood threat across the area as
convection has weakened. A stratiform rain will develop later
tonight, mainly after midnight into Sunday morning. An additional
0.25 to one inch of rainfall is possible, but this will be over
a 12-18 hour period.
Otherwise, no other hydrologic problems expected.
&&
.TIDES/COASTAL FLOODING...
There is a high rip current risk through this evening due to a
combination of a strong onshore flow (S 15-20kt) and southerly wind
waves of 4-5ft and 7 seconds. For Sunday, the risk at the very
least will be moderate, and possibly high with a southerly swell
of around 3 ft and 7 seconds. However, winds will be less of a
factor due to being offshore and generally less than 10 kt.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...BG/JM/DW
NEAR TERM...JM/DW
SHORT TERM...JM
LONG TERM...BG
AVIATION...JP
MARINE...BG/JM/DW
HYDROLOGY...JM
TIDES/COASTAL FLOODING...

NWS OKX Office Area Forecast Discussion