discussion on 2023-10-09

000
FXUS61 KOKX 100005
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
805 PM EDT Mon Oct 9 2023

.SYNOPSIS...
A rather large upper level low continues to rotate across
southeastern Canada as it gradually weakens through midweek. High
pressure will nose in from the Ohio Valley on Wednesday, followed
by a weak front into Thursday morning. Another high pressure
system then takes control through Friday. Low pressure and its
associated frontal system will impact the area this weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
Forecast remains on track with only minor adjustments made to
account for current observations.

As low pressure continues to spin round and round south of
Hudson Bay and just north of the Great Lakes, spokes of upper
level energy will rotate through. One of the stronger spokes /
shortwaves will rotate through tonight. Look for more in the way
of clouds, especially this evening and into most of the
overnight. Have kept PoPs in chance category across far eastern
sections, otherwise slight chance across city and much of coast,
with PoPs closer to 10 percent well inland to the NW. There is
a large daytime spread with temps and dew points which will be
tough to overcome during the night, especially further west.
Much of the higher RH will reside between 5 and 10 kft with the
lowest 5 kft staying relatively dry. Look for mostly to partly
cloudy skies and dew points eventually about 3 to 5 degrees or
so higher than last night with a light SW wind. This will help
keep temperatures a touch warmer than last night, probably more
so in the more rural locations where more clouds should preclude
stronger or extensive radiation cooling. However, less
consistent cloud cover than forecast would allow temperatures to
drop to lower levels than currently forecast.

For Tuesday look for the region to likely be in-between more
discernible or stronger shortwave features. The synoptic induced WSW
flow will continue with the upper level feature not budging across
SE Canada. The air mass overall will modify a bit and with a good
deal of sun expected, look for temperatures to warm a touch and get
closer to normal with mainly middle 60s for daytime maxes.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Another shortwave suggested by the majority of NWP will rotate
through or nearby Tuesday night. Look for a bit more in the way of
mid level clouds for Tue evening / first half of the night. The
lower levels should remain relatively dry, thus precluding precip
chances, thus kept PoPs minimal for Tue night despite a bit more in
overall cloud cover. The more strung out vorticity and dry low
levels had led to the minimal PoP forecast. It will be a difficult
temp forecast as any meaningful breaks or lack of cloud cover could
allow specific areas to have some radiational cooling. For now will
keep min temps similar to Mon night, but allow for a few more breaks
in the clouds from time to time with some rural locations
potentially degree or two cooler than the previous night under a
continued light WSW flow.

For Wednesday weak high pressure from the Ohio Valley begins to
build. This should provide a good deal of sun. Temps will get to
near normal with mainly middle and upper 60s across the majority of
the area on a WSW flow at around 10 mph on average.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Flow remains mostly zonal as a low meanders over Canada Wednesday
night with lows in the low-50s to low-40s and dry.

Ridging builds Thursday and Friday. This will keep us mostly dry for
the end of the week as the low over Canada is slowly pushed eastward
towards the Maritimes by the ridge of high pressure. However, due to
enhanced jet dynamics and a cold front with increasing PWATs 0.9-
1.1" indicated by the latest 12Z guidance, Thursday night into
Friday morning could see isolated showers, with the best chance for
western portions of the area. Precip will likely be light, if it
occurs. This is because model soundings overnight Thursday indicate
a large dry layer of air below 850mb with surface dewpoint
depressions around 20 degrees. Temperatures Thursday afternoon will
be in the mid/upper-60s, reaching only the upper-50s to low-60s
Friday afternoon due to overnight FROPA bringing cooler north winds.

Confidence in unsettled weather for the upcoming weekend continues
to increase, but specific details on exact timing of the rain and
evolution of the system remain of lower confidence. A potent closed
upper level low over the Northern Plains is progged to push eastward
Friday night into Saturday. The primary surface low associated with
the system is likely to approach the ridging over or near the New
England coast with a deepening secondary low nearby at some point
later Saturday or Sunday. The system could be a bit slower given a
complex interaction with the initial upper low over the Maritimes
and North Atlantic. The possibility exists for the rain to hold off
until late Saturday or Saturday night/Sunday, but for now is timed
to start early/midday Saturday. It appears to be a long duration
widespread rainfall event thanks to broad lift by the upper-level
system and PWATs maxing out in some areas around 1.3", which is the
90% moving average for this time of year. The latest NBM
probabilities for greater than 1 inch in any 6 hour period this
weekend are low, generally around 10% or less with a few isolated
pockets of 20%. The median NBM shows the event`s QPF around 1.5-2"
however, significant spread still exists in guidance with the NBM`s
25th percentile having areas of 0.5" of total QPF for the event
while the 75th percentile has areas of 2.5 to 3.5". High
temperatures will be 5-10 degrees below seasonal values this
weekend.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --Weak trough of low pressure moves across late tonight. On Tuesday
this trough of low pressure moves well east of the area, leaving
weak high pressure across the area but centered well to the
southwest.

Mainly VFR conditions are expected through the TAF period. However,
there is possible MVFR with rain showers near KGON tonight and
for the rest of the area, late tonight into early Tuesday
morning, with relatively higher chances at KISP.

Winds will be 10 kt or less tonight into much of Tuesday morning and
near 10 kt late morning Tuesday into early Tuesday evening from
a WSW to SW direction. There are forecast to be some gusts
15-20 kt during the day into early evening hours on Tuesday.
Gusts may be more intermittent.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Possible brief rain showers late tonight, mainly between 03 and
07Z Tuesday. Low chance of MVFR.

Gusts may not occur each hour on Tuesday as they may be more
occasional. Timing of gusts could be a few hours off compared to
TAF.

OUTLOOK FOR 00Z TUESDAY THROUGH SATURDAY...

Tuesday Night-Wednesday: VFR. SW gusts diminish early Tuesday
night.

Thursday: Mainly VFR. Chance of rain and MVFR, especially late
at night.

Friday...Chance of rain and MVFR early morning. Otherwise,
mainly VFR during the day. Increasing chances for rain and MVFR
at night.

Saturday...MVFR/IFR in rain. E wind G15-20kt.

Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90-- End Changed Discussion --

&&

.MARINE...
Look for marginal small craft seas to continue this evening across
the eastern ocean zones with a SCA until midnight, but may be
lowered a few hours sooner during the later portion of the evening.
Otherwise the western and central ocean zones, along with the non-
ocean zones will remain below SCA thresholds. Into Tuesday look for
eastern ocean seas to get down closer to 3 to 4 ft overall. By
Tuesday night into Wednesday as weak high pressure starts to build
ocean seas should average close to 3 ft on a WSW wind. Sub-SCA
conditions are expected through Saturday afternoon.

Saturday night a frontal system will impact the region bringing
increasing wave heights above 5 feet over the ocean and wind
gusts around 25-30 kts across all waters.

&&

.HYDROLOGY...
No significant hydrologic impacts are expected through Friday. A
potent low and associated frontal system could impact the area
this weekend bringing the possibility of 1-2 inches of rain with
locally higher totals possible. Confidence in amounts are not
strong at this time, but it could pose some localized issues.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ350.

&&

$$

SYNOPSIS...JE/BR
NEAR TERM...JE/BR
SHORT TERM...JE
LONG TERM...BR
AVIATION...JM
MARINE...JE/BR
HYDROLOGY...JE/BR