000
FXUS61 KOKX 270948
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
548 AM EDT Sat Apr 27 2024

.SYNOPSIS...
High pressure continues sliding to the southeast through
this afternoon. A warm front approaches tonight and moves north
on Sunday. Weak high pressure returns late Sunday into Monday.
A back door cold front moves through Monday night. A frontal
system approaches from the west and moves through the area on
Tuesday. High pressure then briefly follows for midweek before
another frontal system potentially impacts the area Thursday
into Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Forecast on track early this morning. Frost advisory remains in
effect until 9 am for interior NE NJ, Lower Hudson Valley, S
CT, and LI Pine Barrens.

Sprawling high pressure over the eastern seaboard will
continue to slide to the south and east through the day. A high
amplitude upper ridge axis will remain overhead, but in the
middle levels (around 700-850 mb) a weak trough approaches. This
system will be moving around the periphery of the ridge, but
will be accompanied by increasing clouds through the afternoon
and evening. An associated warm front will lift NE across the
region tonight as well. Guidance has been hinting at a weakening
band of showers moving in from the west late afternoon and
evening, but likely is just a signal of increasing middle level
moisture. Think it remains dry until after 6 pm as low levels
will be too dry to support rain reaching the surface. Scattered
showers are possible tonight with slightly higher probabilities
across the interior closer to more organized forcing.

Temperatures today will continue below normal, but several of
the cooler spots from Friday should moderate a bit. Highs will
range from the upper 50s near the coast and lower 60s elsewhere.
Milder conditions are expected tonight with lows in the middle
to upper 40s.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The warm front lifts north and washes out Sunday morning with
any lingering showers ending around 12z. The upper ridge looks
to reestablish itself to our west and the resulting subsidence
should keep conditions dry into the afternoon. There is a
lingering surface trough lying nearby, especially in the
afternoon and evening and some weak shortwave energy riding
over top the ridge. The latest CAMs have been simulating some
isolated shower activity associated with the surface trough in
evening and potentially first half of the night. Have gone ahead
and included a slight chance PoP for showers. The surface
trough looks to shift offshore early Monday morning.

The main challenge for Sunday will be temperatures as much
warmer air moves in with the warm front. Mostly cloudy
conditions are likely to continue in the morning but some
partial clearing is expected in the afternoon. The deterministic
NBM is falling at or just below its 25th percentile for highs,
The flow away from the coast will be SW and this should give
temperatures a boost despite potential cloud cover. As previous
shifts have done, will lead towards a 50th percentile NBM for
highs which yields readings in the middle to upper 70s along and
west of the Hudson River and middle 60s to around 70 further
east. The 75th percentile of the NBM has highs reaching or
exceeding 80 degrees at Central Park and points north and west,
so it is not out of the question for highs to be warmer if more
sunshine occurs. Lows Sunday night will be unseasonably mild
with readings in the 50s, potentially around 60 in the NYC
metro.

The passage of the surface trough Sunday night leaves behind
a weak NW-N flow into Monday morning. High amplitude ridge axis
settles overhead with a surface ridge axis extending north from
high pressure over the southeast. Confidence continues to
increase for more summer-like temperatures to occur on Monday.
The question is just how high will temperatures reach. The
ingredients are there including the region in the warm-sector,
strong ridging, and offshore flow the first half of the day.
Past events this time of year have shown that the NBM
deterministic and statistical guidance usually run too cool
(only showing highs in the middle 70s to lower 80s). The 50th
percentile of the NBM has highs in the upper 70s to middle 80s
with the 75th percentile indicating some upper 80s in the usual
warmer spots. Have elected to use the 50th percentile of the NBM
for this update, but could still be too low. A reasonable high
end scenario is for temperatures approaching 90 degrees in NE
NJ. Coastal locations will end up cooler, but still have
potential to come close to 80 degrees before onshore flow
develops in the afternoon.

The ridge axis remains overhead Monday night with any
shortwave energy well to the north. Surface high pressure
moving across southeast Canada will likely help push a back door
cold front from NE to SW across the area. This may start to
bring in some cooler air, but lows will still be well above
normal ranging from the upper 40s east to middle to upper 50s
west. Have kept the forecast dry with any shortwave energy to
the north.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
There has not been a significant change in the forecast
thinking for this update, and stuck closely to the national
blend.

*Key Points*

*After a warm start to the week, cooler conditions Tuesday and
 Wednesday, but still above normal. A slight warmup then for
 week`s end.

*Mainly dry conditions expected with a few chances of showers and
 thunderstorms as multiple frontal systems impact the area
 during the period.


Upper ridging flattens by Tuesday as the ridge axes heads east
of the area. A mid level shortwave within the flow approaches
from the west by afternoon bringing with it a weak cold front.
The backdoor front from Monday also remains in the region and
looks to move back over, or north of the area as a warm front
Tuesday AM. Thus, widespread easterly flow should keep clouds
around and limit high temperatures relative to Monday, 10-15
degrees cooler. NBM temperature spread has decreased somewhat
with current cycle, with high end values lowering a few degrees,
adding some confidence to the temperature forecast.

Showers and possibly a thunderstorm especially N/W of NYC still
looks probable for Tuesday afternoon, with some very marginal
surface based instability. Best chances for thunder are N/W of
NYC where the instability is better, with BUFKIT soundings
showing a few hundred J/kg of MUCAPE during the afternoon.

After weak high pressure builds in behind the Tuesday system
for Wednesday and Thursday, another upper low ejects out of the
Northern Plains and heads into Canada Thursday into Friday. An
accompanying frontal system with this low then impacts the area
late Thursday and Friday, with additional chances of showers and
possibly some thunder.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
High pressure shifts east as a warm front approaches the region
later today.

VFR through most of the TAF period; MVFR possible early Sunday.

Southerly flow, at times light and variable overnight. Southerly
flow persists on Saturday, with speeds increasing to 10 to
15 kt and gusts of 15 to 20 kt in the afternoon. Lowering
ceilings during the day as a warm front approaches.

Showers cannot be ruled out after 00Z Sunday, though confidence
and coverage remains low. For now, have treated with Prob30s,
with cigs looking to remain high end MVFR 06-12Z Sunday.

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

No unscheduled amendments expected.

OUTLOOK FOR 06Z SUNDAY THROUGH TUESDAY...

Saturday PM: Becoming MVFR late with a chance of rain.

Sunday: Return to VFR by afternoon. Light SW flow.

Monday: VFR. Winds under 10 kt.

Tuesday: MVFR or lower possible with afternoon showers and isolated
thunderstorms.

Wednesday: VFR. Winds under 10 kt.

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

&&

.MARINE...
Winds and seas will remain below advisory levels through the
weekend under a weak pressure gradient regime. Coastal jet
development this afternoon and evening could bring marginal SCA
wind gusts (20- 25kt) near the entrance to the NY Harbor.

Much of next week looks to be below sub-SCA with a weak flow
across the waters. Potential fog development will have to be
watched due to warmer air moving over the colder waters (SSTs
near 50F), but it is much too early for any specific details on
timing and extent.

&&

.HYDROLOGY...
No hydrologic concerns through the end of next week.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...Frost Advisory until 9 AM EDT this morning for CTZ005>008-012.
NY...Frost Advisory until 9 AM EDT this morning for NYZ067>070-079-
     081.
NJ...Frost Advisory until 9 AM EDT this morning for NJZ002.
MARINE...None.

&&

$$

SYNOPSIS...DBR/DS
NEAR TERM...DS
SHORT TERM...DS
LONG TERM...DBR
AVIATION...DBR
MARINE...DBR/DS
HYDROLOGY...DBR/DS