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fxus61 kokx 221033 
afdokx

Area forecast discussion
National Weather Service New York New York
533 am EST Mon Jan 22 2018

Synopsis...
a warm front stalls across the area today, before shifting
northward tonight into Tuesday morning. A cold front quickly
follows for Tuesday evening. High pressure builds during the
mid and late week period. The high moves east next weekend ahead
of a cold front that likely passes sometime Sunday.

&&

Near term /until 6 PM this evening/...
updated to reflect current temperature and dew point trends. As
mentioned in the previous discussion, the T/dew point forecast is
proving to be challenging, as the warm front has moved northward
across portions of Long Island early this morning. Temperatures
have risen across eastern Long Island quickly in response. Hi-
res models suggest there could be some wavering in the placement
of the front, and as such there is potential for temperatures
to go up and down across portions of the forecast area in the
wavering flow. Trends will be monitored closely.

Weak isentropic lift ahead of the approaching warm front has
led to the development of some light showers and patchy drizzle
across the area this morning. Model forecasts indicate the
potential for minimal drier air above the surface to advect
eastward in westerly flow later this morning into the early
afternoon, which may help at least decrease the coverage of
showers, though patchy drizzle will remain possible at times.

Temperatures will largely by the most difficult portion of the
forecast today. In general, above normal temperatures will
continue in subtle warm advection, though daytime highs are
expected to be cooler than over the weekend. Highs will depend
on the northward progression of the warm front, which typically
ends up stalling across Long Island. Cold air damming to the
north of the front, primarily across the lower Hudson Valley and
Connecticut in combination with the overcast skies and light
drizzle will likely keep temperatures a few degrees below
guidance. Farther south across northeastern NJ, the NYC Metro
and Long Island, there is some potential for temperatures to be
higher than guidance/forecast if the warm front progresses
northward faster.

&&

Short term /6 PM this evening through 6 PM Tuesday/...
well above normal temperatures are expected for tonight as
overcast skies and warm advection prevail. A non-diurnal trend
will occur as the warm front begins to shift northward through
the area. Similar to the uncertainties of Monday, low
temperatures will largely depend on the speed in which the warm
front passes to the north, while highs will be around 10-15
degrees above climatological normals as the front moves
through.

After the passage of the front, low-level mass response to the
potent upper short wave will allow for quick moisture advection,
with southwest flow just above the surface ranging from 50-70
kt. Deep layer moisture represented by precipitable water
values around 1-1.20 inches will be potentially close to a
climatological maximum for this time of year, setting the stage
for periods of moderate to locally rainfall. With strong warm
advection in the low- levels and cooling temperatures aloft with
the approaching upper short wave, there will be a period of at
least marginal elevated instability, which will support
thunderstorms and locally heavy rainfall. Should temperatures
rise enough at the surface to lead to a weakened inversion,
there is potential for the stronger winds above the surface to
mix down in any thunderstorms. Regardless, a tight pressure
gradient will lead to strong winds across the area through the
day.

With deep-layer flow strongly veered initially, expect heavy
showers to be scattered in nature. As the front approaches, low-
level flow will veer, creating a more unidirectional deep-
layer profile oriented along the boundary that may support the
development of a line of showers and thunderstorms. Thereafter,
precipitation will rapidly decrease from west to east following
the frontal passage.

&&

Long term /Tuesday night through Sunday/...
the main question among available guidance is speed of downstream
trough as is passes across the country. The GFS not surprisingly
remains on the faster side of the guidance. European model (ecmwf) is trending
quicker, while ensemble guidance suggests a slightly slower
progression east.

This obviously impacts surface features and associated cold front as
well.

Overall, dry weather prevails Tuesday night through early Saturday,
and quite possibly through Saturday night. Any lingering rain with
the cold front Tuesday evening quickly ends. Upper shortwave passes
across the northeast, and is followed by another weak upper level
shortwave Wednesday night, with little fanfare with this second
shortwave.

Then ridge builds ahead of aforementioned trough next weekend.

Dry forecast until Saturday night/Sunday. Capped pops at high chance
Sunday due to timing uncertainty.

Temperatures return to near normal as cold air advection ensues behind the cold
front. It may take some time for the colder air to settle in, which
likely happens behind sfc trough associated with second shortwave,
so readings may eclipse seasonal norms Wednesday before falling back
closer to seasonal norms Wednesday night through Friday.

Then temps rebound to above climo in return flow ahead of trough,
cold front next weekend.

Due to this warmup, plain rain is expected with the next system.

&&

Aviation /12z Monday through Friday/...
a warm front will likely remain fairly stationary across the
NYC Metro and Li terminals today, moving slowly through the
region tonight. Exact timing and placement are uncertain, but it
appears the front will likely stall south of kteb, klga and
northern terminals through this evening.

MVFR conditions develop early this morning with drizzle, light
rain, and fog. Conditions likely lower to IFR for the terminals
mentioned north of the front during or just after the morning
push, and likely continue through the evening push. Meanwhile
the terminals south of the front (kjfk, kewr, kisp) likely
remain MVFR and possibly briefly improve to VFR in the aft/eve.

Winds will be light se for terminals to the south of the warm
front, and light NE to the north.

New York Metro enhanced aviation weather support...

Detailed information, including hourly taf wind component
forecasts, can be found at: http:/www.Weather.Gov/zny/n90

Kjfk taf comments: light southeast winds likely, with MVFR conditions
possible for morning and evening push.

The afternoon kjfk haze potential forecast is yellow...which
implies slant range visibility 4-6sm outside of cloud.

Klga taf comments: light NE winds and MVFR conditions likely
for morning and evening push. Low probability for IFR conds for
evening push.

The afternoon klga haze potential forecast is yellow...which
implies slant range visibility 4-6sm outside of cloud.

Kewr taf comments: light southeast winds likely, with MVFR conditions
possible for morning and evening push.

The afternoon kewr haze potential forecast is yellow...which
implies slant range visibility 4-6sm outside of cloud.

Kteb taf comments: MVFR conds possible for morning push. Light
NE winds and MVFR conditions likely for evening push.

Khpn taf comments: MVFR conditions likely for morning push,
with IFR conditions possible. IFR conds likely for evening push.
Light E/NE winds through the period.

Kisp taf comments: light southeast winds likely, with MVFR conditions
possible for morning and evening push.

Outlook for 06z Tuesday through Friday...
late tonight...IFR. Low level wind shear developing toward 12z. Showers become
likely.
Tuesday...IFR/LIFR in shra, isolated thunderstorm possible. Low level wind shear. S
winds g25-30kt. 30 to 35 kt possible for kisp/kgon.
Tuesday night into Wednesday...VFR. West-northwest g25-30kt.
Thursday-Friday...VFR.

&&

Marine...
with light flow across the area as the warm front approaches,
expect seas to remain tranquil through much of the day. A rapid
shift in conditions will then occur later tonight as the warm
front slowly moves north of the waters. South- southwest flow
will rapidly strengthen, with at least Small Craft Advisory-level winds
developing late tonight. Depending on the strength of the
inversion, there is potential for strong low-level jet winds to
mix to the surface, with at least isolated gale-force winds on
Tuesday. Gale-force winds will also be possible in any
thunderstorms that can develop. A gale watch remains in effect.
Seas will rapidly build in response to the strengthened flow,
remaining elevated even as the cold front moves through Tuesday
evening. Winds may briefly drop off as the front moves through,
before rapidly strengthening again following its passage.

A wind shift to the west occurs behind the cold front Tuesday night,
and Small Craft Advisory level winds in the 25 to 30 kt range are expected. A few
gale force gusts are possible, but not too confident in this
happening.

By Wednesday, gusty westerly winds persist as the pressure gradient
remains rather tight. A trough moves through Wednesday evening, and
winds shift to the NW, and remain gusty through Thursday. High
pressure finally approaches from the west, and winds should diminish
as the high draws closer Thursday night and Friday.

Rough ocean seas Tuesday night and Wednesday gradually subside
Wednesday night and Thursday, but likely do not subside below 4 ft
until the winds diminish Thursday night and Friday. In fact, seas
are expected to be rather tranquil Friday.

For the non ocean waters, choppy waves/seas subside Thursday and
Friday as the high approaches.

&&

Hydrology...
total rain Monday night through Tuesday is expected to range mostly
1/2 to 1 inch, with locally 1 to 2 inches possible. No significant
hydrologic issues are anticipated at this time.

No hydrologic impacts are anticipated Wednesday through early next
weekend.

&&

Equipment...
NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) is off the
air for an extended period of time.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory from 6 am to 6 PM EST Tuesday for anz335-
338.
Gale watch from Tuesday morning through Tuesday afternoon for
anz330-340-345-350-353-355.

&&

$$
Synopsis...MD/pw
near term...Maryland
short term...Maryland

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