Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
946 PM EST Friday Nov 21 2014
high pressure moves nearly overhead tonight before moving offshore
on Saturday. A warm front then moves across the region late
Saturday night. A warm front approaches from the south Sunday and
lifts across the area Sunday night into Monday morning. A cold
front moves through Monday night and then stalls offshore through
the middle of the week. Low pressure may ride along the front and
pass to the east Wednesday...with another low possibly tracking
Near term /until 6 am Saturday morning/...
a large 1035 mb surface high pressure system was centered over the Middle Atlantic
States and will continue moving east-southeastward off the coast tonight.
Surface winds continue to decrease and decouple from the upper level winds. Temperatures
are plummeting where surface winds become nearly calm as strong radiational
cooling under mostly clear skies is in progress.
Another cold night is in store for the local area.
Used a blend of met/mav MOS guidance to start...but then dropped
lows from 5-7 degrees across the interior portions of the lower
Hudson Valley and southern CT...and across eastern Long Island.
The urban heat island effect will keep overnight lows in NYC in
the middle to upper 20s. Otherwise...lows will drop into the upper
teens to around 20 for most coastal areas...and as low as the
single digits to low teens across the interior. These temperatures are
15-20 and as low as 25 degrees below normal.
Short term /6 am Saturday morning through Saturday night/...
mostly sunny for much of the day Saturday as high pressure continues
to depart. SW flow will usher a milder air mass into the region
with highs in the upper 30s across the northern portions of the
County Warning Area...and in the lower 40s across the southern portions. These
temperatures...however...are still 10-15 degrees below normal.
Clouds begin to increase late in the day and at night as a warm
front approaches from the south and west. Some light...overrunning
precipitation will develop after midnight Saturday night. Best focus will
be across far northern zones where probability of precipitation will be low chance...and
will carry slight chance most elsewhere. With surface temperatures below
freezing across interior portions of NE New Jersey...the lower Hudson
Valley...southern CT and The Pine Barrens of eastern Long
Island...ptype could be freezing rain across northern zones and
freezing rain/rain farther to the south. NYC/Long Island should
stay as plain rain...with some freezing rain possible for The Pine
Barrens of Long Island.
Lows Saturday night will drop into the upper 20s to low 30s inland
and in the middle/upper 30s across NYC/Long Island.
Long term /Sunday through Friday/...
early Sunday...weak shortwave energy moves north of the
region...with upper ridging quickly building during the day. This is
in response to digging middle west trough.
The ridge gives way to southern stream shortwave that tracks
northeast...passing just to the west of the area early Monday.
Meanwhile...main trough amplifies and closes off across the Upper
Middle west Sunday night and Monday. This closed low weakens and lifts
northeastward through the week as main trough slowly makes eastward
progress. Trough axis moves overhead by late in the week.
At the surface...a warm front approaches from the south Sunday as
low pressure tracks toward the Great Lakes region. The warm front
moves through early Monday as local area becomes warm sectored. The
deep low pressure passes across eastern Canada as a cold front moves
through by Tuesday. This front settles east of the area middle week as
a wave of low pressure rides along it...likely passing just
southeast of the benchmark. By Thursday...low pressure and front to
the west approaches. With upper trough axis overhead late
Thursday/Friday...surface low pressure may intensify off the middle
Atlantic coast Friday.
As for weather...any lingering light rain or freezing rain ends
Sunday. Temperatures warm into the lower 50s. With south
winds...temperatures remain relatively mild Sunday night for this
time of year...then warm into the 60s Monday as area becomes warm
Behind the cold front...expect temperatures to gradually fall
back closer to seasonal norms by middle to late week.
Probability of precipitation and weather will depend on eventual placement of low pressure
middle week and again late week. Kept probability of precipitation in the chance range for
now...with highest probabilities east of NYC. Weather type will be
dependent on boundary layer temperatures.
Aviation /03z Saturday through Wednesday/...
high pressure builds in from the west tonight and passes south of
the area Saturday.
VFR through the taf period. Some middle and high level clouds
expected later tonight and Saturday morning...with a middle level
deck moving in late Sat aft/eve.
Winds shift to the west and will be quite light late tonight.
Southwest winds increase to 10 to 15 knots with g20kt after 14-15z
Outlook for 00z sun through Wednesday...
Sat night and sun...VFR. Brief MVFR ceiling possible at kswf Sat evening.
Sun night-Mon...becoming MVFR/IFR. Possibly sub-IFR. Rain and fog
with low level wind shear possible.
Wednesday...mainly VFR...although possible rain or a rain/snow mix may
impact the area...especially east of NYC metropolitan.
the Small Craft Advisory/Small Craft Advisory for eastern Long Island Sound...the South
Shore inland bays and Peconic and Gardiners Bay was extended until
10 PM for wind gusts to 25 knots.
Otherwise...the Small Craft Advisory for the Atlantic coastal waters from Fire Island
east remains in effect until 1 am Saturday.
Tranquil conds through Saturday afternoon with high pressure building
over the waters. That high moves offshore on Saturday...and the
gradient tightens Saturday afternoon. Small Craft Advisory conds likely for at
least the ocean waters late Saturday and Saturday night.
Westerly winds shift toward the SW Sunday as a warm front
approaches. South winds are expected Sunday night and Monday ahead
of and then behind the front...with a slight shift from S/southeast to S/SW.
Then winds shift again back to the west Monday night and Tuesday
behind the cold front. These winds turn toward the northwest Tuesday night and
Wednesday as high pressure builds. Developing low pressure east of the
waters may turn the winds toward the north/northwest late Wednesday.
Winds remain gusty through much of the period. In fact gales are
possible Monday behind the warm front and ahead of the cold
Winds do diminish Tuesday night into Wednesday briefly as the high builds.
Seas should remain rough through much of this period.
dry conds through Saturday...and only light precipitation possible
Saturday night through Sunday morning.
Marine...Small Craft Advisory until 1 am EST Saturday for anz350-353.