Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
328 PM EST Monday Nov 30 2015
Strong high pressure slowly retreat east out into the
North Atlantic tonight. Low pressure along an approaching warm front
will pass to the south and east Tuesday into Tuesday night. A cold
front approaches on Wednesday and works its way across the region
Wednesday night. High pressure builds into the region for the end
of the week and into the start of next week.
Near term /through Tuesday/...
A large and deep closed low will slowly drift NE through the
northern plains...orienting a deep and moist SW flow towards the
region. This will also steer southern stream energy over the
Tennessee/Ohio valleys towards the area tonight. At the surface...an
associated cold/occluded front will push through the Ohio Valley
tonight into Tuesday with a warm front over the southern middle
Atlantic slowly lifting north through the middle Atlantic at the same
time with southern stream energy inducing a wave of low pressure
along the coast.
Strengthening Theta-E advection over a slowly retreating Canadian
surface high should allow for precipitation to develop over the region from
SW to NE after midnight through early Tuesday morning. Have leaned
towards quicker timing based on southern stream energy
Temperatures will be warm enough aloft to make precipitation fall as liquid...but
potential for a period of freezing rain across locations well north and
northwest of NYC based on extent of cold air damming. Freezing rain hazard
will be heavily predicated on any evening clearing of stratocu
overhead...allowing for better radiational cooling of air and
ground...before strato cumulus over PA and high clouds move in. Cold
air drainage down the Hudson and Connecticut River valleys could
also hold/drop temperatures to around freezing late tonight into early
Tuesday morning. With confidence low on how above mentioned factors
will come together...will hold off on Freezing Rain Advisory...but instead
handle with Special Weather Statement for potential freezing rain threat across Orange
Lows tonight should range from around 30 in the river valleys of
lower Hudson Valley and southern CT...to the lower 30s across the
remainder of the interior...to middle/upper 30s coastal sections...to
the lower 40s in NYC.
Easterly winds increase on Tuesday as surface low pressure
approaches the region. Wind gusts of 20 to 25 miles per hour likely. Any
lingering early morning freezing rain should change to plain rain
fairly quickly after sunrise with continued warm air advection aloft and a bit of
solar isolation. Models differ a bit in track of the surface wave
across or to the south of the region Tuesday evening...but will lean
towards a track on the southern edge of guidance based on cold air
damming. In terms of sensible weather...a steady light to moderate
rain with breezy and cool conditions can be expected through the day.
High temperatures will be in the upper 40s to near 50 for NYC/Long
Island...and in the 40s to the north/west. Interior valleys could
hold in the upper 30s.
Short term /Tuesday night through Wednesday/...
Models in good agreement with the closed upper low drifting from the
upper Mississippi River valley Tuesday evening through the Great Lakes on
Wednesday. Resultant primary low pressure begins to fill over the
upper Mississippi River valley/Great Lakes.
Initial wave of low pressure track NE of the region Tuesday
evening...which may allow for a brief respite in steady rain but
likely replaced by fog and drizzle as warm front settles near the
Meanwhile secondary low pressure develops across the southern
Appalachians along the associated cold front Tuesday night in
response to approaching middle and upper level energy ahead of the
closed low. Models are in good agreement with this low tracking NE
up the coastal plain towards the region Wednesday and then across
the area Wednesday evening. The warm conveyor belt of moisture (2-3
stds above normal) interacting with increasing middle/upper level
dynamics and convergence ahead of low pressure and cold/occluded
front should allow for a second round of moderate rain late Tuesday
night into Wednesday evening. Models in decent agreement with cold
front and surface wave passing east by around 06z Wednesday night
with rain tapering off.
Long term /Wednesday night through Monday/...
Storm system departs Wednesday night as low pressure over the area moves
towards the Gulf of Maine. This will drag a cold front through the
region during that time. The heaviest precipitation will be in the
evening...and then showers taper off after midnight.
Upper trough then swings through the area Thursday morning. Few
lingering showers possible then...but conds should dry out by
Thereafter...high pressure builds into the region for the end of the
week before moving overheard late in the weekend. The high then
moves offshore for the start of the new work week.
Temperatures will be near to slightly above normal during this time.
Aviation /20z Monday through Saturday/...
Hi pressure over the region tonight will give way to low pressure passing S of
Long Island Tuesday.
Scattered-broken clouds around 2500-3000 feet through this evening...becoming broken-overcast
around 2000 feet tonight. Widespread MVFR overnight through Tuesday. Periods of
IFR possible Tuesday afternoon...mainly after 18z. Steadiest rain along and east
of a line from kjfk-klga-khpn after 16-18z Tuesday.
NE winds gradually veering to the east-northeast through this evening...then remaining
generally east-northeast through the day Tuesday. In the extended tafs...there could
be a shift to the north-northeast just before 00z Wednesday.
..NY metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts can
be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: no unscheduled amendments expected.
Klga fcster comments: potential for ceilings to become scattered resulting in
periods of VFR through 00z.
Kewr fcster comments: no unscheduled amendments expected.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: brief pockets of VFR possible through 00z.
Outlook for 18z Tuesday through Saturday...
rest of Tuesday...MVFR or lower with east winds becoming vrb overnight.
Wednesday...MVFR or lower with southerly flow.
Wednesday night...possible improvement to VFR by 12z Thursday. Winds shifting to
Thursday...VFR. West-northwest flow 10-20kt.
Friday...VFR. West flow 10-20kt.
Sat...VFR. Winds shifting to the north.
Small Craft Advisory remains in effect for the ocean with seas at the buoys around 5
feet. Small Craft Advisory winds expected to return late tonight into Tuesday as east-NE winds
increase between low pressure approaching from off southern middle
Atlantic coast and retreating strong high pressure.
If the low is stronger and/or tracks closer to the area on Tuesday...the
ocean waters could experience a brief period of minimal gales.
Easterly flow Tuesday night will lighten as an area of low pressure
passes to the east. As a warm front remains in the vicinity late Tuesday
night into Wednesday...winds may vary as they continue to lighten.
Small Craft Advisory ocean east/southeast swells will be slow to subside through Wednesday.
S/SW winds expected ahead of cold front/surface low on Wednesday...with
marginal Small Craft Advisory winds possible late Wednesday into Wednesday evening ahead of it.
Pressure gradient tightens between departing low pressure and high pressure
building in from the west Wednesday night and Thursday. Few gales
gusts possible on ocean waters Thursday...otherwise...strong Small Craft Advisory
conds will develop on the waters.
High pressure builds in for the weekend and into the start of the new
week with sub-Small Craft Advisory conds.
Quantitative precipitation forecast 1 to 1 1/2 inches expected late tonight through Wednesday evening.
Most of this should fall from late Tuesday night into Wednesday evening. No
flooding issues anticipated.
Marine...Small Craft Advisory from 1 am to 10 PM EST Tuesday for anz330-
Small Craft Advisory until 6 am EST Wednesday for anz350-353-