Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1245 am EST Monday Nov 30 2015
high pressure over eastern Canada builds southeast tonight and into
northern New England by morning. The high will then give way to a
storm system over the middle section of the country...which impacts
the region Tuesday into Wednesday. A warm front moves near the
area Tuesday night into Wednesday followed by cold front moving
through on Wednesday. High pressure then builds in for the end of
the week into next weekend.
Near term /until 6 am this morning/...
winds have remained up in some outlying areas...allowing for
mixing and thus warmer temperatures than forecast. Have adjusted
hourly temperatures and increased lows in these areas
somewhat. Otherwise...forecast remains on track.
Polar high pressure over eastern Canada drops into northern New
England through tonight. This will provide a cold and mostly clear
night across the region. The only caveat to the sky forecast is
some high clouds off to the west that could graze southern
portions of the region. Have adjusted sky grids through the
night to account for this...but overall should see mostly clear
These clouds should be rather thin so do not think they will have
effect temperatures too much. Adjusted temperatures across
outlying locations...including The Pine Barrens of Long
Island...where readings have fallen off quicker than previously
forecast. Lows will range from around 20 well inland and across
The Pine Barrens...to the lower 30s NYC metropolitan. This is a few
degrees below normal.
Otherwise...a split flow regime will continue across North
America with the southern branch being the dominant play maker
across the Continental U.S.. the upper trough across the NE and eastern
Canada lifts out quickly as short wave ridging approaches from the
west. Farther west...a cutoff low continues to spin across the
northern plains. The latter of which will send a storm system
north into the upper Midwest...with its associated warm front
approaching from the south Monday night.
Short term /6 am this morning through 6 PM Tuesday/...
forecast dilemma for Monday is to what extent does stratus develop
beneath the subsidence inversion. Both the 12z NAM...GFS...and 09z
sref show saturation just below 900 mb working in from the coast in
the morning to inland locations by after. Models in past events have
been too aggressive with the low-level moisture. However...model
consensus does support widespread stratus by Monday after. This should
keep Monday high temperatures from getting much higher than the low to middle
40s. Used a blend of the met/mav MOS...which does not have a good
handle on the low clouds. Thus...it could even be a bit cooler.
For Monday night...middle and high level clouds will increase in
association with warm air advection ahead of the storm system
over the middle section of the country. Surface warm front will be
working north across the middle Atlantic region with cold air damming
likely along the Lee of the Appalachians.
Light precipitation will overspread the area toward daybreak Tuesday.
There is the possibility for a brief period of light freezing rain
across western portions of Orange County in the lower Hudson
Valley. This is a low probability event and will depend on the
extent of the cloud cover early Monday evening. If there is some
clearing...it would allow for better radiational cooling.
Lows Monday night will range from the lower 30s well inland...to the
lower 40s across Long Island/NYC. Temperatures will likely become steady
by midnight but could fall slightly with the onset of the light
Long term /Tuesday night through Sunday/...
unsettled weather pattern to begin the long term period as a complex
frontal system impacts the area Tuesday into Wednesday. First on
Tuesday...models are coming into better agreement with a weak wave
of low pressure developing along the middle Atlantic coast and
tracking to the north-northeast. The 12z European model (ecmwf)/CMC/NAM/sref all take this wave
across the area. However...the 12z GFS and many of its ensemble
members move this wave east of the 40/70 benchmark. Followed a
closer blend of the European model (ecmwf)/CMC/NAM/sref with this package with the
track of this wave. There are strength differences among the models
with this track solution and some of this appears to have to do with
the strength of some shortwave energy as well as how much damming
from the high offshore is allowed to ridge down into the region.
Will show probability of precipitation throughout the day...first starting out as chance
west...to becoming likely late in the day and evening. There
continues to be a chance of some light freezing rain across interior
Orange County at the onset...but confidence is growing that surface
temperatures may be too warm for any p-type but rain at daybreak.
Much of the rain should be light on Tuesday with the lift in the
form of warm advection as the best large scale lift remains well to
the west through the day. As this wave moves to the north and
east...a warm front approaches from the south.
The warm front will be near the area Tuesday night into Wednesday
morning so will continue with likely probability of precipitation...but do think there is a
possibility of a brief lull in steady rain. Late Tuesday night into
Wednesday morning...divergence aloft ahead of shortwave trough and
better forcing should bring widespread rain. Then on Wednesday...a
cold front will swing through the region. Timing differences among
the models continue with the latest 12z cycle. Have elected to
follow timing close to the European model (ecmwf) as the GFS may be too quick to move
the front and shortwave through. Rain tapers off Wednesday night as
the front moves well offshore.
Forecast temperatures average above normal Tuesday and Wednesday.
Thursday-Sunday...dry conditions return to the tri-state. Shortwave
trough lifts to the NE on Thursday with high pressure building from
the southwest. Shortwave energy may linger aloft as as another wave
passes to the north on Friday. There continue to be differences in
the amplitude and timing of this wave. The wave should send another
cold front through Friday night..but the atmosphere looks too dry
for any precipitation. Otherwise...ridging builds aloft and at the
surface this weekend. Temperatures should average near normal during
Aviation /06z Monday through Friday/...
Canadian high pressure builds to the north this morning...then
slowly retreats to the northeast through tonight...as a coastal low
develops near the middle-Atlantic coast.
VFR through at least 12z. MVFR ceilings possible from late this
morning/early this afternoon on. High confidence in occurrence of
MVFR ceilings...low-very low confidence on timing.
North-NE winds around 10 knots or less veering to the NE throughout by
around 12z. Winds veer to the east-northeast-east this afternoon/early this
evening. Light and variable winds inland tonight. Exception is at
kswf where winds should be light and variable through the taf period.
Mainly isolated gusts to around 15-20kt at city terminals through
around 7-8z. There is a low chance of gusts to 15-20kt for
eastern terminals from around 9-18z. Confidence in this is too low
to put in tafs at this time.
Outlook for 06z Tuesday through Friday...
late Monday night...MVFR. Light rain developing...with brief freezing rain
possible at kswf.
Tuesday...brief freezing rain possible at kswf early. IFR or lower likely
with rain. Easterly winds g15-20kt possible.
Tuesday night-Wednesday...IFR likely/LIFR/vlifr possible.
Wednesday night...becoming VFR.
Thursday...VFR. Northwest winds g15-20kt possible.
forecast remains on track and no changes made to the Small Craft Advisory that GOES
into effect across the ocean at 02z.
As high pressure builds southeast from from eastern Canada tonight...it
will allow for a tightening of the NE pressure gradient. This will
result in marginal gusts around 25 knots with seas building to around 5
feet. The gradient weakens by middle morning...but it will take seas
until early sun evening to fall below 5 feet.
Small Craft Advisory conditions are likely on the ocean Tuesday into Wednesday as
a frontal system impacts the region. Wind gusts up to 25 knots on the
ocean expected Tuesday...with seas 5 to 6 feet. The frontal system
moves away from the waters Wednesday night into Thursday. Small Craft Advisory
conditions are likely to continue behind the front. Sub Small Craft Advisory
conditions are then forecast on Friday.
a low pressure system could bring approximately one half to one
inch of rain Tuesday through Wednesday.
Marine...Small Craft Advisory until 6 PM EST this evening for anz350-