Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
702 am EST sun Nov 29 2015
a cold front will continue to move south of Long Island with a
weak surface low moving along it today. High pressure builds in
later today and tonight...continuing to build in through Monday.
Low pressure traveling west of the region will bring a warm front
near Tuesday with a cold front following on Wednesday. Then...high
pressure builds for the end of the week into next weekend.
Near term /until 6 PM this evening/...
weak radar reflectivity echoes are present across northeast
New Jersey...NYC metropolitan and will move across portions of Long Island this
morning. However...without much low level clouds as there is a lot
of dry air...rain is not making it to the ground...evaporating
before it does so. So there will still be the chance of a shower
this morning and this chance will diminish by late morning and
afternoon as the front pushes farther south. Otherwise...rest of
forecast is on track with minimal changes.
A northerly flow continues behind the cold front. A wave of low
pressure along the front due to a jet streak moving in aloft will
enhance lift. A lot of models are keeping the rain south of Long
Island but due to the region being near the left front quadrant of the
jet streak...added in a slight chance of light rain for southernmost
portions of the region through this morning.
Cloud coverage lowers this afternoon...as clouds move farther
south with the southward progress of the front when the high
pressure center moves into Quebec. Still a northerly flow which
will continue the low level cold air advection. Highs will be
lower due to limited vertical mixing...only to near or just below
950mb...with the decrease in pressure gradient as the day
progresses. Cold air advection evident within the forecast BUFKIT
profiles conveying the backing of winds with height from low to
GFS has been verifying recently a little better compared to the NAM
so used a combo of mav/gmos for highs.
Short term /6 PM this evening through 6 PM Monday/...
for tonight...high pressure continues to build in from the north
but its center will be moving towards Maine. This will shift winds
locally at the surface to more of an easterly component. This will
act to moderate temperatures along the coast with more onshore
flow...preventing efficient radiational cooling. The interior will
be remarkably colder with winds being more light and variable
so there will be more optimal radiational cooling. The mav
guidance was used for lows.
For Monday...the high center moves into the Gulf of Maine with
winds gaining more of an easterly component. With the center of
the high within close proximity...the pressure gradient will be
weak with winds speeds remaining lighter as a result.
However...with temperatures decreasing a few degrees aloft near
the top of the estimated mixing layer...which again will only be
to around 950mb...maximum temperatures are forecast to be
approximately five degrees colder than the previous day. A mav/met/gmos
combo was used for maximum temperatures Monday.
Long term /Monday night through Saturday/...
aloft...brief ridging Monday night through Tuesday with a
deepening trough approaching from the west for the midweek
period. The deep trough pushes south of the region Wednesday
For Monday night and Tuesday...high pressure will start to weaken
as the high center moves farther southeast of Nova Scotia. The
next low pressure area will be moving into Minnesota/Wisconsin region
with its associated warm front approaching the local region. Here
residual subsidence initially will give mostly clear sky
conditions but clouds will move in later that night with warm air
advection aloft...particularly between 800 and 1000mb. Precipitation
starting time will be crucial and what precipitation types will be in
the forecast ahead of the warm front will be contingent on the
precipitation starting time. The mav/met/gmos was used for min
temperatures Monday night and maximum temperatures Tuesday.
The lifting is also conveyed from isentropic lift late Monday
night into daybreak Tuesday. This is more conspicuous within the
GFS model isentropic surfaces compared to the NAM. European model (ecmwf) and the
Canadian models also are the first models to bring in
precipitation...showing some light quantitative precipitation forecast extending through northeast New Jersey
into NYC between 06z Tuesday and 12z Tuesday. The warm front
continues to slowly approach as a low develops along it. The
prolonged southeasterly winds will continue with rain becoming
more continuous across the region.
For Tuesday night through Wednesday night...the rain continues
Tuesday night with the wave of low pressure passing south of Long
Island. Once the low exits east of the region...more of a
southerly wind will result. The warm front will be slow to lift
north across the region but is forecast to do so by the overnight
period. The associated cold front will move across Wednesday with
high pressure building in from the west thereafter. The rain
continues into Wednesday before starting to decrease Wednesday
night. European model (ecmwf) and Canadian are also showing anafrontal
characteristics with some rainfall lingering after winds shift to
more westerly direction Wednesday night. The prolonged rain will
be favorable due to synoptic lift as diagnosed by positive
vorticity advection aloft as well as another left front quadrant of
the trough associated jet streak moving across the local region.
There is a consensus amongst the different models of mainly
conditions resuming late Wednesday night. Used gmos for
temperatures Tuesday night and Wednesday...and a combo of gmos/wpc
for temperatures Wednesday night.
Thursday-Saturday...shortwave trough lifts to our NE on Thursday
with upper ridging taking shape overhead. High pressure builds in at
the surface Thursday...and will remain in control through Saturday.
Some differences noted aloft between the latest models...but overall
these differences will have minimal impact on sensible weather. Dry
conditions during this period with temperatures averaging near
Aviation /12z Sunday through Thursday/...
VFR as strong high pressure builds southeast from Ontario today...
into upstate New York and New England tonight. High confidence in
north winds 8-12 knots today...diminishing slightly and veering NE
tonight. G15-20kt possible in NYC metropolitan and along the coast
Outlook for 12z Monday through Thursday...
Monday...VFR. NE-east winds g15-20kt possible until around midday.
Tuesday-Wednesday morning...rain likely with IFR conds. LIFR and southeast winds
g20kt both possible Tuesday night.
Wednesday afternoon-Thu...VFR. West-northwest winds g20-25kt.
NE flow will strengthen tonight between high pressure building into
upstate New York and New England...and a weak low off the southern middle
Atlantic coast. This should bring Small Craft Advisory conds to the ocean waters
tonight into Monday afternoon. Conds should briefly abate Monday
night...then another round of Small Craft Advisory conds is likely for the ocean
waters Tuesday-Thursday both ahead of and behind a passing frontal system.
Small Craft Advisory conds are also likely for all waters in Post-frontal west-northwest flow
Wednesday night...and gusts on the eastern ocean waters may approach minimal
any rain early today will only be a few hundredths of an inch or
less. Approximately one inch of rain will be possible with the low
pressure system Tuesday through Wednesday night with locally lower
and higher amounts.
Marine...Small Craft Advisory from 9 PM this evening to 6 PM EST Monday