Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
933 PM EST Tuesday Nov 24 2015
Canadian high pressure builds in through tonight...then slowly
slides to the east through Friday. A weak low pressure trough will
develop along the middle Atlantic coast on Thanksgiving day as the
high retreats. A cold front will approach from the west on
Friday and pass through on Saturday...followed by high pressure
building in for the rest of the weekend. A warm front will slowly
approach from late Sunday night into Tuesday.
Near term /through Wednesday/...
clouds across the western periphery of the County Warning Area continue to erode
while temperatures across the remainder of the area plummet. Temperatures
across the west should follow as the clouds dissipate. Lowered temperatures
across the board as a result. Wind across the County Warning Area will remain
nearly calm as hi pressure strengthens into the 1040s over the northestern
Continental U.S. Tonight.
Little cloud cover is expected for Wednesday...with temperatures
rising to near normal values.
Short term /Wednesday night/...
as high pressure moves east of the area...onshore flow will return
with a subtle increase in moisture, particularly below 6000 ft,
expected. The NAM is an outlier with how quickly moisture returns
to the area and suggests drizzle will be possible for Wednesday
night. Given the antecedent dry conditions...currently expecting
any drizzle to be delayed until Thursday morning at the earliest.
Long term /Thursday through Tuesday/...
as the core of the high passes south of Nova Scotia...a weak
inverted trough will develop along the middle Atlantic coast and up
into the local area...helping focus 800 mb-9 moisture beneath a
subsidence inversion and provide enough low level
convergence/lift to make Thanksgiving day a mostly cloudy
day...with some potential for light rain or drizzle. Multiple
models have been signaling this for over a day now...but kept
measurable precipitation chances low...in the 20-30 percent range...since
the GFS also overplayed a similar event back on Nov 18th...where
broken-overcast stratocu but little if any precipitation did develop. Daytime
heating should bring a break in these conditions west of the
Hudson Thursday afternoon...then clouds should return throughout Thursday
night via cooling beneath the inversion...and last into Friday
morning. Thursday will be relatively mild despite cloud cover and
precipitation...with highs ranging from 55-60.
Friday looks dry and mild...with temperatures on the high side of guidance
and ranging from 60-65. The front will be slow to approach Friday
night...with chances for showers late at night and into Sat
morning. Dry colder weather will follow for Sat afternoon into
Sunday...with highs in the 40s to near 50s...and lows in the upper
20s and 30s.
Models continue to trend north/west with a closed low ejecting out
of the SW states this weekend..and heading toward the Great Lakes
on Tuesday. Most of the associated light precipitation with its leading warm
front should be in the form of rain...but with potential for low
level cold air damming at precipitation onset as high pressure moves
east...precipitation type at onset may not necessarily be in the form of
rain well inland late Sunday night into Monday morning.
Aviation /03z Wednesday through Sunday/...
high pressure remains in place.
VFR. Light northwest winds for the city terminals veer north overnight.
Light and variable winds elsewhere.
For Wednesday...winds becoming southeast in the afternoon under 10kt. Chance
mainly east of the city of ceilings around 3000ft developing late
afternoon or evening.
Outlook for 00z Wednesday through Sunday...
Wednesday night-Thursday night...chance of MVFR or lower ceilings.
Friday-Saturday...mostly VFR. MVFR ceilings possible in showers
Friday night into Saturday. Chance north-NE gusts 20-25kt Sat morning.
Sunday...chance of sub-VFR in rain late.
winds will remain 10kt or less on all waters through Wednesday.
Mainly sub-advisory conditions will continue through Friday with a
weak pressure gradient.
Small Craft Advisory conds may be possible on the ocean Friday night into Sat...first
via incoming swells generated by the pressure gradient between a
sprawling high pressure system along the coast and over the
waters...and a subtropical low or trough near Bermuda. Maximum wave
heights may reach 6-7 feet on Sat. Wind gusts in northerly flow
after a cold frontal passage on say may also reach 25 knots.
dry through Wednesday. Light drizzle possible Thursday with
minimal accumulations. A cold frontal passage Friday night into
Saturday may bring light precipitation (less than 1/4 inch).
water levels are expected to remain below minor flooding
benchmarks at high tide Wednesday morning.