Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
207 am EDT Wednesday may 27 2015
Bermuda high remains anchored well off the East Coast through
Thursday. A weak cold front will approach the area from the west
Wednesday night...and dissipate across the area on Thursday. A
stronger cold front will then impact the area Sunday into early
Near term /until 6 am this morning/...
forecast is generally on track. Removed probability of precipitation overnight as forcing
looks very weak.
Fog has developed in northern portions of Orange County where
dewpoints spiked into the 70s after the showers exited. Winds are
calm and should remain this way...so added fog to the forecast up
there through the night. It could become locally dense at times.
Patchy fog is possible elsewhere towards morning. There is a low
chance that fog becomes locally dense near the coast...but it
remains uncertain how widespread this would end up being. There is
a greater likelihood for stratus to develop with persistent
onshore flow...especially near the coast. Sky conditions should
remain mostly clear to partly cloudy until then.
Low temperatures will be in the middle and upper 60s.
Short term /6 am this morning through 6 PM Thursday/...
potential for convection increases on Wednesday as the upper level
ridge begins to move further offshore. The development of a pre-
frontal/thermal trough will provide a source for lift in the
afternoon...mainly north and west of the city. Cape values in the
models differ in the afternoon and this is due to how much heating
they forecast. The NAM has much higher surface based cape with
its warmer surface temperatures in combination with dew points in
the middle 60s. Feel cape values may be a bit too high in the
NAM...but it has the right idea with its warmer temperatures
leading to higher amounts of instability. Any morning clouds will
break late morning and early afternoon to allow for enough
sunshine to realize this higher instability.
Showers and storms should develop in the afternoon and linger into
the afternoon with the above in mind. Storm Prediction Center has the interior of NE
New Jersey and the lower Hudson Valley in a marginal risk for severe
thunderstorms. An isolated severe wind gust cannot be ruled out
here...but feel storms should remain below severe limits. Locally
heavy rainfall is possible in any storm with urbanized minor
flooding a possibility. Chance probability of precipitation continue for mainly west of
the Hudson River.
The question for Wednesday evening is how far east the convection
gets. The marine influence and proximity of the upper ridge will
most likely weaken the storms considerably as they move near the
Hudson River. No higher than slight chance probability of precipitation forecast in the
evening east of the Hudson. Probability of precipitation do increase to low chance for
eastern zones overnight as the pre-frontal trough remains nearby
and elevated instability could promote development of a few
High temperatures on Wednesday will be in the middle and upper 80s
from NYC north and west and mainly middle and upper 70s across
southern CT and Long Island. Lows Wednesday night will be in the
There is a moderate risk for the development of rip currents at
Atlantic Ocean beaches on Wednesday.
Long term /Thursday night through Tuesday/...
a high amplitude ridge along the eastern Seaboard will expand
westward back into the MS River Valley as short wave energy over the
Great Lakes dampens and lifts to the NE Thursday. This will allow the
sub tropical ridge to remain in place through next
weekend...pumping in warm...humid air across the region.
A weak cold front will move across the area on Thursday before
dissipating offshore on Friday. There may be a few showers or
thunderstorms through Thursday evening...but dry air looks to be a limiting
factor. Heights build aloft Friday into Sat with strong subsidence
capping the airmass. Any convection will be isolated...diurnal in
nature...and likely well inland.
Forecast dilemma remains the timing of a stronger cold front Sat
night into sun. The 12z operational GFS still remains the
faster...and more aggressive solution. However...deferred to the
slower European model (ecmwf) which has maintained the best run-to-run continuity.
The European model (ecmwf) does not bring the front through until sun after and then
keeps it in close proximity through early next week.
There is the potential for an organized rainfall event late in the
weekend into early next week as the cold front moves into the area.
Conditions will remain unseasonably warm through Sat...then cools
down sun into Monday behind the cold front.
Aviation /06z Wednesday through Sunday/...
a weak cold front will approach the region today...and dissipate
over the area Thursday.
Mainly VFR this morning...however there is the potential for some
pockets of stratus and br which could bring MVFR. Any MVFR Burns
off by 13-15z except kgon where there is the potential that it
could linger most if not all of the day. Otherwise...afternoon thunderstorms
likely to develop across the lower Hudson Valley after 18z. The
activity may hold together to impact areas roughly along and west of
a khpn-kewr line.
MVFR or lower at times tonight with stratus and possibly fog.
SW flow through the taf period. Highest speeds this afternoon into early
evening...especially in vicinity of kjfk where sustained around 20kt expected.
Outlook for 06z Thursday through Sunday...
late Wednesday night...MVFR or lower at times with SW flow.
Thursday...morning MVFR or lower. Scattered thunderstorms possible in vicinity of a weakening
cold front. SW flow diminishing and possibly becoming northwest or vrb.
Friday...VFR with light NE winds veering through the day.
Sat...morning MVFR or lower possible. Chance showers and thunderstorms in the
afternoon and overnight with MVFR or lower. Strong southerly flow.
Sun...possible improvement to VFR. NE winds.
looking at observations around the Great South Bay...frequent wind
gusts to 25 knots have come to an end...so will allow the Small
Craft Advisory for the South Shore bays of Long Island to expire
as scheduled. Otherwise...the Small Craft Advisory on the ocean waters continues
through Wednesday night. Wind gusts around 25 knots at 44065 will
decrease over the next few hours and then increase again on
Wednesday and Wednesday evening with prolonged southerly flow.
Seas will also build to 5 feet tonight and remain near 5 feet through
Winds may also approach Small Craft Advisory levels on the New York Harbor and South
Shore bays again on Wednesday afternoon.
There is also the potential for areas of dense fog to form on the
waters late tonight into Wednesday morning. Confidence remains
low on this and for now have continued to forecast patchy fog.
Marginal Small Craft Advisory conditions on the ocean waters possible Thursday-sun with a
moderate southerly flow. There will be a brief period of offshore winds
Thursday night behind a dissipating cold front.
generally less than two tenths of an inch of basin average
rainfall is expected through Wednesday. However any stronger
convection that forms...especially if there is any training of
storms...could lead to minor flooding of urban and/or poor
There is the potential for an organized rainfall event late in the
weekend into early next week as cold front moves into the area.
Marine...Small Craft Advisory until 6 am EDT Thursday for anz350-353-