Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
743 am EDT Sat may 30 2015
high pressure will remain over the western Atlantic through this
evening. A cold front approaches tonight...moves near the region
Sunday...and stalls in the vicinity Sunday night. The front lifts
back north on Monday as a wave of low pressure moves across the
area Monday night into Tuesday morning. High pressure will then
build in from the north late Tuesday into Wednesday...and shift to
the south Thursday into Friday.
Near term /through tonight/...
areas of fog and low stratus remain across eastern Long Island
and southeastern Connecticut. The dense fog advisory continues
until 13z for the Twin Forks of Long Island and New London County
Connecticut. An Special Weather Statement remains for Middlesex
and New Haven counties. The fog has become locally dense
here...but already seeing improvements on latest New Haven Airport
Fog should lift fairly quickly this morning with stratus hanging
around a bit longer near the coast. Skies should become partly to
mostly sunny this afternoon with temperatures reaching the middle
80s from the city north and west and the upper 70s further east
with onshore southerly flow. It will also be breezy this afternoon
and evening with southerly wind gusts to 25 miles per hour for many
locations and possibly near 30 miles per hour near the coast.
With the approach of a cold front from the northwest and
differential heating...a few showers and thunderstorms will
develop across the northwest interior this afternoon. Cape values
1000-2000 j/kg are forecast by the models and this makes sense
given the degree of heating expected and dew points in the lower
60s. Any activity that develops will likely dissipate this evening
as it moves east with loss of daytime heating. Have probability of precipitation capped at
chance across the northwest interior through this evening.
Probability of precipitation increase slightly tonight from west to east as the front
slowly sinks south towards the region. There may be just enough
elevated instability as well so have mentioned slight chance of a
thunderstorm. Lows will be in the 60s. Patchy fog is also possible
overnight due to warm and moist air mass in place.
There is a high risk of rip currents at the Atlantic beaches
today. Strongest rip currents would occur during the afternoon as
the southerly winds increase.
Short term /Sunday through Monday night/...
the front will be slow to move south through the region on Sunday.
In fact...models have slowed the timing down from previous
forecasts. This makes sense given the deep ridging over the
western Atlantic. Broken sky cover should allow for decent
instability to develop away from the coast. Showers and
thunderstorms are likely from the city north and west and across
southern Connecticut...in closest proximity to the front. Long
Island may not see much activity during the day on Sunday. Locally
heavy rainfall is possible in any storm with precipitable waters
between 1.5 to 1.7 inches. Not expecting any severe
weather...although an isolated damaging wind gust cannot be ruled
The front will likely stall in the vicinity of the region Sunday
night. Showers are likely with a few storms as well. The best
chance again remains from the city north and west. A weak wave of
low pressure developing to our west along the front. This wave of
low pressure approaches Monday and moves through Monday night.
The front likely lifts back north during the day Monday. The
models also have also come into better agreement with the timing
and amplitude of a closed low deepening across the Great Lakes
region Monday night. The region also will be located in the right
entrance region of an 80 knots upper level jet providing some large
scale ascent Monday into Monday night. Showers will continue with
a few thunderstorms as there should be just enough instability.
Precipitable water values may actually increase a bit from Sunday
with deep SW flow tapping into the Gulf of Mexico so locally
heavy rainfall continues to be possible Monday into Monday night.
Highs on Sunday will be in the upper 70s to lower 80s...warmest
in vicinity of the NYC metropolitan. Have increased temperatures by several
degrees from previous forecast on Monday with the expectation the
front will lift back north. Highs will be in the upper 60s to
Long term /Tuesday through Friday/...
wave of low pressure and associated frontal system clear the
region on Tuesday. The European model (ecmwf) continues to the be slowest with this
and keeps showers going across eastern zones through the early
afternoon. For now have chance probability of precipitation...but may eventually need to
increase probability of precipitation for Tuesday...especially over eastern zones.
High pressure builds in behind the departing low with drier
weather Wednesday into Thursday. Temperatures returning to normal.
Friday likely remains dry as well with the high offshore and the
next cold front well off to the northwest.
Aviation /12z Saturday through Wednesday/...
high pressure remains offshore today and tonight. Meanwhile a cold
front will be approaching from northwest...moving near the NYC area
terminals toward 12z Sunday. Southerly flow will prevail through the
VFR. And lingering IFR ceilings and visibilities in stratus and fog
along the coast will dissipate 13z to 14z. Scattered showers and
isolated thunderstorms will be possible late this afternoon into
tonight mainly north and west of the NYC terminals with marginal VFR
conditions. Showers and thunderstorms spread farther to the south
and east late...moving into the NYC terminals after 09z. Areal
coverage and timing of convection is uncertain with low to
moderate confidence in the forecast.
Along the coast after 08z there is a chance of IFR ceilings
developing in stratus. Low confidence of this occurring.
Outlook for 12z Sunday through Wednesday...
Sunday-Tuesday...there will be a chance of marginal VFR to IFR
ceilings late at night and into the morning...especially tonight and
Sunday night. Marginal VFR to IFR at times in showers and
Tuesday night...becoming VFR.
reduced visibilities in fog across many areas overnight into early
this morning...especially across the ocean waters east of Fire
Island Inlet...and the eastern Long Island Sound. A dense fog
advisory remains in effect for the eastern forecast waters.
Otherwise wind and seas remain below small craft levels into tonight
as high pressure remains across the northern Atlantic. With sea
breeze enhancement along the South Shore of Long Island some gusts
this afternoon may be near 25 knots at times.
With a prolonged southerly flow...by Sunday morning seas on the
ocean waters will likely build to 5 feet and remain into Sunday
night...and possibly into Monday as the southerly flow remains ahead
of an approaching cold front.
Winds shift to easterly and subside somewhat on Tuesday...but a
lingering swell may keep ocean seas at Small Craft Advisory levels through the
day...and probably through most of Wednesday as well.
forecast rain amounts from Sunday through Monday night currently
range from 1.25 to around 2 inches. As usual...locally higher
amounts will be possible in thunderstorms. Minor urban/poor
drainage/small stream flooding would be most likely. There is a
low chance for flash flooding Sunday and then again on Monday into
Monday night...but confidence is not high enough to include in
the hazardous weather outlook...especially with antecedent dry
conditions for the past month or so.
CT...dense fog advisory until 9 am EDT this morning for ctz008-012.
New York...dense fog advisory until 9 am EDT this morning for nyz079-081.
Marine...dense fog advisory until 10 am EDT this morning for anz330-340-