Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1052 PM EDT Thursday may 28 2015
a cold front moves through tonight...then high pressure returns
through the early portion of the weekend. High pressure then gives
way to a slow moving cold front approaching from the west. The
front eventually moves in Saturday night and stalls near the
region for Sunday into early next week. High pressure builds in
from the north late Tuesday into middle next week and once again
becomes established offshore in the western Atlantic.
Near term /until 6 am Friday morning/...
cold front continues to work its way through the region...and is
now through the lower Hudson Valley...northeast New Jersey...NYC...and
much of southern CT as shown by winds shifting to the north and
temperatures falling into the 70s behind it. Surface dewpoints also falling
into the 50s across the western portions of the County Warning Area.
This trend will continue from west to east as the cold front works
its way across the region. Skies will clear out as well from west
Some patchy fog is also possible away from NYC late tonight and
towards daybreak as there is some lingering low level moisture due
to rainfall across the interior and areas along the coast from
being near the ocean.
Forecast lows are expected to range from middle 50s to middle 60s.
Short term /6 am Friday morning through Friday night/...
deep-layered ridging will provide the subsidence and drying for a
sunny day on Friday. Mav/NAM MOS blend in good agreement...and was
used for high temperatures. High temperatures above average...even across the
coastal zones in spite of a light onshore flow.
Clouds and moisture then increase Friday night. Remaining dry...but
patchy fog developing late at night. Stratus development also
possible for the coastal zones.
Long term /Saturday through Thursday/...
the jet stream stays north of the region until early next week when
it will move south from New England and then with ridging...the jet
pushes back north of the area middle to late next week. In the
middle levels...the offshore ridge becomes less amplified Saturday.
There will be a shortwave moving through southeast Canada for the
rest of the weekend...resulting in a broadening quasi zonal flow
across the local region. Another shortwave approaches closer to the
area Monday night and moves across Tuesday into Tuesday night. Upper
level ridging builds in thereafter.
A slow moving cold front approaches from the west Saturday. The
parent low attached to this front will not be that strong...slowly
deepening with eastward progress through Saturday and then deepening
more within the Canadian Maritimes Sunday through Sunday night. The
cold front will be moving within into the region through this time.
The front will then stall near the region with low pressure and
inverted trough developing at the surface to the southwest of the
region along the front Monday and Monday night. High pressure
gradually returns Tuesday from the Canadian Maritimes...but
weakens and moves into the western Atlantic middle to late in the week.
In terms of weather...there will be a gradual increasing chance of
showers and thunderstorms first north and west of NYC Saturday ahead
of the cold front. Farther east across Long Island...conditions
likely remain dry through Saturday. The chances for showers and
thunderstorms increase Saturday night across the whole forecast
region and furthermore on Sunday.
Thunderstorms will be more limited Sunday and Sunday night with
decreasing instability with a more northerly and easterly flow
developing during the day. The instability will be located
farther south of the region. With the front stalling near the
region...showers remain into early next week...before becoming more
minimal Tuesday as the front pushes farther south of the area with
mainly dry conditions returning late Tuesday night through next
The airmass will stay mostly as maritime tropical through the long
term but cooler for Monday and Tuesday next week. Highs well into
70s and into lower 80s Saturday but upper 60s to lower 70s Sunday.
Highs lower into mainly the 60s early next week trending back to
near normal values. Lows within the 60s Saturday night and within
the 50s on average Sunday night through early next week. Then they
trend back to normal as well middle to late next week.
Aviation /03z Friday through Tuesday/...
a cold front will pass east of the entire region by around 06z.
Weak high pressure slides southeast through the region on Friday.
VFR with mainly clear skies through Friday.
Variable winds...becoming north this evening. Light NE winds Friday
morning for NYC/New Jersey metropolitan terminals...becoming S/southeast in the
afternoon with seabreeze development.
Outlook for 00z Saturday through Tuesday...
Friday night-Sat...morning MVFR or lower possible...then VFR.
Increasing S flow on Sat...with 15 to 20 knots after seabreeze for
Sat night-Mon...MVFR or lower in showers/thunderstorms at times.
Shifting winds to the E/NE.
Monday...MVFR or lower likely in rain. East/NE flow.
Monday night-Tue...mainly VFR with lingering showers possible.
cold front moves across the waters tonight. Seas will remain below
5 feet...and winds will become 5 knots or less on Li sound/New York Harbor/Li
bays and 5-10 knots on the ocean.
Sub-Small Craft Advisory conds then continue into Friday and Friday night with
winds remaining below 15 knots.
Southerly flow increases Saturday and Saturday night with high
pressure moving farther offshore. The southerly fetch will build
seas on the ocean to 5 feet Saturday late in the day. The ocean
seas remain within Small Craft Advisory range...mainly 5 to 7 feet...for the rest of
the marine forecast period with winds being more marginal except
for western ocean Saturday with Ambrose jet likely enhancing winds
and then again on Monday...when gusts will reach near 25 knots. The
flow switches to more easterly Sunday into early next week which
will help keep swells and higher seas within the ocean forecast
there will be potential for an extended significant widespread
rainfall...mainly Sunday through Monday with a cold front stalling
near the region. It is difficult to specify exact rainfall
amounts...but there will be potential for heavy rainfall
especially Sunday and Sunday night into early Monday morning when
precipitable waters reach 1.5 to 1.75 inches. Any showers and
thunderstorms could produce locally heavy rainfall and therefore
at least minor flooding of urban/poor drainage areas will be a