Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New York New York
357 PM EDT Thursday may 28 2015

Synopsis...
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/...
Severe Thunderstorm Watch 233 is in effect until 7 PM EDT this
evening for most of the County Warning Area. A cold front slowly passes through
tonight and should clear the entire County Warning Area by daybreak. Lift associated
with this front plus some from a shortwave aloft will combine with
available cape to produce scattered thunderstorms...some
potentially severe early this evening. Main threats with these
thunderstorms look to be strong gusty winds and brief heavy
downpours. Smaller hail could be possible as well...given forecast
wet bulb zero heights and the amount of cape in the hail growth
zone...but with marginal directional/speed shear...severe hail not
as likely. Expecting dry weather by 06z with diminishing clouds.

There is a MDT risk for rips at the ocean into this evening.

&&

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
Thursday.

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 /20z Thursday through Tuesday/...
a cold front will approach late this afternoon and pass tonight
before dissipating offshore on Friday.

Mainly VFR late this afternoon and early evening...with the
exception of pesky lingering stratus over eastern Li and southeast CT
coasts. Thunderstorms will remain isolated to scattered...with
timing for any thunderstorm to impact the airports through 22z or 23z.

Then skies clear tonight and through Friday.

South winds shift to the north this evening. Northeast winds are
expected Friday morning.

New York metropolitan enhanced aviation weather support...

Detailed information...including hourly taf wind component forecasts can
be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)

Kjfk fcster comments: amendments for any thunderstorms are possible
through 22z or 23z. South winds shift this evening...and timing of
any wind shift may be off an hour or two. Gusts may be occasional.

Klga fcster comments: amendments for any thunderstorms are possible
through 22z or 23z. South winds shift this evening...and timing of
any wind shift may be off an hour or two. Gusts may be occasional.

Kewr fcster comments: amendments for any thunderstorms are possible
through 22z or 23z. Sea breeze southeast flow will shift this evening and
lighten.

Kteb fcster comments: amendments for any thunderstorms are possible
through 22z.

Khpn fcster comments: amendments for any thunderstorms are possible
through 22z.

Kisp fcster comments: becoming VFR. Possible late day shower.

Outlook for 18z Friday through Tuesday...
Friday afternoon-Friday evening...VFR. Southeast winds.
Friday night-Sat...morning MVFR or lower possible...then VFR.
Increasing southerly flow.
Sat night-Mon...MVFR or lower in showers/thunderstorms at times.
Shifting winds to the E/NE.
Monday...possible improvement to VFR if showers/thunderstorms move to the
south. East/NE flow.
Monday night-Tue...mainly VFR with lingering showers possible.

&&

Marine...
have dropped the Small Craft Advisory on the ocean waters. With a weakening cold
front moving in and a weak pressure gradient shifting in with a
trough...not expecting winds to pick up too much into early evening.
There could be a gust or two up to 25 knots...but thinking this likely
would not be a widespread case. Seas likely remain just below 5 feet
before subsiding overnight. 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
waters.

&&

Hydrology...
thunderstorms into early this evening could produce locally heavy rainfall.
Flash flooding is not out of the question...but does not look to be
widespread. Most locations that receive rainfall with these storms
would probably see minor urbanized/small stream flooding at most.

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 possibility.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...none.

&&

$$
Synopsis...jc/jm
near term...jc
short term...jc
long term...jm
aviation...precipitable water
marine...jc/jm
hydrology...jc/jm

National Weather Service Glossary of Abbreviations