Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
420 PM EDT Thursday Jul 28 2016
low pressure approaches from the southwest tonight and passes
through the region Friday. The low departs late in the day Friday
with high pressure building to the north. Weak high pressure
briefly builds into the region for parts of Saturday. Unsettled
weather returns Saturday night through Sunday night with the
passage of another low pressure system. Drier weather is expected
for the first half of next week.
Near term /until 6 am Friday morning/...
a coastal trough remains along with a deepening low over
Virginia. This low is associated with the vigorous shortwave
moving through the northern trough over the eastern states. A
combination of the deepening low and warm frontogenesis through
southern New Jersey to south of Long Island 03z to 06z will bring
increasing chances for showers, and with marginal instability
thunderstorms. A deep layered southwest flow around sub tropical
high pressure off southern coast and into the northern stream
trough was transporting tropical moisture into the region. There
will be potential for heavy rain developing later this evening
and overnight as lift increases with the frontogenesis. A Flash
Flood Watch has been posted to this evening and into Friday.
Short term /6 am Friday morning through Friday night/...
timing and tracking of the deepening low across the region during
Friday is still somewhat uncertain, although there is now more
consistency with the low tracking just south of Long Island
Friday afternoon. Increasing shear along the warm front late
tonight into Friday afternoon will increase the threat of severe
storms across Metro NYC, Long Island, and into coastal CT, along
with continues heavy rainfall. Speed of the low has increased and
precipitation is now expected to taper off from the west during
the afternoon. Weak ridging builds behind the shortwave late
Friday into Friday night with surface high pressure building from
the northwest. Friday night will be dry with a cooler airmass
moving into the area.
Long term /Saturday through Thursday/...
weak high pressure will remain over the region Saturday morning,
resulting in a dry Saturday morning. An approaching shortwave may
set off a few scattered showers and thunderstorms Saturday
afternoon, mainly west of NYC. East of NYC, conditions appear to
remain mostly dry. The unsettled weather becomes more widespread
Saturday night into Monday, as the shortwave and its associated low
pressure system moves across the region. Expect showers and
thunderstorms, through this time frame with some storms producing
locally heavy rainfall.
High pressure builds back into the region early next week, providing
mostly dry conditions. A few isolated showers or thunderstorms
cannot be ruled out during the first half of next week...mainly north
and west of NYC during the afternoon hours.
Temperatures will remain seasonable through the long term with
highs each day climbing into the 80s.
Aviation /20z Thursday through Tuesday/...
high impact weather forecast until 18z Friday...
Low pressure is forecast to gradually intensify as it moves northeast
across the area Friday.
Widespread IFR conditions in heavy rain and fog with embedded thunderstorms
are forecast north of the low's track across the lower Hudson
Valley and CT, mainly between 06z and 16z Friday.
There is a potential for thunderstorms with damaging wind gusts along
and south of the lows' track along coastal NJ, NYC, and
Weather conditions improve from west to east 18z-23z Friday.
New York Metro enhanced aviation weather support...
Detailed information including hourly taf wind component fcsts can
be found at: http:/www.Weather.Gov/zny/n90
Kjfk taf comments: g20kt possible 20z-23z.
Klga taf comments: brief g15-18kt possible 21z-23z.
Kewr taf comments: slight chance of a thunderstorm aft 22z. Brief g15-18kt possible
The afternoon kewr haze potential forecast is green, which implies
slant range visibility 7sm or greater outside of cloud.
Kteb taf comments: slight chance of a thunderstorm aft 22z. Brief g15-18kt possible
Khpn taf comments: no unscheduled amend.
Kisp taf comments: no unscheduled amend.
Outlook for 18z Friday through Tuesday...
Friday afternoon...MVFR improving to VFR as rain ends west to east
Friday night until noon Saturday...VFR.
Saturday noon into Monday night...chance of showers/tstms with
MVFR or lower conds.
winds and seas are expected to remain below Small Craft Advisory
levels tonight through Friday. A wave of low pressure is forecast
to track through or near the waters Friday. Depending on the track
of the low briefly higher winds and seas near small craft levels
will be possible on the ocean waters east of Moriches Inlet.
Showers and thunderstorms will be possible from this evening
through Friday. Some of the thunderstorms Friday may produce gusty
winds in excess of 35 kts, especially over the ocean waters. At
this time fog formation is not expected.
A light pressure gradient over the area waters will result in sub-
sca conditions this weekend and early next week. However, any
thunderstorms that develop on the waters may produce brief Small Craft Advisory
a Flash Flood Watch is in effect for the entire County Warning Area tonight
through Friday for the potential of 2 to 4 inches with locally
higher amounts. The axis of heaviest rain at this time is expected
across northeastern New Jersey into the lower Hudson Valley and
NYC, and into southwestern Connecticut. Uncertainty remains as to
where the heaviest rain occurs and depends on the track of low
pressure through the region. Also, the speed of the low will
affect the timing of precipitation.
Another round of showers and thunderstorms can be expected Saturday
night through Sunday...with some storms possibly producing heavy
rainfall. Exact precipitation amounts are unclear at this time.
CT...Flash Flood Watch from 8 PM EDT this evening through Friday
afternoon for ctz005>012.
New York...Flash Flood Watch from 8 PM EDT this evening through Friday
afternoon for nyz067>075-078>081-176>179.
New Jersey...Flash Flood Watch from 8 PM EDT this evening through Friday
afternoon for njz002-004-006-103>108.
long term...British Columbia