Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
427 PM EDT Wednesday Jul 29 2015
weak high pressure will slide off the middle Atlantic coast tonight.
A cold front will approach on Thursday...and move across Thursday
night. Weak high pressure will return Friday through Saturday. A
weak low pressure trough will move through Saturday night into
early Sunday...followed by another weak trough Sunday night. A
cold front will approach Monday night...and remain nearby through
Near term /until 6 am Thursday morning/...
isolated shower that formed in vicinity of the weather forecast office along sea breeze front has
dissipated...and do not expect further activity into this evening.
Conds should be dry this evening...then widely scattered convection in
parts of the middle Atlantic and central Appalachians at this time should
move into area from NYC west late tonight with approaching
shortwave providing lift.
Lows tonight are a touch above a mav/met blend...with lows in the
70s...remaining in the middle and upper 70s in NYC with similar heat
A moderate rip current risk continues into this evening at the
Short term /6 am Thursday morning through Thursday night/...
could see widely scattered elevated convection from NYC metropolitan north/west
in the morning as the leading shortwave moves through.
Approaching cold front should bring scattered to numerous thunderstorms from
late afternoon into the evening as air mass destabilizes...with
SBCAPE up to 1000 j/kg. There should be enough shear to support
an organized line of storms or multi-cell clusters...and given a
SW low level jet up to 35 knots as forecast per NAM...these storms have a better
chance of surviving as they move past NYC metropolitan and the lower
Hudson Valley into Long Island and CT. Stronger cells have
potential to produce strong wind gusts and dump locally heavy
rainfall as precipitable water increases to just over 2 inches.
Highs on Thursday should be not quite as warm as today...generally
85-90...but with higher dewpoints maximum heat index values should
still be similar to those of today...still reaching the middle 90s
except in the higher elevations and eastern coastal sections...so
the heat advisory will continue for NYC.
Long term /Friday through Wednesday/...
long wave upper level trough will be over the northeast U.S. For
much of this time period. At the surface...a cold front will remain
just off the East Coast Friday...with weak high pressure building
in. Subsidence from this high should keep the area dry through much
of Saturday. A weak surface trough approaches late
Saturday...weakening as it does so. 12z GFS does seem more potent as
opposed to the 00z European model (ecmwf) and brings the trough through late Saturday
night with a brief period of showers and thunderstorms. Some
instability preceding the trough...so thunderstorms are possible.
However...jet dynamics look weak...though lift with the trough at
least early in the night looks decent according to the 12z GFS.
However...lift quickly weakens as the trough moves east late
Weak high pressure builds in for Sunday and Monday with a cold front
approaching Monday night. Cold front slows its approach and becomes
nearly stationary in the vicinity Monday night into Wednesday.
Again...some instability over the area as the front moves
through...mainly for eastern sections...so thunderstorms are once
again possible. Lifted indices -8 to -2 during Tuesday night...with
lift being provided by the front. Moisture is also available...with
surface dewpoints in the 60s and precipitable water ranging from 1...
they are not exceptionally high.
Aviation /20z Wednesday through Monday/...
a weak low pressure trough will remain over the area this
afternoon...while high pressure remains to the west.
VFR with southerly flow / coastal sea breezes this afternoon. VFR
continues through at least 6z.
MVFR visibility in fog/haze toward 12z Thursday. Likely rain showers/thunderstorms and rain after 17z
Thursday at western terminals and after 20z for eastern terminals.
..NY 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: wind direction may vary 160-180 this afternoon.
Klga fcster comments: wind direction may vary 160-180 this afternoon.
Kewr fcster comments: wind direction may vary 150-210 this afternoon.
Kteb fcster comments: wind direction may vary 160-210 this afternoon.
Khpn fcster comments: wind direction may vary 160-200 this afternoon.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 18z Thursday through Monday...
Thursday...early morning haze with MVFR conditions...then scattered
afternoon/evening thunderstorms with MVFR or lower conditions.
Monday...mainly VFR...possible MVFR or lower conditions towards
evening with scattered thunderstorms.
quiet through Thursday morning. Then as SW flow increases to 15-20 knots
with favorable fetch...ocean seas should build to 5-6 feet Thursday
afternoon and night. Low level jet passing ohd should mix to the
surface...with gusts up to 25 knots likely on the ocean and the bays of
Long Island. Small Craft Advisory issued for these hazards. Thunderstorms will also be a
hazard with a cold frontal passage Thursday afternoon/evening.
Ocean seas could build to around 5 feet Sat night into Sunday...
and again late Sunday into Monday morning. Then a more prolonged
period of 5-feet ocean seas is possible from Monday night into middle
basin average quantitative precipitation forecast of 1/2 to 3/4 inch possible in the lower Hudson
Valley and NE New Jersey...with up to 1/2 inch elsewhere. With precipitable water over 2
inches Thursday afternoon and evening...locally heavy rainfall is
possible with any stronger convection. Minor urban/poor drainage
flooding is the most likely outcome.
New York...heat advisory until 8 PM EDT Thursday for nyz072>075-176-178.
Marine...Small Craft Advisory from 2 PM to 8 PM EDT Thursday for anz340-
Small Craft Advisory from noon Thursday to midnight EDT
Thursday night for anz355.
Small Craft Advisory from noon Thursday to 6 am EDT Friday for