Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
131 am EDT Wednesday Sep 2 2015
high pressure over the area weakens tonight and is replaced by a
trough of low pressure from New England southwest across New
Jersey through tonight. A cold front approaches from the north
Thursday...moving through the tri-state Thursday night. High
pressure builds in from the north for the weekend into early next
Near term /until 6 am this morning/...
based on current observations showing the development of patchy
radiational ground fog earlier than predicted...the near term
forecast was updated. A few patches of dense fog may briefly
restrict visibility to 1/4 mile.
Otherwise...an upper ridge and surface high pressure remain over
the region. The upper ridge weakens as a shortwave associated
with convection across Illinois and Indiana moves southeast
across the Ohio Valley by 12z Wednesday.
There will be some high cloudiness moving in late at night as the
shortwave approaches. Winds will be light.
Short term /6 am this morning through 6 PM Thursday/...
as the shortwave moves into the middle Atlantic Wednesday the upper
ridge will rebuild farther to the west through Wednesday night.
This will allow a trough to the east to begin to dig into the
northeastern states. Meanwhile at the surface high pressure
weakens over the Ohio Valley and a surface trough develops across
New England into northern New Jersey into southeastern
Pennsylvania. The area remains dry Wednesday and Wednesday night
with no triggers or upper support present. Another shortwave does
approach in the northwest upper flow toward 12z Thursday.
Long term /Thursday night through Tuesday/...
gradually increasing drought and fire weather concerns through the
A weak northern stream shortwave slides through the region late
Thursday/Thursday night...while a strong northern stream upper low digs
through the Canadian Maritimes. Models in good agreement with upper
ridging building into the region for the weekend...before gradually
flattening early to middle next week.
Late Summer heat and humidity will continue on Thursday. A Canadian cold
front approaches from the north late Thursday/Thursday evening as shortwave energy
digs southeast through the Canadian Maritimes. This will bring potential of
isolated/scattered showers/thunderstorms late Thursday into Thursday night as the front
sags south. Daytime highs will be in the lower 90s Thursday with heat
index values in the lower 90s across NYC and urban NE New Jersey.
Canadian high pressure builds south-southwest across the region Friday into
Saturday. This will advect a cooler and drier Canadian maritime
airmass into the region for Friday and Sat. Although humidity levels
should be in the 50s...gusty east winds on Friday may pose a
enhanced concern for spread of brush fires due to 400-500 kbdi
values and available fine fuels. Along the coast...potential exists
for a high rip current risk Friday into Sat. Highs are still expected
to run near seasonable...upper 70s/lower 80s.
Dry conditions are expected through early next week as high pressure
sinks southeast of the region. This will also spell a steady moderation in
humidity and late Summer heat through early next week.
Aviation /06z Wednesday through Sunday/...
brief MVFR and possible IFR visibility in br at terminals away from
knyc through around 12z. Otherwise...VFR.
Light/vrb winds through daybreak...and then S winds increase to
5-10 knots during the day.
Outlook for 06z Thursday through Sunday...
Wednesday night...mainly VFR. Local MVFR visibility in br away from
Thursday-Thursday night...mainly VFR. MVFR or below possible with
a chance of showers/thunderstorms. Afternoon sea breezes
Friday...a slight chance of showers and thunderstorms early on
with MVFR or below possible. Otherwise VFR. East-northeast winds g15-20kt.
a weak pressure gradient will be across the forecast waters tonight
through Wednesday night. High pressure will be across the region
with a weak surface trough developing along the coast Wednesday
afternoon and remaining into Wednesday night. Wind and seas will
remain below small craft levels into Wednesday night.
Sub Small Craft Advisory conditions expected Thursday ahead of an approaching cold front.
The next chance for Small Craft Advisory level winds and seas is
Friday following the passage of a cold front. Potential exists for
easterly winds of 15 to 20 knots with gust 25 knots and ocean seas
building to 5 to 6 feet. Small Craft Advisory gusts possible on Li sound and nearshore
Winds and seas appear to gradually subside Friday night into Sat...with
sub Small Craft Advisory conds likely for the end of the weekend.
dry through Wednesday night.
No widespread significant rainfall is forecast through next weekend.
Drought will continue to develop region wide...but especially across
Long Island and southern CT through the period with no significant
widespread rainfall in the forecast.