Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 301018
Area Forecast Discussion
National Weather Service New York NY
618 AM EDT THU JUN 30 2016
An area of high pressure will move over the area today, with a
warm front approaching on Friday. A cold front will move across
Friday night, followed by high pressure Saturday through Monday.
Another low will approach next Tuesday.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Weak high pressure continues to build into the region today,
providing dry conditions and mostly clear skies. Humidity levels
will be comfortable with dew points in the 50s for much of the
region. Temperatures will be seasonable.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
A warm front approaches the region Thursday night, with a weak
area of low pressure developing along this boundary. Winds will
shift to the south tonight and then the southeast by Friday as the
front moves closer on. This will once again introduce a humid air
mass. There is just a slight chance for showers and an isolated
thunderstorm late tonight.
The warm front continues its approach on Friday, while at the same
time, a surface cold front approaches from the west. A digging
upper level trough over the Great Lakes region will also approach
in conjunction with the cold front. Most models have some sort of
negative tilt with this trough, with the NAM being the most
tilted. This could allow for the development of some strong to
possibly severe storms across the CWA. A inverted V shape sounding
was noticed in the forecast soundings, indicating that gusty winds
would be a primary threat. Other factors lending to strong to
severe storms are the frontal boundaries that will be in the
vicinity, providing lift, a humid airmass that will be in place,
with surface dew points likely approaching 70, and at least some
instability, though this does not look overly impressive. Surface
based CAPE only looks to be 1000-1500 J/kg and most unstable CAPE
is near 2000 J/kg. 700-500mb lapse rates of 5-6 degrees only
points to a weak threat. We are also under an 850 mb jet, but the
jet speed is also not that impressive.
Overall, parameters point to either a weak to possibly moderate
severe threat for Friday and SPC has place the western portions,
mainly west of NYC, in a marginal risk for severe weather. For
now, used enhanced wording of gusty winds and heavy rain Friday
afternoon into the evening.
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Potential for Severe Thunderstorms Friday Evening
The SPC is forecasting a Marginal Risk for isolated severe TSTMs
producing wind gusts up to 60 mph across the Lower Hudson Valley and
Northern NJ Fri aftn and eve with the approach of a well defined
cold front moving into a warm moist unstable maritime tropical air
Saturday...Weather will feature increasing fire danger as WNW winds
increase to 10-20 mph and humidities decrease to 30-40 pct as high
pressure moves southeast from the Great Lakes.
Fair weather with near normal temperatures are on tap for the July
fourth weekend through Monday as a large area of high pressure moves
slowly SE across the region.
The next chance of rain will occur next Tuesday with the approach of
a short wave moving SE along the upstream ridge accompanied by a low
lvl flat wave mvg toward the mid atlantic coast.
.AVIATION /10Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --High pressure will build east from the Ohio valley overnight and
pass south of the area this afternoon. A thermal trough sets up
to the north and west of NYC in the afternoon.
VFR. Light NW flow overnight gives way to late morning/early
afternoon seabreeze development. KLGA will likely develop a NE
wind off the East River in the morning which often can persist
deep into the afternoon. There is some uncertainty as to how long
this direction will persist. Due to the light nature of the
winds, there will likely be some variability until the seabreeze
works across the terminals.
There is low confidence of showers moving in after 06Z Friday at
the 30h TAF sites.
NY Metro Enhanced Aviation Weather Support...
Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90
KJFK TAF Comments: Timing of seabreeze likely to vary 1-2 hours.
KLGA TAF Comments: Amendments likely for timing of winds shifts.
KEWR TAF Comments: Timing of seabreeze likely to vary 1-2 hours.
The afternoon KEWR haze potential forecast is GREEN...which implies
slant range visibility 7SM or greater outside of cloud.
KTEB TAF Comments: Timing of seabreeze likely to vary 1-2 hours.
KHPN TAF Comments: Timing of seabreeze likely to vary 1-2 hours.
KISP TAF Comments: Timing of seabreeze likely to vary 1-2 hours.
.OUTLOOK FOR 06Z FRIDAY THROUGH MONDAY...
.Friday and Friday night...MVFR or IFR conditions possible in
.Saturday...VFR. NW winds G20-25KT.
.Sunday and Monday...VFR.
-- End Changed Discussion --
Winds and seas should remain below SCA conditions for the short
term as weak high pressure moves over the waters provides a lack
of a pressure gradient.
Friday Night and Saturday...Weather conditions will approach Small
Craft Advisory/SCA levels of 25 kt winds and 5 ft seas across the
Atlantic Ocean coastal waters. Scattered TSTMs along with S winds 10-
20 kt will precede and accompany an approaching cold front. Winds
will shift from the WNW 10-20 kt with the passage of the front
around Sunrise Saturday and will continue through the day Saturday.
Sunday through Monday will be tranquil with winds and seas remaining
below SCA levels as high pressure moves SE across the region.
No significant rainfall expected for the short term.
Friday Aftn/Night...Scattered showers and TSTMs will bring up to
1/4-inch rainfall with isolated higher amounts, otherwise, no
significant rainfall is forecast.