Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 211400
Area Forecast Discussion
National Weather Service New York NY
1000 AM EDT SUN AUG 21 2016
A frontal system approaches from the Ohio Valley this afternoon
and moves through the region tonight. High pressure then
dominates the upcoming week. A cold front approaches late in the
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --Upper level ridge and embedded shortwave over the Great Lakes and
into the Ohio Valley continue to move east through the day and
begins to become negative this evening, then lift into New England
late tonight. At the surface...a cold front associated with
Canadian low pressure approaches the region late today...and then
moves across the area tonight.
Variable cloudiness in the warm and humid airmass remains as bands
of convection stream across the eastern portions of the CWA and
any remaining stratus continues to dissipate. A weak shortwave
across Long Island and into coastal southern New England, and
surface convergence combine to produce scattered showers. With the
wave weakening and slowly moving to the northeast this morning
into tonight expect the showers to gradually end.
There is a moderate risk of rip currents along the Atlantic
facing beaches today...with 3 ft SE wind waves and 1 to 1 1/2 ft
long period se swell.
Late in the day and tonight with the approach of the longwave
trough...showers and thunderstorms will become more numerous and
likely. Best forcing appears to lag north and west of the region
as the front moves through...with late developing modest deep
layer shear in a marginal instability environment. With a tropical
airmass heavy rain will be likely in any of the showers and
The threat for any strong to severe storms appears to be quite
low at this time due to late day/evening timing...weak
instability...and lagging deep layer shear. With strengthening
low-level shear/veering wind profile ahead of weak wave
development...low lcl`s...and weak surface instability will have
to monitor for shallow rotating updrafts in any
tstms...particularly along the coastal plain.
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.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
Shortwave axis slides through the Northeast on Monday. At the
surface...high pressure builds in from the west.
Mostly sunny outside of early sct instability cu. Otherwise...a
noticeably drier airmass with near seasonable temps in the lower
80s to 85 coastal plain and upper 70s to lower 80s interior on a
gusty nw flow.
High pressure continues to build in Monday night with relatively
cool and dry conditions. Good radiational cooling conds possible
across outlying areas...with lows generally in the mid to upper
50s outside of the urban centers. Lows in the lower 50s...possibly
upper 40s across rural areas. Generally lower to mid 60s nyc/nj
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Northern extent of southern upper ridging gradually builds into the
region through midweek...flattening a bit late week into weekend.
At the surface...sprawling high pressure builds in from the west
through midweek...and then gradually centers itself south and east
late week. Models signal a northern stream shortwave approaching and
moving through northern New England Fri/Sat. An associated weak cold
frontal appears to approach on Fri...but low confidence on
whether it makes it through the region intact based on dominance
on southern ridging.
In terms of sensible weather...sunny...dry and gradually
increasing warmth and humidity through the week. A late week
chance of shra/tsra if front holds together.
Overnight lows through midweek should be rather comfortable in the
50s and 60s...gradually rising for late week.
.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
A cold front approaches from the west today.
Unsettled weather continues. A pop up shower is possible at any
time, but coverage is expected to be sparse through the morning.
Otherwise, any patchy stratus and associated MVFR ceilings should
lift. Generally expect VFR conditions with broken CU, except in
any heavier shower.
Showers and thunderstorms become likely late in the day, approaching
western terminals after 20-22z, and eastern terminals 22-00Z.
These showers and storms move through during the evening hours,
and should end around midnight.
SE winds increase this morning with speeds of 10 to 15 kts.
Cannot rule out occasional gusts in the 15 to 20 kt range.
Winds begin to shift this evening as the cold front moves
through, and after midnight eastern terminals.
.OUTLOOK FOR 12Z MONDAY THROUGH THURSDAY...
.Monday-Thursday...VFR. NW winds G15-20kt possible Monday
-- Changed Discussion --Winds and seas are expected to remain below small craft levels
ahead of an approaching cold front, as southeasterly winds
increase. There may be occasional gusts near 25 KTS this
afternoon, and seas may approach 5 feet on the outer forecast
waters. However, with the short duration and uncertainty will not
have an advisory posted.
Behind the front winds shift to NW and an occasional gust to 25
kt cannot be ruled out during the day Monday.
High pressure builds in for Tuesday through Thursday with winds
and seas remaining below advisory levels.
-- End Changed Discussion --
This afternoon into tonight an average of 1/2 to 1 inch of rain
is expected...with localized swaths of 1 to 2 inches possible.
Minor urban flooding is the primary hydrologic threat...with a
localized flash flooding threat from any training cells.
Note...coupling of any heavy rainfall rates with high tide across
NYC/NJ metro and LI late this evening will increase the urban
flood threat in coastal areas.
Dry weather is then expected for much of next week.
Water levels will approach minor flood levels across SW CT during
the afternoon high tide and western Great South Bay during the
late morning and evening high tides. Se winds of 10 to 15 mph may
have a few spots briefly touching minor flood levels. Note...coupling
of any heavy rainfall rates with high tide across NYC/NJ metro and
LI late this evening will increase the minor flood threat in