Area Forecast Discussion
Issued by NWS Upton, NY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KOKX 240625
Area Forecast Discussion
National Weather Service New York NY
225 AM EDT Mon Apr 24 2017
High pressure moves offshore overnight into Monday. A wave of
low pressure over the southeastern states moves to the southeast
coast Monday, then tracks up along the eastern seaboard through
midweek. High pressure will build back in for the end of the
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Only minor adjustments at this time to temperature, dew points,
and cloud cover for trends. Also raised overnight lows along
the coast, mainly the twin forks, several degrees with light
Region will lie in a near zonal upper flow between a polar
upper low over interior Quebec and a closed upper low moving
through the deep south. At the surface...high pressure continues
to move east of Long Island and southern New England overnight.
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
Models in fairly good agreement with a closed upper low over the
deep south Monday...slowly sliding to the southeastern US coast
Monday Night. In response...a broad southern low should develop into
a coastal low pressure along the Southeastern US coast Monday
Locally...weak ridging surface/aloft on Monday appears to give way
to approaching lead short wave energy ahead of the upper low...with
surface high pressure gradually sliding offshore. Timing and
strength of the approaching shortwave energy and of associated theta-
e advection range from late Monday afternoon into Monday
night...which is resulting in timing spread of onset of rain
development into the region. Latest trend is slower onset of rain
late Monday into Monday night...with increasing likelihood of rain
from south to north late Monday Night. In addition e/ne winds will
be increasing along the coast Monday Night...with gusts 25 to 30 mph
possible by daybreak Tuesday.
Despite higher temps aloft than Sunday...increasing high and
mid cloud cover and easterly flow will likely keep temps near
seasonable levels on Monday. Near seasonable temps Monday
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Models have come into better agreement with the track of the
low up the east coast Tue/Wed....with the GEM and NAM both
shifting eastward as compared to 24 hours ago. NWP is in good
agreement through the end of the week...but then differences are
apparent for next weekend leading to a low confidence forecast.
Low pres over NC Tue morning will track to the Mid Atlantic
coast Tue night while weakening. A tight pres gradient will
remain across the area due to departing high pres to the north
producing gusty easterly winds. 40-50 kt LLJ lifts through late Tue
aftn/eve...but a low level inversion should keep most of these
Rain becomes widespread Tue morning with strengthening
overrunning pattern. Timing of heaviest rainfall will coincide
with the LLJ late Tue aftn/eve and location is pointing towards
the eastern Long Island/CT. See hydro section for rainfall
amounts and potential impacts. Winds abate on Wed as the low
approaches and passes just S of Montauk Wed night. Noting mid
level drying from west to east on Wed...have transitioned to
light rain/drizzle. Sfc Low is slow to depart and continues to
weaken Wed night/Thu before being absorbed back into the
Meanwhile...a broad upper trough will be developing over the
rest of the CONUS with a shortwave tracking through the Great
Lakes on Thu. Downstream ridging will limit the eastward
progression of this system with a sfc cold front moving into the
area Thu night and stalling nearby with potentially unsettled
weather through the weekend.
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --VFR through the first half of Monday evening as a low-level
ridge across the area gradually gives way to low pressure
moving slowly up the East Coast.
Mid and high level ceilings will gradually lower through the day
with the potential for MVFR/IFR conditions in light rain after
Light and variable winds overnight, then E/SE winds at 10 kt or
less. There will likely be some variability of the flow by 20
degrees with the ridge axis in close proximity. Winds begin to
back around to the E/NE Monday evening.
.OUTLOOK FOR 06Z TUESDAY THROUGH FRIDAY...
.Monday night...MVFR/IFR in rain late.
.Tuesday...IFR/LIFR in rain. NE gusts 20-25 KT near coast
possible during the day.
.Wednesday...MVFR, possibly improving to VFR later in the day.
-- End Changed Discussion --
Winds and seas forecast on track and no changes were made at
With high pressure influencing the waters overnight into Monday
morning, tranquil conditions are expected on the waters.
A low pressure system will slowly move up the southeastern coast
Monday into Monday Night...allowing for a tightening E/NE
gradient over the waters late Monday into Monday night. A return
to SCA conditions are expected on the ocean waters Monday
night...and likely across the nearshore waters later Monday
SCA conds will likely continue on the waters into Wed morning
for both winds and seas. Gusts then diminish...although seas
will remain elevated through Fri due to swells from the
weakening storm system. There is a low potential for gale force
winds...mainly on the ocean waters Tue/Tue eve.
Between 3/4 and 2 inches of rainfall is possible late Monday
into Wednesday. Highest amounts are expected across eastern Long
Minor flooding of low lying and poor drainage areas is
Potential for minor coastal flooding for vulnerable coastal
communities...mainly along the southern bays of Western LI and
Western LI Sound...with the Tue eve high tide cycle. This is in
response to a low pressure system moving northward along the
eastern seaboard. Only 1/2 to 1 ft of surge is needed to reach
minor flood thresholds Tue evening.
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for ANZ330-
Small Craft Advisory from 6 PM this evening to 8 PM EDT
Tuesday for ANZ350-353-355.