Scientific Forecaster Discussion
fxus61 kokx 201653
Area forecast discussion
National Weather Service New York New York
1253 PM EDT sun may 20 2018
a cold front slowly crosses the area this afternoon. High
pressure will briefly build into the region tonight and Monday,
before a weak frontal system affects the area from late Monday
night into Wednesday. High pressure returns to close out the
Near term /until 6 PM this evening/...
forecast remains on track, with a few showers developing west of
the region and moving east. Minor updates with this afternoon
forecast to temperatures/dewpoints to reflect current
Otherwise, a weak cold front slowly passes through the region
this aft/eve. Sct showers and iso tstms are expected to develop
along the cold front, to the northwest of the NYC Metro, in a
marginally unstable airmass early this afternoon. This activity
should traverse eastward through through the afternoon. Some
uncertainty on extent of convective coverage with subsidence in
wake of morning convection and late approach of next piece of
shortwave energy. With marginally strong deep layer shear, a
conditional isolated strong thunderstorm with strong wind gust
is possible with if pockets of higher instability develop.
Expectation is for convection to weaken as it moves eastward
towards the coast in the late aft/eve due to maritime influence.
Temperatures today will be above seasonable, well into the 70s,
except lower 80s for NYC/New Jersey Metro.
Short term /6 PM this evening through 6 PM Monday/...
a couple of shortwaves move east through Quebec tonight, with
zonal upper flow developing across the region into Monday. At
the surface, high pressure builds into the region through
Clearing conditions expected tonight, with mostly sunny
conditions on Sunday. Temps tonight will be near seasonable,
with highs on Monday a few degrees above seasonable levels.
Highs generally in the mid to upper 70s, except lower 70s across
south coasts with afternoon seabreeze development.
Long term /Monday night through Saturday/...
the upcoming week looks to be relatively benign with a weak
frontal system impacting the area late Monday night into early
Wednesday. There are some small timing differences with the
global models with both the onset of warm advection rain Monday
night and the possibility of scattered convection lingering
into Wednesday as the airmass change behind a cold front is
subtle. This does not look to be a significant rainfall event.
Additionally, while the westerlies and an upper trough will
remain across the area through midweek, the instability at this
time looks to be only marginal.
The second half of the week will feature building heights aloft
as the trough works offshore, resulting in dry weather and
above normal temperatures.
Aviation /18z Sunday through Friday/...
a cold front passes late this aftn.
MVFR cigs improve to VFR this aftn. Iso/sct shower or thunderstorm this
afternoon mainly after 19/20z. Thunderstorm probability too low to include
in tafs at this time. Will go with vcsh for now.
SW winds around 10 kt with gusts up to 20 kt bcmg west this aftn, then
finally northwest early evening. Winds diminish tonight.
Outlook for 12z Monday through Thursday...
Monday...VFR with light S winds.
Tuesday-Wednesday...most likely VFR with low chance of MVFR in
any shower. S winds g15-20kt possible Tuesday afternoon.
Wednesday night-Thursday...VFR. North-northwest winds g15-20kt possible.
marginal Small Craft Advisory conditions are expected across the coastal ocean
waters into tonight, with sub small craft conditions expected
A weak gradient is expected Monday through Wednesday, keeping all
waters below Small Craft Advisory levels.
no widespread significant hydrologic issues are anticipated
through early next week.