Scientific Forecaster Discussion
fxus61 kokx 280608
Area forecast discussion
National Weather Service New York New York
208 am EDT sun may 28 2017
high pressure will remain fairly stationary to the east of the
region through Sunday night...retreating northeast on Monday. A
frontal system will approach the region Sunday night and cross
the area Monday. A series of weak fronts or troughs of low
pressure will follow through the end of the week.
Near term /through today/...
forecast is on track with only minor changes made to reflect
current conditions. Any showers have for the most part ended
across the area. Can't rule out an isolated shower across NYC
Metro and points northwest through around midnight with a separate
northern stream shortwave/jet streak digging into eastern New
England, but not enough confidence to put it in the forecast.
Otherwise...weak upper ridging builds into the region
overnight...with surface high strengthening to the east of New
England. This will have a Canadian maritime airmass taking hold
of the region.
Combination of low-level onshore flow and nocturnal cooling will
likely result in stratus development overnight into Sun morning.
Models are signaling potential for some patchy fog and/or drizzle
developing late tonight...although confidence is low as
saturation doesn't appear to be sufficient. Temps should remain
near seasonable in the 50s.
Short term /tonight through 6 PM Monday/...
upper ridge axis moves across the region Sunday...with a deep
upper low sinking south into the upper Mississippi River valley
through Sunday night. Ahead of it southern stream
energy/moisture expected to ride into the region Sunday
night...preceding approaching northern stream shortwave energy.
Canadian maritime airmass will be entrenched on Sunday...with
any morning stratus likely slowly to erode into the afternoon.
The stable low-level airmass should keep the region dry on
Sunday...with temps running below seasonable in onshore flow
and and with cloud cover.
Developing diffluent flow aloft...approaching shortwave
energies and jet streak...combined with an increasingly moist
S/SW flow ahead of an approaching frontal system will result in
increasing likelihood for rain late Sunday night. Model spread
exists in timing and intensity of rainfall...which is likely
related to model handling of convectively induced vort/shortwave
energy originating over the mid-Mississippi and Tennessee River
valleys and riding into the region and associated
moisture/instability influx. Should see some better agreement
on these details Sunday.
Long term /Monday night through Saturday/...
global models are in decent agreement with the overall 500 mb pattern
through the period. However...there are timing differences from mid
week on with regards to pieces of upper level energy moving across
Cutoff low pres over southern Ontario will slowly track ewd through
the week although maintain it's hold on the weather pattern across
the area. Mid level shortwave trough moves through the area on Mon.
The NAM is the strongest with the upper level energy associated with
it and thus strongest at the sfc with highest quantitative precipitation forecast as well.
Differences appear to be associated to the convection over the
Midwest today which is where this system is originating from.
Hopefully next 24 hours will converge better. At any rate...Mon
looks like a wet day with rain becoming widespread during the
morning. Elevated instability present could trigger some tstms. See
Hydro section for info on totals and impacts.
Weak ridging builds in Mon night with rain ending as the shortwave
trough exits to the NE. A weakening cold front approaching from the
west on Tue could trigger a few showers/tstms during the aftn and
into the evening as it moves into the area. Chc showers may linger
through the night.
The closed upper level low remaining over southeast Canada will send rounds
of upper level energy through the area through the end of the week.
Have maintained schc to low chc pops at times through the period but
will need to be fine tuned as the week progresses.
Temps will be above normal levels during the daytime with the
exception of Monday when they will be near to slightly below normal
with clouds and rain.
Aviation /06z Sunday through Thursday/...
high pressure will remain fairly stationary to the east through
tonight. A frontal system will begin to approach late Sunday
While broken-overcast higher-based clouds cover most of the area,
satellite shows no sign of low cloud development south of Long
Island or east of the Jersey Shore, so for the most part have
omitted mention of lower cigs through the morning, except at
kbdr/kisp, where even the most optimistic of forecast guidance
still insists on MVFR cigs anywhere from 09z-15z. Confidence
here is medium at best, and will still have to closely monitor
for any low cloud development. Confidence should be higher
with the 09z amd's.
Light southeast-S flow should become southeast 8-12 kt by afternoon, then
diminish again tonight.
Some light rain with MVFR conds could reach the NYC Metro
terminals just before 06z Mon.
Outlook for 06z Monday through Thursday...
late Sunday night...MVFR conds developing from west to east,
with light rain especially from NYC Metro on west.
Monday...showers likely and chance of tstms. IFR conds
Monday night...still a chance of showers/tstms early from
kbdr/kisp east with MVFR or lower conds, otherwise VFR.
Tuesday...chance of showers and possibly a tstm with brief with
MVFR or lower conds in the afternoon/evening.
Wednesday...mainly VFR. Chance of showers/tstms mainly northwest of
the NYC Metro terminals.
tranquil through Sunday night as ocean swells gradually subside
and winds remain light. Southeast winds increase to 15-20 kt late
Sunday night into Mon with possible gusts up to 25 kt on the
ocean waters...which could lead to seas reaching 5 ft.
Otherwise...tranquil conds are expected through the remainder of
the forecast period.
total rainfall amounts on Monday could range from 1/4 to 3/4
inches...with the potential for 1 to 1 1/2 inches if a stronger
solution verifies. No significant widespread hydrologic impacts
are expected attm through at least the middle of next week.
widespread minor coastal flooding is expected for the high tide
cycle tonight along the South Shore bays of Brooklyn, Queens,
and Nassau, also for the shores of Westchester/Fairfield along
western Long Island Sound. A coastal flood advisory continues
for these areas. Brief/localized minor flooding possible
elsewhere along western Long Island Sound and lower New York Harbor.
While astronomical tides are lower for the Sunday night high
tide, surge will likely increase a bit with strengthening southeast
flow. The net result looks to be additional widespread minor
coastal flooding for the South Shore bays of western Long
Island, with localized/brief minor flooding possible for the
rest of the areas that have been affected over the last
CT...coastal flood advisory until 3 am EDT early this morning for
New York...coastal flood advisory until 3 am EDT early this morning for
Coastal flood advisory from 10 PM this evening to 3 am EDT
Monday for nyz179.