Area Forecast Discussion
Issued by NWS Upton, NY
FXUS61 KOKX 300604
Area Forecast Discussion
National Weather Service New York NY
204 AM EDT Sun Apr 30 2017
A weak cold front continues to move south of the area tonight
as high pressure builds to the north. The high moves east today
into tonight as the front returns north as a warm front. A cold
front will slowly approach from the west on Monday, and pass by
Tuesday morning. High pressure builds in briefly for the middle
of the week, then low pressure brings rain for the end of the
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Minor updates to reflect current temperature/dew point trends.
A surface high will continue to build into New England beneath
confluence aloft between a departing trough and building high
pressure centered off the southeast coast. North-northeast flow
on the leading edge of the high will continue across the area
through the morning. Lows remain above seasonable tonight...upper
40s interior to lower 50s coast...mid 50s nyc/nj metro.
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Weak cold advection will continue through the day Sunday as the
ridge shifts to the east. Winds will back to the east and
southeast keeping the area cool. Low level moisture increases
and a low level inversion develops and strengthens through the
day. Low level clouds are expected to develop late Sunday. High
temperatures Sunday will be close to the lows that occur Sunday
morning, maybe rising a couple of degrees early, then holding
nearly steady. Did not use a diurnal trace for temperatures for
Stratus and fog develop Sunday night as the east flow remains.
Initially weak cold advection continues then becomes weak warm
advection after 06Z as the frontal boundary to the south begins
to return as a warm front. Forcing will remain weak until
toward 12Z Monday. So removed probabilities of precipitation,
and mentioned drizzle. There is a chance that showers do develop
ahead of the warm front, however, that would be more into
Monday, and across the far southern sections of the CWA. If the
front move quicker, which is unlikely as the surface and upper
lows remain well to the west. Sunday night lows may occur during
the evening, then hold steady or slowly rise toward morning.
Again did not use the usual diurnal trace for hourly
temperatures Sunday night.
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
The models were in good agreement through the extended, so the
Superblend was generally used. After some residual fog and drizzle
Monday morning, a warm front is progged to lift just north of the
forecast area before stalling. It is possible that the front does
not get as far north as the models depict, but for now the model
consensus has been followed. This should allow the drizzle to cut
off across the southwestern portion of the area, with some lingering
light stuff still possible in the vicinity of the front. Chances
for showers will increase through the day as the cold front and
upper support draw closer, but the main window for rain looks to be
Monday night closer to the frontal passage. Isolated thunderstorms
have been included for this period with the enhanced lift with the
system acting on some elevated instability. Lapse rates increase on
Tuesday as cooler temperatures aloft move in. The best chance for a
stray shower will be on the northern fringe of the forecast area per
the model consensus at this time. A dry day is progged for Wednesday
with high pressure building in from the west. Chances for
overrunning light rain then increase Wednesday night ahead of
developing low pressure over the Ohio Valley. The low then tracks
through the area Thursday night and Friday, bringing moderate rain
to the Tri-State Region.
The temperature forecast for Monday is complicated, as the
combination of southerly flow, the exact location of the warm front,
and the influence of onshore flow will all play a part. It is
possible a 20 degree difference will set up from southwest to
northeast. Temperatures will be uniformly mild on Tuesday due to
good mixing on southwesterly flow behind the cold front. Readings
will then cool on Wednesday with the colder airmass in place. Cooler
and damp thereafter with the rain and clouds, although nighttime
temperatures will likely be above normal due to these same elements.
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
High pressure builds down from Southeastern Canada today, then
retreats to the northeast tonight.
VFR through at least 20Z, but will see 4000-5000 FT ceilings by
around midday. MVFR conditions develop by late afternoon/early
evening, except by mid evening KSWF, and at KGON, where it
should remain VFR through the TAF period. IFR conditions are
probable by late evening/around midnight at all but KSWF and
Winds continue to veer around from the NNW to the E this
morning, with speeds generally around to just under 10 kt. Winds
veer to the ESE-SE this afternoon, with speeds around 10kt.
Mainly occasional gusts to 15-20kt are possible this afternoon,
with frequent gusts most likely at KHPN. Gusts should abate by
late afternoon/early evening at all terminals. Winds back to the
E at all terminals late this afternoon/early this evening, with
speeds 10 kt or less.
.OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY...
.Late tonight-Monday...IFR or lower likely through Monday
morning. There is a chance for improvement to MVFR or VFR in the
.Monday night...IFR or lower conditions, LLWS and scattered
thunderstorms are possible.
.Tuesday-Wednesday night...VFR. SW-WSW winds G15-20KT possible
Tuesday. W-NW winds G15-25KT possible Wednesday/Wednesday
.Thursday...MVFR or lower conditions developing is possible.
Winds and seas are expected to below small craft advisory
levels through Sunday night. There may be a brief period of
marginal SCA winds and seas on the ocean waters west of Fire
Island Inlet Sunday evening.
Southerly winds will increase on Monday, with the ocean
reaching Small Craft Advisory criteria. The protected waters
will be close to criteria by Monday night, but all areas will
reach 25 kt on Tuesday behind a cold front. Seas will then
linger above 5 ft on the ocean through Wednesday. Winds and seas
are progged to remain below Small Craft Advisory levels on
No hydrologic impacts are expected through the forecast period.