Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
807 PM EDT sun may 24 2015
the Bermuda high remains in place through the middle of the week.
The high then moves farther out into the Atlantic and weakens
across the local region with multiple lows passing from the Great
Lakes into southeastern Canada from middle to late week. A frontal
boundary becomes nearly stationary across the region next weekend.
Near term /until 6 am Monday morning/...
cirrus continues to work its way over the top of the ridge to our
west over the tri-state...and looking upstream do not expect much
in the way of breaks/dissipation tonight. So going with a partly
to mostly cloudy forecast for tonight.
A blend of mav/met/ecs guidance was used for lows...with values
expected to be around 5 degrees above normal.
There is a moderate risk for the meteorological enhancement of rip
current formation at area Atlantic beaches this evening.
Short term /6 am Monday morning through Monday night/...
a deep layered ridge axis builds over the area Monday...then
slides to the east Monday night. The associated subsidence should
keep things dry.
Do expect some breaks in the cirrus so going with a mostly
cloudy/partly sunny forecast. For highs Tuesday used a blend of
mixing down from 975-850 hpa per BUFKIT soundings with NAM 2-meter
temperatures and a blend of warmer met/mav/ekd guidance. Highs
should be generally a few degrees warmer than today...which would
place them around 5-10 degrees above normal. Should see gusty
winds with seabreeze again Monday afternoon...with gusts up to 25
to 30 miles per hour...with isolated gusts to 35 miles per hour possible nearshore. A
40-45kt jet at 1000 feet will help to enhance the gustiness of the
Main uncertainty for Monday night is whether any low clouds/fog
form with third night of onshore flow. NAM BUFKIT soundings have
backed away from this idea...but still should see plenty of debris
cirrus working its way up the backside of the ridge - so went with
partly to mostly cloudy sky cover. For lows Monday night a blend
of mav/met/ecs guidance with NAM 2-meter temperatures was
used...with readings forecast to be around 5-10 degrees above
There is a moderate risk for rip currents at the Atlantic beaches
Long term /Tuesday through Sunday/...
an upper East Coast ridge remains in place Tuesday into Wednesday
then begins to weaken Wednesday night into Friday as a southerly
stream shortwave moves into the ridge. Much of the area remains dry
with the Bermuda high well established Tuesday and Wednesday.
Diurnally drive air mass thunderstorms will be possible Tuesday and
Wednesday afternoons and evenings across the interior...around the
high as energy moves into northern New England and southern Canada.
As the shortwave moves into the ridge the upper flow becomes more
westerly...allowing a couple of waves to move across the region
Thursday and Friday. This results in more widespread precipitation
for a longer period of time Thursday and Friday.
A westerly flow persists into next weekend with the northern stream
more dominant across the southern tier of Canada while the southern
flow weakens considerably across the Continental United States.
There is expected to be a brief break in the precipitation then with
the weak flow the next wave and surface frontal boundary become
nearly stationary across the area Saturday into Sunday.
Finally with increasing low level moisture...with dew points
rising...and a south to southwest flow there will be the increasing
likelihood of stratus and fog developing at night into early morning
middle to late in the week. May be more of a stratus deck across Long
Island and possibly coastal Connecticut with the flow more
southwesterly than south.
Aviation /00z Monday through Friday/...
high pressure remains to the east of the area for the next
VFR through the taf period.
Decreasing S-SW flow this evening...then less than 10 knots all terminals
overnight. S-SW winds increase after 12z Monday with gusts returning
as well. Gusts 20-30kt expected by late afternoon.
Outlook for 00z Tuesday through Friday...
Monday night...VFR. Winds diminishing.
Tuesday-Friday...MVFR or lower possible in stratus and/or fog
late at night/morning...otherwise VFR. Low chance rain showers/thunderstorm each
afternoon...but mostly northwest of city terminals Tuesday and Wednesday. Coastal
sea breezes likely each afternoon...with S-SW winds g15-20kt
sub-small craft conditions are expected on all waters through
Monday morning...with a persistent SW flow.
Winds increase Monday afternoon/night in response to a tightening
pressure gradient and the passage of a 40-45 knots jet at 1000 feet. At
the same time will be fairly deeply inverted...which will minimize
the amount of this jet that mixes down...but with the wind maximum at
or just under the nose of the ridge...more mixing could occur in
this scenario than one would typically expect.
Based on this have issued a Small Craft Advisory for the coastal
ocean waters and the South Shore bays of Long Island from 18z
Monday-10z Tuesday with gusts of 25-30kt. Seas on the coastal
ocean waters should build to 4-6 feet as well. On the remainder of
the waters Monday afternoon-night...given the forecast track of
the low level jet...expecting mainly gusts to 20 knots...with some
occasional gusts to 25 knots at this time. However...cannot rule out
that 25 knots gusts end up being more frequent than currently
expected on the sound/Harbor/eastern bays of Long Island Monday
A persistent southwest flow will continue Tuesday through
Thursday with wind speeds under small craft levels.
However...nearshore wind gusts during the afternoons Tuesday and
Wednesday could approach small craft levels.
On going small craft seas Tuesday morning continue through much of
Thursday. As high pressure weakens over the waters and a front
approaches from the west wind speeds are expected to diminish
Thursday into Thursday night...and seas will slowly subside to below
5 feet Thursday night. Sub small craft seas remain into Friday
night as a weak pressure gradient remains across the waters.
Fog will become more likely by middle week and into late
week...especially at night and into the early morning.
relative humidities outside of Long Island and coastal CT remain
below 30 percent with gusty winds...so the enhanced risk of fire
spread continues there into this evening.
For Monday afternoon...relative humidities will increase 10-15
percent over this afternoon...but winds will be 10-15 miles per hour
stronger...including the gusts. If deeper mixing occurs than is
currently forecast...then the possibility of enhanced risk of fire
spread could be realized Monday afternoon and evening as well.
it will be dry through at least Monday night.
No significant widespread rain is expected Tuesday through Sunday.
Marine...Small Craft Advisory from 2 PM Monday to 6 am EDT Tuesday for