Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1040 PM EDT Tuesday Jun 2 2015
high pressure builds down from southeastern Canada through
Wednesday...then begins to retreat to the northeast Wednesday
night...as a frontal boundary slowly slides farther to the south
of Long Island. High pressure over the Gulf of Maine will move
offshore on Thursday as low pressure works its way up along the
coast and departs Friday morning. A cold front approaches Friday
afternoon and moves across the region on Saturday. High pressure
briefly returns on Sunday...followed by another frontal system for
the start of the new week.
Near term /until 6 am Wednesday morning/...
back edge of light rain just about to push south of NYC and Li.
Any light rain should pass to the south by midnight with a few
hundredths of an inch or less.
For lows tonight used a blend of 12z mav/met/ecs guidance with
NAM 2-meter temperatures. Values should be around 5 degrees below
Short term /6 am Wednesday morning through Wednesday night/...
persistent on shore flow will keep cloud cover at best partly
sunny Wednesday...even with subsidence from north stream ridge passing
over the area. For highs Wednesday used a blend of mixing down
from 925 to 875 hpa with a blend of ecs/mav/met guidance and NAM
2-meter temperatures. Highs should be around 10 degrees below
As an inverted trough approaches up the middle Atlantic coast late
Wednesday night...appears could see some weak isentropic lift.
This is sufficient to warrant a slight chance of light rain
across S zones after midnight...along with increasing cloud cover
from SW to NE.
For lows Wednesday night a blend of met/ecs/mav guidance and NAM
2-meter temperatures was used...with values forecast to be around
5 degrees below normal.
Long term /Thursday through Tuesday/...
high pressure over the Gulf of Maine will slowly move out to sea
Thursday and Thursday night. Meanwhile...low pressure developing off the
southeast U.S. Coast along a stalled frontal boundary will lift
north along the coast. Depending on how strong the high is and
exactly where it is placed will impact how far north showers will
spread into the region. 12z GFS has the high a bit farther to the
north as compared to the 12z European model (ecmwf)...and as a result...has
overrunning precipitation spreading into the County Warning Area whereas the European model (ecmwf) holds
the precipitation off until Thursday night/Friday morning.
Will go ahead and carry low chance probability of precipitation for southern zones and
slight chance probability of precipitation for northern and eastern zones starting on
Thursday and continuing through Friday morning when the low moves
into the open Atlantic waters.
There should be a period of dry weather around middle-day Friday. A
cold front then approaches western zones Friday afternoon and slowly
works its way across the region through Saturday. Scattered showers/thunderstorms
possible Friday afternoon for western zones...and then there will be
chances for showers/thunderstorms Friday night/Saturday as the front passes
through the region.
Dry weather on tap for Sunday as high pressure passes north of the region.
By Monday...another low pressure system will work its way across
southern Canada...dragging a cold front into the region for the
start of the new work week. Unsettled weather possible with its
With easterly flow and extensive cloud cover on Thursday...not
expecting temperatures to climb much higher than the middle 60s...which is
about 10 degrees below normal. Temperatures rebound a bit on
Friday...warming into the upper 60s/low 70s...and then temperatures return
to seasonal levels for the weekend with highs generally in the middle
Aviation /03z Wednesday through Sunday/...
hi pressure will gradually build in from the north through Wednesday.
Rain will continue to taper off as the back edge tracks southeastward at
around 8kt. There is some uncertainty with respect to ceilings after the rain
ends...as most of the data suggests improvement to MVFR. Some
sports however have jumped to VFR...and some other data shows a
chance that ceilings remain blw 1000ft until after 12z. 3z amend have trended
Improvement to VFR by 12-15z Wednesday. Tafs indicate around 13z at this time. VFR
thereafter through the remainder of the taf period.
NE winds mainly blw 10kt tonight. Highest speeds at klga with channeled
NE flow. Winds veer to the east-southeast Wednesday afternoon around 10kt.
Outlook for 00z Thursday through Sunday...
Wednesday night-Thursday night...possible showers Wednesday night into
Thursday as well as Thursday night with MVFR possible.
Friday-Friday night...chance of showers with marginal VFR
conditions in the morning. Chance of thunderstorms near kswf
afternoon into evening. MVFR or lower possible.
Saturday...a chance of showers. A chance of thunderstorms in
afternoon. MVFR or lower possible.
sub-Small Craft Advisory conditions with NE winds and seas just below criteria
tonight. Winds gradually weaken and veer around to the east/southeast by
Wednesday night. Winds and seas are forecast to build back to Small Craft Advisory
levels Wednesday night with a strengthening east flow...however confidence
in this is not high enough to issue an Small Craft Advisory at this time.
On the non ocean waters winds are forecast to be 10 knots or less
tonight through Wednesday night.
Small Craft Advisory level winds/seas possible on Thursday for the
ocean waters with sub-Small Craft Advisory conditions elsewhere due to a tightening
easterly gradient between high pressure passing to the north and low
pressure approaching from the south.
Tranquil conditions expected for the end of the week and over the weekend
as the gradient relaxes.
light precipitation amounts...generally 1/4 inch or less...possible
from late Wednesday night through Saturday. More widespread
precipitation is then possible starting on Monday.