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Area forecast discussion 
National Weather Service New York New York
817 PM EDT Monday may 4 2015

Synopsis...
high pressure remains over the Atlantic as a cold front approaches
from the northwest tonight. The cold front moves across the area
Tuesday and Tuesday night. High pressure builds over the region
for the middle to the end of the week. A frontal boundary passes
north of the area this weekend.

&&

Near term /until 6 am Tuesday morning/...
temperatures were pretty much right in line with forecast values
but dewpoints had to be adjusted slightly downward. Otherwise...no
other significant changes made to the forecast database with the
forecast remaining on track.

Models remain in good agreement with surface high pressure drifting
east tonight over the western Atlantic as a cold front approaches
from the northwest. The front should move into the northwest portion of the County Warning Area
between 6 and 10z overnight.

Aloft...ridge axis moves east this evening...with zonal flow
prevailing across the northeast for the remainder of the night.
Closed low well up in eastern Canada moves east.

A general SW flow will decrease throughout tonight. Mostly clear
conditions will yield to more clouds ahead of the front late
tonight. Mesoscale models including arw and WRF-nmm show showers
along and ahead of the front dissipating as they near the area
late tonight. NCEP models including sref mean indicate light quantitative precipitation forecast
via weakening shower activity before 10z tonight...so will
maintain minimal probability of precipitation for northwest zones as they near the area.

Above normal temperatures expected overnight...with lows ranging from
around 50 across the interior to the lower 60s in and around NYC.

&&

Short term /6 am Tuesday morning through Tuesday night/...
zonal flow initially will give way to a late day and overnight 500-
700 hpa trough. This feature is more pronounced in the 12z NAM.

Any morning isolated shower activity will give way to slightly
higher coverage during the afternoon and into the evening hours.
NAM...WRF-nmm show convection upstream in PA riding along the ridge
early in the day approaching our region late. It appears that the
better coverage will be just south of the front from NE New Jersey/NYC
southward. European model (ecmwf)/GFS and sref mean support less coverage with lower
probability of precipitation. At this time...will not stray too far from previous
forecast...raising probability of precipitation slightly but capping them in the chance
range. Highest probability of precipitation SW zones...and lowest NE. This supported by
latest day 2 Storm Prediction Center outlook for thunderstorms as marginal instability
is present to the south and west...if not a lot of upper support.

Depending on the location of the front...any lingering shower or
thunderstorm activity will remain or pass south Tuesday night...with probability of precipitation
lowering through the night. Expect high pressure to the north to
push the front just to our south during the evening hours.

Another unseasonably warm day is on tap despite the clouds.
Readings may be slightly lower...but still expect 80 degrees away
from the water...with near 70 over eastern sections of the County Warning Area.
With the front in our proximity...winds will not be as strong...so
less disparity in temperatures from what occurred earlier today.

Tuesday lows will run above normal...but will be a few degrees
cooler than tonight's expected temperatures.

&&

Long term /Wednesday through Monday/...
cold front continues to move south and east of the area Wednesday
morning. Just a slight chance for some lingering showers over
southeast zones in the morning...and then conds clear out for the
afternoon.

High pressure both at the surface and aloft will build east and over the
area for the middle to the end of the week...and then the high moves
offshore on Friday. Dry conds with near to above normal temperatures
through the end of the work week with highs generally in the
70s...warming into the lower 80s across the interior by Friday. With
a light pressure gradient...can expect afternoon sea breezes...resulting
in cooler afternoon temperatures for coastal areas.

Low pressure slowly tracks through the Great Lakes and into the Ohio
Valley for this weekend...and a frontal boundary will extend from
this system and move well north of the region. Saturday should be
dry...but the front will begin to Sage to the south for Sunday and
Monday...and scattered showers and afternoon thunderstorms are
possible for the start of the new week. Will cap probability of precipitation at low chance
for now...with highest probability of precipitation across the interior...which will be
closer to the front.

Near to above normal temperatures will likely continue for the weekend and
start of the new week.

&&

Aviation /00z Tuesday through Saturday/...
high pressure moves off the coast this evening as a weak frontal
boundary approaches. The front moves into the area toward 10z
Tuesday and remains in the vicinity through the remainder of the
forecast period.

With the frontal boundary in the vicinity the wind forecast at all
the terminals will be tough and have low to moderate
confidence.

There is little forcing with the front and the chance of showers
will be low and activity is expected to be scattered. So forecast
with the vicinity showers. The better forcing and instability will
be near the cost and indicated a chance of thunder also with
vicinity.

Conditions remain VFR with a low chance of marginal VFR if a heavier
shower of thunderstorm does happen to move through one particular
terminal.




New York metropolitan enhanced aviation weather support...

Detailed information...including hourly taf wind component forecasts
can be found at:
http:/www.Erh.NOAA.Gov/zny/n90 (lower case)

Kjfk fcster comments: no unsched amend expected this evening. Low
confidence on the wind forecast for Tuesday...as will be dependent
on where weak frontal boundary sets up. With weak flow tomorrow a
sea breeze is likely. Higher confidence in sea breeze development.

Klga fcster comments: no unsched amend expected this evening. Low
confidence on the wind forecast for Tuesday...as will be dependent
on where a weak frontal boundary sets up. With weak flow have
moderate confidence that a sea breeze will move through the
terminal...and may be even later than forecast at this time.

Kewr fcster comments: no unsched amend expected this evening. Low
confidence on the wind forecast for Tuesday...as will be dependent
on where a weak frontal boundary sets up.

Kteb fcster comments: no unsched amend expected this evening. Low
confidence on the wind forecast for Tuesday...as will be dependent
on where a weak frontal boundary sets up.

Khpn fcster comments: no unsched amend expected this evening. Moderate
confidence on the wind forecast for Tuesday...as will be dependent
on where a weak frontal boundary sets up...moderate confidence the
front will be south of the terminal.

Kisp fcster comments: no unsched amend expected this evening. Moderate
confidence on the low level wind shear this evening. Low confidence on the wind
forecast for Tuesday...as will be dependent on where weak frontal
boundary sets up. With weak flow tomorrow a sea breeze is likely.
Higher confidence in sea breeze development.



Outlook for 00z Wednesday through Saturday...
Tuesday night through Saturday...VFR.

&&

Marine...
SW gusts near 20-25 knots this evening across the nearshore waters
will gradually lower this evening. The 25kt gusts are expected to
be generally occasional in frequency. In addition...ocean seas
per wave watch iii build to 5 feet tonight where Small Craft Advisory remains in
effect. Elsewhere...south to southwest flow will lighten as the
night progresses.

A cold front approaches and tracks just north of the waters
Tuesday...and settles overhead Tuesday night. Winds lighten and will
eventually shift around to the north/NE late Tuesday night...depending on
the exact location of the front.

With high pressure and a light pressure gradient over the waters for the
middle to the end of the week...can expect tranquil conds during the
long term period. Some afternoon gusts to 20 knots possible across the
near shore waters due to sea breezes.

&&

Fire weather...
there may still be localized spots where relative humidity will
be below 30 percent and winds will occasionally gust above 25 miles per hour
early this evening. Overall though...the majority of the
area will have wind speeds gradually lower this evening and
relative humidity levels will increase as temperatures lower.
The decrease in pressure gradient continues overnight through middle
week...with wind speeds generally around 10 miles per hour or less. Minimum
relative humidity will range mainly between 40 and 60 percent
Tuesday and between 30 and 40 percent for Wednesday.

&&

Hydrology...
generally expect from 1/10 to 1/4 inch of basin average rainfall
Tuesday and Tuesday night from scattered rain showers/isolated thunderstorms. However
cannot completely rule out locally heavy rainfall in any stronger
convection. If this does occur over an area...then localized minor
flooding of urban and poor drainage areas would be possible. This
is a low probability though.

Dry conditions are expected Wednesday through the weekend. Next
chance for rain showers/thunderstorms and rain will be on Sunday and Monday.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 am EDT Tuesday for anz350-353-355.

&&

$$
Synopsis...mps/pw
near term...jm/pw
short term...precipitable water
long term...mps
aviation...met
marine...jm/mps/pw
fire weather...
hydrology...mps/pw

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