Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1049 PM EDT Thursday Jul 2 2015
the first in a series of waves of low pressure will pass to the
south of the area tonight. High pressure then builds east across
the area on Friday. A second weak low will pass to the south on
Independence day. A broad area of high pressure will then build in
through the middle of next week.
Near term /until 6 am Friday morning/...
forecast remains on track this evening. Shortwave approaching from
the southwest around mean upper trough has developed a few showers
across southern zones of NYC/New Jersey metropolitan and southwestern Long
Island. 00z okx sounding depicted some low level dry air that has
likely prevented much measurable precipitation so far out these
showers. Nothing more than a few hundredths of an inch expected
out of this activity. The showers slide to the east in the next
few hours...exiting the area around midnight.
Otherwise...mostly cloudy sky conditions will slowly clear from
west to east during the early morning hours as the shortwave
shifts east. Lows tonight will range from the middle 50s in the
interior...to the lower 60s elsewhere. This is actually slightly
Short term /6 am Friday morning through Friday night/...
short wave ridging on Friday will allow high pressure from the Great
Lakes to build east through Friday night ahead of the next piece of
short wave energy dropping into the Great Lakes. The latter of
which will send a second area of low pressure into the Middle
Atlantic States by daybreak Sat.
Friday into Friday night will be dry with highs once again in the upper
70s to lower 80s...and lows in the upper 50s to middle 60s. This is
at or slightly below normal. Clouds will be on the increase from
the SW Friday night.
There is moderate risk of rip currents on Friday.
Long term /Saturday through Thursday/...
forecast for the 4th of July is tricky with models in disagreement
regarding our chances of rainfall. For the 12z suite...NAM is dry
during the day and night...with GFS/ECMWF/CMC showing some quantitative precipitation forecast
output. Most of the models would imply that the morning hours are
more likely to remain dry and any rainfall would be associated with
a wave of low pressure passing to the south. Still...will be keeping
at least a slight chance of showers for the southern zones for the
morning. For the afternoon and evening...an upper trough approaches
and could tap into enough instability to produce a shower or
thunderstorm for mainly the northwest zones. Will keep a slight chance of a
shower for the southern zones due to the proximity to the offshore
low. In any case...this does not look like a washout...but the
chances of a mostly sunny day doesn't look too high at this point.
Went slightly cooler than a mav/NAM MOS blend for high temperatures.
Sunday on the other hand looks like it will feature a good deal of
sunshine for much of the day with weak high pressure...but there
could be some cloud buildup in the afternoon over the eastern zones
as the flow aloft remains cyclonic. The atmospheric column at least
looks too dry for a mention of showers. Highs in the 80s.
Rest of the long term period probably remains dry for the most part
with high pressure in place. European model (ecmwf) remains a quick outlier with
bringing in rainfall associated with a weak wave of low pressure
along a stationary front to the south starting late in the day
Monday. Will go with dry weather for Monday through Tuesday
night...but leave in a slight chance of showers in the grids for
Wednesday and Thursday when the other guidance indicates that some
showers could occur. Highs in the 80s through Thursday...although
with the cloud cover...Thursday is forecast to be only around 80.
Aviation /03z Friday through Tuesday/...
weak high pressure builds to the north of the terminals overnight
into Friday morning as a wave of low pressure passes to the south.
The high shifts to off the northeast coast Friday afternoon.
VFR through the taf period. Showers are likely until around 07z
across Suffolk County and possibly into southeastern Connecticut
with VFR conditions.
The wind will be generally light and variable overnight with a light
north to northeast flow developing early in the morning.
Sea breezes are expected to move through the terminals during the
afternoon...17z through 21z. Moderate forecast confidence.
Outlook for 00z Saturday through Tuesday...
Friday night...VFR. Light southeast flow.
Saturday...VFR...a low chance of showers.
sub-Small Craft Advisory conditions through Friday night as weak low pressure passes
south of the waters tonight and high pressure builds to north on
Winds and seas likely remain below Small Craft Advisory levels through the long
term period as a weak pressure gradient remains in place...resulting
in light winds. A swell could potentially bring ocean seas close
to 5 feet during Saturday...but confidence in this occurring is low.
widespread significant precipitation not expected.
with a recent full moon...tidal departures of only 3/4 to 1 1/2
feet are needed for minor coastal flooding benchmarks to be reached
at the peak of the nighttime high tides the next few days. Minor
benchmarks could briefly be touched along the South Shore bays of
Nassau County through late this week.