Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
722 PM EDT Monday Jul 6 2015
a diffuse warm front gradually moves north into the region
through Tuesday. A cold front moves across the region on
Wednesday...followed by a series of low pressure systems. High
pressure returns for the end of the work week and into the weekend
with a return to unsettled weather for the start of next week.
Near term /through Tuesday/...
warm front lies across south-central New Jersey and is lifting to the
north. Can be noted by slightly warmer temps/dewpoints...but
maritime tropical airmass spreads along the coast and into
the local area with surface dewpoints around 70.
Isolated showers over central Jersey will clip the western part
of the forecast area this evening. Main showers and storms are
confined to Virginia into central PA where a weakening upper low over
eastern Ohio and a fairly well defined vorticity maximum near Knoxville Tennessee
(both seen in the water vapor imagery) help provide dynamics to
the instability. The pseudo mesoscale convective vortex feature over north-central Virginia
appears to have weakened and is now difficult to locate in the
Have confined any mention of probability of precipitation to far western zones for this
evening and for after midnight.
Some fog is possible with the moist onshore flow. Used "patchy"
wording...but not expecting an impacts. The possible exception is
the South Shore of Long Island. Narre-tl is pointing for the
Jersey coast. With it being climatologically unfavorable for
fog...will hold off on anything more than patchy.
Short term /Tuesday night/...
warm and humid with significant cloud cover.
With a maritime tropical air mass over the region, the approach
of the weakening short wave continues to have the potential to
generate showers and an isolated thunderstorm...especially Tuesday
afternoon. The highest probability of precipitation are northwest where nwp and 15z sref mean are
focused. Instability is better than today with forecast surface based
convective available potential energy of 500-1500 j/kg (highest in gfs).
Forecast highs should be a few degrees above normal and are close to
the slightly warmer NAM MOS.
There is a moderate risk for rip currents at ocean beaches on
Long term /Wednesday through Monday/...
cold front slowly works its way across the area Wednesday and should
be south of the region by Wednesday evening. There will be abundant
low level moisture across the region with surface dew points around 70
and precipitable waters over 2". As a result...can expect heavy rain at
times...and with training of cells...at least minor urban/small
stream flooding is possible.
There is little consensus among the models as to timing and strength
of storms...so will keep probability of precipitation capped at chance for now with nest
chances in the afternoon/evening. 12z NAM has little quantitative precipitation forecast over the
area...generally less than 1/4"...while the 12z European model (ecmwf) is similar in
terms of less than 1/4" widespread quantitative precipitation forecast...areal coverage is more
widespread than the NAM. The 12z GFS develops surface low pressure over the
Delaware-Maryland-Virginia Wednesday evening...and if it were to track close enough to
southern portions of NE New Jersey...NYC...and Long Island...those areas
could pick up around an inch Wednesday night while the other models
have the region drying out. Mainly...this appears to be due to a
strong 500 mb shortwave noted in the GFS passing through the
region...while the European model (ecmwf) has a weaker shortwave much farther south.
This is a fluid situation...and further model runs will be needed.
Conds dry out by Thursday morning...but then another wave of low
pressure moves through the region in the afternoon...touching off some
more showers/storms in the afternoon/evening.
High pressure then builds in thereafter with dry conds for Thursday
through Sunday. Temperatures will be mild with highs generally in the 80s
and lows in the upper 60s/low 70s.
The high moves offshore on Sunday...and the next wave of low pressure
approaches for Sunday night/Monday.
Aviation /00z Tuesday through Saturday/...
a warm front approaches from the southwest tonight and lifts north of
the region Tuesday.
VFR early this evening.
With 2nd night of onshore flow and a favorable S-southeast wind direction
ahead of the approaching warm front...MVFR conds should develop
around 03z. Conds then lower to IFR mainly after midnight. LIFR
continues to be expected after 06z at kgon/kisp/kbdr and cannot rule
it out for kjfk.
Chance for showers and thunderstorms in the 13-20z time period Tuesday...especially
along and west of a klga-kswf line.
Winds throughout much of the taf period will be out of the
southeast...generally 10 knots or less.
... 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: isolated rain showers possible west of the Airport through 6z.
Klga fcster comments: isolated rain showers possible west of the Airport through 6z.
Kewr fcster comments: isolated rain showers possible in vicinity of the Airport through 6z.
Kteb fcster comments: isolated rain showers possible in vicinity of the Airport through 6z.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 00z Wednesday through Sat...
Tuesday night...MVFR/IFR conds possible.
Wednesday...shra/tstms possible with MVFR or lower conditions at times.
Thu-Fri...chance of showers with MVFR or lower conditions at times.
rather tranquil through Tuesday...though winds are expected to
increase. Fog could affect the waters late tonight and Tuesday
morning along the South Shore of Long Island with visibility
reduced to 1 to 3 nm...and possibly below 1 nm at times.
A cold front moves across the waters on Wednesday...followed by a
series of low pressure waves through Thursday night. This will keep
at least a chance for showers/thunderstorms in the forecast. High pressure
builds in for the end of the week and the weekend with dry conds.
The gradient over the waters should remain relaxed enough to keep
conds below Small Craft Advisory levels during this time.
Summer convection is forecast for Tuesday and Wednesday (more likely)
aftns. With precipitable water values near 2 inches...heavy
rainfall is possible. With the convection also being rather slow
moving...localized urban and poor drainage flooding could
occur...with a low probability of flash flooding.
This hazards is highlighted in the hazardous weather outlook text
product from Fairfield and Nassau counties on west...including NYC
for Wednesday afternoon and evening.