Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
805 PM EDT Monday Sep 1 2014
weak high pressure remains over the region tonight in the wake of a
surface trough. A cold front then approaches during Tuesday before
passing through Tuesday night. High pressure builds in for the latter
half of the week. Another cold front will impact the region this
Near term /until 6 am Tuesday morning/...
some minor adjustments with probability of precipitation for convection...temps...and
dewpoints. Overall...forecast is on track. Any convection just
expected to be isolated and early in the evening with agreement
with multiple mesoscale models of mostly dry conditions middle
evening through the rest of the night.
Isolated/scattered convection diminishes this evening from the combination
of atmospheric stabilization...loss of moisture convergence due to
dissipating surface trough and seabreeze boundaries...and upper
lift shifting east out of the area. Precipitable water values will still be on
the high side around 1.5 to 1.7 inches...so heavy downpours
remain possible in any showers/tstms.
Dry weather by around midnight...but remaining muggy as dewpoints
hover around 70. Patchy light fog probably develops overnight as
Short term /6 am Tuesday morning through Tuesday night/...
cold front approaches during the day Tuesday. A pre-frontal trough
ahead of it develops near our western zones. Shower/thunderstorm threat
begins in the afternoon along this trough...and ends for most spots
overnight when the trailing cold front passes through. Capped probability of precipitation
in the chance category. Parameters during the afternoon and early
evening support the potential of thunderstorms with strong wind
gusts. Large hail would be less of possibility due to relatively
high wbz/freezing level heights. Thunderstorm strength diminishes after
early evening with less cape in spite of better lift from the
passing cold front. Precipitable waters still rather high...so heavy downpours
possible in any shower.
Above normal temperatures with muggy conditions continue through
this period. With 850mb temperatures of 17-18c...partly to mostly sunny
conditions for most of the day and a SW flow...expecting parts of NE
New Jersey to reach into the low-middle 90s...with low 90s in the city and a
good portion of the lower Hudson Valley. Most other spots expected
to end up at 85-90. Regarding heat advisory concerns in the
city...although it appears that a decent portion of the city will
reach a heat index of at least 95 for an hour or two tomorrow
afternoon...indices had failed to reach 95 Monday afternoon. No
advisories will therefore be posted as per local policy.
There is a moderate risk of rip currents on Tuesday.
Long term /Wednesday through Monday/...
cold front offshore will continue to push east on Wednesday as high
pressure builds in. Dry conditions are expected through Friday as
the center of the high moves over the region and off the East Coast
by Thursday while aloft there will be a rather zonal pattern.
Humidity levels during this period will ease up a bit as dewpoints
drop to the lower 60s on Wednesday...with some upper 50s dewpoints
possible on Thursday. However...they creep back up towards the lower
and middle 60s again on Friday on the return flow with the high
A cold front will approach the area Friday night into
Saturday...pushing offshore sometime Saturday night. There is some
model consensus on pushing the cold front offshore Saturday
night...but there are differences thereafter. The 00z European model (ecmwf) stalls
the front just offshore and there would be a chance for Post-frontal
rain through Sunday night. The 12z GFS and CMC keep the system
progressive...ending the rain Saturday night...keeping Sunday dry.
GFS ensemble mean is actually more progressive with the cold
front...pushing it offshore during the day Saturday...but also ends
it Saturday night. Also...models differ in development and placement
of low pressure along the frontal boundary...which lead to large
differences in placement of any heavy rainfall. Although the GFS is
more progressive...the front has slowed down significantly from the
previous 06z run. So...given uncertainty will keep at least slight
chance probability of precipitation in for Sunday morning...drying out by the afternoon.
Temperatures will be above normal through Saturday.
Thereafter...below normal temperatures expected as a Continental
polar airmass builds in.
Aviation /00z Tuesday through Saturday/...
a surface trough will dissipate as it moves east overnight. A
cold front approaches late Tuesday.
MVFR/IFR stratus/fog likely along eastern terminals...possible
across interior terminals.
Any morning stratus and fog Burns off with VFR conds.
Light SW winds tonight into Tuesday morning...giving way to
afternoon seabreeze development along the coast.
Increasing chance for scattered rain showers/thunderstorms and rain Tuesday evening across NYC
terminals and to the west & northwest.
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: seabreeze development expected between 17z
and 19z. Maxing out at 15 to 18 knots after 21z.
Klga fcster comments: seabreeze development likely between 19z
Kewr fcster comments: low probability of after seabreeze
Kteb fcster comments: low probability of after seabreeze
Khpn fcster comments: seabreeze development likely between 19z
Kisp fcster comments: seabreeze development expected between 18z
Outlook for 00z Wednesday through Friday...
Tuesday night...mainly VFR except for scattered evening/nighttime shra/tsra.
Wednesday-Friday night...VFR conditions are expected.
Sat...sub VFR possible in scattered shra/tsra.
sub-Small Craft Advisory conditions expected on the waters through the forecast
period with a relatively weak pressure gradient most of the time.
There could be showers and thunderstorms Tuesday night...and again late
Friday into Saturday as a front approaches.
isolated/scattered showers and thunderstorms this evening should be short-
Isolated/scattered showers/thunderstorms late Tuesday/Tuesday night would likely result in
no more than localized minor urbanized/small stream flooding.
No hydrologic issues expected Wednesday through the weekend.