Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
719 am EDT Thursday Jul 31 2014
high pressure will remain off the northeast coast through Friday
while weak disturbance moves through the region. A frontal
boundary will back in from the ocean this weekend and impact the
area through the beginning of the week. High pressure then builds
into the region.
Near term /until 6 PM this evening/...
forecast for the day currently on track. Tweaked temperatures and dew
points for current observation but trend was on track. A few light showers
have developed in the lower Hudson Valley and NE New Jersey...consistent
with our slight chance probability of precipitation so no changes were made there.
Otherwise...upper low continues to spin south of Hudson Bay with next
weak shortwave pivoting through this morning into early afternoon.
Considerable diurnal cumulus and mean troughing should keep temperatures a few
degrees below seasonable norms...generally upper 70s to lower 80s.
With limited moisture/instability to work with...overall rain showers
activity today should be low in coverage. A few shower possible well
n&w this morning with a weak low level jet. Most activity should be n&w of NYC
metropolitan developing from early afternoon into early evening...along weak
pre-frontal trough and off higher elevations of eastern PA and hills
of New Jersey/lower Hudson Valley...drifting NE. In-situ thunderstorm development
looks to be isolated in Low Cape environment...but moderate
shear/wind fields could sustain activity developing to the west/SW and
There is a low threat for rip development this morning...becoming
there moderate risk this afternoon with afternoon seabreeze
development and 3 feet S/southeast swells.
Short term /6 PM this evening through 6 PM Friday/...
any shower activity will taper off in the evening. Temperatures near
seasonable as moisture levels gradually increase with light
onshore flow...generally in the 60s. Patchy fog possible across
outlying areas as a result.
Deep troughing across eastern 1/2 of the US...deepens southerly flow
up the East Coast. Increasing moisture/instability along with
southern stream shortwave energy riding up the coast and weak right
rear jet lift will present a better chance for diurnal rain showers/thunderstorms and rain
activity for NYC metropolitan and particularly points n&w Friday aft/eve.
Overall shear looks weak...so would expect convection to be more
pulse in nature...but cant rule out a few strong storms. 15 knots south-southeast
steering flow will lend to an urban/poor drainage flood potential.
Temperatures near seasonable in moderating airmass...lower 80s to 85.
Long term /Friday night through Wednesday/...
deep upper trough remains to the east of the area Friday night along
with a strong western Atlantic high pressure area. As the high
retrogrades west...it will push a front to the west with it. With
the blocking pattern in place due to the upper low to the west...the
front will sit near and/or over the area through the weekend.
A continuous south-southwest flow will also help bring sufficient
moisture into the area. The right entrance region of an upper jet
also sits over the region through the weekend. A combination of
these will keep unsettled and showery conditions over the area. Some
of the showers/thunderstorms could produce moderate to heavy
12z European model (ecmwf) is a wetter solution with the front setting up across the
area while the GFS/NAM keeps it to the south which keeps the area
dry through Sunday morning. With so much uncertainty remaining...did
not make any major changes to the pop grids and left chance for much
of the area Saturday and Sunday.
Temperatures through the weekend will be near normal...maybe
slightly below normal for highs. With increasing dew points due to
the multiple nights of southerly wind...have added patchy fog for
Sunday and Monday nights.
A surface low then develops over the southeast in response to the deep
upper trough. This quickly tracks NE over the local area on Monday.
European model (ecmwf) flattens the upper levels quicker on Monday while the GFS
leaves the surface low lingering across the northeast with a wet
Sunday and Monday. Again...will make no major changes to the pop
Dry weather then expected Tuesday and Wednesday. Temperatures will begin to warm
Monday-Wednesday as heights rise a few degrees with more breaks in the sun
than the weekend. Lows will remain near normal.
Aviation /12z Thursday through Monday/...
high pressure will remain offshore through Friday.
Isolated-scattered rain showers and thunderstorms likely to develop after 15-17z...especially
north and west of knyc. The probability of direct impacts at a particular
terminal too low to include in the tafs...except for kswf where
rain showers have been retained in a tempo group.
Rain showers/thunderstorms decrease in intensity and coverage after 22z.
VFR outside of any precipitation.
Vrb winds become SW this morning then veer to the S and increase through
the day with a sea breeze component. Speeds lighten again tonight
as the sea breeze influence weakens.
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 unscheduled amendments expected.
Klga fcster comments: no unscheduled amendments expected.
Kewr fcster comments: no unscheduled amendments expected.
The afternoon kewr haze potential forecast is green...which
implies slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 12z Friday through Monday...
Friday...mainly VFR. Isolated rain showers/thunderstorms possible in the aftn/eve. S
Sat-sun...areas of MVFR or lower. East flow Sat becoming S sun.
Monday...becoming VFR with winds shifting to the west.
with high pressure over the waters...can expect sub-Small Craft
Advisory conds through Friday. Winds and seas will remain below
Small Craft Advisory levels through the extended period.
locally heavy downpours in scattered thunderstorms on Friday will present
mainly a urban/poor drainage flood threat due to around 15 knots
movement...with a low and localized flash flood threat with any
training of cells.
An increasingly moist air mass will be conducive to the development
of heavy showers this weekend.