Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
154 PM EDT Thursday Aug 21 2014
high pressure remains centered to the north and east of the area
through tonight. Meanwhile...waves of low pressure aloft move
across the region today and tonight. An upper level disturbance
will track through the area on Friday as high pressure builds down
from eastern Canada. The high will continue to build southward
into the region on Saturday...and remain anchored over the area
through the beginning of next week.
Near term /until 6 PM this evening/...
isolated-scattered showers mainly north/west of NYC metropolitan with a stray thunderstorm
possible through this afternoon as an upper level trough pivots through the
region. Mesoscale models still showing development mainly over western
areas later this afternoon aftr 18z where the best instability can be
expected...generally around 1000 j/kg. Onshore flow over eastern
areas/along the coast will maintain a more stable atmo...resulting
in mostly dry conditions till this evening. Overall trend is more
suggestive precipitation will move in aftr 00z this evening. Flow aloft
less than 10 kts...so while flash flooding is not a big
concern...there is the potential for a brief period of heavy
rainfall with the slow moving cells. With a lack of a significant
lifting mechanism...not looking for anything strong or severe.
Cloud cover will help to keep temperatures slightly below normal
for the most part. Generally highs will be in the upper 70s to
lower 80s. Temperatures are thus far on track for the day.
Short term /6 PM this evening through 6 PM Friday/...
the chance for showers continues tonight as the closed upper low
associated with the trough moves into New England and a shortwave
moves around its base. With the loss of daytime
heating...the chance for thunderstorms decreases...and thus just
plain showers are in the forecast. Southwesterly flow off the
ocean early tonight will allow for a moist airmass. Dewpoints
will rise into the middle 60s. Winds shift more to the northeast
late tonight...and dewpoints will come back down to the lower 60s
by daybreak Friday. This northeasterly flow will then mean an even
cooler day on Friday as compared to Thursday...with highs
generally in the lower to middle 70s. Some upper 70s for the NYC
High pressure from the northeast will nose into the area
Friday...allowing the chances for showers to end from east to
west on Friday.
Long term /Friday night through Wednesday/...
solid model consensus through Tuesday. Hipres builds into the area then
strengthens as the upper ridge translates eastward. On Wednesday...the European model (ecmwf)
brings a cold front close...but the GFS keeps the feature off the local
map. Have sided with the slower GFS solution as this fits a fast model
bias at this time range.
A maritime polar airmass is locked in Friday night into the first part of
Sat. Virtually no lift in the moist layer...so have only forecast
sprinkles. The clouds begin to clear in the afternoon from NE to SW as
strong subsidence kicks in.
Dry with light winds sun-Wednesday courtesy of the high. Some cirrus at
Temperatures blw normal Sat...then a gradual warming trend takes place
sun-Tuesday as heights increase.
Aviation /18z Thursday through Tuesday/...
weak high pressure remains over the area.
Mainly VFR conditions are expected through the afternoon hours.
There will be isolated to scattered showers...and any shower could
reduce ceilings or visibilities to MVFR briefly. Best chance for showers
across NYC metropolitan and north and west...later in the day. Isolated
thunder is a low possibility. By 23z...chance of showers
increases slightly for coastal areas
A higher coverage of showers is expected tonight as an upper level
disturbance moves through. Still...best chance NYC metropolitan and
north and west. VFR ceilings and visibilities may lower to MVFR or even
IFR late at night.
Ceiling improvement on Friday will slow due to moist onshore flow.
Southeast or south wind 5 to 10 kts is expected this afternoon.
Winds tonight should lighten as they turn to the East.
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: amendments possible for timing of ceilings
Klga fcster comments: amendments are possible for timing of ceilings
Kewr fcster comments: amendments are possible for timing of ceilings
Kteb fcster comments: amendments are possible for timing of ceilings
Khpn fcster comments: amendments are possible for timing of ceilings
Kisp fcster comments: amendments possible for timing of ceilings and
Outlook for 18z Friday through Tuesday...
Friday morning...sub VFR possible in low clouds and fog.
winds and seas forecast on track for today. There will be a
chance for showers today as an upper level disturbance moves
toward the area. An isolated thunderstorm is possible across the
western sound and Harbor. Winds and seas should remain below Small Craft Advisory
criteria...but may approach Small Craft Advisory criteria briefly in any
thunderstorm. The chances for showers continue into tonight and
Friday...with chances diminishing throughout the day Friday. Winds
and waves continue to remain below Small Craft Advisory for tonight and Friday.
Winds will approach Small Craft Advisory levels Friday night...then diminish during the day
on Sat. Seas on the ocean will build to around 4 feet late Friday
night...then linger through most of Sat before subsiding. A Small Craft Advisory may be
needed especially on the ocean Friday night and Sat. Otherwise...winds
and seas will be blw Small Craft Advisory levels sun-at least Tuesday.
a few slow moving thunderstorms are possible today across the
lower Hudson Valley and interior NE New Jersey and into NYC. These storms will
have the potential to produce locally heavy rain...but basin
averaged totals are forecast to remain light with the isolated
nature of the storms. Trace amounts of precipitation are possible Friday night into
Sat. It will then remain dry through the beginning of next week.