Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
723 PM EDT Wednesday Aug 20 2014
high pressure remains centered to the north and east of the area
through Thursday night. Meanwhile...waves of low pressure aloft
move across the region tonight and again Thursday into Thursday
night. An upper level disturbance will track through the area on
Friday as high pressure builds down from eastern Canada. This high
will gradually build down the eastern Seaboard through the middle
of next week.
Near term /until 6 am Thursday morning/...
forecast remains on track. Some showers approaching western
zones...but with abundant low-level dry air in place...most of the
showers are drying up before reaching the ground. As the upper
level low centered over north Michigan opens up and slides to the
southeast...a shortwave rotating around it will influence the area
overnight. With height falls aloft...especially across northwest
zones...chances for showers will increase towards morning. With a
surface high nosing in from the northeast...drier air will be
present beneath h9 or so. However...it appears there will be
enough forcing for some precipitation...primarily across the lower
Temperatures will be a few degrees milder than the previous night in most
areas...as increasing cloud cover reduces the ability for
radiational cooling. Generally used a mav/met/ecs blend as there was
Short term /6 am Thursday morning through Thursday night/...
there will be some showers ongoing during the first half of the
day...as a shortwave swings across the area. Best chances will again
be across western and northern zones...as ridging noses in across
our eastern sections. Included isolated thunder across the approximate
western third of the area...where model fields indicate a little
more in the way of MUCAPE. Additionally...these areas will be less
influenced by the maritime air being advected across the area thanks
to east/southeast onshore flow.
Due to the aforementioned onshore flow and increased cloud
cover...temperatures will be cooler than the previous day...with many areas
staying in the 70s / below normal for this time of year.
As the first wave departs to the east Thursday afternoon and
evening...subsidence aloft and the continued surface ridging poking
in from the north and east will allow most places to be dry later in
the day. Chances will then increase again overnight...as the upper
low to the northwest opens and approaches the area.
Long term /Friday through Wednesday/...
models are in good agreement that the 500 mb pattern across noam at the
start of the long term period will consist of a strong broad ridge
across the southeast Continental U.S. With a deep trough out west with an upper low
cutting off over the Pacific northwest and an Omega block over eastern Canada with
a weak cutoff low moving through New England.
Some uncertainty with the specific details and timing of vorticity maxes
moving around the left side of the upper low once it slides
offshore...but the general trend appears to be decreasing chc's of
showers during Friday as deep layered ridging builds into the northeast
from the north. May need to add slight to low chance probability of precipitation at times through
Sat in subsequent forecast packages to account for these timing
differences. Additionally...the amount of cloud cover for Friday and
Sat is also questionable as a result.
Otherwise...expect dry and seasonable conds through the middle of
next week as the 500 mb flow amplifies in response to the blocking
pattern. Surface high pressure will build down the eastern Seaboard during this
time with an Ely flow expected at least into Monday. This will
contribute to below normal temperatures thought this time...but as
heights rise Tuesday and Wednesday...temperatures will rebound to near normal
Aviation /00z Thursday through Monday/...
weak high pressure remains over the area.
VFR...except tempo IFR visibilities at kgon late tonight.
Scattered -shra with no reduction in flight category west of kisp-kbdr
Thursday morning could start off with some ceilings around 030...these
should rise slightly to at least 035-040 by afternoon.
... 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.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 00z Friday through Monday...
Thursday night...VFR. Scattered thunderstorms mainly south and west of the New York metropolitan.
with high pressure still extending across the waters Thursday...and
only starting to lift out Thursday night...winds and seas will
remain below Small Craft Advisory criteria during this time. Easterly flow will be on
the increase late Thursday though.
Wind gusts are expected to remain below Small Craft Advisory levels...although could
come close to 25 knots on the ocean waters late Friday/Friday evening. An
increasing east-NE flow will result in building seas on the ocean with
Small Craft Advisory conds expected between Friday night and Sun night. The gradient
relaxes thereafter with seas diminishing.
a few thunderstorms are possible on Thursday across the lower Hudson
Valley and interior NE New Jersey. Any storms will have the potential to
produce locally heavy rain...but basin averaged totals are forecast
to remain light...as any thunderstorms should be isolated.
No significant rainfall is expected in the extended.