Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
343 am EDT Wednesday Aug 20 2014
high pressure will be anchored over eastern New England through
Thursday. An upper level disturbance moves through for Friday.
Surface high pressure builds into the region for the
weekend...then slowly slides offshore early to middle next week.
Near term /until 6 PM this evening/...
broad area of hi pressure from Quebec into southern New England at 7z. A
break in the middle clouds will allow for patchy fog through
sunrise...mainly in the outlying areas.
Developing southeast flow today. With subsidence hanging
on...particularly across central and eastern areas...most of the County Warning Area
should be partly cloudy and dry. Across the far western/northwestern fringe...falling
heights along with up to 1000 j/kg of SBCAPE per the NAM could
Spring some shra/tstms. Main threat still west of the County Warning Area with the
embedded shortwave not arriving until about 00z.
Temperatures right about or just blw climatology. Forecast is close to the gmos25.
Short term /6 PM this evening through 6 PM Thursday/...
instability wanes with continued onshore flow along with a loss of
surface heating. Therefore the shortwave is expected to have a minimal
effect at this time and produce only a few rain showers as it traverses the County Warning Area
this eve/tngt. Any thunderstorms would need to be elevated due to the
stable marine layer. As a result...have not included thunderstorms in the
forecast for tonight.
00z model consensus is that the upper low spinning over the up of Michigan
will drop heights on Thursday and attempt to trigger rain showers or thunderstorms.
Instability will be the limiting factor...with a marine stratus
deck likely penetrating almost the entire County Warning Area. Included thunderstorms only
on the western and northern periphery of the County Warning Area...with only rain showers
elsewhere. Where the instability does materialize...the setup is
ripe for multicellular heavy rainers in a low shear environment and precipitable water/S
about 125-150 percent of normal.
Temperatures cooler due to the clouds and onshore flow.
Long term /Thursday night through Tuesday/...
deep upper trough in place for Thursday night...with weak cut off
upper low weakening over the eastern Great Lakes region into Friday
morning.. at the surface...high pressure over southeastern Canada
will build south into the northeast. Upper trough will set off some
showers Thursday night into Friday afternoon...mainly for western
sections. Some surface based cape...a few hundred to just under 1000
j/kg depending on which model you look at...will allow for some
isolated thunderstorms early Thursday night. With a lack of any
strong lifting mechanism...the chance for any thunderstorms should
diminish as the sun sets.
Omega block in the upper levels will allow high pressure to continue
to slowly build into the region for the weekend and into early next
week...with dry conditions in store. An extended northerly flow will
mean below normal temperatures for this time of year for the
weekend. Highs will be in the lower to middle 70s on Saturday...and
slightly warmer Sunday. Lows Saturday night and Sunday night will be
in the upper 50s to lower 60s...even in the NYC metropolitan region.
The high pushes off the northeast coast Monday night into Tuesday.
The return flow will bring temperatures back up to more normal
values for this time of year.
A cold front approaches for the middle of the week...but conditions
should remain dry.
Aviation /09z Wednesday through Sunday/...
weak high pressure remains over the area.
Mainly VFR early this morning...although cannot rule out patchy
stratus and fog outside of NYC metropolitan for a few hours.
Then expect few to scattered cumulus today. An isolated shower or thunderstorm
is possible well north and west of NYC this afternoon. However any
activity would be too isolated to include in terminal forecasts.
Light winds become southeast/south at 6 to 11 kts this afternoon most
Winds lighten by evening.
..NY 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: winds remain south or southeast today...with
speeds increasing during the afternoon to around 10 kts.
Klga fcster comments: a east to northeast wind off the sound will
eventually give way to south/southeast winds. Timing of wind shift
may be off an hour or two.
Kewr fcster comments: winds remain south or southeast today...with
speeds increasing during the afternoon to around 10 kts.
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: stratus is possible between 1 and 3 kft before
Kisp fcster comments: stratus is possible between 1 and 3 kft before
Outlook for 06z Thursday through sun...
tonight...scattered showers/thunderstorms possible across NYC metropolitan and lower
Hudson Valley terminals. As such...sub VFR possible.
winds and seas blw Small Craft Advisory levels through Thursday. Sub-Small Craft Advisory conditions expected
Friday through the day on Saturday. A persistent northeasterly flow
will allow waves to build to 5 feet for the central and eastern
ocean zone Saturday night through the day on Monday. Gusts on
Saturday will reach the lower 20 knots range...and slightly less on
Sunday. Gusts at or just above 25 knots are possible for the
weekend...but does not look likely as of now. Gusts diminish into
the beginning of the work week as the center of high pressure
moves over the waters.
a few thunderstorms are possible Thursday...mainly across the Hudson Valley
into New Jersey away from the coast. Any thunderstorms will have the potential to
produce locally heavy rain...however basin Ave precipitation of less than 1/4
inch is expected at this time. The potential exists for minor poor
drainage flooding from any of this thunderstorm activity.
No significant rainfall is expected in the extended.