Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
154 PM EDT Friday Sep 19 2014
high pressure to our north moves east over the Atlantic on Saturday.
A cold front crosses the area Sunday night. High pressure returns
on Monday and remains in control through the end of the week.
Near term /until 6 PM this evening/...
forecast is on track with no sig changes at this time.
High pressure over northern New England slides east to the Gulf
of Maine causing winds to veer to southeast.
Few-scattered strato-cumulus below the subsidence inversion today...overall
a sunny to mostly sunny afternoon.
Temperatures 10 or so degrees below normal.
Moderate risk of rip currents at Long Island beaches.
Short term /6 PM this evening through 6 PM Saturday/...
zonal upper flow early...give way to East Coast ridging as northern
stream digs into the Great Lakes.
At the surface...Canadian high pressure continues to slide well
offshore with return flow developing.
Stratus development possible late tonight...particularly across NYC
metropolitan and points W/NW...with return flow trapping moisture under
subsidence inversion. With potential for cloud cover and onshore
flow temperatures likely don't bottom out...but still run several degrees
below seasonable. Temperatures in the 50s along the coast...and 40s
Gusty southeast warm air advection flow on Saturday which should allow for a moderation in
T/TD. Models signaling some light precipitation developing in return
flow...but with rather dry soundings and lack of forcing this may
indicate potential for stratus to linger into the afternoon under a
lifting but lingering subsidence inversion. Temperatures moderating to near
seasonable levels with noticeable increase in humidity by late day.
Long term /Saturday night through Thursday/...
model guidance is in good agreement with the 500 mb flow through the
weekend. Timing and amplitude differences then come into play
thereafter. One other element that bears watching is how quickly the
developing low off the southeast coast is picked up by the digging trough.
There seems to be large disagreement with this leading to high
variability in the systems forward speed and track. Since there is
such high spread amongst the guidance won't go into much details at
this point...but probability of precipitation might need to be increased Sat night into sun
ahead of the cold front as moisture streams in from this system. It
could also remain far enough offshore keeping all precipitation there as
well. Have added schc probability of precipitation from areas east of Fairfield County CT and
Nassau County north New York for now as guidance has been indicating this at
times over the last few days.
Otherwise...the digging trough slows up over the East Coast due to
downstream ridging...but still is progressive enough for the surface
cold front to push east of the area Sun night. Decent shortwave
accompanies the front aloft...but it should be a fairly quick shot
of rain with a somewhat moisture starved atmosphere. The NAM has
been discounted as it is the only solution that develops a wave in southern
New England and is a slow outlier with the wave off the southeast coast.
The shortwave also pivots into New England during the evening taking the
best dynamics with it. Highest chances of precipitation will be west of the
Hudson River. Have also added schc thunderstorms Sun afternoon/night with
marginal instability possible. Highs sun are expected to be several
degrees above normal with increasing humidity levels.
The front is expected to clear the area by Monday morning...followed by
the trough axis Monday evening. Deep layered ridging then builds from the
plains resulting in dry and seasonable weather through the remainder
of the week.
Aviation /18z Friday through Wednesday/...
high pressure centered over New England at 17z will move off the
coast this evening and slowly east through 18z Saturday.
A northeast to east flow will shift around to the southeast and
south as the high moves east.
Marginal VFR ceilings south of Long Island will move into the region
after 07z as the flow shifts to the southeast...with ceilings 2kft
to 3kft. Saturday morning ceilings gradually lift to VFR and then
become unlimited with scattered cumulus. Visibilities are not expected to
be impacted tonight.
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 through
Klga fcster comments: no unscheduled amendments expected through
Kewr fcster comments: no unscheduled amendments expected through
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Khpn fcster comments: no unscheduled amendments expected through
Kisp fcster comments: no unscheduled amendments expected through
Outlook for 18z Saturday through Wednesday...
Saturday...marginal VFR ceilings improve to VFR after 14z.
Saturday night-Sunday...marginal VFR conditions in
fog/clouds...possibly locally IFR after 04z with drizzle. Conditions
improve to VFR in the morning with areas of marginal VFR in showers
and isolated thunderstorms.
Sunday night...showers ending with conditions improving to VFR.
NE winds gusting to near 25 knots on the ocean early this afternoon will
slowly veer southeast and diminish by evening. Wind gusts along with 3
to 5 feet seas on the ocean result in the Small Craft Advisory remaining in effect.
Southeast winds tonight into Friday. Sub Small Craft Advisory winds and diminishing
residual east swells from Edouard allow seas to fall just below Small Craft Advisory
Winds are expected to remain below Small Craft Advisory levels Sat night into middle
week. Seas on the ocean waters may build to marginal Small Craft Advisory levels
behind a cold front Sun night into Monday. Sub-advsy conds are then
expected until late Tuesday night into Wednesday with an increasing northerly
flow. Small Craft Advisory seas on the ocean are again possible.
no rainfall is expected through Sunday.
Less than 1/2 inch of rainfall is expected with the cold frontal
passage Sun night. Dry weather then expected for the rest of the
Marine...Small Craft Advisory until midnight EDT tonight for anz350-353-