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fxus61 kokx 181430 
afdokx

Area forecast discussion
National Weather Service New York New York
1030 am EDT Tue Sep 18 2018

Synopsis...
the remnants of Florence will pass through the region this
morning, followed by a cold front this afternoon. High pressure
then ridges down southeastern Canada through Thursday, then
retreats to the northeast Thursday night. A cold front
approaches from the west on Friday, then crosses the area Friday
night, followed by high pressure building in for the weekend
into early next week.

&&

Near term /through tonight/...
main change this morning was increasing chances for flash
flooding this afternoon. Flash Flood Watch for the lower Hudson
Valley, northeast NJ, western Long Island, and southwest CT
including NYC from 11am until 7pm. This is a combination of
where heavy rain occurred during the previous day and where
heavy showers and thunderstorms are expected this afternoon.
This includes the highly urbanized portions of the region and
these areas are where many mesoscale models are showing a heavy
line of showers and thunderstorms moving across this afternoon.
While these heavy showers and thunderstorms are still expected
even for easternmost portions of the region (namely southeast CT
and Suffolk County ny), these portions of the region have
higher flash flood guidance so flooding would be more minor
nuisance flooding.

The remnants of Florence lift to the northeast this morning
followed by a 850-500 hpa trough passing this afternoon.

Instability is increasing per laps, and will continue to do so
until the surface trough/cold front passes this afternoon. The
position of the main low, tracking roughly along the Mass Pike,
will keep the best directional shear north of the area. As a
result, severe thunderstorms are not expected, although the
mesoscale environment will continue to be monitored through the
day.

Pops were updated to reflect faster end time of high resolution
models and the 6z runs of NAM and GFS. Expect precipitation to
be done across most of the tri-state by 6pm, with the entire
area in the clear by 8pm.

Southerly flow this morning with the low level jet should
produce the strongest gust potential through 15-17z. The surface
trough coming through then lightens wind as it progresses across
the County Warning Area. Light wind fields behind the front with winds up to
850 hpa maxing out at 20 kt.

A blend of the MOS was used for temperatures today and tonight.

There is a high rip current risk today.

&&

Short term /Wednesday/...
high pres builds across Quebec with a drier airmass building in.
Pwats fall to an inch or less. There is hint of a weak backdoor
frontal passage, which could spark an isold shower. The fcst was
left dry for now as the convergent region of the jet arrives.
However, if the modeling becomes more consistent a few shwrs or
sprinkles may need to be added. The nbm was used for temps.

There is a moderate rip current risk for Wed.

&&

Long term /Wednesday night through Monday/...
the core of a deep layered ridge builds to our southwest then south
Wednesday night through Thursday night, with its axis sliding
offshore on Friday.

Subsidence under the ridge should keep things dry Wednesday night-
Thursday night and relatively cloud free Wednesday night and
Thursday. Week low level warm advection should bring some cloud
cover on Thursday night.

Lows Wednesday night should be a few degrees above normal. Highs on
Thursday should be a few degrees below normal and lows Thursday
night around 5 degrees above normal.

A 700 hpa shortwave working its way up the back side of the ridge on
Friday warrants slight chance pops for showers/thunderstorms to the
northern tier of the lower Hudson Valley/west Passaic County/far North
Fairfield County, with dry conditions expected elsewhere. Highs on
Friday should be around 5 degrees above normal.

A northern stream trough passes to the north Friday night, with
mainly zonal flow over the region, the bulk of the energy associated
with this trough will stay north of the area. As a result only have
slight chance pops Friday night.

The region remains under zonal-WSW flow aloft Saturday-Monday. The
European model (ecmwf) is along in suggesting shortwaves embedded in the flow could
bring some showers on Sunday and possibly Sunday night. So have
slight chance pops Sunday/Sunday night and have gone the remainder
of the time frame from Saturday-Monday.

Temperatures should be above normal Friday night, then near normal
Saturday, with below normal temperatures forecast Sunday and
Monday.

&&

Aviation /14z Tuesday through Saturday/...
the remnants of Florence will interact with a cold front
approaching from the northwest today. The front will move across the
region this afternoon and evening.

MVFR to locally IFR conds prevailing across the terminals and
should generally persist until the cold front passes this
afternoon/evening. Showers continue to increase in coverage as
the front nears with a line of tstms expected in the 16z-23z
timeframe, northwest to southeast. VFR returns thereafter, except there could
be patchy MVFR/IFR fog development outside of NYC tonight.

S-SW winds 10-15 kt with a few gusts 20 kt coastal terminals,
5-10 kt elsewhere. Winds then diminish this afternoon. Winds
shift to the northwest-north after the frontal passage this aftn/eve.

New York Metro enhanced aviation weather support...

Detailed information, including hourly taf wind component fcsts,
can be found at: http:/www.Weather.Gov/zny/n90

Kjfk taf comments: wind direction could be off by 30 degrees
16-00z, depending on cold frontal progression. Improving
conditions may be off a few hours as well.

The afternoon kjfk haze potential forecast is yellow, which
implies slant range visibility 4-6sm outside of cloud.

Klga taf comments: wind direction could be off by 30 degrees
16-00z, depending on cold frontal progression. Improving
conditions may be off a few hours as well.

The afternoon klga haze potential forecast is yellow, which
implies slant range visibility 4-6sm outside of cloud.

Kewr taf comments: wind direction could be off by 30 degrees
16-00z, depending on cold frontal progression. Improving
conditions may be off a few hours as well.

The afternoon kewr haze potential forecast is yellow, which
implies slant range visibility 4-6sm outside of cloud.

Kteb taf comments: wind direction could be off by 30 degrees
16-00z, depending on cold frontal progression. Improving conds
may be off a few hours as well.

Khpn taf comments: wind direction could be off by 30 degrees
16-00z, depending on cold frontal progression. Improving
conditions may be off a few hours as well.

Kisp taf comments: wind direction could be off by 30 degrees
18-02z, depending on cold frontal progression. Improving
conditions may be off a few hours as well.

Outlook for 12z Wednesday through Saturday...
Wednesday ... north winds g15-20kt possible.
Thursday...VFR.
Friday...chance of showers with MVFR conditions at times.
Saturday...mainly VFR.

&&

Marine...
minor changes were made with this update to reflect the latest
trends in observations and guidance. Main change was to
accelerate the end time of any precipitation.

Winds and seas build to Small Craft Advisory (sca) levels on
the coastal ocean waters today, and just below on the remaining
waters. A few 25 kt gusts cannot be ruled out especially on the
S shore bays. The Small Craft Advisory on the coastal ocean waters was extended
through tonight as seas stay in the 3-5 ft range, and may need
to be extended through Wednesday as the NE flow builds seas
once again. Winds below Small Craft Advisory levels elsewhere.

The waters around Long Island should experience a light to moderate
pressure gradient from Wednesday night-Saturday night, with winds
around 15 kt or less. Gusts to around 20 kt are possible on the
coastal ocean waters Wednesday night. Seas on the coastal ocean
waters could be around 5 ft, especially over the southern 1/2 of
each zone Wednesday night and Thursday. Otherwise, sub-Small Craft
Advisory conditions are expected from Wednesday night through
Saturday night.

&&

Hydrology...
up to 1-2 inches of rainfall can be expected with the shower and
thunderstorm activity through this afternoon. Some locally lower
and higher amounts are possible.

Rainfall rates of one inch per hour or greater can be expected
at times, especially this afternoon as the main frontal system
comes through. Some minor flooding can be expected, with a
chance for flash flooding, highest chances across western
sections of the region where Flash Flood Watch is in effect and
lower chances to the east.

No significant hydrologic impacts are expected from later tonight
through Monday.

&&

Equipment...
NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) remains off
the air for an extended period of time.

&&

Okx watches/warnings/advisories...
CT...Flash Flood Watch until 7 PM EDT this evening for ctz005-006-
009-010.
New York...Flash Flood Watch until 7 PM EDT this evening for nyz067>075-
176>179.
High rip current risk until 8 PM EDT this evening for nyz075-
080-081-178-179.
New Jersey...Flash Flood Watch until 7 PM EDT this evening for njz002-004-
006-103>108.
Marine...Small Craft Advisory until 6 am EDT Wednesday for anz350-353-
355.

&&

$$
Synopsis...jmc/maloit
near term...jmc/maloit/jm
short term...jmc

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