Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kokx 271151 

Area forecast discussion
National Weather Service New York New York
651 am EST Mon Feb 27 2017

high pressure centered south of Long Island will continue to
drift out to sea today. A warm front will lift north of the area
on Tuesday, followed by a secondary warm front approaching
from the south Tuesday night then pushes to the north
Wednesday. A strong cold front crosses the area Wednesday
night, followed by weak high pressure building in Thursday and
Thursday night. A clipper system passes near the area Friday,
followed by high pressure building over the area into Saturday
then to the southeast through Sunday.


Near term /through tonight/...
made minor changes this update to reflect the latest trends in
observations and guidance. The forecast appears on track.

A clear sky this morning will give way to rapidly increasing
mid and high clouds today. Based on satellite, the leading edge
over southwestern Pennsylvania gets here by 13z, with the
thickest stuff over the Ohio Valley arriving by noon. It should
be an overcast afternoon as a result. Subsidence today weakens
by 00z with some weak lift developing thereafter. At this point
however the deepest moisture will be exiting, so the forecast
has been kept dry right through tonight.

Temperatures will rebound quickly as the inversion breaks this
morning. The Pine Barrens on Long Island could be the big
Winner, where temperatures in the teens should shoot up around
20 degrees in a matter of minutes as the inversion mixes out.
The guidance was in good agreement and reasonable based on
temperatures aloft and southwesterly flow, so a blend was used
through the period.


Short term /Tuesday/...
the main question is whether it actually rains. The models
continue to back off, as they are just not supplying any
moisture to the region. With the Gulf of Mexico opening up,
there is a concern the models are not pumping enough moisture
into the flow. As a result, chances for precipitation have been
essentially been kept the same, with high chances by the end of
the day. With regard to temperatures, it will be mild again with
southerly flow. This temperature structure is likely to result
in enhanced sea breeze flow particularly across southern
portions of Queens and Nassau counties, as well as Brooklyn.


Long term /Tuesday night through Sunday/...
a deep layered ridge axis lifts to the northeast Tuesday night,
allowing for a moist SW flow to set up aloft, with southerly
flow at the surface - this set up continues into Wednesday
morning. This will allow for spotty light rain and areas of fog
over the tri-state from Tuesday night into Wednesday morning.

As the secondary warm front lifts to the north by Wednesday
afternoon, placing the region solidly in the warm sector, with
the surface flow going SW as well. There should be sufficient
instability at the surface inland and aloft over the County Warning Area for
scattered showers Wednesday afternoon (numerous far northwest zones)
with a chance of thunder northwest 1/3 of the County Warning Area and slight chance of
thunder elsewhere. Showalter indices lower below zero everywhere
Wednesday night, so increase chances of thunder to chance
throughout, and pops to likely everywhere during Wednesday
evening. Precipitation should tapper off from northwest to southeast Wednesday
night as a 700-500 hpa trough builds in aloft and colder/drier
low level air builds in behind the cold front.

With a 60-65 kt low level jet passing just to the south, around
500-1000 j/kg over western interior zones and 60-70 kt of bulk
shear, there is the potential for strong to possibly isolated
severe storms across NE New Jersey/lower Hudson Valley/SW CT Wednesday

Lows Tuesday night should occur in the evening, then should see
steady to slowly rising temperatures overnight. Wednesday should
be rather warm - with highs in the upper 60s to lower 70s across
NE New Jersey/lower Hudson Valley and northern NYC, and from around 60
to the mid 60s elsewhere. This is around 15 degrees above normal
and could approach record levels. See the climate section of the
afd for details.

The best cold push won't occur immediately behind the cold
front, as is fairly typical, so lows Wednesday night will still
end up closer to normal highs, if not a few degrees above them
(and 15-20 degrees above normal lows).

A northern stream trough exits to the east Thursday, followed by
zonal flow Thursday night. It should be dry through at least
Thursday evening as a result.

There are then timing/track differences between the models on a
clipper system with the GFS running faster/a little
stronger/a little farther north than the European model (ecmwf). The GFS has been
very consistent with this system so far, so opted for a blend of
the two models late Thursday night/Friday.

As a result, have introduced slight chance pops for snow late
Thursday night and maintained a chance for snow across northern
zones and snow and rain across southern zones on Friday. There is
still a chance this system could miss the area completely, so not
confident enough to go higher then low end chance pops at this
time. At this time though, it appears that any accumulations
should be relatively light, with a sub- advisory snow the most
likely outcome with this system.

Northwest flow aloft Friday night and Saturday gives way to northern
stream ridging passing to the north Saturday night and Sunday.
As a result it should be dry during this time frame.

Temperatures Thursday-Sunday were based on the superblend (with
European model (ecmwf) 2-M temperatures blended in Friday-saturday), and start
out above normal Thursday, go below normal Friday and Saturday,
then should return to above normal levels on Sunday


Aviation /12z Monday through Friday/...
VFR through the taf period as high pressure off the mid
Atlantic coast moves east. High confidence in SW flow less than
10 kt and increasing to 10-15g20kt by late morning and into the
afternoon. Winds will then diminish for tonight and back to the
S-southeast late.

..NY Metro enhanced aviation weather support...

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

Kjfk taf comments: start time of gusts may be off by +/- 2

Klga taf comments: start time of gusts may be off by +/- 2

Kewr taf comments: start time of gusts may be off by +/- 2

The afternoon kewr haze potential forecast is green...which
implies slant range visibility 7sm or greater outside of cloud.

Kteb taf comments: start time of gusts may be off by +/- 2

Khpn taf comments: start time of gusts may be off by +/- 2

Kisp taf comments: start time of gusts may be off by +/- 2

Outlook for 12z Tuesday through Friday...
Tuesday...chance of light rain/MVFR conds.
Tuesday night-Wednesday morning...areas of fog with light rain
continuing. MVFR/IFR and possibly lower. Low level wind shear possible with SW
winds 45-55 kt at 2kft. SW winds g15-20kt Wednesday morning.
Wednesday afternoon-Wednesday night...showers and a chance of
thunderstorms. MVFR or lower possible. SW winds g20-30kt. Winds
become westerly late Wednesday night.
Thursday...VFR. West-west-northwest winds g20-30kt.
Friday...MVFR/IFR possible with a chance of light snow. West-northwest
winds g20-25kt.


made minor changes this update to reflect the latest trends in
observations and guidance. The forecast appears on track.

Southwest winds will produce Small Craft Advisory conditions on
the eastern two thirds of the coastal ocean waters today and
tonight. Elsewhere, winds and waves are expected to remain just
below criteria at this time. For Tuesday, light flow will allow
seas on the ocean to remain below 5 feet.

Small craft conditions are possible on the coastal ocean waters
Tuesday night with seas maybe building to 5 ft on far southern
portions of those zones, with sub-small craft conditions
expected elsewhere.

A deep marine layer will keep the bulk, if not all of a 60-65 kt
low level jet from reaching the water Wednesday, but still
should see small craft conditions on all waters. The pressure
gradient remains tight Wednesday night, then low level cold
advection Thursday should allow for small craft conditions to
continue on all waters through most, if not all the day on

The winds should fall below Small Craft Advisory levels on all waters
Thursday night, but maybe not the seas on the coastal ocean
waters. There is the potential for Small Craft Advisory conditions on all waters
with a low chance of gales on Friday, depending on the exact
track and strength of a coastal low.


rainfall from Tuesday afternoon through Wednesday night should
run from 0.5 to 0.75 inches, with locally higher amounts

Release from Spring snow melt is occurring down the Connecticut
and Housatonic rivers.


record highs for Wednesday March 1

Location.......record high/year set.....Forecast high

Central Park............73/1972...............70
j f Kennedy.............58/2004*..............63

* = and in previous years

Okx watches/warnings/advisories...
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 am EST Tuesday for anz350-353.


Okx watches/warnings/advisories...
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 am EST Tuesday for anz350-353.


near term...12
short term...12
long term...maloit

National Weather Service Glossary of Abbreviations