Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service New York New York
953 PM EST Tue Feb 21 2017
high pressure drifts offshore tonight, as a weakening cold front
moves towards this area. This front then dissipates as it moves
into western portions of the area Wednesday, as the region comes
under the influence of high pressure centered well off the
Carolina coast through Thursday. A Spring-like pattern for the
end of this week will transition into a more seasonal pattern
for the second half of the weekend into the beginning of next
Near term /through Wednesday/...
just minor adjustments made to based on latest conditions.
Temperatures will fall little from here on out with cloud cover
and warm advection.
A deep layered ridge slides offshore this evening, allowing for
a northern stream 700-500 hpa shortwave to track across
southeastern Canada, as zonal flow sets up over the region.
All models show weak warm advection at 850 hpa late tonight, so
do bring in slight chance pops (chance far West Orange county) for
light rain after midnight.
Lows tonight were based on a blend of mav/met/ecs guidance and
NAM 2-meter temperatures and should be around 10-15 degrees
Short term /Wednesday night/...
the low level warm advection should come to an end by Wednesday
afternoon and a weak northern stream 700-500 hpa shortwave
ridge should build over the area, confining any light rain to
the morning hours. There does appear to be sufficient consensus
on the occurrence of the light rain to raise pops to chance
over all but the SW corner of the County Warning Area - where only slight chance
pops as the best warm advection should be north of there.
As the northern stream shortwave ridging slowly works east, it
appears that low-mid level drying should occur overnight,
leaving a moist near surface layer underneath. Noting SW-west-southwest
flow aloft, there is the potential for patchy drizzle/fog late
Wednesday night as well as some stratus with the second night
of onshore flow.
Highs Wednesday were based on a blend of mav/ecs/met guidance,
NAM 2-meter temperatures and a mix down from 975-950 hpa per
BUFKIT soundings. Highs should be around 10-15 degrees above
normal - with lowest departures over Long Island/S CT and
largest departures over NE New Jersey/lower Hudson Valley.
Lows Wednesday night were based on a blend of met/ecs/mav
guidance and NAM 2-meter temperatures and should be around 15-20
degrees above normal - and fairly close to normal highs for this
time of year.
Long term /Thursday through Tuesday/...
southwesterly flow into California and southerly flow from the Gulf
of Mexico per water vapor both indicate a mild pattern setting up
until a Pacific trough south of Alaska slowly tracks across the
Forcing will be limited Thursday and Friday to some weak
frontogenesis associated with a warm front Friday. This should be
the best chance for measurable rain. Otherwise, patchy drizzle and
fog, along with extensive cloud cover, are expected due to the
persistent onshore flow. This will limit temperatures both days,
especially across Long Island and Connecticut. There is the
potential for readings to soar into the 70s west of the Hudson River
on Friday if the clouds mix out due to a pure southerly flow as
opposed to southeasterly.
Showers will then be possible in the warm sector Friday night into
Saturday. However, the marine layer may set up over most of the area
and keep the region in the fog and drizzle. The Pacific trough
finally arrives over the weekend, and the associated cold front will
produce a round of rain across the forecast area. The European model (ecmwf) remains
about 6 hours slower than the GFS, so the probability for this rain
was capped at 70 percent and extended from Saturday afternoon into
A cooler airmass will build in for Sunday, although it won't be
particularly cold with 850 millibar temperatures around -9c and deep
mixing on westerly flow.
There is a bit of a break down in model consensus Monday and Tuesday
as the GFS continues to produce a weak system on Monday and
isentropic lift ahead of a warm from on Tuesday. The European model (ecmwf) has
nothing on Monday and a little with the warm front on Tuesday.
Chances for precipitation were capped at 30 percent.
Although the official forecast highs for Monday are generally in the
40s, this incorporates more of a model consensus coupled with
climatology. If the potential system were to be forecast explicitly,
highs would be in the 30s with mainly snow.
Aviation /03z Wednesday through Sunday/...
a weak cold front moving through the eastern Great Lakes region will
dissipate as the front approaches the region late tonight into
Wednesday. Meanwhile high pressure remains off the mid Atlantic and
North Carolina coast.
VFR. There is a slight chance of MVFR ceilings, 2500-3000 feet,
after 10z to around 15z, with a slight chance of light rain.
Winds southerly to light and variable inland. A south to southwest
flow is likely Wednesday. Wind speed is expected to be under 10 knots.
Outlook for 00z Thursday through Sunday...
Wednesday night...VFR early. Then MVFR to IFR possible late in
stratus and fog.
Thursday-Friday...MVFR, possibly lower, in stratus and fog.
Saturday...MVFR likely with showers.
Sunday...VFR...gusty northwest winds.
a relaxed pressure gradient over the waters around Long Island
tonight through Wednesday night will limit winds to 10 kt or
less and seas on the coastal ocean waters to 2 ft or less and
seas/waves on the non-ocean waters to 1 ft or less during this
Winds and seas are forecast to remain below Small Craft Advisory
levels from Thursday through Friday night. Small Craft Advisory
criteria is likely over the weekend associated with the
approach and passage of a cold front.
a few hundredths of an inch of precipitation or less is
possible through Friday night, with no hydrologic impact
Around an inch of rain is possible Saturday and Saturday night.
Thereafter, widespread significant precipitation is not
expected at this time.
the following are record maximum minimum temperatures for Wednesday
February 22, 2017 along with the forecast minimum temperature.
Record Max minimum temperature forecast minimum temperature
Central Park........46 (1996) 42
LaGuardia...........45 (2012) 42
Kennedy.............44 (1981) 41
Islip...............44 (1996) 40
Newark..............46 (1996) 41
Bridgeport..........39 (2002) 38
The following are record maximum minimum temperatures for Thursday
February 23, 2017 along with the forecast minimum temperature.
Record Max minimum temperature forecast minimum temperature
Central Park........55 (1985) 47
LaGuardia...........54 (1985) 47
Kennedy.............47 (1990) 43
Islip...............46 (1990) 40
Newark..............51 (1985) 46
Bridgeport..........40 (1985) 40