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Area forecast discussion 
National Weather Service New York New York
1226 am EST Friday Feb 12 2016

Synopsis...
low pressure over the Canadian Maritimes continues to lift to the
northeast...while high pressure to the west builds across the Middle
Atlantic States by morning. An Arctic cold front will approach
Friday night...and pass through toward daybreak Saturday. Arctic
high pressure then builds in from the west...settling right across
the region Sunday night. The high pressure area shifts east of the
region Monday...with a developing low well west of the region that
will be approaching. The low moves across Tuesday through Tuesday
night. Another cold front moves across Wednesday with high
pressure starting to build thereafter.

&&

Near term /until 6 am this morning/...
clouds have mostly dissipated across the region and skies were
mostly clear as high pressure and drying air moves into the
region. Winds and gusts were also diminishing as cold advection
weakens.

Very cold temperatures tonight combined with the gusty winds will
produce wind chill values in the single digits. Some readings may
even be near or below zero. Used a met/mav MOS blend for overnight
lows...ranging from single digits inland...to the lower and middle
teens at the coast. This is below normal by 10 to 15 degrees.

&&

Short term /6 am this morning through 6 PM Saturday/...
another cold day is on tap for Friday with highs in the lower to middle
20s. Winds will be substantially lighter as high pressure passes
south of the area in the morning. An amplified upper flow with
ridging across western North America then allows the polar vortex to
drop south across Hudson Bay and into southeast Canada Friday into Friday night.
This will send an Arctic cold front over the upper Great Lakes Friday
morning into the lower lakes by Friday evening...with the cold frontal
passage toward daybreak Sat.

Middle and high level clouds will move into the area Friday after and
then lower as large scale height falls move into the area in the
evening. There looks to be enough moisture and lift for scattered snow
showers. Models also have been showing a higher probability across
eastern Li/southeast CT after midnight as a weak inverted trough sets up to
the northwest of a coastal low passing well south and east of the area. At
this time...not expecting much more than a dusting...but perhaps a
light accumulation across eastern areas is not out of the question.
Confidence is low for measurable snow at this time.

Temperatures Friday night will actually be nearly steady in the upper teens to
the lower 20s...before dropping off sharply behind the Arctic cold
front Sat morning. Readings will be in the lower teens by morning
across the interior...to the middle and upper teens at the coast.

&&

Long term /Saturday night through Thursday/...
looking at the large scale with the upper level jet stream...this is
well south of the region for this weekend into Monday. The jet
splits for Monday night through Tuesday. A jet streak maximizes in
speed west of the region Tuesday...associated with a negative
tilting sharpening trough. The jet again pushes south of the region
for the middle of next week with a ridge to the west approaching for
next Thursday.

A deep middle level low at 500mb pushes south into New England Saturday
and moves east towards Nova Scotia Saturday night into Sunday. More
of a split flow at 500mb after that with weak shortwave approaching
from the west for early next week. The trend for geopotential
tendency at this level will be positive Sunday night through Monday.
A sharpening trough approaches Monday night and moves across Tuesday
into Tuesday night. A general negative trend resumes thereafter in
the height tendency with another large shortwave trough moving in
for Wednesday and Wednesday night timeframe.

Extremely cold weekend with highs staying below 20 degrees. Wind
chills range -15 to -30 Saturday night into early Sunday...coldest
across the interior where wind chill watch has been issued.
Overall...wind chills stay in the single digits to below zero for
much of the weekend. Some rebound in temperatures early next week
especially Tuesday with warm air advection allowing for
temperatures in the upper 40s to near 50.

Precipitation...snow showers Saturday mainly south of Long Island in
response to inverted trough. The high pressure area still well west
of the region. The high moves closer Saturday night into Sunday.
Gusty winds Saturday and Saturday night with a decrease in winds
Sunday as high center approaches. The high center moves overhead
Sunday night and offshore Monday. Another low approaches from the
west Monday night and moves across Tuesday into Tuesday night.
Initially winter precipitation will transition to all rain Tuesday which
could be potentially heavy at times.

After the low...cold air advection resumes but no extreme cold is
expected. The temperatures will trend to close to normal. There will
be another chance for snow showers Wednesday into Wednesday evening
as another cold front moves across. Drier trend to weather late
Wednesday night into next Thursday with high pressure returning from
the west.

&&

Aviation /05z Friday through Tuesday/...
weak high pressure remains over the region into Friday. An Arctic
cold front will move through the region towards daybreak Saturday.

VFR. Moderate to high confidence in wind forecast. Gusts will
linger through 08z to 10z before diminishing and become SW on
Friday. Occasional gusts up to 20 knots possible at NYC terminals Friday afternoon.
Arctic front approaches Friday night and may trigger some flurries or
snow showers with MVFR conds. Probabilities are too low to
include in the tafs at this time.

Outlook for 06z Friday through Tuesday...
late Friday night-Saturday...mostly VFR. Chance MVFR in widely scattered
flurries/snow showers. Northwest winds 15-25g25-35kt developing Sat
morning.
Sunday...VFR.
Monday...VFR daytime...chance sub-VFR with snow and rain/snow mix at
night.
Tuesday...sub-VFR and rain. Chance mixed precipitation early. Southeast-S gusts to
30kt possible. Chance low level wind shear.

&&

Marine...
wind gusts have been slowly diminishing through the evening and
have fallen below gale force across the Long Island Sound waters
and the Long Island bays. Wind gusts were still up to 30 knots...and
will continue to diminish through the overnight. Wind gusts on the
ocean waters were right around 35 knots. So will continue the Gale
Warning on the ocean waters and downgraded the Gale Warning to a
Small Craft Advisory on the remainder of the waters.

As high pressure continues to build in winds and gusts will
continue to diminish and the advisories and warnings may be
discontinued before 600 am.

Sub Small Craft Advisory conditions are forecast Friday into Friday night as SW winds
develop ahead of an approaching Arctic cold front. Frontal passage
is forecast around daybreak Sat with northwest gales developing soon
thereafter.

Rough conditions for all waters this weekend. Gales likely
Saturday and Saturday night. Gales prevail into early Sunday before
decreasing to 20-30 knots during the day. Freezing spray expected as
well this weekend for most of the waters. Weak pressure gradient
Sunday night through Monday night will lead to below Small Craft Advisory conditions.
Conditions trend back up though ahead of low pressure next Tuesday
with Small Craft Advisory becoming probable once again.

&&

Hydrology...
liquid equivalent of less than a tenth of an inch is forecast Friday
night in the form of snow showers.

Low pressure moving up the coast has potential to produce liquid
equivalent quantitative precipitation forecast at least 1 to 2 inches. Part of this will fall as
snow initially...but then runoff via melting snow and heavy rain
Tuesday into Tuesday night could cause at least Urban and Small Stream
flooding problems. It is too early to say if main Stem rivers
would be affected.

&&

Climate...
with the extremely cold air mass forecast Saturday into
Sunday...record minimums and record low maximums may be reached.
Here are the records and forecasts...

Station......record/fcst minimum...record low maximum/forecast high
for 2/14 for 2/14

NYC...........2 (1916) / 3.............17 (1979) / 16
LGA...........1 (1979) / 5.............15 (1979) / 16
JFK...........4 (1979) / 4.............17 (1979) / 17
isp...........7 (2015) / 0.............26 (1987) / 14
ewr...........0 (1979) / 2.............15 (1979) / 16
bdr...........3 (2015*) / 0.............18 (1979) / 15

*in 1979 as well

&&

Okx watches/warnings/advisories...
CT...wind chill watch from Saturday evening through Sunday morning
for ctz005>012.
New York...wind chill watch from Saturday evening through Sunday morning
for nyz067>070.
New Jersey...wind chill watch from Saturday evening through Sunday morning
for njz002-103.
Marine...Small Craft Advisory until 6 am EST early this morning for
anz330-335-338-340-345.
Gale Warning until 6 am EST early this morning for anz350-353-
355.

&&

$$

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