Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New York New York
141 PM EST Thursday Mar 5 2015

a series of weak low pressure systems will track along an Arctic cold
front moving further south of the area today. Canadian high pressure
builds in tonight through Friday...then builds to the south
through early next week as several weak impulses pass to the
north. The high slides offshore Monday night and Tuesday. A cold
front passes through on Wednesday...followed by Canadian high
pressure for Thursday.


Near term /until 7 PM this evening/...
upgraded Winter Weather Advisory to Winter Storm Warning for southern
Middlesex and southern New London counties in CT based on current snowfall
observations and near term forecast trends.

Back edge of heavy snow band is moving southeast from across central New Jersey NE across
southeast CT...with hourly snowfall rates of 1 inch plus.

At 18z/1 PM...5.5 inches at Central Park...5.0 inches here at the
National Weather Service office with more than 4 inches at JFK and LGA airports.

We are on track for a widespread 6-8 inch snowfall across the
warning area.

Redevelopment of snow continues across northwest New Jersey with a lighter band possible
across the region from 19z-21z.

Will be dropping advisory across the northern interior with the
next forecast update as dry Arctic air continues to filter southeast across
this region with dew points already near zero.

Difficult travel conditions expected through this afternoon with snow
covered roads and temperatures dropping through the 20s causing icing
of untreated surfaces.

For the latest snowfall amounts refer to the latest public information
statement under the National Weather Service web Page top news of the day.

Snow should end from northwest to south-southeast between 00z and 03z...with frigid and
dry conditions tonight.

Temperatures expected to drop into the single digits...lower teens NYC
metropolitan...on gusty northwest winds. Wind chills likely dropping to around
zero for much of the region by Friday morning.


Short term /7 PM this evening through 6 PM Friday/...
high pressure builds in from the west tonight. Skies will clear
from west to east. Winds should diminish late and with dry
conditions...expecting an unseasonably cold night with
temperatures falling into the single digits for most locations and
lower to middle teens in the NYC metropolitan.


Long term /Friday night through Thursday/...
a mean trough will remain east of The Rockies through early next
week. A split flow then develops across the Continental U.S. With a fast active
northern stream across southern Canada and a broad trough in the
southern stream extending from the central US through Mexico. Zonal
500 mb flow develops across the northeast as a result.

Overall...expect mostly dry conditions with highs warming into the
40s by the middle of next week. A decent shortwave moves through the
northeast Friday night...but strong subsidence with limited moisture is
expected to keep the local area dry. A trough of low pressure
approaches the area Sat and moves through Sat night. Down sloping
flow aloft will likely keep precipitation confined to the windward side of
the Appalachians with only perhaps flurries or a few snow showers at
best late Sat night. The NAM/GFS are indicating a weak low pressure
system moving from the Great Lakes through the New England on
Sunday. Ec is much weaker with no precipitation. Have maintained dry forecast
as precipitation remains confined mainly to the north where better dynamics are

Final northern stream shortwave passes through Monday. GFS is slightly
more amplified aloft with the vorticity maximum passing directly over the
area...although not much precipitation due to ridging nosing in from the S.
Ec is further north. Have maintained schc probability of precipitation.

SW-west flow aloft then develops at 500 mb...although large differences
become prevalent by the middle of the week. The GFS becomes much
more amplified Wednesday/Thursday with southern stream energy becoming picked
up in the flow and passing near the area Wednesday. Ec is much flatter
with dry weather prevailing. Remaining dry weather then prevails
possibly until middle week.

Temperatures will start off below normal with lows in the teens Friday night
and lower 30s Sat...but a moderation will then commence early next
week as heights aloft gradually rise...with temperatures near normal in the
middle to upper 40s for highs and lower 30s for lows next week.


Aviation /19z Thursday through Tuesday/...
periods of moderate to heavy snow continue near the coast through
the afternoon. Radar data and latest hrrr guidance strongly
suggest last band of heaviest snow will cross NYC terminals between
18-21z so we have extended period of heavier snow by an additional
1-3 hours in taf. Based on the latest data...back edge of snow
should swing through region by 00z and expect VFR to return after
00z. Kswf is already north of the heaviest MVFR to VFR
is expected.

Winds will be out of the northwest around 10-12 knots through tonight with
some gusts to 15-20 knots this afternoon. Winds diminish late tonight
into Friday.

Overall...higher confidence with winds and lower confidence with
categorical changes which could vary a few hours with subsequent

Expected runway snow accumulations:
kisp...6-8 inches.
Kjfk/klga/kewr/kteb/kgon...4-6 inches.
Khpn/kbdr...3-5 inches.
Kswf...1-2 inches.

... 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: forecast timing of category changes could
differ 1-3 hours from observed.

Klga fcster comments: forecast timing of category changes could
differ 1-3 hours from observed.

Kewr fcster comments: forecast timing of category changes could
differ 1-3 hours from observed.

Kteb fcster comments: forecast timing of category changes could
differ 1-3 hours from observed.

Khpn fcster comments: forecast timing of category changes could
differ 1-3 hours from observed.

Kisp fcster comments: forecast timing of category changes could
differ 1-3 hours from observed.

Outlook for 18z Friday through Tuesday...
Fri-Tue...mainly VFR.


Small Craft Advisory conditions continue on the coastal ocean waters
into Friday morning as a series of low pressure waves tracks to the
south of the waters and high pressure builds in from the west.
Marginal Small Craft Advisory gusts today...with strongest winds tonight. Seas will
run 4 to 6 feet through the period...with southerly swells predominant

Light freezing spray expected to develop this afternoon across the
ocean waters...possibly becoming moderate late tonight. A period of
freezing spray possible on Li sound as well late tonight.

Sub Small Craft Advisory conds return Friday as high pressure builds over the waters.

Small Craft Advisory conds are possible...mainly on the ocean waters Sat in the wake
of a trough of low pressure. Otherwise...sub-advsy conds are expected
through the period.


1/10 to 7/10 inch liquid equivalent precipitation today. This
will be hydrologic impacts are not expected.

No significant precipitation is expected through early next week.
However...temperatures forecast to warm into the 40s may result in the
start of ice break up on area rivers and streams.


National oceanic and atmospheric administration weather radio weekly test will be delayed until Friday between
11 am and noon due to on going hazardous weather.


Okx watches/warnings/advisories...
CT...Winter Storm Warning until 7 PM EST this evening for ctz011-
Winter Weather Advisory until 7 PM EST this evening for
New York...Winter Storm Warning until 7 PM EST this evening for
Winter Weather Advisory until 7 PM EST this evening for
New Jersey...Winter Storm Warning until 7 PM EST this evening for njz006-
Winter Weather Advisory until 7 PM EST this evening for njz002-
Marine...Small Craft Advisory until 11 am EST Friday for anz350-353-355.


near term...gc
short term...Nevada
long term...24

National Weather Service Glossary of Abbreviations