Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service New York New York
153 am EDT Wednesday Apr 16 2014

Synopsis...
a strong cold front will continue out to sea overnight. High
pressure then builds in from the Ohio Valley on Wednesday. The
high then lifts up into the Canadian Maritimes Wednesday night
into Thursday and up into the North Atlantic on Friday. A low
pressure system develops along a stalled front to the south Friday
night and passes east of the region on Saturday. High pressure
returns Sunday into Monday before shifting offshore with the
approach of a cold front on Tuesday.

&&

Near term /until 6 am this morning/...
the cold front was moving through Cape Cod early this morning as
high pressure was building over the region. Rain was transitions
to light snow before ending as the cold air moves into behind the
front. At midnight the snow was as far east as central southern
Connecticut...near bdr to just west of Islip. And the snow was
ending across western Orange County and into western Passaic
County. Forecast probability of precipitation and precipitation type on track. Updated wind and
temperatures for current conditions.

Slowed the ending of precipitation across the County Warning Area due to the
slower trend indicated by radar...supporting the slower 18z NAM
solution.

Overnight lows will be in the middle 20s to around freezing. Thus...
the freeze warning has been expanded to also include NYC...Long
Island...and coastal CT. This is in addition to most of NE New Jersey and
Rockland and Westchester counties in New York. Guidance has been
trending colder. Based on the anomalously cold air mass...used
model 2m temperatures for lows...which was several degrees below MOS
guidance. Lows will be close to records.

&&

Short term /6 am this morning through 6 PM Thursday/...
high pressure builds east from the Ohio Valley on Wednesday with an
anomalously cold air mass. Highs will be in the middle and upper
40s...which is some 10 to 15 degrees below normal. Gusty northwest winds
will linger into the after...making it feel more like the middle and
upper 30s.

Wednesday night will feature another possible record cold night with
most locations outside of the NYC metropolitan dropping below freezing.
Another freeze is possible.

&&

Long term /Thursday night through Tuesday/...
at the beginning of the long term on Thursday and Friday...the
region will be on the west side of upper level ridging across the
western Atlantic with a trough across the central states. At the
surface...high pressure over New England Thursday shifts into the
Canadian Maritimes by Friday. This pattern sets up an east to
northeasterly flow in the low levels. This onshore flow serves to
keep temperatures on the cool side with readings in the upper 40s
and lower 50s on Thursday and lower and middle 50s on Friday.
Increasing low level moisture late Thursday night into Friday
morning could promote drizzle or light rain...mainly across
southern zones. Have included slight chance probability of precipitation during this time.

The trough across the central states approaches Friday night into
Saturday with a wave of low pressure developing along a stalled
front offshore. Much of the guidance keeps the low far enough
offshore to prevent a widespread precipitation event. The models differ on
the amplitude...timing...and placement of the vorticity maxima
within the upper trough however. At the very least...Saturday will
be mostly cloudy and have continued a chance for showers with the
upper trough passage. Due to clouds and
precipitation...temperatures continue below normal in the 50s.

A general zonal flow sets up on Sunday and continues into Monday.
Surface high pressure builds back in during this time with dry
conditions. Slightly below normal temperatures will continue on
Sunday and then warming to near normal on Monday.

A shortwave and associated cold front may approach on Tuesday
bringing a chance for showers. High uncertainty exists at this
time so have only included chance probability of precipitation. Temperatures should be
near normal in the 60s.

&&

Aviation /06z Wednesday through Sunday/...
cold front continues to work its way across the terminals...and
then high pressure builds over the area into this evening.

Conds will improve from west to east from MVFR/IFR to VFR as the
back edge of the precipitation works its way across the region. By
08z...conds should be VFR throughout.

Main issue will be the winds. Northwest winds...320-350 true...will range
from 15-20 knots with 25-30 knots gusts through this morning. Winds
gradually diminish during the day as winds veer to the north. Wind
gusts should abate by late afternoon as the winds continue to veer
to the north.

Outlook for 06z Thursday through Sunday...
Wednesday night-Thursday...VFR. East wind g around 20kt possible.
Thursday night-Friday night...VFR.
Saturday...possible MVFR conditions with low chance of -shra. West-northwest
wind g25-30kt possible.
Saturday night-Sunday...VFR

&&

Marine...
seas on the ocean waters have begun to subside in the northwest
flow and have been running a foot to 2 feet below forecast
values...so lowered seas through early Wednesday morning.

Gale Warning in effect for all waters for northwest flow up to 35 knots
overnight.

Marginal Small Craft Advisory conditions are then possible on Wednesday...mainly with
lingering 5 feet seas.

Small Craft Advisory winds and seas likely on Thursday as easterly flow increases.
Winds will trend below Small Craft Advisory levels Friday but seas on offshore waters
should stay above Small Craft Advisory through Friday night. Winds and seas will
relax on Saturday as region weaker flow sets up over the waters.
Seas and winds could return to Small Craft Advisory levels on Sunday with increased
northwesterly flow.

&&

Hydrology...
the heaviest rainfall has ended across the region. In general...up
to 3/4 of an inch of additional precipitation can be expected...with
the highest amounts east of NYC.

Note...minor flooding continues along the Connecticut River.
Additional heavy rainfall will likely cause water levels to continue
to rise through the week...with potential for moderate flood levels
to be reached. Monitor the latest flood warnings from National Weather Service Taunton Massachusetts.

No significant precipitation is expected from Thursday into early
next week.

&&

Climate...
record lows for Wednesday April 16:

Ewr - 26 in 1943 forecast low - 29
bdr - 29 in 1981 forecast low - 29
NYC - 29 in 1928 forecast low - 29
LGA - 31 in 1943 forecast low - 29
JFK - 33 in 1962 forecast low - 30
isp - 32 in 2008 forecast low - 30

&&

Okx watches/warnings/advisories...
CT...freeze warning until 10 am EDT this morning for ctz009>012.
New York...freeze warning until 10 am EDT this morning for nyz069>075-
078>081-176>179.
New Jersey...freeze warning until 10 am EDT this morning for njz004-006-
103>108.
Marine...Gale Warning until 6 am EDT early this morning for anz330-335-
338-340-345-350-353-355.

&&

$$
Synopsis...jmc/ds/dw
near term...jmc/dw
short term...dw
long term...ds
aviation...mps
marine...jmc/ds/dw
hydrology...ds/dw
climate...