Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
122 PM EST Monday Dec 22 2014
high pressure over the Canadian Maritimes slowly departs today as
low pressure approaches from the south. That low will weaken as it
moves north through the area Tuesday and Tuesday night. A more
significant storm system affects the area Wednesday through early
Christmas day with a cold front passing through late Wednesday
night into Thursday morning. High pressure builds in late Thursday
through Friday. A weak trough moves through dry Saturday into
Saturday night. Another low approaches from the south Sunday.
Near term /until 6 PM this evening/...
weak surface trough to the south of Long Island continues to generate
patchy light precipitation. Moisture is shallow...so where it is warm
enough...p-type is patchy drizzle...and where temperatures are closer to
freezing well inland across SW CT and adjacent portions of the
lower Hudson Valley...also flurries as it appears to be just cold
enough for ice nuclei to be present.
Meanwhile...breaks in the overcast have developed over far eastern CT
and along the South Shore of southeast Nassau/SW Suffolk counties. Do not
expect these to last long as additional clouds stream in from the
southwest and the east.
Otherwise...low pressure will develop over the middle-Atlantic area today
and will begin to lift north late as the high continues to depart.
Warm front associated with the low will push into SW zones late
afternoon/early evening. Some rain showers possible into NYC and
parts of NE New Jersey by the evening commute.
Highs today will range from the lower and middle 40s across coastal
zones to the upper 30s across the interior.
Short term /6 PM this evening through 6 PM Tuesday/...
warm front lifts north into the region this evening ahead of the
low. With cold air across the interior slow to depart...can expect
a period of freezing rain...mainly for Orange County...to develop
this evening and to last through much of tonight. Will go ahead
and hoist a Freezing Rain Advisory for Orange County from 6 PM
Monday through 4 am Tuesday. By early Tuesday morning...enough
warm air should surge northward to change precipitation to plain
rain...but not before a light ice accumulation develops. The
evening commute may become hazardous due to the ice.
Otherwise...temperatures will be warm enough to support plain rain for
the rest of the County Warning Area.
Low pressure then weakens as it tracks north along the coast...and
that low will move through the region during the day Tuesday
before departing Tuesday night. Think there will be a brief lull
in the precipitation Tuesday morning in between the first wave of precipitation
associated with the warm front and the second wave associated with
Low temperatures tonight will drop into the lower 30s across the interior
and will slowly rise during the overnight. Elsewhere...can expect
lows generally in the middle to upper 30s.
With warm air advection behind the warm front...highs on Tuesday will climb into
the middle and upper 40s for most areas...and into the low 50s for
Long term /Tuesday night through Sunday/...
some lift associated with the weakened low approaching from the
south brings the likelihood of light rain Tuesday night.
For Christmas evening and Christmas day...low pressure moves through
the Great Lakes region...sending a cold front across the County Warning Area late
night Wednesday into Thursday morning. Rain Wednesday and Wednesday
night. With a strong low level jet...the rain could be heavy at
times Wednesday afternoon and evening. By daybreak on Christmas...rain
will be likely only for a few hours across eastern Li and southeast CT.
Farther west...only a chance of a shower early on...so most of the
day will be dry. As for winds during this period...looks like we
will fall short of Wind Advisory criteria during Wednesday/Wednesday night
in spite of the strong low level jet that will passing over the
eastern zones. These stronger winds will have a difficult time
mixing down through a strong low level inversion. There is however
a chance of a few gusts getting up to near advisory criteria on
Thursday if GFS verifies. European model (ecmwf) is weaker with winds however. Best
guess right now is that we fall just below criteria...but gusts to
criteria are still not out of the question. Temperatures both days
will be above normal...in the 50s both days.
High pressure builds in on Friday with plenty of sunshine and
temperatures still above normals. For Saturday...a weakening cold
front approaches and either washes out or passes through as trough
Saturday night. Not much moisture with this feature...so kept a
dry forecast for both periods.
Models are in disagreement about what happens on Sunday. For a
couple of runs now...European model (ecmwf) has low pressure passing through or
nearby...with the GFS favoring a northern stream low pressure
center passing well to the north...dragging a cold front through
here. Will go with chance probability of precipitation for now. Will keep precipitation
type simple for now with just rain...snow...or a mix of the two.
Aviation /18z Monday through Saturday/...
weak low pressure will track slowly north from the middle Atlantic
coast today to just south of Long Island on Tuesday where it will
dissipate. This will place the area in an easterly flow with the
development of widespread IFR conditions and mainly light rain
Steady light rain is not likely until early this evening and will
continue through the overnight and taper off to a drizzle Tuesday
NE-east winds 5 to 10 knots...strongest near the coast where they could
get up to 10-15 knots tonight.
New York 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: timing of IFR conds and -ra could arrive an
hour or two earlier.
Klga fcster comments: timing of IFR conds and -ra could arrive an
hour or two earlier.
Kewr fcster comments: timing of IFR conds and -ra could arrive an
hour or two earlier.
Kteb fcster comments: timing of IFR conds and -ra could arrive an
hour or two earlier.
Khpn fcster comments: timing of IFR conds and -ra could arrive an
hour or two earlier.
Kisp fcster comments: varying ceilings this after...with IFR conds
possibly arriving earlier.
Outlook for 18z Tuesday through Saturday...
Tuesday afternoon-Tuesday night...IFR likely.
Wednesday-Wednesday night...high impact event likely. IFR with
occasional +ra. S/southeast winds 15-20g20-25kt possible. Low level wind shear probable
southern and eastern terminals. Winds shift to the SW late at
Thursday-Thursday night...improving to VFR in the morning from west
to east. West-southwest-northwest winds g30-35+kt likely.
Friday...VFR. West-northwest winds g20-25kt possible.
Saturday...VFR. SW winds g20 knots.
east-NE winds will increase this afternoon to 15-20 knots...with occasional
gusts to 25 knots on the ocean waters...as the pressure gradient
tightens between high pressure to the north and an approaching
warm front to the south. Then after a relative lull this
evening...the pressure gradient will tighten again over the
eastern ocean waters late tonight and Tuesday...with Small Craft Advisory in effect
for the ocean east of Moriches Inlet due to wind gusts up to 25 knots
and seas building to 4-6 feet. Small Craft Advisory may have to be expanded to all
ocean waters Tuesday night. All other waters should remain below
Small Craft Advisory criteria.
A deepening low pressure system over the Midwest Wednesday will
result in an increasing southerly flow...and gusts will increase
to small craft levels across all the waters by late Wednesday.
Then Wednesday night the wind gusts on the ocean increase to gale
A cold front associated with the low passes through the waters
late Wednesday night into early Thursday morning. Southerly wind
shifts to the west to northwest and becomes very gusty in the
colder air. Gale force gusts will probably for all waters during
Thursday before subsiding below gale force Thursday night...and
possibly below small craft by the end of Friday as high pressure
builds in. Seas on the ocean will however remain at criteria
levels through Friday.
rainfall from this afternoon through Thursday morning could total
1 1/2 to 2 inches with locally higher amounts. Much of the
rainfall is expected to occur Wednesday into Wednesday night.
Minor urban and poor drainage flooding is possible.
Dry weather returns Thursday afternoon through Saturday night.
New York...Freezing Rain Advisory from 6 PM this evening to 4 am EST
Tuesday for nyz067.
Marine...Small Craft Advisory from 1 am to 6 PM EST Tuesday for anz350.