Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
836 PM EST Thursday Dec 18 2014
high pressure from the Great Lakes builds over the northeast
through the weekend. Low pressure will pass south of the area
Monday and Monday night. Strong low pressure will impact the
region Tuesday night through Wednesday night.
Near term /through Friday/...
cloud cover forecast remains tricky. Strato-cumulus from moisture trapped
under a strong inversion at 900 hpa has scattered out for a good
portion of the region for now. Have followed close to a blend of NAM
and GFS MOS along with persistence for the overnight cloud cover.
Winds diminish with sunset...but remain up overnight in the 5-10
knots range (around 10 in the New York metro). MOS min temperature guidance is
close. Have matched forecast to the NAM which is a degree or so colder
that GFS which may have overdone the cloud cover.
Short term /Friday night/...
cloud cover forecast is again the only issue seen as high pressure
builds in from the west. Northerly winds gradually diminish and
veer NE Friday night.
MOS blend seems very reasonable and was accepted for maxes and
mins. Temperatures are very close to...if not exactly...seasonable.
Note that the high clouds currently in Ohio will pass across the
local area this evening into the overnight. May have underdone
this in the sky cover grids - depending on if it turns more opaque
Long term /Saturday through Thursday/...
main feature during the long term period will be developing low
pressure that will impact the region on Christmas evening.
Surface high pressure currently over the Great Lakes will build east and
park itself nearly overhead this weekend. Meanwhile...a series of
500 mb shortwaves will pass through the region during this time.
With a lack of surface moisture and limited lift...not expecting much
than some light rain and/or snow...and will cap probability of precipitation at slight
chance for Saturday afternoon through Sunday. Temperatures this weekend
will be within a few degrees or normal...topping off in the upper
30s to around 40 on Saturday and in the low 40s on Sunday.
A new moon on Sunday...along with an onshore flow...may result in
minor coastal flooding for the start of the new week.
High pressure moves offshore on Monday. Deep upper trough will dig into
the central states with low pressure developing on Monday. Surface low pressure
will also develop at the base of the trough in the Gulf Coast
states. The secondary low moves towards the middle-Atlantic during the
day Monday before passing south of Long Island Monday night through
Tuesday. The parent low and deep upper trough will both continue to
track east early in the new week...and then another low will then
form over the middle-Atlantic as several strong shortwaves dive into
the base of the trough over the Gulf Coast.
This new low will intensify as it tracks along the coast on
Christmas evening. Models in good agreement with the low passing over
NYC and into New England. This will keep the region in the warm
sector and precipitation will be all rain...and may be heavy at times.
Cannot rule out convection and possible street flooding during the
day as well. A cold front will swing through the region Wednesday
night behind the departing low...ushering a colder air mass into the
region. Latest European model (ecmwf) has the low starting out as 993 mb near Cape
Hatteras at 12z Wednesday before ending up as a 965 mb low over
western Quebec at 12z Thursday. With a 28 mb drop in 24 hours...can
expect strong westerly winds...possibly to Wind Advisory criteria...
to develop on Christmas day.
Although models are in good agreement...this system is still a week
away...and many things can change before then.
Aviation /00z Friday through Tuesday/...
deepening low pressure will drift through the Canadian Maritimes
through the taf period.
Scattered 035-040 ceilings overnight with gusts diminish this evening.
On Friday...sct-bkn 035-040 ceilings...with low probability of MVFR ceilings at
kswf/khpn in morn/aft. Winds generally 320-360 degree magnetic
with speeds of 10-15 knots gusts near 20 knots.
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: winds generally right of 310 magnetic.
Klga fcster comments: winds generally right of 310 magnetic.
Kewr fcster comments: winds generally right of 310 magnetic.
Kteb fcster comments: no unscheduled amendments are expected.
Khpn fcster comments: low probability of 3000 feet ceilings Friday morning into
Kisp fcster comments: no unscheduled amendments are expected.
Outlook for 00z Sat through Wednesday...
Sat night...MVFR or lower in ceilings. Light east winds.
Sunday...MVFR or lower in ceilings. Light east winds.
Monday...VFR. MVFR or lower possible in onshore southeast flow.
Monday night-Tue...IFR likely at times in rain...ceilings and visibilities. Southeast winds
Wednesday...high impact event possible...IFR likely with heavy rain and
strong gusty southeast winds 25kt+ shifting to west late.
the pressure gradient has weakened enough that the wind and gusts
across the Long Island bays...New York Harbor and Long Island
Sound have diminished below small craft levels. Therefore the
advisory has been cancelled.
Wind gusts remain above 25 knots on the ocean waters and seas were
slowly subsiding...around 4 and a half feet. Expected gust next
few hours to remain around 25 knots and will continue the small craft
for the ocean waters.
High pressure builds from the west on Friday with tranquil conds on the
waters that continue into Monday.
Low pressure passes south of Long Island Monday night and Tuesday...and
conds may build to Small Craft Advisory levels during that time. A stronger low will
impact the waters Wednesday through Thursday...resulting in at least
Small Craft Advisory conds on the waters with gales possible
starting on Thursday.
no measurable precipitation through Sat with no Hydro impacts into early
1/4 to 1/2 inch of rain is possible Monday afternoon through Tuesday
as low pressure passes south of Long Island. Some wet snow is possible
Monday afternoon...and then again Monday night across the lower
Hudson Valley and interior portions of southern CT. No hydrological
Rain on Wednesday may average 1-2 inches across the region. Minor
street flooding is possible.
Marine...Small Craft Advisory until 6 am EST Friday for anz350-353-355.