Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
728 am EDT Friday Aug 22 2014
multiple upper level disturbances cross the tri-state through
Saturday...as high pressure builds down from southeastern Canada.
This high continues to build over the area early next week...then
passes east by middle to late week.
Near term /until 6 PM this evening/...
precipitation tapering off this morning...so have significantly
lowered probability of precipitation and also removed thunder from this morning.
Otherwise...only minor changes made to reflect the latest trends
in observations and guidance. Remainder of forecast appears on
700 and 500 hpa shortwaves are more disjointed in their passage
during the day today...and focused mainly over the west portion of
the County Warning Area...so focus chance probability of precipitation there...with mainly dry conditions
over far east portions of the County Warning Area. Showalter indices are forecast to
be around zero across roughly the SW 1/2 of the County Warning Area...so have
isolated thunder in that area this afternoon to account for
possibility of mainly elevated embedded thunderstorms that form
along with isolated-scattered rain showers there.
Soundings suggest at best broken cloud coverage with at most
occasional peaks of sun. This supports highs 5 degrees or so
below normal - consistent with a blend of mav/met guidance and NAM
Short term /6 PM this evening through Sunday night/...
700-500 hpa trough axis approaches tonight...then pushes to the S
Saturday. Do restrict probability of precipitation this evening mainly to the northwest 1/2 of
the County Warning Area...and mention of thunder to the SW 1/2 of the County Warning Area - as
this is the only area where have any forecast instability - once
again mainly aloft. Precipitation chance fall off fairly rapidly
after midnight Friday night. Note the European model (ecmwf) is the only model
showing any precipitation late Friday night/Saturday morning so
have discarded as an outlier for now. Do expect rain showers to return
mainly across the northern tier Saturday afternoon ahead of the
final vorticity lobe right in the wake of the 700-500 hpa trough
For lows tonight used a blend of mav/met guidance with NAM 2-meter
temperatures...with once again abundant cloud cover expected. Lows
should be near to slightly above normal. For highs Saturday...with
the potential for some sunshine in the late afternoon...used
a blend of mixing down from 875 hpa with NAM 2-meter temperatures
and a blend of mav/met guidance. Highs should be around 5 degrees
Even with NE low level flow...will see gradual clearing from
Saturday night through the remainder of the weekend as deep
layered ridging builds over the area and surface high pressure
builds down from southeast Canada. Expect this time frame to be dry as a
Lows Saturday night were based on a blend of mav/met guidance with
NAM 2-meter temperatures...and should be near to slightly below
normal. For highs Sunday used a blend of mav/met guidance with NAM
2-meter temperatures and a mix down from 875 hpa per BUFKIT
soundings. This yields values a couple of degrees below normal.
For lows Sunday night used a blend of mex/men/ekd/ece/ecm/wpc
guidance with NAM 2-meters. Expect lows to be around 5 degrees
Long term /Monday through Thursday/...
amplified pattern early on with large ridge building through Tuesday
before flattening and giving way to upstream trough later Wednesday
Surface high pressure over the area slowly drifts offshore Tuesday
and Wednesday...as a cold front approaches Thursday from the west.
Expect dry and seasonable conditions through the middle of next week
courtesy of the ridge. Temperatures slowly modify from slightly below normal
Monday...to near or even above normal by middle week.
Aviation /12z Friday through Tuesday/...
high pressure builds southward into the area today.
Ceilings right around 3000 feet today...so bouncing between MVFR and
VFR is likely. Scattered-broken cumulus should begin to pop this morning as temperatures
approach 70. Solid MVFR is expected tonight...with broken MVFR ceilings Sat.
Some variability in wind direction early...becoming around 100
true through most of the taf period. Slight backing to around 080
true expected tonight. Speeds generally blw 12kt.
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: ceilings likely to bounce from VFR to MVFR
today. Vrb wind between 100 and 060 true through 15z.
Klga fcster comments: ceilings likely to bounce from VFR to MVFR
today. Some vrb wind between 100 and 070 true through 15z.
Kewr fcster comments: ceilings likely to bounce from VFR to MVFR
today. Light and vrb wind possible until 15z.
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: ceilings likely to bounce from VFR to MVFR through
at least 15z.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 12z Sat through Tuesday...
Sat...becoming VFR with east-northeast flow.
minor changes made to reflect the latest trends in observations
and guidance. Forecast appears on track.
For now forecasting sub-Small Craft Advisory conditions on all waters through
Sunday night. However a persistent east-NE flow of 10-15kt with gusts
up to 20 knots from tonight into Sunday night over the coastal ocean
waters could possibly builds seas to at least 5 feet by late
Saturday. However...latest wavewatch iii guidance shows seas only
reaching 4 feet...so have forecasted accordingly for now but cannot
rule out seas ultimately being 1-2 feet higher than this over the
coastal ocean waters from late Saturday into Sunday night.
Elsewhere through Sunday night...winds will be mainly 10 knots or
less over the remainder of the waters around Long Island.
High pressure builds over the waters Monday and Tuesday resulting in
light winds and rather tranquil seas.
forecasting generally 1/3 an inch or less with any rain showers/thunderstorms
through this morning...then mainly dry through Saturday. No
significant hydrologic impact is expected from any precipitation
through the 1st half of the weekend.
It should then be dry into the middle of next week.
long term...precipitable water