Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1112 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/...
700 and 500 hpa shortwaves are more disjointed in their passage
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. Overcast skies already in place though may limit the
heating today...minimizing any threat of convection.
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
2-meter temperatures. Temperatures on track for the day.
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 /15z Friday through Tuesday/...
high pressure slowly builds southward into the region through the
taf period. Conditions vary between MVFR/VFR today and mostly MVFR
tonight. Shower activity confined to near kswf. Generally east flow
around 8-10 knots through taf period.
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: there is a chance ceilings could lower to MVFR
between 2k-3kft before 02z.
Klga fcster comments: there is a chance ceilings could lower to MVFR
between 2k-3kft before 02z. NE flow could last 1-2 hours later
than indicated in taf before switching to more east flow.
Kewr fcster comments: MVFR could linger with ceilings between 2k-3kft
16-18z. There is a chance of MVFR 18z-02z.
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: MVFR could linger with ceilings between 2k-3kft
16-18z. There is a chance of MVFR 18z-02z.
Khpn fcster comments: MVFR could occasionally improve to VFR through
Kisp fcster comments: MVFR could occasionally improve to VFR through
Outlook for 12z Sat through Tuesday...
Sat...becoming VFR with east-northeast flow.
winds and seas forecast appears on track for today.
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 1/4 an inch or less with any rain showers/thunderstorms
through early afternoon...then mainly dry through Saturday. No significant
hydrologic impact is expected from any precipitation through the
first half of next week.
long term...precipitable water