Scientific Forecaster Discussion

Return to Local Conditions & Forecast
Area forecast discussion 
National Weather Service New York New York
218 PM EDT Friday Apr 18 2014

Synopsis...
a weak trough pushes north of the region late tonight with another
area of high pressure then building down from southern Canada
through the weekend. The high then slowly slides to the east into
Tuesday. A frontal system will impact the area from Tuesday into
Wednesday. High pressure then builds down from south central
Canada into Thursday.

&&

Near term /until 6 PM this evening/...
clouds are holding a stronger influence in terms of maximum
temperatures this afternoon. While low level clouds have
scattered...many middle and high clouds remain...mitigating solar
insolation. Hence...maximum temperatures were lowered slightly again with the
update. Maximum temperatures expected to range from upper 40s to lower 50s
with lower 50s across most western areas such as Orange
County...farthest away from the easterly wind.

Generally dry weather today with high pressure slowly pushing to the
northeast as a weakening front approaches from the north and west.
General model consensus has trended in keeping the front to the
north...with no precipitation expected to impact the area as the main
northern stream energy remains over northern New England as well.
A passing vorticity maximum will keep the middle and high level clouds for
the remainder of the afternoon. Despite a warming trend with
warm air advection...the combination of the northeast flow...and cloud cover will
help to keep temperatures still around 12 degrees below normal.

&&

Short term /6 PM this evening through 6 PM Saturday/...
surface high retreats to the northeast by tonight...with a weak
trough setting up briefly over New England. The trough is quickly
replaced by the next high pressure...building south and east from
Canada. Upper level trough swings through tonight but again main
forcing is to the north and with little to no forcing at the surface
along with minimal moisture...should see a dry night. Ridging sets
up quickly behind the departing trough for Saturday and with
building subsidence...Saturday looks to be a dry and sunny day once
the morning clouds scatter out. Temperatures expected to rebound
back to near normal for tonight...and then even a few degrees above
normal on Saturday with downsloping influence.

Increased winds and low relative humidity values on Saturday could lead to an
enhanced risk of fire spread. Northwest winds will increase...with
sustained 10-15 miles per hour...and gusts up to 20 miles per hour during the
afternoon...corresponding with relative humidity values dropping to around 30
percent.

&&

Long term /Saturday night through Thursday/...
a northern stream ridge builds over the area Saturday night and
Sunday...then slides to the northeast Sunday night. Associated
subsidence should keep the area dry and with minimal cloud cover in
this time frame. For lows Saturday night used a blend of mav/met
guidance...with values near normal in NYC proper...and a few degrees
below normal elsewhere. For highs Sunday used a blend of mixing down
from 925-875 hpa per BUFKIT soundings...with NAM 2-meter
temperatures and a blend of mav/met guidance. Expect readings to be
slightly below normal. For lows Sunday night used a blend of NAM
2-meter temperatures with a blend of mex/men/ekd/ece/ecm/wpc
guidance...with values a few degrees below normal.

Another northern stream ridge builds over the area Monday...then
exits to the northeast Monday night. Associated subsidence will keep
things dry...but could see an increase in mainly middle to high clouds
by late Monday night ahead of an approaching developing full
latitude trough.

Trough continues to sharpen as it slowly moves east into the western
Appalachians on Tuesday...with any precipitation ahead of it likely
confined to the northwest 1/3-1/2 of the County Warning Area. As the trough moves into east
PA/upstate New York Tuesday night...and begins to take on a bit of a
negative tilt...would expect widespread showers across the County Warning Area
Tuesday night. However...noting some differences in model
timing...and inherent uncertainty this far out...have capped probability of precipitation at
chance at this time.

Some uncertainty as to how quickly the precipitation exits to the east
on Wednesday...though the 00z European model (ecmwf) has come closer to the 00z CMC
and GFS when compared to the 12z European model (ecmwf). Main question is how soon
will a cutoff low develop as the trough continues to negatively tilt
as it lifts northeast...and how quickly will this cutoff lift to the
NE. For now...have leaned towards the slightly slower European model (ecmwf)
solution...as slower is often the better forecast with negatively
tilted systems. As a result do have slight chance probability of precipitation over most of
the area Wednesday morning...and the NE 1/3 of the County Warning Area Wednesday
afternoon.

A deep layered ridge begins to build in from the Midwest Wednesday
night and Thursday...so have gone with a dry forecast for now.
However...with a developing cutoff low forecast to be not to far to
the NE...cannot completely rule out that the forecast could later
evolve into a cloudier one with isolated-scattered showers in this time
frame.

For temperatures Monday-Thursday used a blend of
mex/men/ekd/ece/ecm/wpc guidance. Temperatures should run near
normal on Monday...above normal on Tuesday...with the possibility of
some areas mainly from NYC on west hitting 70. Wednesday and Thursday
for now should see temperatures within a few degrees on either side
of normal. However...if the aforementioned cutoff low ends up closer
to the area...then below normal temperatures would be possible.

&&

Aviation /18z Friday through Wednesday/...
high pressure will slowly move east while weakening tonight.

MVFR ceilings have move south of Long Island. With just middle and high
level clouds. East-southeast flow expected through the
afternoon...with local sea breezes turning winds S at 8-12 knots.

Winds diminish to 5 knots or less tonight. Winds will shift to the
west then northwest after midnight as a weak trough moves through
the region. Winds tomorrow will remain from the northwest around
8-15kt.

Low confidence as to whether or not stratus will redevelop after
00z Saturday...so will leave out of the tafs for now. VFR expected
during the day on Saturday.

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: low chance of MVFR ceilings returning this evening.

Klga fcster comments: wind direction may vary this afternoon. Low
chance of MVFR ceilings returning this evening.

Kewr fcster comments: wind direction may vary this afternoon. Low
chance of MVFR ceilings returning this evening.

Kteb fcster comments: wind direction may vary this afternoon. Low
chance of MVFR ceilings returning this evening.

Khpn fcster comments: wind direction may vary this afternoon. Low
chance of MVFR ceilings returning this evening.

Kisp fcster comments: wind direction may vary this afternoon. Low
chance of MVFR ceilings returning this evening.

Outlook for 18z Saturday through Wednesday...
Saturday-Tuesday morning...VFR.
Tuesday late afternoon-Wednesday...MVFR possible with showers...cold
frontal passage.

&&

Marine...
Small Craft Advisory for hazardous seas extended until 10z Saturday as lingering
easterly swell keeps higher seas within the forecast coastal ocean
zones. This afternoon...buoy 44017 seas were running about 1 feet higher
than wavewatch.

Elsewhere...sub-sca conditions expected through Saturday. Once
the seas on the ocean subside tonight...sub-sca conditions
expected there as well.

At this time...sub-sca conditions are forecast from Saturday
night-Tuesday...with winds on non-ocean waters 10 knots or less.
However...there is a chance that the coastal ocean waters could
experience wind gusts to around 25 knots late Saturday night and
Sunday. Otherwise winds on the coastal ocean waters should also be
10 knots or less until late Tuesday.

&&

Hydrology...
no significant precipitation is expected through the weekend.

There is the potential for a significant rainfall from late Tuesday
into Wednesday morning. At this time...there is too much uncertainty
to specify exact amounts or any potential impacts - if any.

Note...minor flooding continues along the Connecticut River. For
additional information...please refer to the latest flood warnings
from National Weather Service Taunton Massachusetts.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory for hazardous seas until 2 am EDT
Saturday for anz350-353-355.

&&

$$
Synopsis...maloit/Sears
near term...jm/Sears
short term...Sears
long term...maloit
aviation...British Columbia
marine...jm/maloit/Sears
hydrology...maloit/Sears