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Area forecast discussion 
National Weather Service New York New York
810 PM EDT Tuesday Apr 21 2015

Synopsis...
a cold front will track towards the tri-state into Wednesday
morning...then move through the area Wednesday afternoon and
evening. Low pressure will then meander about northern New
England through Friday before weakening and consolidating with a
deepening area of low pressure southeast of Nova Scotia this
weekend. This low will fall back into northern New England early
next week as high pressure builds to the west. Another storm
system may impact the local area during the middle of next week.

&&

Near term /until 6 am Wednesday morning/...
a cut off low over southeast Quebec slowly drifts east tonight. Forcing
from this system should stay far enough to the west and north that there
should be fair weather tonight with a dry airmass over the
northeastern and Middle Atlantic States. Guidance suggests that the
deep layered west-southwest flow will not completely decouple...thereby
keeping temperatures from dropping to fullest potential. In
addition...increasing clouds should help to keep a lid on
temperature falls...particularly across the western 2/3 of the County Warning Area.

Lows are based on a blend of available guidance...and should be a
few degrees above normal.

&&

Short term /6 am Wednesday morning through Wednesday night/...
combination of strong upper jet...surface front and steep lapse
rates should produce a round of showers and embedded thunderstorms Wednesday
into early Wednesday evening. Window for the best thunderstorm chances looks to be
from 16-22z...perhaps lingering a bit longer across eastern portions
of Long Island and CT.

Best elevated instability from interior Fairfield County...into
the lower Hudson Valley then S and west through the city and New Jersey. NAM
indicated most unstable cape in the 500-700 j/kg range in these
areas. Cold temperatures aloft should aid in the production of small hail
although residence time will be extremely limited. In
addition...strong winds aloft as well as some potential cold pool
development could yield some gusty winds as well. 35-50kt gusts
have been reported this afternoon even outside of showers/thunderstorms
from southeastern Ontario into the Midwest. Have included small hail and
gusty winds in the forecast as a result.

The precipitation ends from west to east by early evening. Although a rogue
shower or sprinkle cant be completely ruled out per the NAM
forecasts...kept the forecast dry due to downslope and a general lack
of moisture.

Temperatures a blend of guidance which was in good agreement.

&&

Long term /Thursday through Tuesday/...
a blocky pattern looks to dominate the long term period across the
Continental U.S.. a persistent cutoff low pressure system is forecast to plague
the northeastern quarter of the country through this time which will
result in instability clouds during the day with below normal
temperatures. Several surface troughs will track across the
region during the period...mainly once per day between Thursday and
sun.

990mb low over northern New England Thursday morning will meander
about the region through Friday while weakening and sliding offshore.
This low will merge with a offshore low heading towards the
Canadian Maritimes Friday night which intensifies as it retrogrades
back towards the Mainland over the weekend. This system weakens
off the New England coast early next week. There are large
discrepancies with the upper pattern and the potential impacts
from the next storm system approaching for middle to late next week.
Both the GFS and the ec originate the energy associated with this
system in the Pacific northwest...but the ec breaks a piece off in The
Rockies with the southern trough becoming the dominant energy
source for the developing system while the GFS keeps this confined
to the northern stream. There is the potential to be impacted from
this...especially if the northern track verifies.

Much of the period will also be breezy with such strong areas of low
pressure nearby. Have not forecasted any instability showers due to
predominately northwest downsloping flow...but there could be some added in
the coming days when things become a bit clearer. Sat currently
looks to be the nicest day with high pressure building in from the west and
lighter winds.

Other area of concern both Thursday and Friday will be fire weather. Relative humidity
is forecast to be below 30 percent both days with gusty northwest winds.

&&

Aviation /00z Wednesday through Sunday/...
primarily a VFR forecast outside of convection Wednesday after.

Cold front over Midwest approaches Wednesday after...and passes through
in the evening. A line of convection with gusty winds is likely in
the after from west to east. Confidence in thunderstorms and rain is lower east of
the NYC terminals.

A strong SW flow will precede the front with the potential for
gusts up to 35 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: amendments likely with the timing of
convection along and ahead of cold front Wednesday after.

Klga fcster comments: amendments likely with the timing of
convection along and ahead of cold front Wednesday after.

Kewr fcster comments: amendments likely with the timing of
convection along and ahead of cold front Wednesday after.

Kteb fcster comments: amendments likely with the timing of
convection along and ahead of cold front Wednesday after.

Khpn fcster comments: amendments likely with the timing of
convection along and ahead of cold front Wednesday after.

Kisp fcster comments: amendments likely with the timing of
convection along and ahead of cold front Wednesday after.

Outlook for 00z Thursday through Sunday...
Wednesday night...west 10-15 knots with gusts up to 25 knots.
Thursday-Friday...mainly VFR...with low chance MVFR in any
-shra. West-northwest winds g15-20kt possible.
Saturday and Sunday...VFR.

&&

Marine...
seas on the ocean continue to run above guidance due to persistent
southeast swell. Have added 1 feet to wavewatch iii guidance this update
for seas on the ocean to reflect this.

The Small Craft Advisory on the ocean was extended through Wednesday night as winds and
seas will remain up through the period. On the protected
waters...gusts generally in the 20kt range this evening. The winds
increase however on Wednesday...so a Small Craft Advisory was issued for the
afternoon and evening hours.

Small Craft Advisory conditions will likely persist into Friday on all
waters...and into Saturday on the ocean. Winds will gust up to 30
knots with a tight gradient in place. The pressure gradient relaxes
over the weekend with sub-advisory conditions returning.

&&

Hydrology...
quantitative precipitation forecast for Wednesday comes from the river forecast center grids.
Locally higher amounts to around a half inch are possible due to
convection however. Any thunderstorms forecast to track to the east around
20kt so no flash flood threat at this time.

Thereafter...no significant precipitation expected into early
next week.

&&

Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory from 11 am to 11 PM EDT Wednesday for
anz330-335-338-340-345.
Small Craft Advisory until 6 am EDT Thursday for anz350-353-
355.

&&

$$

Synopsis...maloit/jmc/24
near term...maloit/maloit
short term...jmc
long term...24
aviation...dw
marine...maloit/jmc/24
hydrology...jmc/24

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