Area forecast discussion
National Weather Service New York New York
132 am EDT Monday may 20 2013
Synopsis...
a warm front will slowly approach overnight...then lift to the
north today. This front will then remain nearby through middle
week...possibly sinking south on Tuesday and lifting back north as
a warm front on Wednesday. A cold frontal passage will occur late
in the week. High pressure will return next weekend.
&&
Near term /until 6 am this morning/...
light rain still lingering mainly across Suffolk County and
southern CT. Minor update to temperatures and dew points to reflect
latest observation trends.
Strongest low level jet energy continues to move east with axis of steady
light rain pushing east. In its wake...continued weak Theta-E
advection and an approaching diffuse warm front will likely
maintain drizzle and isolated shower activity into the overnight.
The drizzle activity may taper once the warm front pushes to the
north or washes out. Temperatures should remain nearly steady tonight in
the middle and upper 50s...and could slowly increase toward daybreak.
As higher dewpoint air advects in...potential for fog will also
increase overnight.
&&
Short term /6 am this morning through 6 PM Tuesday/...
the region will be warm sectored today. Expect at least
partial clearing to occur...which will determine amount of daytime
heating/instability. Forcing relatively weak...so expect only
isolated to scattered showers in the afternoon. With weak steering flow
and precipitable water near 1.5 inches...any shower/thunderstorm could dump locally heavy
rain. High-res mesoscale models such as Storm Prediction Center WRF and high-res arw
agree on this scenario.
Expect daytime highs to reach the lower 80s from NYC north/west
and into the 70s elsewhere. Temperatures could be a couple degree higher if
more afternoon sunshine takes place than forecast.
Any convection should wane Monday evening. It now appears that a back
door cold front approaching from New England should hold off until
Tuesday morning...so with area remaining in the warm sector would
expect redevelopment of fog...especially along the coast.
&&
Long term /Tuesday night through Sunday/...
medium range models/ensembles are in decent general agreement
with the region lying on the northern periphery of East Coast
ridging during the midweek...with phasing eastern Canadian and
central US troughs...eventually translating a deep trough to the
East Coast for the end of the week/weekend.
For Tuesday through Thursday...models continue to differ in location
of a frontal boundary. The predictability issues are based on
subtle differences in interaction of the upper energies and
relationship with East Coast ridging. The location of upper
confluence will determine how strongly Canadian high pressure builds
southeast into New England...and the timing and movement of a back door
cold front. Latest guidance pushes the backdoor cold front south
through the region on Tuesday...and then back north as a warm front
on Wednesday.
To the south of the front...an unseasonably warm and moist air mass
will be in place. Depending on the timing and location of the
frontal boundary...shortwaves at the southern edge of the
westerlies...favorable instability and wind fields present the
potential for convective complexes to develop and propagate along
this boundary. Any mesoscale convective system would bring the threat for flash flooding and
severe weather.
By the end of the week...models are signaling varying degrees of
phasing of the Midwest upper trough and eastern Canadian upper
trough. Models have trended faster with this phased energy working
to the East Coast. Have trended cold frontal passage a bit sooner as
a result...some time late Thursday through Friday...with shower and
thunderstorm activity finally exiting in it wake. Degree of phasing
of upper energies will determine timing and activity along the front.
Model guidance is signaling a drier and slightly below seasonable
weekend...with East Coast mean troughing and Canadian high pressure
builds into the region.
&&
Aviation /06z Monday through Friday/...
a nearly stationary front will remain south of the area as it
weakens early this morning. The front will redevelop to the north
of the terminals as a warm front middle to late morning.
The area will then be in the warm sector ahead of low pressure
moving into the upper Midwest. Scattered showers and isolated
thunderstorms will be possible in the afternoon. The wind will be
southerly...and become more southwesterly late in the afternoon into
the early evening. Sea breeze influence is likely.
Widespread fog and drizzle...with low clouds will persist early
this morning with IFR to LIFR conditions...and at times vlifr.
Conditions improve after 13z...timing of the improvements is not
certain.
Outlook for 06z Tuesday through Friday...
tonight...mainly VFR...MVFR or lower conditions possible in
fog...mainly east of the New York City terminals.
Tuesday-Friday...chance of MVFR of lower conditions in
showers/tstms.
&&
Marine...
as a warm front approaches late this evening...se-S winds will
increase to 15 to 20 knots...mainly across the ocean waters. Ocean
seas of 3-4 feet...should reach Small Craft Advisory criteria of 5 feet this
evening. Small Craft Advisory level ocean seas should last into Monday
afternoon...possibly into Monday evening out east.
With expectation of a frontal boundary to be meandering across the
region during the middle week period...sub Small Craft Advisory winds are expected.
Will have to monitor magnitude of southerly swells through middle
week...but seas should likely remain below Small Craft Advisory with weak flow.
A strengthening S-SW flow on Thursday could build ocean seas to Small Craft Advisory...
particularly out east. Have undercut wavewatch by 1-2 feet during
this time period due to the usual warm season bias.
Cold frontal passage sometime Thursday night into Friday...with wind shift
to the northwest behind it. A gradual subsiding of southerly swells would
be expected behind the front.
&&
Hydrology...
up to 1/4 inch quantitative precipitation forecast expected through tonight. Scattered showers/thunderstorms Monday
through Friday are capable of producing locally heavy rainfall...with
an attendant low end flash flood threat.
&&
Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 9 am EDT this morning for anz355.
Small Craft Advisory until 6 PM EDT this evening for anz350-
353.
&&
$$
Synopsis...Goodman/NV
near term...jp
short term...Goodman
long term...Nevada
aviation...precipitable water
marine...Goodman/NV
hydrology...Goodman/NV
