Area forecast discussion
National Weather Service New York New York
952 PM EDT Sat may 18 2013
Synopsis...
high pressure will continue to slide east of the area tonight.
A warm front will approach from the Middle Atlantic States Sunday into
Sunday night. A warm front will pass to the north on Monday. The
front then remains in close proximity to the area through the
week...quite possibly passing south as a cold front late Tuesday
and then back north as a warm front on Thursday. A cold frontal
passage occurs late in the week or early weekend.
&&
Near term /until 6 am Sunday morning/...
forecast is on track...only minor changes made.
The bulk of jet streak induced light rain shower and sprinkle
activity continues to move southeast of the region. After a brief
respite through late this evening...several convection allowing
models as well as hrrr/NAM are indicating showers re-developing
across SW zones late tonight into Sunday morning. Forcing appears
to be quite subtle (theta-east advection/frontogenetic)...so have only
raised probability of precipitation to high chance. Will have to watch this activity
overnight...with potential for some embedded heavier showers if it
makes it this far north. Lows will fall into the 50s...with the
warmest spots in and around the NYC metropolitan area.
&&
Short term /6 am Sunday morning through Sunday night/...
a warm front south of the region will approach the area Sunday and
Sunday night. Skies will remain cloudy with an increasing threat
of showers through the day. Will still limit probability of precipitation to just chance
at this time...due to the difficulty in timing and placement of
any shower activity.
Moisture continues to increase Sunday night as a shortwave
approaches along the warm front. Would expect light rain or
drizzle along with areas of fog to develop.
Temperatures on Sunday will be slightly below normal due to cloud
cover. Expect highs in the lower and middle 60s. Sunday
night...lows will be mild with temperatures only falling into the
middle and upper 50s to near 60.
&&
Long term /Monday through Saturday/...
predictability issues during this time period have to do with the
interaction of eastern Canadian troughing and central US troughing
this week. The interaction of these two energies will determine the
magnitude of East Coast ridging for the midweek. Models signaling a
return to East Coast troughing for the weekend as East Coast ridging
builds offshore into the western Atlantic.
Models in decent agreement with a split upper flow on Monday...with
weak shortwave energy over the middle Mississippi River
valley...tracking south of the region on Monday. The resultant S/SW
flow should allow for warm frontal passage Monday morning...if not
sooner. With surge of a more unstable airmass...thunderstorms are
possible with the warm frontal passage Monday morning. Then once in the
warm sector Monday afternoon...there is potential for isolated to
scattered afternoon convection with weak shortwave forcing/thermal
troughing.
On Tuesday...models continue in fairly good agreement with an
unseasonably warm and humid air mass working into the region. 12z
GFS pushes a backdoor cold front south of the region by Tuesday
morning...but majority of guidance holds off on this till late
day/night. Depending on the timing of the frontal
boundary...favorable instability and wind fields present the
potential for some strong to severe convection ahead/along this
boundary Tuesday afternoon/evening. Showers and thunderstorms could
continue Tuesday night...with indications of a wave of low pressure
tracking east along the sagging frontal boundary. Moisture pooling
and steering flow parallel to the surface boundary would present a
flash flood threat if this pattern materialized.
Then for the middle-late week period the interaction of the earlier
mentioned upper features will be critical to the location of the
frontal boundary. Latest guidance has strongly converged on the
backdoor cold front pushing south through the region Tuesday
night...and then back north as a warm front on Thursday. If the
front does pass south...onshore flow and clouds would likely drop
maximum temperatures to seasonable or slightly below seasonable levels for
Wednesday...several degrees cooler then forecasted.
Regardless of where the warm front ends up...if this boundary
remains close to the region...shortwaves at the southern edge of the
westerlies may allow for convective complexes to form and track west
to east along this boundary through the middle-late week period. Any
mesoscale convective system would bring the threat for heavy rain 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. This will have a cold front passing through the region
sometime Friday into Sat...with shower and thunderstorm activity
finally exiting in it wake. Degree of phasing of upper energies will
determine timing and activity along the front.
&&
Aviation /02z Sunday through Thursday/...
high pressure remains east of the region from eastern Canada to off
Cape Cod. Meanwhile a frontal boundary nearly stationary from the
Ohio Valley to the middle Atlantic coast will move very slowly
northward as a warm front Sunday.
VFR with periods of light rain possible through 09z. MVFR ceilings
develop toward morning...09z to 10z...with periods of light rain
still possible. MVFR ceilings and visibilities more likely from late
Sunday morning into the afternoon with the best chance of light rain.
South to southeast wind 10 knots or less through the forecast period.
Outlook for 00z Monday through Thursday...
Sunday night...MVFR...possibly IFR conditions...in light rain and
fog.
Monday...improvement to VFR by middle to late morning. Scattered
showers...and isolated thunderstorms with brief MVFR conds possible
in the afternoon.
Monday night...MVFR or lower conditions likely with low clouds and
fog.
Tuesday-Thursday...chance of MVFR of lower conditions in showers
and thunderstorms.
&&
Marine...
high pressure east of the waters continues to move offshore. This
will result in conditions remaining below Small Craft Advisory levels tonight.
A warm front south of the waters will approach tonight into Sunday
night...resulting in a strengthening southeast flow. Seas will gradually
increase tonight into Sunday to 5 feet. Wavewatch has seas reaching
6 feet...however at this time...I am thinking it may be a little too
high so have capped seas at 5 feet. With seas reaching 5 feet...will
be going with a Small Craft Advisory for the ocean waters from
Sandy Hook New Jersey to Moriches Inlet New York starting Sunday morning and
continuing through Sunday night. For the waters from Moriches
Inlet New York to Montauk New York...the Small Craft Advisory will start at noon on Sunday and
also run through Sunday night. An occasional gust to 25 knots can not
be ruled during this timeframe.
Small Craft Advisory ocean seas are likely by Monday morning with a persistent southeast
flow ahead of an approaching warm front. The warm front should move
north of the waters Monday...and should remain to the north through
Tuesday. The front will likely remain in the vicinity of the waters
through middle week...possibly sagging south of the waters late Tuesday
and then back north on Thursday.
Once the warm front moves north on Monday a long fetch southerly
flow will maintain southerly swells...and should keep ocean seas at
Small Craft Advisory levels into middle week. Marginal Small Craft Advisory winds are possible on
Monday...but winds should be generally below Small Craft Advisory levels for the
remainder of the early to middle week period. Marginal Small Craft Advisory winds could
return for Thursday.
&&
Hydrology...
no significant rainfall is expected through Sunday night.
Periods of showers and thunderstorms are possible Monday through
Friday...which would be capable of producing locally heavy rainfall.
There is currently a low threat of flash flooding from organized
shower thunderstorm activity during this time period.
&&
Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory from 6 am Sunday to 6 am EDT Monday for
anz353-355.
Small Craft Advisory from noon Sunday to 6 am EDT Monday for
anz350.
&&
$$
Synopsis...BC/jp
near term...
short term...British Columbia
long term...Nevada
aviation...Goodman/met/pw
marine...BC/NV
hydrology...BC/NV
