Area forecast discussion
National Weather Service New York New York
629 am EDT Sat may 18 2013
Synopsis...
high pressure will slide east of the area today and move further
out to sea tonight. A warm front will approach from the Middle Atlantic
States Sunday into Sunday night and then pass to the north on
Monday. The front then remains in close proximity to the area
through the week until a cold frontal passage occurs late in the
week or early weekend.
&&
Near term /until 6 PM this evening/...
forecast is on track.
High pressure over the area this morning will move
offshore by afternoon with an onshore flow developing. Have gone more
optimistic with the cloud forecast for this afternoon across the NE 2/3
of the area...but if middle clouds end up further north and east than
expected it could end up being a partly sunny day in more
locations. Highs will be similar to yesterday (unless cloud cover
is more extensive)...although slightly cooler at the coast due to
the onshore flow.
&&
Short term /6 PM this evening through Monday/...
the high moves further offshore tonight with cloud cover gradually
increasing from SW to NE. Stratus may develop late tonight but
still expect dry conds.
A warm front will approach sun and Sun night from the SW.
Increasing cloud cover and late day shower activity are expected
in this warm air advection pattern. The continuation of the increasingly moist southeast
flow into Sun night points towards cloudy conditions with light
rain...patchy drizzle and areas of fog developing.
Models in decent agreement with a weak shortwave approaching Sun
night into Monday...with a warm frontal passage on Monday...and
region warm sectored into Tuesday. Looks like the front moves
through in the morning...and with the surge of a more unstable air
mass thunderstorms are possible with its passage. The potential
for scattered afternoon convection also exists but there is
uncertainty in how much clearing there will be in the afternoon. It is
still too early to discuss severe weather or flood potential with
this activity with uncertainty on magnitude of instability and
forcing.
Temperatures on Sunday will be slightly below normal due to cloud
cover...otherwise...they will be near normal levels.
&&
Long term /Monday night through Friday/...
there are still some discrepancies amongst the global models with
the magnitude of upper troughing across eastern Canada as an upper
ridge over the Mississippi Valley translates east through the
upcoming week. The interaction of the eastern Canada troughing and
central US troughing will determine the magnitude of East Coast
ridging for the midweek. Models are then signaling a return to East
Coast troughing for the weekend as East Coast ridging builds
offshore into the western Atlantic.
On Tuesday...models are in good agreement with an unseasonably
warm and humid air mass working into the region. Depending on the
location of the frontal boundary...favorable instability and wind
fields present the potential for some strong to severe convection
ahead/along this boundary. Location of the boundary will be key.
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 and whether the region remains under an
unseasonably warm and unstable air mass Wed-Fri...or whether the
picture is more muddled with a frontal boundary meandering across
the region for much of the time period with clouds and seasonable to
slightly below seasonable temperatures.
Regardless of where the warm front ends up...if this boundary remain
close to the region...short waves at the southern edge of the
westerlies may allow for convective complexes to form and track west
to east along this boundary through the midweek period. These would
bring the threat for heavy rain and severe weather...but it is too
far out discuss specifics.
&&
Aviation /12z Saturday through Wednesday/...
VFR today as high pressure moves east of the area.
Light and variable winds early this morning will increase to 5 to 10
kts after 13-15z...generally from the south. Winds increase during
the afternoon at a few coastal airports such as kjfk.
Mainly middle and high clouds are expected today...with few to
scattered cumulus.
VFR ceilings are forecast through the evening as south to southeast winds
lighten.
Outlook for 06z Saturday through Wednesday...
Sat night...ceilings possibly lowering to MVFR.
Sun...MVFR ceilings. Southeast surface wind around 15 knots.
Sun ngt-Mon...southeast surface flow with IFR ceiling into Monday morning. Showers.
Scattered afternoon thunderstorms.
Tuesday and Wednesday...chance of sub-VFR conds in showers and thunderstorms.
&&
Marine...
high pressure passes to the east of the waters...resulting in a
southerly flow this weekend. Small Craft Advisory thresholds are not
expected until possibly Sunday night or Monday as winds increase and
ocean seas build due to the persistent southerly fetch.
A warm front moves north of the waters Monday...and should remain to
the north through Tuesday. The front may sag south again and remain
in the vicinity of the waters through middle week.
South to southwest winds persist into Tuesday. Once the front
settles back toward the waters...winds lighten and may
shift...depending on how far south this front moves. Stay tuned.
&&
Hydrology...
no significant rainfall is expected through Sun night.
Although widespread heavy rain events are not expected Monday-
Friday...thunderstorms are possible through this period...which would
be capable of producing locally heavy rainfall.
&&
Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...none.
&&
$$
