Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1016 PM EDT Monday may 4 2015
high pressure remains over the Atlantic as a cold front approaches
from the northwest tonight. The cold front moves across the area
Tuesday and Tuesday night. High pressure builds over the region
for the middle to the end of the week. A frontal boundary passes
north of the area this weekend.
Near term /until 6 am Tuesday morning/...
some minor adjustments with respect to temperatures...dewpoints
and cloud coverage to better match observed trends. Overall...the
forecast remains on track.
Models remain in good agreement with surface high pressure drifting
east tonight over the western Atlantic as a cold front approaches
from the northwest. The front should move into the northwest portion of the County Warning Area
between 6 and 10z overnight.
Aloft...zonal flow prevails across the northeast for the
remainder of the night. Closed low well up in eastern Canada moves
A general SW flow will decrease throughout tonight. Mostly clear
conditions will yield to more clouds ahead of the front late
tonight. Mesoscale models including arw and WRF-nmm show showers
along and ahead of the front dissipating as they near the area
late tonight. NCEP models including sref mean indicate light quantitative precipitation forecast
via weakening shower activity before 10z tonight...so will
maintain minimal probability of precipitation for northwest zones as they near the area.
Above normal temperatures expected overnight...with lows ranging from
around 50 across the interior to the lower 60s in and around NYC.
Short term /6 am Tuesday morning through Tuesday night/...
zonal flow initially will give way to a late day and overnight 500-
700 hpa trough. This feature is more pronounced in the 12z NAM.
Any morning isolated shower activity will give way to slightly
higher coverage later in the morning...during the afternoon and
into the evening hours. NAM...WRF-nmm show convection upstream in
PA riding along the ridge early in the day approaching our region
late. It appears that the better coverage will be just south of
the front from NE New Jersey/NYC southward. European model (ecmwf)/GFS and sref mean
support less coverage with lower probability of precipitation. At this time...will not
stray too far from previous forecast...raising probability of precipitation slightly but
capping them in the chance range. Highest probability of precipitation SW zones...and
lowest NE. This supported by latest day 2 Storm Prediction Center outlook for
thunderstorms as marginal instability is present to the south and
west...if not a lot of upper support.
Depending on the location of the front...any lingering shower or
thunderstorm activity will remain or pass south Tuesday night...with probability of precipitation
lowering through the night. Expect high pressure to the north to
push the front just to our south during the evening hours.
Another unseasonably warm day is on tap despite the clouds.
Readings may be slightly lower...but still expect 80 degrees away
from the water...with near 70 over eastern sections of the County Warning Area.
With the front in our proximity...winds will not be as strong...so
less disparity in temperatures from what occurred earlier today.
Tuesday lows will run above normal...but will be a few degrees
cooler than tonight's expected temperatures.
Long term /Wednesday through Monday/...
cold front continues to move south and east of the area Wednesday
morning. Just a slight chance for some lingering showers over
southeast zones in the morning...and then conds clear out for the
High pressure both at the surface and aloft will build east and over the
area for the middle to the end of the week...and then the high moves
offshore on Friday. Dry conds with near to above normal temperatures
through the end of the work week with highs generally in the
70s...warming into the lower 80s across the interior by Friday. With
a light pressure gradient...can expect afternoon sea breezes...resulting
in cooler afternoon temperatures for coastal areas.
Low pressure slowly tracks through the Great Lakes and into the Ohio
Valley for this weekend...and a frontal boundary will extend from
this system and move well north of the region. Saturday should be
dry...but the front will begin to Sage to the south for Sunday and
Monday...and scattered showers and afternoon thunderstorms are
possible for the start of the new week. Will cap probability of precipitation at low chance
for now...with highest probability of precipitation across the interior...which will be
closer to the front.
Near to above normal temperatures will likely continue for the weekend and
start of the new week.
Aviation /03z Tuesday through Saturday/...
a weak frontal boundary approaches overnight...and moves into the
area toward 10z Tuesday. The front then remains in the vicinity
through ooz Wednesday.
With the frontal boundary in the vicinity the wind forecast at all
the terminals will be tough and have low to moderate
There is little forcing with the front and the chance of showers
will be low and activity is expected to be scattered...so forecast
vicinity showers. Better forcing and instability will be near the
coast and indicated a chance of thunder...also with vicinity.
Conditions remain VFR with a low chance of marginal VFR if a heavier
shower or thunderstorm does happen to move through one particular
Outlook for 00z Wednesday through Saturday...
Tuesday night through Saturday...VFR.
winds gust 20-25 knots on the ocean with lower winds for other waters.
As low level jet increases ahead of cold front...will not have to
mix much to bring down higher winds. Inversion holding could limit
gusts to mainly near 20 knots. Seas per wave watch iii build to 5 feet
tonight where Small Craft Advisory remains in effect. Elsewhere...south to
southwest flow will lighten as the night progresses.
A cold front approaches and tracks just north of the waters
Tuesday...and settles overhead Tuesday night. Winds lighten and will
eventually shift around to the north/NE late Tuesday night...depending on
the exact location of the front.
With high pressure and a light pressure gradient over the waters for the
middle to the end of the week...can expect tranquil conds during the
long term period. Some afternoon gusts to 20 knots possible across the
near shore waters due to sea breezes.
generally expect from 1/10 to 1/4 inch of basin average rainfall
Tuesday and Tuesday night from scattered rain showers/isolated thunderstorms. However
cannot completely rule out locally heavy rainfall in any stronger
convection. If this does occur over an area...then localized minor
flooding of urban and poor drainage areas would be possible. This
is a low probability though.
Dry conditions are expected Wednesday through the weekend. Next
chance for rain showers/thunderstorms and rain will be on Sunday and Monday.
Marine...Small Craft Advisory until 6 am EDT Tuesday for anz350-353-355.
short term...precipitable water