Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
1044 PM EDT Monday Apr 27 2015
a series of lows near the Canadian Maritimes will move south through
Tuesday night before consolidating into one low pressure system well
east of New England by Wednesday. At the same time...weakening high
pressure over the middle section of the country slowly builds in from
the west. A weak trough moves across the region on
Wednesday...and then low pressure slowly passes south and east of
Long Island through the end of the work week. High pressure builds
east for Saturday...and then a weak cold front may impact the area
Near term /until 6 am Tuesday morning/...
forecast is generally on track. What should be the last of the
showers/sprinkles are currently moving through the lower Hudson
Valley and capital region as of 03z. Have extended slight chance
probability of precipitation and sprinkles across western portions of the County Warning Area through 05z
to account for this. Further east...conditions are expected to remain
dry overnight. Also increased gusts a few knots across the area as
cloud cover is allowing for better mixing due to higher temperatures.
Clouds are expected to scattered out late tonight and may lose gusts for
a few hours...mainly outside of NYC.
Upper trough axis associated with closed upper low near Nova
Scotia has slid south of the region per latest water vapor
imagery. Cyclonic flow will remain through the night with some
residual middle level moisture and mainly broken cloud cover
Short term /6 am Tuesday morning through Tuesday night/...
cyclonic flow remains Tuesday through Tuesday night as the upper
low slowly weakens and moves East. Heights will be rising through
the period as upper ridging builds east from the Midwest. No
precipitation is expected with near zero probability of precipitation as only a weak
vorticity maximum rotates around the low Tuesday. This vorticity
maximum and daytime heating will be enough for a few clouds to
develop. The airmass continues to modify and warm advection does
set up during the day. So have leaned toward the warmer met
guidance for highs.
Long term /Wednesday through Monday/...
weak surface trough moves across the region on Wednesday...but with a
lack of upper level support and limited low-level moisture...not
expecting much beyond some middle and high level clouds. With west to
northwest winds...expecting downsloping flow to warm temperatures into the
70s for most areas west of the Hudson River and highs in the middle to
upper 60s most elsewhere. If the flow is weak enough...afternoon
sea breezes are possible...and that would result in cooler
afternoon temperatures for coastal areas.
For Thursday through Friday...closed low over the Great Lakes dives
into the southeast U.S. Surface low then develops over the Gulf Coast
and tracks towards the Carolinas. Weak high pressure will build over
the northeast and depart during this time...and this high should
be strong enough to keep the low from tracking too far to the
north as it tracks well south of Long Island...and south of the
40/70 benchmark...Friday through Saturday. Will carry mainly low
chance probability of precipitation during this time as some wrap-around precipitation
could impact the local area. Due to the cloud cover and onshore
flow...can expect below normal temperatures with highs in the low 60s on
Thursday and in the 50s on Friday. Any precipitation that falls
will be light.
By Saturday...the low moves into the western Atlantic and ridging
at the surface and aloft builds west of the region. With rising
heights...can expect improving conditions from west to east...and
temperatures moderating back into the low-middle 60s.
Weak cold front then tries to push across the region on Sunday.
Mainly expecting dry conditions...but with westerly flow
increasing...temperatures look to warm up through the 60s and back into
Aviation /03z Tuesday through Saturday/...
the region remains in between low pressure southeast of Nova
Scotia and high pressure to the north and west into Tuesday
VFR through the taf period. Unlikely exception is at kgon...where
MVFR is possible in the highly unlikely event anything other than
a sprinkle or light shower occurs there. Ceilings between
3500-6000 feet overnight.
Northwest-north winds g20-25kt. Could see some areas lose gusts for a little
bit overnight - however confidence in this at any one location is
not high enough to reflect in the tafs at this time. Winds
Tuesday strongest kswf - where gusts could be slightly higher.
Winds begin to subside middle- late Tuesday afternoon.
Outlook for 00z Wednesday through Saturday...
Tuesday night...VFR. Northwest winds g20kt possible in the evening.
Thursday-Thursday night...mainly VFR...low chance MVFR in any
rain showers. NE winds g15-25kt possible late Thursday night eastern
Friday-Saturday...mainly VFR...with low chance MVFR or lower in
any rain showers or rain. NE-north winds g20-30kt possible.
a series of lows near the Canadian maritime continue to
rotate through the maritime before moving east Tuesday night as
weakening high builds slowly east. A northwest to west flow will
persist across the forecast waters. Winds and seas are expected to
remain below Small Craft Advisory levels tonight through Tuesday
night. However...there could be occasional near shore gusts that
approach 25 knots tonight into Tuesday...mainly along the South Shore
of Long Island with better mixing over the land.
Easterly pressure gradient tightens on Thursday and Friday as low pressure
passes south of Long Island. Small Craft Advisory level winds/waves likely for the
ocean waters...and Small Craft Advisory winds possible for the South Shore bays.
Gradient slackens for the weekend...but lingering swells will keep
ocean seas above Small Craft Advisory levels.
significant precipitation is not expected through Wednesday.
Light precipitation is possible as low pressure passes south of Long
Island late in the week.