Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
208 PM EDT Sat Apr 25 2015
an upper level system over the northeast will dominate the weather
into the beginning of next week. High pressure builds in for the
middle of the week...followed by a frontal system for the end of
Near term /through Sunday/...
forecast on track...with upper low will drifting S of Nova Scotia
today. At the same time...low pressure will approach the NC coast
today and out to sea on Sunday.
This puts the County Warning Area in a subsident region today...and despite the
cold pool aloft...should suppress precipitation chances. SW portions of the
tri-state will be clipped by the northern edge of a cirrus
shield...with mostly sunny skies to the NE. Highs generally in
the middle to upper 50s...several degrees below seasonable.
Subsidence begins to weaken tonight...but instability is also
reduced with the loss of surface heating. Potential for frost across
interior and eastern Li portions of the tri-state late tonight
with window for radiational cooling.
Instability increases during the day on sun...with convective
temperatures in the upper 50s to near 60. Some weak middle level lift should
help provide a trigger. Kept probability of precipitation low...but went with coverage
wording. Temperatures through the period close to gmos25.
Short term /Sunday night through Tuesday night/...
cooling bl Sun night so precipitation chances diminish. Stronger upper support on
Monday...so precipitation coverage expected to be greater than sun. Changed
wording to scattered...with probability of precipitation around 40 reasonable at this time. Chances again
wane a bit overnight...but there is a better chance at showers hanging
in past dark with the shortwave energy moving through. Another chance for
some isolated showers Tuesday afternoon...especially CT and perhaps Li...with
the 500 mb low over 400 miles east of Montauk. Daytime heating is lost
and the upper forcing is weak to non by Tuesday night...so a dry forecast.
Long term /Wednesday through Friday/...
a broad area of hi pressure builds over the northestern Continental U.S. On Wednesday. Dry weather
expected as a result. Increasing heights will allow for a
noticeable warming trend...with temperatures approaching 70 along and west
of the Hudson. With weak flow...sea breezes will likely limit
temperatures on Li and CT. The GFS brings an upper low through in the Thursday-Friday
period. The European model (ecmwf) brings this upper level system to the NC coast and
spawns a 980s low over the Atlantic. This low is prognosticated to generally
track to the east-northeast and therefore not impact the County Warning Area. Made no changes
to probability of precipitation for the period...keeping the low chances already in the
grids. Temperatures close to gmos25 for this period.
Aviation /18z Saturday through Thursday/...
a low weakens in the Canadian Maritimes as another weak low passes
south of the region. VFR continues through the taf period. Wind
gusts 15-20 knots will gradually diminish late afternoon into early
evening along with variation in wind direction.
A trough looks to set up locally this afternoon...making for varying
wind directions. Kjfk would have a sea breeze and southerly flow
while interior terminals wind will remain northwest or slightly become more
northerly. CT coasts will have a SW flow but kisp remains
uncertain when the sea breeze will arrive. It does remain quite
Confidence is high with the category forecast. Confidence is
moderate with the wind forecast. Sea breeze timing could vary
1-2 hours compared to forecast. Wind direction uncertainty of 20-40
degrees with wind forecast into early evening.
Outlook for 18z Sunday through Thursday...
sun-Sun night...mainly VFR. Possible MVFR with showers late afternoon
into early evening.
Mon-Tue...possible MVFR with showers.
Tuesday night-Wednesday night...VFR.
Thursday...possible MVFR with showers.
marginal Small Craft Advisory gusts across eastern Li sound and rough water near
The Race this afternoon...otherwise sub- Small Craft Advisory conditions are
forecast through the middle of next week as a large area of high
pressure over the middle section of the country works slowly east.
There could be a short period Tuesday morning for margi9nal Small Craft Advisory gusts
as a northerly flow strengthens between a broad area of low pressure
over the western Atlantic and high pressure building in from the
min relative humidity will fall into the 20s this afternoon. Wind gusts are forecast
to be in the 15-20 miles per hour range...which is blw red flag criteria.
significant precipitation is not expected through next week.