Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
358 am EDT sun Apr 19 2015
high pressure over eastern Canada moves into the western Atlantic
later today and moves offshore this evening. A warm front
approaches from the south Monday morning...moving through the
region during the day. A cold front moves across the region on
Tuesday. A series of weak cold fronts and/or troughs of low
pressure will move through during the middle to late week period.
Near term /until 6 am this morning/...
deep layered ridging builds over the region today. The center of
surface high pressure over the Ontario/Quebec will drop over Cape Cod by
the middle of the day...and then continues to track to the east
and move offshore towards this evening.
Generally sunny skies on tap for most of the day...but some high
clouds will begin to build in from the west late in the day.
Much cooler day compared to Saturday...as the departing high will
result in southeast flow.
Highs today will be closer to normal...generally topping off in
the middle to upper 50s for most areas. Across interior portions of
the lower Hudson Valley and southern CT...temperatures will be a bit
warmer...topping off in the low 60s...and temperatures will be in the low
50s closer to the coasts...as ocean temperatures are only in the 40s.
Short term /6 PM this evening through Tuesday/...
high pressure continues to drift offshore this evening. Meanwhile...
surface low pressure with a deep upper trough will move through the Great
Lakes...and a warm front ahead of this will approach from the
southwest late tonight.
Precipitation should move into western portions of the County Warning Area after midnight
tonight...but latest models seem to be a bit slower with the
arrival of the precipitation. Will therefore carry likely probability of precipitation for the
western zones and will keep New London County and eastern Suffolk
County mainly dry for the tonight period.
Warm front then lifts through the region during the day Monday. A
50-60 knots low level jet will lift through with the warm front...and this will
help enhance precipitation with moderate to locally heavy rainfall Monday
morning and into Monday afternoon. Strong southeast winds will develop
across NYC/Long Island/coastal CT on Monday...with winds ranging
from 15-20 miles per hour with gusts as high as 35 miles per hour. Periods of rain will
continue throughout the day...but the heaviest of the rain should
push east by early afternoon.
Low pressure over the Great Lakes then passes north of the area Monday
night...dragging a cold front across the region. With elevated
instability increasing...cannot rule out isolated thunderstorms with the
passage of the cold front. Showers taper off Monday night...but
with a few 500 mb shortwaves moving across the region on
Tuesday...additional scattered showers are possible.
Long term /Tuesday night through Saturday/...
weak surface ridging keeps the region dry Tuesday night into
Wednesday morning. A cold front approaches Wednesday afternoon and
passes through during the night. Chance showers...primarily for late
day and evening hours. Went a little above wpc/gmos blend for
highs...more so over SW portions of the County Warning Area where SW flow won't
advect cooler air from the waters.
For Thursday through Saturday...it looks like the entire period
could be dry. Left in slight chance probability of precipitation due to presence of upper
low/cold pool. Temperatures during this period should average below
normals...but at least in the 50s during the daytime hours.
Aviation /08z Sunday through Thursday/...
high pressure for today with a warm front approaching late
VFR today and through at least most of tonight. NE winds shift east-southeast
towards noon at around 10kt. Timing of this shift could be off by
Outlook for 06z Monday through Thursday...
Sun night...VFR...chc MVFR towards daybreak with -ra. East gusts
Monday...IFR. Rain. Low level wind shear mostly am. East-southeast wind 15 knots to 25 knots...gusts
Tuesday...MVFR early...otherwise VFR. West gusts 25-30kt.
Wednesday...MVFR possible PM with chance of showers. Chance SW gusts 20kt
Thursday...VFR. Chance west gusts 20kt.
southeast winds will range from 10-15 knots...and gusts up to 20 knots will
develop by this afternoon. Winds increase tonight...and Small
Craft Advisory conds will develop on the ocean/New York Harbor/South
Shore bays this evening with gusts up to 25 knots. Ocean seas will
also build to 5-7 feet during the night.
Warm front lifts north through the waters Monday morning. Conds
will deteriorate quickly...with widespread winds gusting to 25-30
knots...along with occasional gusts up to 35 knots. For now...will carry
small craft advisories for all waters...and there is the potential
for a gale watch to be needed on Monday.
Strongest winds end by Monday afternoon as the warm front and low level jet
moves to the east. Cold front then moves across the waters on
Tuesday. Winds shift to the west Tuesday morning...and then to the
Seas on the ocean will probably continue to be at advisory levels
for a portion of Tuesday night. For Wednesday...a west to SW flow
could be strong enough to keep seas close to or slightly above 5
feet across the eastern ocean waters....then winds pick up Wednesday
night and Thursday with Small Craft Advisory conds likely on all ocean waters as
well as possibly the South Shore bays.
significant rainfall will develop across the region late tonight
through Monday night as a warm front lifts north through the
region Monday morning...followed by a cold front Monday night.
Storm total rainfall with this system will range from 1 to 2
inches with locally higher amounts. This could cause possible
minor flooding of urban and poor drainage areas.
For details on specific area rivers and lakes...including
observed and forecast river stages and lake elevations...please
visit the advanced hydrologic prediction service /ahps/ graphs on
our web site.
increasing east/southeast flow Monday may result in local to widespread minor
coastal flooding. Astronomical high tides will be running high
following a new moon. In some cases...departures of only half a foot
above normal are needed. Storm surge could produce waters levels 1
to 1 1/2 feet above normal.
Marine...Small Craft Advisory from 11 PM this evening to 6 PM EDT
Monday for anz338-345.
Small Craft Advisory from 6 am to 6 PM EDT Monday for anz330-
Small Craft Advisory from 11 PM this evening to 6 am EDT
Tuesday for anz350-353-355.