Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
357 am EDT Monday Oct 20 2014
high pressure builds off the middle Atlantic coast today.
Low pressure approaches from the Great Lakes region tonight.
Secondary low pressure will develop near the middle Atlantic coast by
late Tuesday...slowly meander about near the region Wednesday
through Thursday...then pass east of New England Thursday night into
Friday. A cold front will approach from the northwest on
Saturday...then pass through Saturday night. High pressure will
build in from south central Canada on Sunday.
Near term /until 6 PM this evening/...
will maintain frost/freeze headlines...and will need to monitor
temperatures this morning.
Negatively tilted trough departs to the northeast as next vigorous
shortwave/vort...seen on water vapor imagery tracking across
Wisconsin this early morning...dives east/southeast today...carving
out another trough in time.
After morning chill...temperatures will rise through the 40s and into the
50s under partly to mostly sunny skies. Some middle and high level
clouds will filter the sun this morning. Generally expect more of
the sun to be hidden later in the day as more middle/upper level clouds
move in. Light northwest winds this morning turn toward the southwest as
surface high pressure moves south...then east of the area.
For afternoon high/S...expect readings slightly warmer than what was
observed yesterday. However temperatures should only peak in the middle and
upper 50s due to limited mixing.
Short term /6 PM this evening through 6 PM Tuesday/...
at the surface...high pressure passes well east of the 40n/70w
benchmark as low pressure moves across the Great Lakes region. The
low is expected to dive southeastward across Pennsylvania during the
day Tuesday...with a secondary low developing off the middle Atlantic
coast late in the day.
Aloft...digging trough closes off Tuesday near western Pennsylvania
per NAM/gefs mean/12z ECMWF/CMC.
For tonight...weak lift and deepening moisture may result in a few
showers...especially after midnight. With the increasing southerly
flow...eastern locales may have a better chance of observing some
shower activity due to fetch. Will cap probability of precipitation in the chance range.
On Tuesday...ample moisture and weak lift ahead of the upper
trough/closed low should be enough for a higher chance for
showers. Coverage should increase somewhat into the high chance or
likely range...50 to 60 percent coverage.
As for temperatures...lows tonight will be considerably warmer due to the
cloud cover and SW flow. Lows should range from the lower to middle 40s
across the interior and normal cool spots...to the lower 50s in and
Tuesday/S daytime temperatures rebound into the 60s. These expected
high/S should run slightly above normal levels.
Long term /Tuesday night through Sunday/...
weather will be unsettled from Tuesday night through Thursday night as a slow
moving closed low plods across the middle Atlantic region...with
associated low pressure off the middle Atlantic coast through this time
frame. Better upper level forcing initially will be more across NYC
metropolitan and the lower Hudson Valley than southern CT/eastern Long Island...so
the former will maintain previous forecast of likely pop while the latter
will be only at chance. With the upper low passing just to the south
on Wednesday and NAM/European model (ecmwf) showing an inverted trough extending west-northwest of
the surface low...may have to watch out for a band of locally heavy rain
near NYC/western Long Island on Wednesday...then the focus of moderate rain
should shift more east into Long Island/CT...and with a strong middle
level vorticity maximum rotating around the closed low...eastern CT/Long Island
could see a round of heavy rain Wednesday night. As this forcing pivots
around the closed low farther north into New England...rain should
be more on the light side on Thursday...then gradually taper off Thursday
night as the nearly vertically stacked low drifts toward southeast New
England...allowing a drying northwest flow to take hold.
After some lingering light precipitation early across eastern sections Friday
morning...forecast GOES dry for the rest of the period. Moisture starved
cold front/northern northern stream trough will pass through Sat
night...followed by a dry northwest flow on Sunday.
Temperatures should be on the cool side under the influence of the low
through Thursday night...then return to near or slightly above normal for
Fri-Sat...and near normal for Sunday.
Aviation /08z Monday through Friday/...
high pressure slides S and east of the terminals today...with low
pressure approaching from the northwest tonight.
Mainly VFR. Chance of -shra late tonight...mainly kswf and eastern
terminals. Low potential for MVFR ceilings across kisp/kgon late
West winds early this morning..become S/south-southwest by this afternoon.
Speeds generally 10 knots or less. Light S/southeast flow tonight.
..NY metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts can
be found at: http://www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: timing of windshift from west to SW could be
off by 1-2 hours.
Klga fcster comments: timing of windshift from west to SW could be
off by 1-2 hours.
Kewr fcster comments: timing of windshift from west to SW could be
off by 1-2 hours.
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 06z Tuesday through Friday...
late tonight through Tuesday...low potential for MVFR conds and
-shra across kswf and eastern terminals late tonight. MVFR ceiling and
-shra potential gradually increases to moderate through the day.
Tuesday night through Thursday...MVFR or lower conds in rain.
Best chances Tuesday night through Wednesday.
Friday...improving conds. Northwest winds 15-20 knots with 20-25 knots gusts.
winds continue to diminish ahead of an area of high pressure. As
the high moves east of the waters this afternoon...winds will
increase out of the south. In fact...winds may approach Small Craft Advisory levels
briefly tonight...especially for the ocean waters. For the most
part...expect conditions to fall short of the 25 kts for issuance
of a Small Craft Advisory. However...cannot rule out brief 20 to
25 knots winds tonight before winds diminish yet again.
Winds remain light from the south or southeast on Tuesday as low
Seas subside this morning...then may build a foot or two later today
and tonight as the southerly winds increase. However...do not
anticipate 5 footers over the ocean waters.
Small Craft Advisory conds appear likely to develop Wednesday-Wednesday night mainly on the ocean
in east-northeast flow to the north of developing low pressure off the middle
Atlantic coast. These conds may subside on Thursday...then ramp back up
Thursday night-Friday in northwest flow on the back side of the departing low.
dry today...with spotty light rainfall amounts possible tonight.
At least an inch of rain appears likely from Tuesday into Thursday.
Depending on placement of bands of heavier rain Wednesday into Wednesday
night...there is potential for some areas to see over 2 inches of
rain. Hydrologic impacts should be limited to nuisance poor drainage
CT...frost advisory until 9 am EDT this morning for ctz009>012.
Freeze warning until 9 am EDT this morning for ctz005>008.
New York...frost advisory until 9 am EDT this morning for nyz069-070-
Freeze warning until 9 am EDT this morning for nyz067-068.
New Jersey...frost advisory until 9 am EDT this morning for njz004-103-105-
Freeze warning until 9 am EDT this morning for njz002.
near term...precipitable water
short term...precipitable water