Area forecast discussion
National Weather Service New York New York
1047 am EDT Thursday may 23 2013
Synopsis...
a broad area of low pressure slowly approaches through
tonight...dragging a cold front through the area Friday morning.
The center of this system will then exit to the east by the end of
the day...and remains just east of the region through Saturday. It
then tracks north along the New England coast on Sunday. High
pressure over the Great Lakes builds southeast across the area
Monday into Tuesday. A warm front will then approach from the
southwest by middle week.
&&
Near term /until 6 PM this evening/...
latest radar trends suggesting precipitation coming to an end for
this morning. Latest hrrr...NAM...rap and sref and to a lesser
extent the GFS and European model (ecmwf) indicate that the bulk of any rain showers/thunderstorms and rain
this afternoon will occur over the northwest 1/2 of the County Warning Area. This is also
consistent with regional radar looking to our SW. As a result have
increased probability of precipitation over the northwest part of the County Warning Area to categorical this
afternoon but left southeast portion at chance...using areal coverage
wording.
Minor changes to temperatures to reflect latest trends in
observations and guidance - with this part of the forecast
generally on track.
Expanded timing of patchy fog over eastern zones into the
afternoon consistent with recent trends as well.
Otherwise...with models showing plenty of moisture at least in the middle
levels...it looks like clouds will outweigh sunshine across the
area. Perhaps it could be just partly cloudy at times across parts
of CT and Long Island. In spite of this...SBCAPE values are
expected to climb into the range of 1000-1500 j/kg for inland
spots. Lift ahead of the cold front is expected to produce showers
and scattered-likely thunderstorms for roughly the northwest 1/2 of the
area.
With the given cape and bulk shear near 30-35 knots...severe
thunderstorms will be possible. Precipitable water values around 1.75 inches and
potentially training cells will allow for the possibility of at
least localized minor flooding. Please see the hydrology section
below for more details.
&&
Short term /6 PM this evening through 6 PM Friday/...
cold front eventually moves into the western zones late at night
providing lift. Farther east...lift comes courtesy of additional middle
level shortwaves and a strengthening low level jet. On a larger
scale...lift from the right entrance region of a jet streak aloft
shifts in late at night. So showers will be likely along with
thunderstorms...as well as the continued threat of localized
flooding. The severe thunderstorm threat should linger at least into
the evening hours.
Although the center of the system and cold front will be to our east
by the end of the day on Friday. Still expecting some showers right
along the system...as well as a continued threat in the afternoon as
a trailing shortwave moves in from the west. Thunderstorms will
still be possible...but mainly associated with the exiting cold
front.
&&
Long term /Friday night through Wednesday/...
model consensus continues to depict a slower and deeper solution with
the approaching upper trough over the middle section of the
country...taking a closed upper low from the Middle Atlantic States on
Friday NE to over New England on sun. Preference at this time is to
continue to trend forecast towards the slower GFS/European model (ecmwf) solution
based on model trends and the run to run continuity being exhibited
over the last several model cycles.
As for sensible weather...this results in a breezy...cool and wet
weekend. Potential exists for moderate frontogenetic rain banding on
Saturday...with gradually tapering to shower activity Sat night
through Sunday. It is not out of the question that instability
shower activity could linger into Monday. Northwest winds of 15 to 25 miles per hour with
gusts up to 35 miles per hour are possible through the weekend.
Temperatures this weekend could be a good 8 to 12 degrees below
seasonable...with temperatures likely struggling to get out of the 50s with
cold pool aloft...clouds and rain. Temperatures on Sunday will likely not
be any better based on trends. Overnight lows will be close to
seasonable. A gradual warm-up to near seasonable levels is then
forecast Mon-Wed.
&&
Aviation /15z Thursday through Monday/...
high impact weather day for the NYC terminals.
A frontal boundary will remain nearly stationary north of the
terminals through the forecast period. A low pressure system and
cold front approach slowly from the west during the day.
Ceilings have lifted to VFR over kjfk and klga...but do expect them to
drop to MVFR over by about 16z as kewr has already fallen back to
MVFR.
Showers beginning to pop up over northeast New Jersey. If they hold
together...should make it into the city terminals by 15z-16z.
However...the best chance of thunder will be after 19z. For the NYC
terminals as well as kswf and khpn...will carry thunder in a
prevailing group starting at 19z which will go until 01z. While I
do not think thunder will occur at the terminal the entire
time...I do think convection could occur at least half of the
time...resulting in significant terminal impacts.
Conditions overnight are expected to fall to IFR or less in low
clouds and rain showers. Additional thunder will be possible. Will
introduce thunder to the terminals east of NYC in a prob30 group
after 00z as a low level jet moves over the terminals there.
Winds will generally be from the south to southwest 10 to 15 knots
today. Winds away from the coast may go light and variable
tonight.
New York 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: amendments expected today for changing
conditions/timing of any showers or thunderstorms.
Klga fcster comments: amendments expected today for changing
conditions/timing of any showers or thunderstorms.
Kewr fcster comments: amendments expected today for changing
conditions/timing of any showers or thunderstorms.
The afternoon kewr haze potential forecast is yellow...which implies
slant range visibility 4-6sm or greater outside of cloud.
Kteb fcster comments: amendments expected today for changing
conditions/timing of any showers or thunderstorms.
Khpn fcster comments: amendments expected today for changing
conditions/timing of any showers or thunderstorms.
Kisp fcster comments: amendments expected today for changing
conditions/timing of any showers or thunderstorms.
Outlook for 12z Friday through Monday...
Friday...numerous rain showers...isolated thunderstorms possible. MVFR to IFR in
showers...fog and stratus.
Saturday...rain showers likely with MVFR or Lower. North winds 25-30g35kt.
Sunday...most likely VFR with northwest winds 20-25kt. Potential for gusts
up to 40kt.
Monday...VFR. Northwest winds 15-20g25kt.
&&
Marine...
web-cams show visibilities along the Atlantic coast and New York Harbor
going down to under a mile at times...so have issued a marine
weather statement for the waters S and west of Long Island through 4
PM for patchy dense fog.
Otherwise...Small Craft Advisory has been extended through Friday as a lingering
swell likely keeps seas up over 5 feet over a good portion of the
ocean waters. Gusts to 25 kts will be possible as well during
parts of this period on the ocean waters as well. Non-ocean waters
through Friday should see gusts peak at around 20 knots...but a few
gusts to 25 knots cannot be completely ruled out.
Small Craft Advisory conditions are becoming increasingly likely...with the potential
for gale conditions Sat into sun...as low pressure forms over the
waters on Friday and lifts slowly to the north and east. Winds and
seas begin to subside late sun into Monday with high pressure
building in from the Great Lakes region.
&&
Hydrology...
there is the potential for around inch basin average rainfall today
through tonight. Higher amounts will be possible in thunderstorms.
Not expecting any widespread flood threat today and tonight...but at
least some minor flooding is probable. Flash flooding is not out of
the question...and this will need to be closely monitored as the day
wears on. Confidence at this time regarding timing/coverage/placement
of flash flooding is too low to go with a watch for flash
flooding.
The threat for localized heavy rainfall will continue into the first
half of Friday with embedded convection. An additional 1/2 to 1 inch of
rainfall is possible Friday night into sun. This may exacerbate any
ongoing flooding.
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 website.
&&
Okx watches/warnings/advisories...
CT...none.
New York...none.
New Jersey...none.
Marine...Small Craft Advisory until 6 PM EDT Friday for anz350-353-355.
&&
$$
Synopsis...jc/NV
near term...maloit/jc
short term...jc
long term...Nevada
aviation...BC/jp
marine...maloit/jc/NV
hydrology...jc/NV
