Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kokx 220907 
afdokx

Area forecast discussion
National Weather Service New York New York
507 am EDT Sat Jul 22 2017

Synopsis...
a weak cold front will remain nearly stationary just south of
the area today and tonight. Low pressure passes just south
tonight. This frontal boundary will be in the vicinity Sunday as
high pressure builds to the north. The high drifts off the
northern New England coast Sunday as a wave of low pressure
approaches Monday, passing Tuesday. High pressure will follow
late Tuesday and Wednesday. Another wave of low pressure follows
for Wednesday night into Friday through Thursday. A cold front
will approach Friday.

&&

Near term /until 6 PM this evening/...
early showers developed, but should pass south of the area early
this morning. Then dry conditions are anticipated through much,
if not the entire day, 6 PM.

Thunderstorm complex over the lower Great Lakes region will need
to be watched, as this moves eastward. This is associated with
weak shortwave/sfc frontal boundary that approaches late in the
day.

Hot temperatures continue today, but expect dew points to remain
lower than they have been over the past few days. Will maintain
the heat advisory for the metropolitan area, as heat indices
approach 95.

Clouds will be on the increase this afternoon ahead of upstream
shortwave, convection.

There is a moderate risk for the development of rip currents at
ocean beaches today.

&&

Short term /6 PM this evening through 6 PM Sunday/...
the upper level shortwave passes tonight, with an associated
area of low pressure passing just to the south per model
consensus. As mentioned in the near term section of this
product, thunderstorms associated with this feature will need
to be watched, with best chances impacting the southern or
coastal zones tonight. Greatest instability resides to our
south, but ample instability along with support aloft could
result in a few gusty storms. Heavy downpours are also
expected.

Upstream shortwave approaches Sunday, with frontal boundary out
ahead of it. Meanwhile high pressure builds to our north and
east. In general, any shower activity diminishes in coverage and
intensity late tonight and through the day Sunday. Plenty of
clouds are anticipated, with some sunshine possible Sunday.
NAM/WRF hangs onto the ridge longer, and is thus drier Sunday.

Temperatures should cool down some tonight and Sunday, as
heights lower, and cloud cover lingers. 60s/70s at night, and
80s during the day expected.

&&

Long term /Sunday night through Friday/...
exact placement of frontal boundary and low pressure remains in
question Sunday night into Monday, but unsettled weather is
expected, with shower and thunderstorm chances continuing
through Monday, with lowering chances Tuesday as the sharpening
trough moves east. This uncertainty in the models and front
placement is observed in large temp disparity in the MOS this
morning for monday's highs. At this time, will split the
difference between the cooler NAM numbers, and warmer GFS MOS.

Weak ridging will build to the west later Tuesday into
Wednesday as high pressure builds to the west. The upper flow
becomes progressive Wednesday as the western Atlantic ridge
weakens and drifts east. Yet another shortwave and cold front
will affect the area Wednesday night into Friday.

&&

Aviation /08z Saturday through Wednesday/...
a weak cold front will remain nearly stationary just south of
the area through tonight. Low pressure will pass just south
along this front tonight.

VFR through today, with local sea breezes developing this
afternoon. Thunderstorm complexes extending from Iowa east-southeast into
western Ohio before daybreak will need to be watched as they
move eastward late today into tonight. Attm think tstms with
gusty winds and local downpours are likely for the NYC metros
after 00z, and also kisp by late evening or midnight.

Outlook for 06z Sunday through Wednesday...
late tonight...showers/tstms still likely mainly for the NYC
metros and Long Island terminals, with MVFR or lower
conditions and gusty winds possible.
Sunday-Monday night...episodes of showers/tstms with MVFR or
lower conds possible.
Tuesday...an am shower possible at kgon, otherwise VFR.
Wednesday...VFR.

&&

Marine...
a weak pressure gradient overall will keep winds and seas below
Small Craft Advisory (small craft advisory) levels of 25 kt and 5 ft through
Saturday night. However, there is the potential for
thunderstorms Saturday night that could result in larger waves
and higher winds, particularly across the ocean.

Winds will remain below small craft levels Sunday through Wednesday.
However, ocean seas may build to marginal small craft levels Sunday
night into Monday as an easterly flow develops and increases Sunday
into Monday night. Then seas are expected to subside for Tuesday and
Wednesday.

&&

Hydrology...
there is still the chance for heavy rainfall tonight across
coastal locations of NE NJ, NYC and Long Island. However, still
believe that the heaviest precipitation from a convective
complex will be mainly to the south of the region. Rainfall
could very well range from under a tenth of an inch across
portions of southern CT, to between a half to one inch across
NYC Metro.

Additional rainfall is possible Sunday night into Tuesday.
Hydrologic impacts are not expected at this time.

&&

Tides/coastal flooding...
with the approach of the new moon (sun), tides will run high
this weekend into early next week. Positive tidal departures of
1/2 to 1 ft will be needed for minor flooding during the night
time high tides during this time.

Minor flooding is possible starting with the high tide cycle
this evening, mainly in the western South Shore bays of Li. A
bit more widespread minor flooding is possible Sunday night if
an E/NE flow develops ahead of an approaching frontal system.
The threat for minor flooding could continue into Monday.

&&

Climate...
Saturday will mark the 4th consecutive day of 90+ degrees temps
for much of the NYC/New Jersey urban corridor.

&&

Okx watches/warnings/advisories...
CT...none.
New York...heat advisory from noon today to 6 PM EDT this evening for
nyz072>075-176-178.
New Jersey...heat advisory from noon today to 6 PM EDT this evening for
njz006-104-106-108.
Marine...none.

&&

$$
Synopsis...precipitable water
near term...precipitable water
short term...precipitable water
long term...met/pw

National Weather Service Glossary of Abbreviations