Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kokx 211818 
afdokx

Area forecast discussion
National Weather Service New York New York
218 PM EDT Wed Aug 21 2019

Synopsis...
a cold front will slowly approach through Thursday. The front
moves across and southeast of the region Thursday night. The
front will move farther southeast of the region Friday into the
weekend as high pressure builds in from the north. Weak low
pressure areas and a frontal system approach early into the
middle next week.

&&

Near term /through tonight/...

Have decided to go with scattered wording for showers and tstms
based on latest radar and satellite obs. Still think that
showers and tstms will pop up in/near the forecast area given
current cape and shear along with a partly sunny sky. Looks like
the best mid level lift and shear moves through this afternoon.
A Severe Thunderstorm Watch is in effect into this evening. The
biggest threat for severe weather would be with wind gusts,
however large hail, although not likely, cannot be completely
ruled out, particularly in CT where the best combination of
shear and cape in the hail growth zone exists.

Finally, there is an isolated flash flood risk where the heaviest
storms concentrate. This will likely be near boundaries with storm
motion otherwise east around 10-15 kt.

Temperatures and heat indices should recover after a brief
cloudy period earlier this afternoon. No changes therefore to
the heat advisory.

The precipitation is expected to wind down from west to east
late this evening as the upper support exits. There could be
some patchy fog late with a residual moist environment.

&&

Short term /Thursday/...
the models have backed off on thunderstorm chances for the bulk of
Thu, but with the cold front still on the doorstep, at least slight
chances have been retained, particularly in the afternoon. Dewpoints
are modeled to be a bit lower with more of a westerly component to
the wind. However, the models have been a bit low in general, so as
previously mentioned a more humid forecast has been issued.

There is a moderate rip current risk for Thu.

&&

Long term /Thursday night through Tuesday/...
upper trough moves near and eventually northeast of the region
Thursday night into start of weekend. Upper level ridging moves
across for the weekend into early next week. Solution consistent
between GFS and Canadian models but European model (ecmwf) model breaks off a piece
of the trough and keeps it near region as weak upper level low for
the weekend. For next week, the ridge eventually moves east of the
region with a weak trough approaching from the west.

At the surface, the cold front will be within the region to start
Thursday night and by Friday morning should be southeast of Long
Island. The front will continue moving southeast of Long Island
going into the weekend. GFS and Canadian models likewise show a more
steady front movement southeast of Long Island while European model (ecmwf) shows a
little slower movement and closer proximity of low pressure to the
region along the front.

For weather, a continued chance of showers and thunderstorms
Thursday evening but would expect thunder chances to decrease with
the more northerly flow developing behind the front and overall
instability trending downward. Showers chances linger into Friday
morning. Then, dry conditions are forecast for the much of the
weekend. Depending on how low pressure trends along the front to the
south and a frontal system approaching from the west going into
early to middle of next week, there could be a return to rain in the
forecast. Currently, it seems this scenario is more of a low end
possibility, so limited rain to slight chance, with mainly dry
conditions anticipated.

Temperatures overall forecast to be slightly below normal.

&&

Aviation /18z Wednesday through Monday/...
a trough of low pressure develops this afternoon ahead of an
approaching cold front with a chance of showers and
thunderstorms. Coverage of showers and thunderstorms will
increase late this afternoon, with MVFR or IFR possible in any
thunderstorm. Thunderstorm chances diminish later this evening
and overnight. Confidence in timing, placement and coverage
remains low.

Southerly winds increase to 10-15 kt with gusts to around 20 kt
possible at the NYC terminals during the afternoon. Winds
lighten from the SW this evening and overnight.

New York Metro enhanced aviation weather support...

Detailed information, including hourly taf wind component forecasts,
can be found at: http:/www.Weather.Gov/zny/n90

Kjfk taf comments: amendments are likely due to uncertain
coverage of thunderstorms late this afternoon.

Klga taf comments: amendments are likely due to uncertain
coverage of thunderstorms late this afternoon.

Kewr taf comments: amendments are likely due to uncertain
coverage of thunderstorms late this afternoon.

Kteb taf comments: amendments are likely due to uncertain
coverage of thunderstorms late this afternoon.

Khpn taf comments: amendments are likely due to uncertain
coverage of thunderstorms late this afternoon.

Kisp taf comments: amendments are likely due to uncertain
coverage of thunderstorms late this afternoon.

Outlook for 18z Thursday through Monday...
Thursday-Thursday night...mainly VFR, MVFR or lower is
possible in showers and thunderstorms.
Friday-Monday...VFR. MVFR in stratus possble Sunday night.

&&

Marine...
southwest flow will increase today, resulting in the need for a
Small Craft Advisory on the ocean for late today and tonight.
The advisory may need to be extended into Thu, depending on how
quickly seas subside to below 5 ft.

Conditions on the waters are expected to remain below Small Craft Advisory criteria
Thursday night through much of the weekend with the pressure
gradient remaining relatively weak. However, by late Sunday into
Monday, pressure gradient is forecast to tighten between strong high
pressure to the northeast and low pressure to the south and west.
Ocean zones will have greatest chance of seeing Small Craft Advisory conditions late
Sunday into Monday while non-ocean zones have seas remaining well
below Small Craft Advisory but wind gusts approaching 20 kt.

&&

Hydrology...
precipitable water is around 2 inches today. There is therefore
an isolated flash flood threat, as any storms that develop will
be capable of producing torrential rainfall. No hydrologic
impacts expected Thursday through early next week.

&&

Equipment...
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) remains off
the air.

&&

Okx watches/warnings/advisories...
CT...none.
New York...heat advisory until 8 PM EDT Thursday for nyz072>075-176>179.
High rip current risk from 5 PM this afternoon to 9 PM EDT
this evening for nyz075-080-081-178-179.
New Jersey...heat advisory until 8 PM EDT Thursday for njz006-104>108.
Marine...Small Craft Advisory until 6 am EDT Thursday for anz350-353-
355.

&&

$$
Synopsis...
near term...jc
short term...
long term...jm

National Weather Service Glossary of Abbreviations