Scientific Forecaster Discussion
fxus61 kokx 212007
Area forecast discussion
National Weather Service New York New York
407 PM EDT Mon Oct 21 2019
broad and weak high pressure will weaken and drift away tonight. A
complex frontal system will approach during Tuesday with a warm
front, followed by a cold front during Tuesday night. High
pressure will build over the region through the middle of the
week. A frontal system may impact the area late Friday into
Saturday, with another possible by the end of the weekend.
Near term /until 6 am Tuesday morning/...
after the 500 mb ridge axis clear the area early this evening
high clouds initially at around 30 kft will gradually increase
during later this evening. Towards and after 6z the bulk of the
cloud increase will occur with the lower levels following last
closer to 9-10z for much of the area. A northeast flow will
begin to go more easterly closer to daybreak resulting in an
increase in overall lower level moisture. It should remain dry
overnight with lows mainly at or slight above normal. The timing
of the cloud increase will impact overnight lows. For now have
adjusted arrival of clouds up a couple of hours from the
previous forecast, but mainly clear skies initially this evening
should allow temperatures to fall before leveling off later at
Short term /6 am Tuesday morning through Tuesday night/...
a vertically stacked and occluded low pressure system over the upper
Midwest will lift northeast into Canada later Tuesday into Tuesday
night. A complex frontal system to the east and southeast of
the storm will approach during the day on Tuesday bringing
extensive cloud cover in advance of a warm front. Despite good
upper level amplitude, with an overall lack of blocking to the
northeast I do expect the warm front to get through during
Tuesday evening in most places, followed by the cold front for
later Tuesday night, early Wednesday morning.
As far as precip timing and intensity, with the dynamics going
well north of the region we are not anticipating a significant
rainfall event. There should be enough thermal forcing to result
in a light rainfall event where precip amounts average around a
half inch across the cwa, with some higher amounts closer to
three quarters of an inch perhaps across northern and
northwestern sections. The rain should be quite light during the
day on Tuesday with the steadier rain approaching far western
sections during the afternoon hours, say around 20z or so. There
will be some drier air in the mid levels which will preclude any
steadier rainfall until mainly the evening hours. The steadiest
rainfall should fall between 1z and 6z across much of the
forecast area. Towards daybreak Wednesday morning the last of
any rain showers should be getting ready to exit far eastern
sections. Temperatures on Tuesday will average near normal, and
above normal Tuesday night.
Long term /Wednesday through Monday/...
rain will taper off from west to east on Wednesday as the frontal
system pulls away. A westerly breeze can be expected, drying the
area out by afternoon. The nbm was used for temperatures. Winds will
lighten and skies clear Wednesday night. The consmos was favored,
allowing for better radiational cooling. Sunny with highs in the
lower 60s on Thursday with high pressure centered southeast of the
forecast area. The nbm was used for temperatures. A clipper type
system is then progged for late Friday into Saturday. The European model (ecmwf) has
consistent timing and placement with the 00z and 12z runs. The GFS
is further north with the main low. A band of chilly moderate rain
can be expected with an European model (ecmwf) solution, with a few showers possible
under the GFS scenario. A blend of the model data was used for
precipitation probabilities. The nbm was used for temperatures
Friday through Saturday, with the consmos used Saturday night. A
chance of rain returns Sunday and Monday due to a southern stream
upper low and Gulf of Mexico moisture. The European model (ecmwf) is the wet model
with this, with the GFS now dry through the period. The nbm was used
Aviation /20z Monday through Saturday/...
high pressure will gradually give way to a frontal system into
A mainly VFR forecast through the first half of tonight becoming
MVFR into the early morning for all terminals.
NE-north winds averaging around 10kt. Winds veer more east-northeast late
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: ceiling amendments for MVFR possible through
Klga taf comments: no unscheduled amendments expected.
Kewr taf comments: no unscheduled amendments expected.
Kteb taf comments: no unscheduled amendments expected.
Khpn taf comments: no unscheduled amendments expected.
Kisp taf comments: brief MVFR ceiling through 22z possible.
Outlook for 12z Tuesday through Saturday...
Tuesday...MVFR/IFR. Sct -shra daytime then rain at night.
Wednesday-Thursday...VFR. Chc west gusts 20-25kt on weds.
Friday-Saturday...chc MVFR and rain Fri PM into Sat am.
small craft conditions are expected to continue out on the
ocean through at least the day on Wednesday. A dominant easterly
swell will result in rough seas with a period of around 9
seconds, and with waves much of the time running at least 5 to
6 feet for the ocean waters. By Wednesday the winds are expected
to increase to where gusts will approach 25 kts out on the
ocean. Sub Small Craft Advisory conditions are expected for the non-ocean waters
during this time frame, with marginal Small Craft Advisory
winds on the protected waters by Wednesday. Conditions improve
Wednesday night through Friday. Small Craft Advisory conditions
may be needed over the weekend depending on the strength and
position of a frontal system.
no significant rainfall is anticipated through the forecast
for the Tuesday afternoon high tide cycle along the South Shore back
bays minor coastal flood thresholds may be approached. The current
forecast calls for coastal water levels to fall just below or barely
touch minor coastal flood thresholds in some of the South Shore Back
Bay locations of southern Nassau and southern Queens. At this time
no statement or advisories have been issued.
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) remains off the
Marine...Small Craft Advisory until 8 PM EDT Wednesday for anz350-353-