Scientific Forecaster Discussion
fxus61 kokx 160151
Area forecast discussion
National Weather Service New York New York
951 PM EDT sun Sep 15 2019
high pressure over the area gives way to a weak cold front
overnight. This front moves through Monday into Monday evening.
High pressure then returns thereafter and remains in control
through the end of the week.
Near term /until 6 am Monday morning/...
the forecast is mostly on track. Minor adjustments to evening
hourly temps, dewpoints, and winds were made with this update.
An approaching upper level trough will allow for some increase
in clouds. Latest okx sounding fairly dry. Most clouds will be
mid to upper level and conditions are expected to remain dry.
There will be light winds but with the clouds, expect some
partial mitigation of radiational cooling. Mav/met blend was
used for lows, with some manual adjustment down 1-2 degrees for
eastern sections of the region where there will be a greater
time period with less clouds and therefore more radiational
cooling. The range for forecast lows will be mostly from the
upper 50s to upper 60s.
Short term /6 am Monday morning through Monday night/...
the high pressure gives way on Monday to an approaching weak
frontal system. There will be an associated weak cold front
that will approach as well. Models convey the passage of the
front to occur Monday and farther south of Long Island going
into Monday evening. The pressure gradient remains weak so winds
will be light and direction will be variable. Behind the front
Monday night, winds slightly increase and become more NE.
Concerning the rain showers with the front, not much is expected
looking at the consensus from numerical models. The forcing aloft
shown with the 500mb vorticity shows most of the positive vorticity
advection to the northeast of the region. Little to no surface
instability is forecast ahead of the front. Overall, not expecting
thunderstorms or any organized heavy rain. However, will have a
chance (around 30 percent) between 16-00z. For shower coverage,
expecting generally isolated to scattered.
Highs on Monday with the extra clouds and light winds as well as
limited vertical mixing, will be a few degrees cooler than the
previous day for high temperatures (mostly mid 70s to near 80).
Used mav/met/ecs blend but with less weight for met which
seemed too low.
Lows Monday night will once again have some mitigation of
radiational cooling but this time it will be because of
increasing winds late that will keep boundary layer more mixed.
Used relatively warmer mav guidance for lows which mainly range
from the lower 50s to lower 60s.
There is a moderate risk of rip current development at the ocean
beaches on Monday.
Long term /Tuesday through Sunday/...
longwave trough over the Canadian Maritimes will be slow to move
east into the North Atlantic Tuesday into Wednesday. However,
deterministic models and ensemble means indicate ridging aloft and
at the surface dominating the synoptic pattern through the weekend.
Dry weather is expected through the long term. Mostly sunny on
Tuesday, but probably a little more in the way of clouds during
Wednesday as models show some moisture in the 850-925mb layer. There
appears to be a diminishing chance of low stratus and drizzle weds
night through thurs night as winds and the strength of high pressure
over the region through this period become less favorable for
formation. Highs near normal on Tuesday, then a couple of degrees
cooler on Wednesday and Thursday. The wind flow becomes more
offshore for most of the area Friday through Sunday with high
temperatures warmer than normal.
Aviation /02z Monday through Friday/...
VFR conditions overnight, mainly mid and high clouds. A weak
cool front will pass through early Monday morning. Mainly VFR
ceilings are expected Monday, but MVFR is likely at kswf for
most of the day. A few sprinkles are possible during the day
across most terminals.
Light winds overnight shift to the north at most terminals between
9z-12z. Winds should then veer NE later in the morning, maybe
even east-southeast early afternoon at bdr/gon. East/southeast possible at JFK and
isp later in the afternoon.
Outlook for 00z Tuesday through Friday...
Monday night...VFR with clearing skies.
Tuesday and Wednesday...VFR with high pressure in control.
Thursday and Friday...VFR. Can't rule out late night/early
morning radiation fog at the inland terminals.
overall, a weak pressure gradient remains through Monday evening
with some increase in pressure gradient late Monday night.
Conditions will be below Small Craft Advisory through Monday night for all
waters, but NE gusts to near 20 kt are expected late Monday
night mainly for the ocean.
NE winds on Tuesday diminish through the day. This will lead into an
extended period of east-NE sustained winds 10-15 kt with gusts under 25
kt through Thursday afternoon. Winds then become lighter Thursday
night as they veer towards S, then eventually SW-west on Friday.
Small Craft Advisory conditions are however possible on the ocean starting Wednesday
afternoon as ocean swells increase to 5 ft in association with
no significant hydrologic impacts through the end of the week.
NYC National oceanic and atmospheric administration weather radio station kwo35 (162.55 mhz) remains off