Scientific Forecaster Discussion
fxus61 kokx 210619
Area forecast discussion
National Weather Service New York New York
219 am EDT Mon Aug 21 2017
high pressure building into the region through Monday morning
will settle to the south and east Monday afternoon, allowing a
weak warm front to approach Monday night. After a hot and humid
Tuesday, a cold frontal passage on Wednesday will produce a
drastic cool down for the end of the week.
Near term /until 6 am this morning/...
temperatures were slightly lowered compared to previous
forecast. Otherwise, the rest of forecast is on track.
Weak ridging aloft with high pressure building leading to
mostly clear skies overnight. This along with diminishing winds
should allow temps to drop to the 50s and 60s in most areas,
with only NYC remaining above 70 overnight.
Short term /6 am this morning through 6 PM Tuesday/...
sky cover could be tricky in spots for the partial solar
eclipse, which should run from about 120 PM to 400 PM in NYC
and peak at 244 PM. Do expect some sct high clouds and also some
sct cu, possibly a narrow band of broken cu with the sea breeze
closer to the North Shore of Long Island and in southern CT.
South facing coastlines may be better viewing locations as any
lower clouds that form inland with the sea breeze.
Temps should rise quickly into early afternoon, and per 15z run
of the hrrrx which has been modified to incorporate impact on
incoming solar radiation due to the eclipse, may actually drop a
couple of degrees between 2-4 PM, then rebound. Overall temps
should still reach the mid/upper 80s, possibly 90 in parts of
urban NE New Jersey.
The approaching warm front could spark an isolated shower or
tstm toward sunset well west of NYC, with slight chances
overspreading nearly all the area later Mon night. Lows should
be in the upper 60s/lower 70s, and it will become muggy as
dewpoints also increase into that range.
There is a moderate risk of rip currents at Atlantic beaches on
Long term /Tuesday night through Sunday/...
a cold front will reach the area on Wednesday per the 12z suite of
model guidance, which was in good agreement. This means that Tue is
setting up to be hot and humid. Winds progged around 200 degrees
will pump lots of humidity into the area, and across the ern half of
the County Warning Area keep actual temps slightly suppressed despite 850 mb
warming towards 20c. The humidity will compensate for any lack
of heat, with just about all areas likely aoa 90 for a heat
index. Across the normally hottest areas like New Jersey zones, the
heat index attm looks to reach about 100. There could be a few
aftn and eve tstms, particularly north and west of NYC, but there will
at least be an increase in dense cirrus from upstream
convective debris. As a result the fcst GOES mostly cloudy by
Tue eve. Shwrs and tstms ahead of the front Tue ngt and Wed,
then the area dries out for the remainder of the fcst period.
The cold front will be driven by a 100-kt 300 mb jet, so tstms will
be easier to sustain or initiate at ngt. If the timing ends up
slightly slower, a svr outbreak is possible on Wed as cape could
soar to 3000 j/kg or more. Even with the progged faster timing
however, there could still be svr at any time ahead of the front
with the jet acting on MUCAPE around 1500-2000 j/kg. Much cooler
weather will then settle in for Thu-sun, with temps averaging
Aviation /06z Monday through Friday/...
VFR through the taf period as high pressure remains in control.
Isolated shra possible late evening for NYC/New Jersey and northwest
SW winds will increase this morning into the afternoon, with
southerly sea breeze development at coastal terminals. Gusts of
15 to 20 kt likely this afternoon. SW winds diminish to less
than 10 kt this evening.
Outlook for 06z Tuesday through Friday...
Monday night...VFR. Isolated shower possible. Low chance MVFR
or lower stratus/fog at eastern terminals.
Tuesday-Tuesday night...isolated aft shra/tsra. Chance of more
widespread showers and thunderstorms with MVFR or lower Tuesday
night into early Wed morning. VFR SW winds g15-20kt Tuesday
Wednesday...becoming VFR in the morning with northwest gusts 15-20 kt.
high pressure over the waters will lead to sub-Small Craft Advisory conditions
through Monday night. A few gusts up to 20 kt are possible on
the waters west of Fire Island Inlet in the afternoon due to sea
Winds and seas will ramp up on Tue, with Small Craft Advisory conditions
developing on all waters. Winds will decrease after a cold
frontal passage, bringing winds the protected waters blw Small Craft Advisory
lvls by Wed eve. On the ocean, seas should linger around 5 ft
into Wed ngt. Winds and seas are then progged to remain, in the
absence of any increased swell, blw Small Craft Advisory lvls thru the weekend.
no widespread hydrologic impacts are forecast through the week.