Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 222014

Area Forecast Discussion
National Weather Service New York NY
414 PM EDT Thu Oct 22 2020

A mild, humid airmass will remain in place through the end of the
week. A cold front will move through on Saturday, followed by high
pressure building to the north Saturday night into Sunday. A
frontal system will then impact the area through the middle of
next week.


A mid 1020s high stretched from Ontario into nrn New England this
aftn. A weak pres field over the fcst area has resulted in light
flow, and the weak front previously analyzed appears to be mainly

After a brief period of nely flow, winds have returned onshore and
light fog remains near some of the coasts. This suggests a likely
return of fog and dz tngt. The NAM has been the most aggressive, with
the 15Z SREF and NARRE supporting the soln. Dry air aloft lends
further support to the potential for dz. For these reasons, a more
aggressive approach was taken wrt fog and dz coverage tngt.

Because the model data does not support widespread 1/4sm vis or
less, and the deeper llvl moisture profile and dry air aloft adds
support for dz, a dense fog advy has not been issued attm. This does
not rule out the potential for dense fog to develop tngt, along with
the need for a possible short fused advy.

There as of yet is nothing upstream to support the GFS idea of isold-
sct shwrs into this eve, so pops have been kept blw slight chc per
the NBM.


A drier llvl airmass will attempt to gather across ME tngt, then
advect swwd into or close to the fcst area thru Fri. The latest
progs suggests it may at least reach the far ern portion of the cwa.
Confidence is low however with this amount of precision. The
modeling then indicates that even this wedge of dry air will be
overcome by the continual moist onshore flow Fri ngt.

Therefore, fog and dz is expected late into Fri mrng, then some
sprinkles or patchy dz for the rest of the day west of this dry air
slug. Fog and dz is then expected to expand again Fri ngt across the
entire area. Time heights indicate a little subsidence Fri ngt, so
this may have some impact on the coverage of fog and dz. As a
result, went only with patchy in the fcst for now.

For temps, if we were to mix down from h85 highs would be near 80.
But this is not the case, and despite the warm temps aloft, highs in
the mid 60s are expected. The NBM was used with the typical local
adjustments thru the period.


Little overall change in the upper air pattern as the mean
upper trough across the Northern Plains and Upper Midwest
gradually translates slowly east through the period. This
will mean above normal heights and ridging across the western
Atlantic and eastern seaboard. Global models are generally
pointing to a pattern change toward the end of period as the
upper trough works into the northeast quarter of the country.

The biggest change in the extended is the handling of the
frontal system that impacts the area late Sunday night through
mid week. There is had been good agreement in the prior days
runs with a cold frontal passage on Tuesday, followed by high
pressure for the second half of the week. Both the 12Z ECMWF and
GFS now stall the front across area Tuesday with the potential
for multiple frontal waves traversing the region with rain
Tuesday night into Wednesday. The ECMWF is much quicker in
sending the front southward on Wednesday and drying conditions
out, while the GFS continues to load up with southern branch
energy as a closed upper moving into to the Lower Mississippi
shears out to the northeast. Complex interaction between
northern branch shortwave energy dropping into the mean trough
and the interaction with the aforementioned closed upper low
emerging from the Southern Plains will likely result in several
different solutions in coming days until the guidance locks onto
a solution. The GGEM is completely at odds with the both the
GFS and ECMWF, but does interestingly stall another boundary mid
week. Bottom line, forecast is more of a consensus of the ECMWF
and GFS. Thus, looking at inclement weather with a chance of
showers/rain late Sunday night through middle of the week.
Timing will be better resolved as the event approaches.

Prior to then, a dry cold frontal passage on Saturday will be
followed a quick shot of cool air on Sunday before moderating
back to just above seasonable levels for much of the period.
Unseasonably cold air looks to arrive late next week.


A weak frontal boundary will remain over the region tonight into
Friday before dissipating. Conditions in the NYC metro area remain
MVFR/IFR, with little to no improvement expected. Outside of the NYC
terminals, MVFR/VFR can be expected through the remainder of the
afternoon and early evening. Conditions everywhere should lower to
IFR/LIFR tonight. Another slow improvement day is expected again on
Friday. Confidence in timing of flight category changes remains low.

Winds will remain light, but may take on SE direction this
afternoon. Winds become light and variable again tonight.

 ...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...

Amendments are possible for fluctuations in flight categories.

.Friday...MVFR or lower possible.
.Saturday...Becoming VFR.
.Sunday...VFR. N winds G15-20kt AM push.
.Sunday night...Chance of showers with MVFR possible late.
SE winds G15-20kt.
.Monday-Tuesday...Chance of showers with MVFR possible at

Detailed information, including hourly TAF wind component
forecasts, can be found at: http:/


Swells from Epsilon have arrived and a SCA remains in effect
thru Saturday night on the ocean. Areas of fog will result in
low vis at times thru Fri ngt on all waters.

Long period swells will be highest Friday night through Saturday
night, then gradually subsiding Sunday through Tuesday. There
will be gusts up to 20 kt on the ocean waters late Saturday
night through Sunday as strong high pressure passes to the
north and low pressure approaches from the southwest.

Please refer to National Hurricane Center products for further
details on Epsilon.


No hydrologic impacts are expected thru the forecast period.


MARINE...Small Craft Advisory until 6 AM EDT Sunday for ANZ350-353-355.



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