NYC Office Forecast Discussion

841
FXUS61 KOKX 271807
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
107 PM EST Fri Nov 27 2020

.SYNOPSIS...
High pressure over the area will give way briefly to a weak
low pressure trough late this afternoon and this evening. A cold
front will then approach and pass through Saturday morning,
followed by high pressure on Sunday. Developing low pressure
across the Gulf States Sunday night will rapidly deepen on
Monday as it moves up the Appalachians toward the Ohio Valley by
Monday night. The low will then meander across the Great Lakes
region through the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Forecast is generally on track. Made updates to temperatures
and dewpoints as well to account for current observations and
trends. Clearing from this morning over long Island and the NYC
metro has allowed temperatures to rise a bit more than
anticipated so this update accounts for that slight increase.

Skies have become increasingly covered by developing clouds
mainly from daytime heating and the approaching weak trough.
Guidance earlier this morning indicating possible weak showers
over CT and the Lower Hudson Valley have no materialized so
those chance pops were also removed for this update. The
remainder of the day should remain dry though remain quite
cloudy for these areas.

Think a persistence fcst is in order with sky cover til a cold
front passes through on Sat. So for tonight expected partly to
mostly cloudy skies with lows from the upper 30s to mid 40s.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
A longwave upper trough swings through on Sat with an attendant
sfc front, marked more by moisture than temperature change as a
partly to mostly cloudy morning yields to afternoon sunshine in
their wake and falling dewpoints, while temps still rise into
the 50s. Colder Sat night under mostly clear skies and fairly
good radiational cooling as high pressure builds in, with lows
25-30 inland, in the 30s most elsewhere, and around 40 in NYC.

Skies start off sunny to start on Sunday, then should see
increasing high/mid clouds well ahead of the next storm system
as upper ridging passes E and a deep layer SW flow develops.
Highs again in the 50s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Deterministic and ensemble guidance continues to come into
better agreement through early next week, with a rapidly
deepening low pressure system impacting the northeast Monday
into Monday night. Low pressure will develop over the
southeast states ahead of a srn stream cutoff low that will move
eastward through the weekend. The models then show a northern
stream trough amplifying rapidly as the two streams phase Sunday
night into Monday. The process then creates an anomalously
strong upper low that will cover much of the country east of the
Great Plains Monday into Tuesday. The upper low will only
slowly meander north-northeast Tuesday becoming positioned over
northern New England and southeast Canada during mid week.

The most significant impacts from the system currently look to
occur Monday into Monday night from a rapidly developing low
pressure that quickly tracks up the Appalachians on Monday. A
plume of subtropical moisture is likely to bring moderate to
locally heavy rainfall. A strong low and middle level wind field
develops well ahead of the low and in advance of the associated
frontal system. Will have to monitor model trends in the next
several days, but with potential for a 60-70 kt LLJ see
potential for wind gusts up to 45 mph along the coast. Current
model consensus has the frontal system moving across the area
Monday afternoon, and with the storm track well to our west,
all rain is forecast.

The low occludes towards the Ohio Valley or lower Great Lakes
Monday night and becomes vertically stacked Tuesday as it
meanders slowly into southeast Canada. A potent shortwave
trough within the upper low may pivot across on Tuesday,
supporting a continued chance of rain.

The forecast trends dry Wednesday and Thursday as the surface
low slowly weakens. The warmest day will be Monday as
temperatures could approach 60 degrees. It likely stays mild
Monday night with cooler temperatures in the 50s on Tuesday.
Highs for the middle of the week will be in the 40s.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
VFR through the TAF period. Sfc high pressure overhead with a
weak pressure gradient results in light and variable winds.

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

No unscheduled amendments are expected through this evening.

.OUTLOOK FOR 12Z SATURDAY THROUGH WEDNESDAY...
.Saturday and Sunday...VFR. NW winds 5-10kts, G15-20kts
possible Sat. afternoon.
.Monday...MVFR with rain likely. SE wind 10-20kt G20-35kt, strongest
near the coast.
.Tuesday...MVFR with chance SHRA.
.Wednesday...VFR. W winds 10-15 kts.

Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90

&&

.MARINE...
Seas have subsided below 5 ft on the ocean. Winds and seas on
all waters will then remain blw sca lvls thru the weekend. A
strong low pressure system will impact the waters Monday into
Tuesday. Gales are possible on all waters Monday into Monday
night, with small craft conditions possible on Tuesday. High
ocean seas look likely, especially late Monday into Tuesday.
Seas may build to 9 to 12 ft. There may also be 4-6 ft seas on
Central and Eastern Long Island Sound.

&&

.HYDROLOGY...
A period of moderate to heavy rain is expected Monday into
Monday night. Model consensus at this time has the most
significant rain occurring Monday afternoon and evening. A
widespread 1 to 2 inch rainfall is possible, which could lead to
some minor impacts.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until 1 PM EST this afternoon for ANZ350.

&&

$$
SYNOPSIS...DS/MW
NEAR TERM...MW
SHORT TERM...MW
LONG TERM...DS
AVIATION...DBR
MARINE...DS/MW
HYDROLOGY...DS/MW

NWS OKX Office Area Forecast Discussion