Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 220502
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
102 AM EDT Mon May 22 2017

.SYNOPSIS...
High pressure moves east of the area today. A series of low pressure
systems will impact the area through the week, resulting in
periods of unsettled weather.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Clouds continue to overspread the area tonight, although plenty
of dry air remains at low levels per 00Z KOKX sounding and
observations reflecting near 20 degree temperature/dew point
depressions. Recent observations show very little if any rain
currently reaching the ground, and would expect this trend to
continue until towards day break. Last several runs of the HRRR
have been indicating quick development of rain with approaching
shortwave after 06z, so will need to monitor trends over the
next few hours.

Overnight lows of 45-55 degs are fcst, slightly lower than
normal based on southeast winds off the cool Atlantic Ocean.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
Light precipitation will be possible around day break, gradually
increasing into a brief period of moderate rain through the
afternoon as a short wave moves through the area and warm/moist
advection increases. Outside of the afternoon, model sounding
profiles generally lean more towards a stratus/drizzle profile
which should help to reduce overall rainfall amounts.
Additionally, deterministic and ensemble models have trended
southward with the heaviest rainfall, which may now skirt
south of Long Island. Have reduced total QPF values to reflect
these trends, with rainfall totals now expected to be around 1
to 1 and 1/2 over a broad period from today through tomorrow
morning. Minor urban flooding of low lying poor drainage areas
is possible, primarily associated with any locally heavier
downpours that may occur with isolated thunderstorms.

As southeast winds continue blowing off the cool Atlantic
Ocean, day time temperatures will range 60-65 degrees. By
evening, rainfall will gradually decrease from west to east.
There may be a brief period of fog as moisture remains beneath
the inversion until the cold front moves through leading to
drier conditions overnight.

Tuesday...As the upper lvl low digs SE across the Western Great
Lakes, another short wave will rotate arnd the base of this low,
causing cyclogenesis in the SE that will move NE toward the
region, bringing our next chc of rain.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The developing upper trough over the central U.S. will continue
to amplify over the midwest and southern plains Tuesday night,
then move slowly east through the end of the work week. This
will result in unsettled weather through the period as a series
of lows and upper level vorts move through, bringing multiple
chances for rain to the region.

Models are in somewhat better agreement in the large scale trough
evolution, although differences continue in the timing and placement
of individual shortwaves and the associated sensible weather. Based
on the 12Z model suite, the general consensus is for a period of
rain Tuesday night into Wednesday, then again on Thursday, with a
chance of lingering showers in between.

The trough begins to lift to the northeast late in the week as a
ridge builds in for the weekend. This will allow for generally dry
conditions for a period Friday into Saturday. Models then diverge on
the placement of a shortwave undercutting the ridge, which could
bring a chance of rain back to the region on Sunday.

Daytime highs will be near normal through the majority of the
period, before rising to a few degrees above normal by the weekend.
Overnight lows will run around 5 degrees above normal through the
weekend.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
High pressure continues moving offshore tonight as a frontal
system approaches through Monday

Gradually weakening SE winds tonight, especially away from city
terminals. SE winds will increase again around day break and
continue through Monday, generally 8 to 13 kt.

VFR conditions continue until around day break. MVFR and rain
develop in the morning, with conditions lowering to IFR by late
morning and early afternoon. IFR should then continue into the
evening. There is uncertainty with the timing of lowering
conditions as well with the rain. Actual observation could be
off by 2 to 4 hours from forecast.

There is also a slight chance for thunder. Confidence on timing
and placement is too low to include in the TAFs at this time.

.OUTLOOK FOR 00Z TUESDAY THROUGH FRIDAY...
.MONDAY NIGHT-TUESDAY...IFR early then gradually becoming VFR
Tuesday morning. VFR thereafter.
.WEDNESDAY-FRIDAY...MVFR or lower possible in showers. Slight
chance of thunderstorms Thursday evening.

&&

.MARINE...
Sub-advsy conds will remain across the waters through tonight as high
pressure gradually slides off the New England coast.

SE winds will increase to 15-20 kt as seas build to around 4 ft during
the day Monday across the Atlantic Ocean coastal waters. Areas of
fog are forecast to restrict VSBY to 1-3NM area wide through Monday
evening.

While winds will generally remain below SCA conditions, seas will
begin to increase on Wednesday as a series of lows move over the
area. SCA conditions are possible on the ocean waters Wednesday-
Friday before seas begin to subside on Saturday.

&&

.HYDROLOGY...
Rainfall accumulations of a half inch to one and a half inches
is possible from today through tomorrow morning. Minor urban
flooding of low lying poor drainage areas is possible.

Several opportunities exist for widespread rainfall during the mid-
to late-week time period. Around one inch of additional rainfall is
possible during this time period, although considerable uncertainty
exists in the details of these events.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$
SYNOPSIS...FEB/GC
NEAR TERM...FEB/MD
SHORT TERM...GC/MD
LONG TERM...FEB
AVIATION...DS
MARINE...FEB/GC
HYDROLOGY...FEB/GC/MD



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