Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 212031
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
431 PM EDT Sat Oct 21 2017

.SYNOPSIS...
High pressure will be near southern New England
tonight and slowly drift eastward tomorrow continuing the fair and
dry weather with above normal temperatures across the region. Clouds
begin to increase on Monday with still rather mild temperatures.  A
slow moving cold front impacts the area late Monday night through
Tuesday night with periods of showers and windy conditions.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 430 PM EDT...A ridge of high pressure continues to build
in near the Carolinas with mid and upper level heights rising
across the region. At the sfc, an anticyclone /1027 hPa
according to the RAP/ continues to ridge in from near the
Delmarva region and just south of southern New England.

Some cirrus continues to spill in across the region based on
the visible/IR satellite imagery due to a front north of the St
Lawrence River Valley and a weak sfc wave passing over nrn
Maine. The sky should be mostly clear to clear tonight with some
thin cirrus around. Light to calm winds with the mainly clear
skies in the dry lower atmosphere should allow temps to fall
back into the 40s with some upper 30s in the sheltered valleys
of southern VT, in the northern Berkshires and southern
Adirondacks. Some patchy radiational fog is also possible in the
upper Hudson River Valley and CT River Valley east of the
southern Green Mtns.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Tomorrow...The weekend will close with beautiful weather for
Autumn, as the sfc anticyclone drifts further offshore, and the
H500 high amplitude ridge axis settles right over the eastern NY
and western New England border. H925/H850 temps will be 1 to 2
standard deviations /STD DEVs/ above normal according to the 12Z
GEFS. The actual H925 temps will be in the +15C to +18C range,
a tad warmer than today. H850 temps will be +12C to +14C with a
south/southwest flow increasing in the boundary layer. We leaned
closed to the slightly warmer MAVMOS guidance with highs in the
mid and upper 70s over the valley locations, and mid 60s to
lower 70s over the higher terrain. We are not expecting any
records, but the high temps will be a solid 15 to 20 degrees
above normal.

Sunday night...The low-level southerly flow continues to
increase, as the mid and upper ridge acts as block and only
slightly shifts downstream over central and eastern New England,
as a cold front slowly approaches from near the MS River Valley
and Midwest. A potent southern stream upper level trough begins
to lift northeast from the central and southern MS River
Valley. Overall, expecting some low stratus to form and drift up
the Hudson River Valley with increasing clouds. There may be
some patches of drizzle, but we were not super confident prior
to 12Z/Mon. Lows will be mild in the upper 40s to mid 50s.

Monday...The latest GFS/NAM/ECMWF/CAN GGEM and several ensemble
members show an increase of clouds with a tightening low-level
pressure gradient between the offshore anticyclone and low
pressure moving into the central and eastern Great lakes by late
in the day. Low-level moisture will increase, and some lower
stratus and possibly some light showers/drizzle will move into
locations from the Capital District south during the day. A weak
short-wave impulse embedded in the deep southerly flow will
focus the light showers. Highs will be still mild in the 60s to
lower 70s.

Monday night into Tuesday...A potentially active period for the
forecast area with a strong upper level trough pushing toward
the region. Two pieces of short-wave energy may phase near the
Midwest/central Great Lakes Region, as the mid and upper level
low becomes negatively tilted. A strong cyclone moves through
the central Great Lakes Region and gets captured.

Downstream, a cold or occluded front trudges toward the region
with strong moisture convergence and good dynamical lift. The
guidance has sped up this cycle with showers beginning to
increase from southwest to northeast early Tuesday morning, as
we increased the PoPs. The water vapor transport is increased on
an impressive low-level jet. The 12Z GEFS indicates a low-level
+V-component /southerlies/ wind anomaly of 3 to 4 STD DEVS above
normal impacting the region from 06Z/TUE to 18Z/TUE. PWATS rise
to 1 to 3 STD DEVS above normal. The NAM has the H925 winds
increase to 40-55+ kts ahead of the front between 09Z-21Z TUE.
The 30-AGL winds are also in the 40-50 kt range over the higher
terrain of the forecast area. The GFS/ECMWF also has the H850
winds in the 50-65 kt range. A wind headline of some sort maybe
needed late Monday night into Tuesday if some of these strong
winds translate to the sfc. We have gusts in the 30-45 mph range
at this time especially Tuesday morning into the afternoon. We
will mention the gusty winds in the HWO product.

Also, the latest GFS shows some weak sfc based instability of
100-250 J/kg. The latest guidance is hinting at a narrow cold
frontal rainband with a burst of heavy rainfall and gusty winds
especially late Tuesday morning into the afternoon. It is a high
shear/low CAPE environment. We did place a slight chance of
thunderstorms from the Hudson River Valley and points east. The
cold front is a slow mover, a wave may potentially form along it
early TUE evening which may impact the Hudson River Valley
eastward. We believe a dry slot to the system may move into much
portions of the forecast area prior to nightfall. Showers with
moderate rainfall were placed in the grids, some of the rain
could be locally heavy with a half and inch to an inch and a
half expected Monday night into Tuesday. Additional rainfall is
possible Tue night. Flows remain low, and it have been very dry
so we are not expecting any flooding at this time. After mild
overnight lows in the 50s to lower 60s, our max temps TUE will
still be in the 60s to lower 70s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
The long term period starts out active, but ends on a dry note.
A cold front will cross the region Tuesday night with a wave of
low pressure along the front to our south. This looks to result
in some locally heavy rainfall Tuesday evening. Showers Tuesday
night will linger into Thursday as the upper trough axis and
associated vorticity axis crosses the region. Drier weather is
then expected as a weak ridge of high pressure builds across the
region. The ridge of high pressure will hold into Saturday.
Once it moves off the eastern seaboard Friday into Saturday
temperatures will start to moderate once again to above normal
levels.

Highs on Wednesday will be in the mid 50s to mid 60s, in the upper
40s to upper 50s on Thursday, in the mid 50s to mid 60s on Friday
and in the upper 50s to upper 60s on Saturday. Lows on Tuesday night
will be in the upper 40s to mid 50s, in the mid 30s to mid 40s on
Wednesday night, in the mid 30s to lower 40s on Thursday night, and
in the upper 30s to mid 40s Friday night.

Overall expect temperatures and precipitation to be near normal.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
VFR conditions will prevail through most of the period thanks to
high pressure nosing into the region. There will be some passing
high cirrus clouds this afternoon into the evening. A light
south to southwest breeze around 5 kts will also continue into
the evening before going calm tonight.

There is some potential for fog/mist mainly at KGFL/KPSF for
late in the night into early Sunday morning. Elsewhere, the dry
boundary layer and large temperature/dew point spread should
prevent any fog from forming and/or keep it shallow towards
daybreak.

Outlook...

Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: High Operational Impact. Windy With Gusts To 30.0 Likely SHRA...FG.
Tuesday: High Operational Impact. Windy With Gusts To 32.0 Definite SHRA...TSRA.
Tuesday Night: High Operational Impact. Definite SHRA.
Wednesday: Moderate Operational Impact. Chance of SHRA.
Wednesday Night: Moderate Operational Impact. Chance of SHRA.
Thursday: Moderate Operational Impact. Chance of SHRA.

&&

.FIRE WEATHER...
High pressure will be near southern New England
tonight and slowly drift eastward tomorrow continuing the fair and
dry weather with above normal temperatures across the region. Clouds
begin to increase on Monday. A slow moving cold front impacts
the area late Monday night through Tuesday night with periods of
showers and windy conditions.

The RH values will recover to 70 to 100 percent tonight, and
then lower to 25 to 40 percent tomorrow afternoon. An excellent
recovery is expected Monday morning with max RH values in the 90
to 100 percent range.

Winds will be light to calm tonight, and then will be south to
southwest at 5 to 10 mph tomorrow. Expect southerly winds of 10
mph or less Sunday night.

The next widespread soaking rainfall will be Monday night into
Tuesday night.

&&

.HYDROLOGY...
No precipitation is expected prior to Monday with high pressure
in control, as river flows will remain at normal to below
normal levels.

The next chance of widespread rainfall arrives Monday night
into Tuesday night associated with a cold  front. Rainfall
amounts may range from three quarters of an inch to an inch and
three quarters from this system. Some locally heavy rainfall is
possible. The heaviest totals may be east of the Hudson River
Valley across western New England. Some ponding of water on
roadways is possible as well as clogged drains from leaves.

Another round of wet weather is possible later in the week, but
there remains quite a bit of uncertainty with evolution and
track of the system and the QPF with it. For now, light amounts
of additional rainfall are expected. Overall, a trend to drier
weather is expected Friday into Saturday.

For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...Wasula
NEAR TERM...Wasula
SHORT TERM...Wasula
LONG TERM...11
AVIATION...JVM
FIRE WEATHER...BGM/Wasula
HYDROLOGY...BGM/Wasula



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