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Area forecast discussion 
National Weather Service Albany New York
124 am EDT Thursday Sep 3 2015

Synopsis...
a warm and humid air mass will be over the region tonight. A cold
front will move from northern New York...northern New England...
and the eastern Great Lakes region southward across eastern New
York and western New England tomorrow with isolated to scattered
showers and thunderstorms. A slightly cooler and less humid air
mass will build in Thursday night into Friday...but above normal
temperatures will return for the Holiday weekend.

&&

Near term /until 6 am this morning/...
as of 100 am EDT...all is quiet at the moment with a thin scattered-broken
high level cirrus/cs overspreading the region. Per the infrared satellite
trends...clouds top temperatures were warming the past couple of hours
with upstream convection over lower Ontario/Quebec diminishing.
This negates the hires forecast reflectivity forecasts where we
should be seeing a scattered line of convection at this time.
Therefore...we have dropped back the probability of precipitation/weather across the dacks to
slight chance toward sunrise. Otherwise...main issue overnight
will be haze/mist to patchy fog overnight with mild minimum
temperatures.

Previous disc...some radiational cooling will occur ahead of the middle
and high clouds associated with the cold front. Temperatures should not
fall off as much as last night...but some u50s are possible across
the southern dacks...southern Vermont...northern Taconics...northern Berks and eastern
Catskills with lower to m60s in most other spots. Patchy
radiational fog was added to the forecast in the major river
valleys...as well as near Lake George/kgfl...and parts of southern
Vermont...and the Berks.

&&

Short term /6 am this morning through Saturday/...
tomorrow...a shift in air masses is briefly expected with the
cold front moving S/southeast across the aly forecast area tomorrow to close
the work week. After any morning fog dissipates...the skies will
become partly to mostly cloudy with isolated-scattered showers and
thunderstorms popping up in the late morning/early PM...initially
mainly north of the capital district...Mohawk Valley...and
Berkshires...and then expanding to these locations south and east
in the middle PM into the early evening.

The NAM continues to have more instability than the GFS due to
slightly higher dewpoints /more widespread u60s to l70s/ yielding
sbcapes of 1000-2500 j/kg...while the GFS has sbcapes in the
750-1500 j/kg range or so with surface dewpoints mainly in the 60s. The
better upper jet dynamics are north of the region...and shift down
stream. Hence...the 0-6 km bulk shear values are only 15-20 kts
north of the capital region...and 10-15 kts later in the day
further south. The instability is moderate...but the shear is
weak for well organized convection. Some loosely organized cells
or mainly pulse like convection could form with differential
heating boundaries or ahead of the low-level convergence to the
front. The better middle level lapse rates are actually west of the
forecast area during the day...with middle level lapse rates only about
5.5-6c/km over the aly area.

Some strong thunderstorms may be possible with gusty winds...but
we are not expecting any widespread severe threat. If one were to
occur it would be isolated due to the limited deep shear...and would
likely be if a storm sustained a tall enough updraft from the
higher cape values. The GFS does indicate some dcapes values of
greater than a 1000 j/kg from the west-central Mohawk Valley W/SW.
Overall...agree general thunderstorms will be the main
issue...which is in agreement with the latest Storm Prediction Center day 2 guidance.
H850 temperatures still in the 15c to 17c range ahead of the boundary
should allow maximum temperatures to reach the middle and u80s in the
valleys...with a few 90f readings in the middle Hudson Valley/southern
Litchfield city...and u70s to m80s over the hills/mtns. Precipitable waters are
in the inch to inch and two thirds range ahead of the front...so
some locally heavy downpours may be possible with any convection.
The rainfall has been sparse over the past few weeks.

Thursday night...the cold front continues to move south of the forecast
area in the early evening. Isolated showers/thunderstorms should end
prior to midnight over the eastern Catskills...middle Hudson Valley...and
Berkshires...and northwest CT. The low level cold advection is impressive
in the h925-850 layer with the wind veering from the north to the
east. H850 temperatures lower to 12c to 14c over the forecast area. The surface
dewpoints will fall into m40s to l50s over the southern dacks/Lake George
region...with lower to m50s from the capital region north and
west...and m50s to l60s south and east. The skies will clear
from the north/northwest to S/southeast with clouds lingering the longest over the
southern reaches of the forecast area.

Friday...a nice close to the work week to set up for the Holiday
weekend. A Canadian anticyclone will be ridging in from southeast Quebec
and northern Maine. Low level cold/dry advection will continue through
the morning...with h850 temperatures lowering to 11 to 13c over most of
the forecast area. Highs will still be a shade above normal for early
sept...but it will feel less humid than the previous few days.
Mostly sunny conditions will occur most of the day from the
capital region north...and partly to mostly sunny conditions will
return to the south and east...after the clouds break up.
Highs will be in the 75-80f range in the valley areas...with u60s
to m70s over the hills and mountains humidity levels will be
comfortable.

Friday night...a pleasant evening is expected with clear/mostly clear
skies and calm winds...as the surface high moves over New York and New
England. Ideal radiational cooling conditions will occur...and
lows will be mainly in the lower to m50s with a few u40s in the
southern dacks. Some patchy or areas of radiational fog may form...and
may need to be added to the forecast later in time.

Saturday...temperatures will be slightly warmer than Friday with a middle
and upper level ridge building in over the northeast. A closed
anticyclone may set up over New York and New England late in the day.
Temperatures will continue above normal with an abundance of sunshine due
to the subsidence with the middle and upper ridge...and the surface
anticyclone.

&&

Long term /Saturday night through Wednesday/...
the long term portion of the forecast will feature above normal
temperatures and below normal precipitation...continuing the trend
from the short term.

A ridge of high pressure at all levels of the atmosphere will
provide the dry and very warm conditions through at least Labor Day.
500 mb heights and 850 mb temperatures are forecast to be +1 to +2
stdev according to the gefs which will result in middle level capping
suppressing convection with plenty of sunshine. Normal high
temperatures for Albany by early next week will be the middle
70s...however we will experience temperatures in the middle to upper
80s. Humidity levels should remain somewhat comfortable through
Labor Day.

The next chance of any precipitation arrives on Tuesday as a
weakening frontal boundary approaches from the north and west. The
front will tend to flatten out the ridge somewhat...leading to a
slight chance of showers and thunderstorms across much of the region
with chance probability of precipitation in portions of the western Adirondacks. Only
slightly cooler conditions will occur behind the front...leaving
well above normal readings to persist.

There are some indications that a strong cold front may approach the
region late next week...but this is still uncertain. For now...
above normal temperatures can be expected to continue through the
next 7-10 days.

&&

Aviation /05z Thursday through Monday/...
a weak cold front will settle southward across the taf sites this
afternoon/early evening. Isolated showers/thunderstorms will be
possible with or just ahead of this front.

Through 13z/Thu...patchy ground fog is expected to develop...but
may remain fairly shallow as slightly drier air tries to mix into
the boundary layer toward 10z-13z/Thu. At this time...have
indicated periods of IFR for kgfl/kpsf...while VFR/MVFR for kalb
and kpou.

After 13z/Thu...VFR conditions are expected...outside of isolated
showers/thunderstorms which should develop between 18z-22z/Thu.
Most of the convection is expected to remain west and east of the
taf sites...but can not rule out a couple impacting the taf sites
later this afternoon. Brief periods of MVFR/IFR visibilities could occur
within the cores of any showers/thunderstorms.

Convection should decrease after 00z/Fri...with mainly VFR
conditions continuing through 06z/Fri.

Light/variable winds should persist through 13z/Thu...then trend
into the north to northwest at 5-10 knots this afternoon. Winds will
then shift into the north to NE between 01z-04z/Friday in the wake of the
cold front...at 5-10 knots...although could briefly gust into the
10-20 knots range...especially at kgfl due to channeling down the upper
Hudson/Champlain Valley and Lake George.

Outlook...

Thursday nt-labor day: no operational impact. No sig weather.

&&

Fire weather...
a humid air mass will be over eastern New York and western New
England tonight. A weak cold front will bring isolated to
scattered showers and thunderstorms tomorrow...with drier and
slightly cooler weather expected in the wake of the front for
Friday.

The relative humidity values will recover to 90-100 percent tonight with dew
formation likely...and then fall to 45-60 percent tomorrow
afternoon. An excellent recovery is likely Friday morning with
maximum relative humidity values once again of 90 to 100 percent.

The winds will be light and variable in direction tonight. The
winds will then shift to the northwest to north at 5-15 miles per hour
tomorrow afternoon...and then will become north to northeast at 5
to 10 miles per hour at night.

&&

Hydrology...
no Hydro problems are expected the next 5 days ending Labor Day.

Isolated to scattered showers and or thunderstorms will be
possible tomorrow...as a backdoor cold front moves southward
across the region....otherwise it will be dry.

Rainfall amounts may range from a tenth to quarter inch with
locally higher amounts from any thunderstorms.

Above normal temperatures will continue through the
Holiday weekend...as high pressure dominates. River flows will
remain below normal for early September.

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.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...wasula
near term...bgm/NAS/wasula
short term...wasula
long term...jpv
aviation...kl/NAS
fire weather...kl/wasula
hydrology...kl/wasula

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