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Area forecast discussion 
National Weather Service Albany New York
301 am EDT sun Sep 21 2014

Synopsis...
a mild day is expected for this last official weekend of
Summer. However...this will not last too long as a cold front will
bring showers and perhaps a thunderstorm to the region today. Cooler
and brisk conditions in the wake of the frontal passage will return
for tonight into Monday. Looking further ahead...most of next week
looks dry...with seasonable temperatures during the middle of the
week...then above normal temperatures later in the week.

&&

Near term /through today/...
as of 330 am EDT...water vapor loop this morning depicts a couple of
notable waves that will have an impact to our region today. The
first wave was developing just east of the southeast coastline.
The second wave as quickly approaching the western Great Lakes
region and the last wave was further upstream approaching Lake
Winnipeg. The main challenge today will be the coverage of precipitation
across the region. Showers were progressing northward across the
middle Hudson Valley and northwest CT. This is an extension of low level
moisture entrainment from the Atlantic and the aforementioned
coastal low development. Per the latest hrrr/hireswrf reflectivity
forecasts...expect these showers to primarily impact locations
well south and east of the capital region /Mid Hudson valley...northwest
CT and southern Berks/ through this early morning.
Meanwhile...upstream wave continues to track east-northeast. Here
more showers should develop within the higher Theta-E air as we
will increase probability of precipitation for the dacks through this early Sunday
morning.

Through the middle morning hours...the coastal wave continues to
exhibit slow intensification. Furthermore...upstream wave
approaches the central-eastern Great Lakes region. An area of
subsidence should evolve across the middle Hudson Valley and into
western New England as the coastal wave tracks well offshore. This
should allow time for our region to fully feel this warm sector
with breaks of sunshine. H850 temperatures are expected to climb well
into the middle teens which should allow surface temperatures to
approach 80f for valley locations and 70s elsewhere.

As temperatures will be mild...surface dewpoints too will climb to
around 60f or greater for the region. As the upstream wave
approaches with its associated cold front...convective potential
will increase. Per coordination from Storm Prediction Center...the entire region is
now within a "see text" with 5% probabilities. 4km Storm Prediction Center WRF
reflectivity along with the hrrr and local hireswrf show a scattered-broken
line of convection moving across eastern New York late this afternoon.
Forecast soundings suggest sbcapes climb into the middle 100s j/kg
with 0-6km bulk shears climbing toward 50kts. So a Low Cape and
high shear environment where any deeper convective elements will
have the potential to produce some gusty winds /with or without
thunder/.

&&

Short term /tonight through Tuesday/...
the cold front will track across our western New England counties
this evening with the continue threat for scattered-broken line of
convection. In the wake of this frontal passage...the colder Upper Pool with
the trough and the that last wave move across the region
overnight. This will keep the clouds and threat for some showers
which the better probabilities will be across the higher terrain.
Furthermore...lake enhancement from Lake Ontario will also assist
with deeper low level moisture as Delta T/S climb above 13c.

Monday is shaping up to be a rather brisk and cool day with clouds
and the chance for more showers. The Heart of the cold pool /aoa
0c h850/ will be overhead coinciding with a tight surface pressure
gradient to provide gusts over 20kts. Highs Monday will be almost
15 degrees cooler than Sunday/S with mainly 50s across the
terrain and middle-upper 60s for valley locations.

The low level stratus may linger across portions of the region
Monday night with locations downwind of the Catskills likely
experiencing clearing skies including eastern Windham County of
southern Vermont. With the loss the sunlight...showers too should
diminish with overnight lows dipping back to the middle-upper 30s for
the dacks and 40s elsewhere /a reminder that the growing season
has ended across northern Herkimer...Hamilton...northern Warren
counties/.

Tuesday...model trends are favoring another weak frontal boundary
migrating across the region. Frontolysis will be underway as the
thermal column will be warming through the day along with high
pressure building as heights rise aloft. So there will be
diurnally driven clouds through the day...mainly north and west of
the middle Hudson Valley...as high temperatures achieve 65-70f for valley
locations and low-middle 60s for the terrain.

&&

Long term /Tuesday night through Saturday/...
ridging at 500 hpa will be in place for the entire extended
period...with building heights through the entire week. The 00z gefs
shows 500 hpa height anomalies of 1-2 Standard above normal by late in
the week...with anomalies of 2-3 Standard above normal situated just to
our northwest...where the core of where the warmest heights will be
situated.

At the surface...a large strong sprawling area of high pressure will
control the weather through the entire week as well. The high will
slowly move from over upstate New York and New England on Wednesday to off
the coast for Thursday through Saturday. This high pressure allow will
allow for dry conditions with mostly clear skies. Temperatures will
gradually warm up throughout the week...with valley highs in the
upper 60s to near 70 on Wednesday...low 70s on Thursday...and middle 70s for
Friday and Saturday. With the clear skies and light winds...good
radiational cooling will occur each night...and lows will generally
be in the 40s to low 50s /some upper 30s over the high terrain/.
Most areas that still have the growing season ongoing look to avoid
a frost/freeze through the upcoming week.

&&

Aviation /06z Sunday through Thursday/...
flying conditions are currently VFR for the Hudson Valley taf
sites...and MVFR at the higher terrain terminal of kpsf. With a
persistently moist southerly flow...flying conditions will likely
lower to MVFR for all sites through the overnight hours...as low
stratus develops and moves up the Hudson Valley. A few rain
showers...currently located near NYC/Long Island...may scrape near
kpsf/kpou over the next few hours...so have accounted for this in
the tafs with a vcsh. Although it cannot totally be ruled
out...will not include IFR conditions in the tafs at this
time...as model soundings/upstream observation suggest ceilings will only
lower to MVFR levels.

Ceilings will likely return back to VFR by the middle to late morning
hours on Sunday as daytime mixing ahead of a cold front allows for
some clearing. However...the passage of the frontal boundary late
in the day will allow for some rain showers...especially for kgfl...and
a return to broken-overcast lower ceilings. Flying conditions may drop to MVFR
within the passing rain showers.

Behind the boundary...clouds will clear out of the valley
terminals...but lingering low clouds upsloping the terrain may
allow for lower ceilings/visibilities at kpsf for Sun night. Some mist may
develop late Sun night...especially at kpsf...although the extent of this
will ultimately depend on how much rainfall occurs and how quickly
it clear out behind the front.

Outlook...

Monday: low operational impact. Slight chance of rain showers.
Monday night to thursday: no operational impact. No sig weather.

&&

Fire weather...
low level moisture will be high across the region with the
increase probability for showers...so expect relative humidity values to remain
above 50 percent through Monday night. We dry out Tuesday as we
begin a prolonged period of dry weather.

Southerly winds of 5 to 15 miles per hour with some gusts over 20 miles per hour today.
Winds shift to the west-northwest tonight then increase in gust
magnitudes on Monday well over 20 miles per hour at times.

&&

Hydrology...
no widespread Hydro problems are expected through next week.

A low pressure system will approach and cross the region today bringing
some much needed rainfall to the area Sunday into Sunday night.
Rainfall amounts are anticipated to generally be a tenth to a
third of an inch with higher amounts of 1/2 to 1 inch across
Adirondacks.

A return to dry weather is expected for most of the upcoming week.

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...bgm
near term...bgm
short term...bgm
long term...frugis
aviation...frugis
fire weather...bgm
hydrology...bgm



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