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Area forecast discussion 
National Weather Service Albany New York
933 am EDT Tuesday Apr 21 2015

Synopsis...
a frontal system will cross the region this morning...allowing
showers to linger. Some clearing is then expected for this
afternoon in the wake of the front. A strong upper level
disturbance will bring more showers to the region on
Wednesday...with cool and somewhat unsettled conditions lingering
through the remainder of the week due to an upper level low
remaining anchored across southeast Canada.

&&

Near term /until 6 PM this evening/...
as of 930 am am EDT...an occluded has moved east of the region
leaving some lingering showers in its wake across eastern New York
and adjacent western New England. Aloft...a potent vorticity lobe was
tracking north/northeast across the central/northern Appalachians.

We expect occasional showers to persist through middle to late
morning...as the aforementioned strong upper level impulse tracks
across the region. Then...as it passes north of the region this
afternoon...we expect clearing to develop...especially in valley
regions...where the combination of strong subsidence in the wake
of the upper level impulse...and some downsloping aid to scour out
lingering low level moisture. In fact...it is possible that some
valley areas become mostly sunny later this afternoon. Clouds may
be tougher to dislodge across higher elevations...especially across the
western Adirondacks...where some lake moisture and greater low
level instability may allow clouds to persist.

Isolated showers could redevelop across the far western
Adirondacks/Mohawk Valley region and eastern Catskills toward
sunset...as strong middle level cooling...and increasing dynamical
lift with the approach of another upper level impulse occur.

Winds should increase from the west later this morning and
especially this afternoon. Some wind gusts could reach or exceed
35 miles per hour...particularly within close proximity to the Mohawk River
valley/capital region and Berkshires during the late afternoon
hours...once deeper mixing develops.

Maximum temperatures are forecast to reach the Lower/Middle 60s in most valley
regions later today...with mainly 50s across higher
elevations...although temperatures may hold in the 40s across some of the
higher peaks of the Adirondacks and southern Vermont.

&&

Short term /6 PM this evening through Thursday night/...
tonight...the upper level cold pool...with h500 temperatures dropping to
around or even slightly under -30c...will be translating across
the region overnight. These cold middle level temperatures will promote
rather steep low and middle level lapse rates. As some lake moisture
tracks east...some showers of rain/snow/graupel will be possible
across at least the southern Adirondacks and western Mohawk
Valley. In fact...can not rule out a few lightning strikes.
However...the lack of stronger synoptic lift should limit the
overall areal coverage of any activity. Otherwise...expect partly
cloudy and chilly conditions overnight...with most min temperatures
falling into the 30s to around 40. Should any prolonged clearing
occur...even colder mins will be possible.

Wednesday...another strong upper level impulse will be tracking
across the region Wednesday afternoon. This should allow for numerous
showers to develop from west to east during the late morning/midday
hours...and persist into the afternoon. Given how cold the middle
levels will be...and additional cooling from dynamics and
evaporational cooling...some wet snow could mix in at times in the
afternoon across the higher elevations. Even in valleys...any
heavier showers could have some wet snowflakes and/or graupel
mixed in. Otherwise...expect maximum temperatures to reach the 50s in lower
elevations...and 40s across higher terrain...although temperatures will
likely fall once showers occur...into the 40s for valleys...and
middle/upper 30s across higher elevations in the afternoon.

Wednesday nt...showers should taper off early with the passage of the
aforementioned upper level impulse. However...some lake effect
snow showers could develop across the southern Adirondacks...where
some minor accums can not be ruled out. It should be rather
chilly...with min temperatures falling into the Lower/Middle 30s in
valleys...and middle/upper 20s across higher elevations.

Thursday-Thursday nt...some diurnally-driven showers of snow and rain will
be possible given strong low level instability...despite overall
lack of any significant synoptic lift. These showers will be most
numerous/frequent across higher terrain...particularly for the
southern Adirondacks. In valleys...any showers should be much more
isolated and transient. The low level pressure gradient will be
tighter...so it should be rather windy Thursday afternoon...with some
gusts reaching 35-45 miles per hour at times. Temperatures will be below
normal...with maxes reaching the Lower/Middle 50s in valleys...with
mainly 40s across higher elevations...although the higher peaks of
the southern Adirondacks...Catskills...and southern Green Mountains may
struggle to reach the middle to upper 30s. Thursday nt should be quite
cold...with widespread 20s across higher elevations...and lower to
middle 30s in valleys.

&&

Long term /Friday through Monday/...
our region will mainly be on the southern periphery of cyclonic
upper flow...with small upper impulses rotating around the large
cyclonic flow...periodically slightly enhancing scattered shower and
snow shower activity. Most of the enhanced shower and snow shower
activity is expected to be in higher elevations and in Lee of Lake
Ontario.

Temperatures will continue below normal with mostly cloudy to partly
cloudy sky through the period due to the intervals of enhanced
clouds and periods of breaks in the clouds. Specific timing of
enhanced clouds and showers not possible this far out with the
disagreements in guidance...so broadbrushing at this point and will
have to watch evolution of pattern through the week and into the
weekend. The large scale cyclonic flow is expected to slowly build
east of our region by the beginning of next week but some
indications of northerly upper flow over our region in the western
periphery of the exiting large circulation. So...any warming of
temperatures looks to be very slow and gradual...as long as no other
upper lows replace this one over our region beyond 7 days. We can
only wait and see.

Highs in the 50s many areas through the period but around 40 to middle
40s in higher elevations. Lows mainly in the 30s through the period
with below freezing in higher elevations.

&&

Aviation /14z Tuesday through Saturday/...
intervals of lighter showers this morning...ceilings and
visibilities will hover between MVFR and VFR...with some IFR at
kalb. Coverage of showers should continue to decrease at all taf
sites late this morning and carrying vcsh through about 15z-17z in
most areas...but through 19z at kpsf. Ceilings should be VFR this
afternoon through tonight at all taf sites.

Variable winds at 6 knots or less early. Winds will shift to west at
less than 10 knots at all taf sites through this morning. Then winds
should increase to 10 to 15 knots with gusts around 20 knots late this
morning and through this afternoon...becoming south at less than 10
knots this evening and continuing overnight.

Outlook...

Wednesday night: low operational impact. Slight chance of rain showers...shsn.
Thursday: moderate operational impact. Windy with gusts to 37.0 chance
of rain showers.
Thursday night: slight chance of rain showers.
Friday: no operational impact. No sig weather.
Friday night: no operational impact. No sig weather.
Saturday: no operational impact. No sig weather.

&&

Fire weather...
wind gusts of 25-35 miles per hour this afternoon...

Despite gusty winds...and relative humidity values dropping down into the 30-45
percent range late this afternoon...most areas have received at
least 0.25-0.5 inches of rainfall...with some amts of near or over
an inch. Additional showers are expected for Wednesday.

Cool...breezy and somewhat unsettled conditions are expected to
linger through at least Friday.

&&

Hydrology...
rainfall amts have generally ranged from one quarter...to three
quarters of an inch since Monday morning...although some areas
have received over an inch...particularly across the eastern
Catskills. This rainfall...along with some added snowmelt across
portions of the southern Adirondacks and southern Vermont...will lead
to within bank rises on area rivers/streams today through
Wednesday.

Based on current forecasts...only the west Canada creek at
Hinckley dam is expected to exceed flood stage by this evening.

An additional one quarter to one third of an inch of rainfall is
expected Wednesday from showers accompanying a strong upper level
disturbance.

For the rest of the week...the forecast will be dominated by a
persistent upper level trough which will result in cool
temperatures...breezy conditions and occasional chances for mainly
light precipitation.

For details on specific area river and lakes...including observed
and forecast river stages and lake elevations...please visit the
advanced hydrologic prediction service /ahps/ graphs on our web-
site.

&&

Aly watches/warnings/advisories...
CT...none.
New York...none.
Massachusetts...none.
Vermont...none.

&&

$$
Synopsis...kl/11
near term...kl/11
short term...kl
long term...NAS
aviation...11/NAS
fire weather...iaa/kl/11
hydrology...iaa/kl/11

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