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Area forecast discussion 
National Weather Service Albany New York
133 PM EDT Wednesday may 27 2015

Synopsis...
a warm and humid air mass will continue to be over
eastern New York and western New England today. An upper level
disturbance well ahead of a cold front will focus some strong to
severe thunderstorms with locally heavy rainfall this afternoon into
early this evening. The cold front will move through the region on
Thursday with more scattered showers and thunderstorms. High
pressure will build in from the north and west Thursday night into
Friday with drier and less humid conditions.

&&

Near term /until 6 PM this evening/...
..Severe Thunderstorm Watch until 7 PM EDT for all of eastern
New York state and adjacent western New England...

A 17z/Wednesday kaly sounding will be available shortly.

As of 130 PM EDT...scattered showers/thunderstorms have developed
across the the western Adirondacks/Mohawk Valley...with isolated
to scattered showers/storms now also across the southeast
Catskills...with isolated showers/thunderstorms breaking out across the
eastern Mohawk Valley and northern portions of the capital region.

Temperatures have reached the middle/upper 80s...with dewpoints rising into
the middle/upper 60s. Latest Storm Prediction Center mesoanalysis suggests a fairly
widespread area of sb convective available potential energy in the 1500-2000 j/kg range within
close proximity to the Hudson River valley...and generally
1000-1500 j/kg elsewhere.

0-6 km shear is generally 35-40 knots across the western Adirondacks
and Mohawk Valley...and generally 25-30 knots farther S and east. Middle
level lapse rates are not overly impressive...generally in the
5.5-6 c/km range. However...synoptic lift is increasing from west to
east ahead of a shortwave trough approaching from the Great Lakes
region...and also ahead of a weak surface trough across central New York state.

Latest hrrr suggests that the main line of convection currently
developing across northwest areas continues to move S/E...reaching the
capital region between 2 and 4 PM...and across southern Vermont/western
Massachusetts/middle Hudson Valley and northwest CT between roughly 4-7 PM. Additional
isolated thunderstorms could develop ahead of this line before
these approximate times.

The main severe threat for this afternoon will be locally damaging
wind gusts associated with developing cold pools which may allow
portions of line segments to develop into small bowing segments.
Given the increasing middle level shear this afternoon...will also
have to watch for any discrete cells that develop ahead of line
segments which could become more organized and produce some hail
in addition to the gusty winds.

Also...with precipitable water/S approaching 1.5 inches...any thunderstorms
could produce locally torrential downpours. Although any rainfall
will be welcome...should any cells train along lines...localized
flooding...particularly in urban/poor drainage areas can not be
ruled out.

Maximum temperatures will reach 85-90 in most lower elevations...and
Lower/Middle 80s in higher terrain before any convection moves
through.

&&

Short term /6 PM this evening through Friday/...
tonight...the surface trough moves through with the scattered showers and
thunderstorms ending in the early evening. There will likely be a
lull in the activity...but the cold front and upper trough will be
approaching the eastern Great Lakes region and western New York. Some slight and
low chance probability of precipitation were kept in west of the Hudson River valley between
09z-12z showers and possibly thunderstorms ahead of the front.
Lows will still be mild in the middle and u60s in the valley
areas...and u50s to l60s over the mountains

Thursday...the NAM/GFS/ECMWF continues to be in agreement with a faster
progression of the surface cold front and associated upper trough. If
it lags a little...then the southeast extreme of the forecast area /Mid
Hudson valley...southern Berks...and northwest CT/ will have to be monitored
for some strong to severe thunderstorms. Right now...all of our
forecast area is in a general thunderstorm outlook. The instability
looks much less than todays...and the better dynamics with the
upper jet GOES north/NE into southern Quebec...northern New York...and northern New
England. A slight to low chance of thunderstorms was kept in
everywhere into the early to middle PM...then quickly diminished from
the west/northwest to S/se. Maximum temperatures will be tricky with the cold advection
in the wake of the front...and strong mixing or downsloping
occurring. Expect brisk west/northwest winds during the PM. H850 temperatures fall
to +8c to +13c by the 00z/Friday from northwest to southeast over the area. Highs
will range from the u60s to l70s over the southern dacks/W-cntrl Mohawk
Valley to m70s to l80s over the rest of the region...except some
u60s/l70s over the Catskills/southern greens...and m80s over the middle
Hudson Valley/northwest CT.

Thursday night...the upper trough axis moves downstream...and brisk
west/northwest winds will diminish as surface anticyclone ridges in from the
north and west early on...and settles over New York and New England by
Friday morning. Humidity levels will decrease compared to the previous
night with lows in the m40s to l50s over the mountains...and middle and
u50s over the valley areas.

Friday...the synoptic subsidence with the upper level ridge...and
the surface high will continue to close the week. The subtropical
ridge will be in control again. A dry and less humid day is
expected...but the S/SW flow aloft will increase ahead of the next
trough and cold front upstream. Expect mostly sunny conditions
with highs in the lower to m80s in the valleys...and 70s to near
80f over the hills and mountains humidity levels should be fairly nice
still with surface dewpoints in the 50s.

&&

Long term /Friday night through Tuesday/...
well above normal temperatures Friday night-Sat should trend back to
near or below normal sun-Tue...as the East Coast upper level ridge
deamplifies with the approach of shortwave energy from southern
Canada. As it deamplifies...a cold front will cross the region
sometime late Sat or early sun. This should bring showers and
thunderstorms to the region. Depending on additional shortwave
energy rounding the base of the incoming upper level trough
approaching the Great Lakes/southeast Canada...it is possible that the cold
front slows down and/or a wave develops along it and tracks south of
the region. Should this occur...showers could linger in the wake of
the front for sun into Tuesday...but mainly across southern areas.

Warm and somewhat humid Friday night across the region with lows in
the upper 50s to middle 60s. As the cold front approaches on
Saturday...the southerly flow ahead of it will boost temperatures to highs
in the 80s across the region...but somewhat cooler air off the
Atlantic will result in the coolest temperatures occurring over southern
areas. Scattered showers and thunderstorms will also increase across the
region...and have forecast probability of precipitation to rise to low chance across the
southeast by late afternoon...ranging up to likely probability of precipitation over the
Adirondacks. Saturday night probability of precipitation continue to rise...reaching likely
levels across most of the region...with high chance probability of precipitation over the
southern fourth of the forecast area. Lows Saturday night will range
from the upper 40s over the Adirondacks...to the lower 60s over the
far southern part of the forecast area.

Due to the possibility of a wave along the front...probability of precipitation for Sunday
remain fairly high...between 40 and 50 percent during the morning...
and 30 to 45 percent during the afternoon...with the highest probability of precipitation
over the south. Highs Sunday in the 60s to middle 70s.

Still the potential for the front to become stationary far enough
north to result in some showers across parts of the region Sunday
night through Tuesday. Have forecast either dry conditions or slight
chance probability of precipitation from the Adirondacks to the Lake George area during this
period. Slight chance probability of precipitation most other areas...and low chance probability of precipitation
over the extreme south. Lows Sunday night will be in the middle 40s to
lower 50s. Highs Monday in the 60s to lower 70s. Lows Monday night
in the middle 40s to lower 50s once again...and highs Tuesday in the
upper 60s to middle 70s.

&&

Aviation /18z Wednesday through Monday/...
a pre frontal trough with associated showers and thunderstorms will
affect the taf sites through about 24z/01z. Some uncertainties about
exact timing...but selected an hour of MVFR visibilities and ceilings
at each taf site...which can be amended or slight timing differences
as the thunderstorms develop and move east. There may be some very
brief IFR ceilings and visibilities with the thunderstorms but again...
this far out can amend to include IFR depending on how the
thunderstorms develop and move. After about 01z/02z...thunderstorms
should move out of the region...but a few linger showers could be around
through about 04z...when winds should become light and some MVFR
visibilities in fog and some intervals of MVFR ceilings develop at
all the taf sites. Conditions could flirt with IFR at kpsf and kgfl
after 10z...but ceilings and visibilities could lower at all sites
through 10z...but again...the best chance for IFR is at kpsf and
kgfl. By 14z...conditions should return to VFR at all sites.

South winds at 10 to 15 knots...with some gusts around 20 knots at times this
afternoon...diminishing to 6 knots or less tonight. Winds will trend to
southwest through the morning at 10 to 15 knots. Winds will trend to west
by 16z-18z and increase to 15 knots or greater but timing is uncertain...
and will be reflected once the taf valid time extends beyond 18z
Thursday.

Outlook...

Thursday and Thursday night: low operational impact. Breezy.
No sig weather.
Friday: no operational impact. No sig weather.
Friday night: no operational impact. No sig weather.
Saturday: moderate operational impact. Chance of rain showers...tsra.
Saturday night: high operational impact. Likely rain showers...tsra.
Sunday: moderate operational impact. Chance of rain showers.
Sunday night: moderate operational impact. Chance of rain showers.
Monday: low operational impact. Slight chance of rain showers.

&&

Fire weather...
a warm and humid air mass will continue to be over
eastern New York and western New England today. An upper level
disturbance well ahead of a cold front will focus some showers and
thunderstorms with locally heavy rainfall this afternoon into
early this evening. The cold front will move through the region on
Thursday with more scattered showers and thunderstorms. High
pressure will build in from the north and west Thursday night into
Friday with drier and less humid conditions.

The relative humidity values will lower to 45 to 60 percent this afternoon...then
increase to 70 to 100 percent tonight...and the decrease to 35 to
55 percent on Thursday.

The winds will be from the south to southwest at 10 to 15 miles per hour
today with gusts to 25 miles per hour...then 5 to 15 miles per hour tonight. The winds
will shift to the west to northwest at 10 to 20 miles per hour with some
gusts to 30 miles per hour on Thursday with the cold frontal passage.

&&

Hydrology...
no widespread Hydro problems expected this week...however
thunderstorms will be capable of producing locally heavy downpours
today into tonight.

The U.S. Drought monitor has much of eastern New York and western
New England in the d1 category...which is considered moderate
drought at this time.

Warm and humid conditions with chances for showers and
thunderstorms...mainly during the afternoon into the early
evening are expected today. There is a chance of showers and
thunderstorms ahead of the cold front on Thursday.

Precipitable water values of 1.25-1.75 inches with locally higher
values are expected today...so storms will be capable of
producing heavy downpours. An isolated flash flood may be possible
if storms repeatedly move over the same area...or the dry/parched
ground does not absorb the rainfall quickly.

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...kl/NAS/wasula
short term...wasula
long term...gjm
aviation...gjm/NAS
fire weather...bgm/wasula
hydrology...bgm/wasula

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