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Area forecast discussion 
National Weather Service Albany New York
1031 am EDT Sat Jul 26 2014

Synopsis...
high pressure along the Atlantic Seaboard will drift out to sea
today...with a return southwest flow of increasing moisture for
the weekend. Our weather will turn unsettled with bouts of showers
and thunderstorms from late tonight into Monday. A weak frontal
system will cross the region tonight and Sunday morning...with a
stronger cold front and low pressure system expected to move
through Sunday night and Monday. Midweek will bring below normal
temperatures as a large Canadian high pressure system settles into
the Great Plains and builds east.

&&

Near term /through tonight/...
as of 1030 am EDT...made just some minor adjustments to forecast
based on latest observation and trends. A weak disturbance is quickly
moving eastward across eastern PA and New Jersey...which is causing some
light showers there. A few sprinkles may get close to southern
portions of Ulster...Dutchess and Litchfield counties through
early afternoon...but measurable precipitation is not expected so will
not mention any probability of precipitation at this time. A period of added cloud cover
will move across the southern half of the area but should shift
east by middle to late afternoon. High temperatures should be in the middle
70s to middle 80s with south to southwest winds at 5 to 10 miles per hour. The
cooler temperatures will be over the higher terrain.

For tonight...short wave energy will start to move eastward
across the Great Lakes overnight. A pre-frontal trough
accompanying the energy aloft tonight...will provide low level
focus so will mention high chance to likely probability of precipitation with scattered to
numerous showers and a few embedded thunderstorms. The storms
overnight are not expected to be severe. Expect overnight lows in
the upper 50s to middle 60s with winds light and variable.

&&

Short term /Sunday through Tuesday night/...
a large 500hpa cutoff over qb will dominate this period as a
series of short waves wrap around its base...culminating with a
powerful short WV Monday...that carves out a full latitude 500hpa trough
over the eastern Continental U.S....more reminiscent of Oct than late July.

Sunday morning a weak warm front will be along the New York/new eng border to a
weak surface low in the St Lawrence. While a weak cold front front trails from
low into east PA. At 500hpa a short WV is over fca. Between 15-18utc
these systems exit fca along with their associated -shra. This leaves a
warm humid air mass with dew point in 60s across fca...and mix of clouds
and sun for the rest of the day. This is certainly a recipe for
afternoon convection.

During the afternoon convective available potential energy build to 1000-1800 j/kg on GFS...1000-2500
j/kg on NAM. 700-500hpa lapse rates incg to 7c in NAM...but only
5.5 on GFS. 0-6 km bulk shear increasing to 25kt (nam) to 35kts
(gfs).

All guidance shows a bias toward the southeast prtns of fca for highest convective available potential energy/lapse/shear
rates. GFS model soundings indicate little to no capping by afternoon...but
the NAM shows cap around 650hpa...but with sufficient sun this will
be overcome late in the day. So if the sun comes out...this cape
will be tapped in scattered severe thunderstorms...particularly southeast.

Is what isn't as pronounced as pvs runs is the presence of upper
dynamics. The NAM/GFS/Gem all have one short WV exiting fca in late
morning...and a second mvng into EPA/New Jersey during the evening...with the
bulk of this energy staying S of fca...or in S periphery of fca.
Given this scenario best chances for severe thunderstorms is southeast prtns of
fca. Elsewhere marginal for severe storms...but could still be a
concern...but it will be isolated pulse type and not particularly
organized. Storm Prediction Center has outlooked most of fca excpt far north for day 2.

Otherwise a warm humid day with highs in the upper 70s to middle 80s
south. Sun nt this short WV over EPA/New Jersey lifts NE into fca...as
500hpa trough sharpens in response to strong jet maximum and its associated
vorticity mvng into east Great Lakes. In response surface cyclone ensues over east
Great Lakes and tracks NE by Monday Morning. Sun nt -shra/tsms will increasing in
coverage across fca becoming widespread by morning. A much stronger cold front
in the St. Lawrence Valley will be drawn into this deepening cyclone.

On Monday morning this cold front is from rut to New York i88 Corridor. North of it precipitation
will evolve into an Anna front rain/shra...while along it and to
its S & east...wm sector cape values of 1000-1700 j/kg will continue
to allow embedded thunderstorms to form ahead and near the cold front. This cold front
will slowly drag east through the area Monday with -shra/thunderstorms likely.

To its north temperatures will remain in the 70s...reaching the 80s to its S
and east Monday.

Monday night the 500hpa short waves & surface low will race NE into
qb...carving a full latitude trough over the east Continental U.S.. this drags the
cold front to the coast...and -shra will dim as cooler air filters in
on brisk north winds.

Tuesday morning surface high pressure over Great Plains mvs east. Cold front
slides out to sea...scattered -shra end. With 500hpa trough axis still
west of fca...much of fca will remain in dry slot Tuesday and Tuesday nt
as cooler air mass filters into fca. Temperatures will be 5-10 degree below
normals with highs upper 60s to upper 70s. Tuesday nt will see lows
middle 40s to middle 50s under mainly clear skies.

&&

Long term /Wednesday through Friday/...
period begins with unusually strong 500hpa cutoff over qb and
tailing trough over most of east Continental U.S.. over time the cut off lifts NE
in westerlies over north Canada....and a piece of energy breaks off
and retrogrades SW to miss valley by end of period as Bermuda high
pressure ridge back builds toward east Seaboard. While the models suite
is fairly in agreement...there is some spread in solutions.

Fca remains largely on east side of the 500hpa trough as it retreats
north...and for the most part remains in the dry slot associated with this
feature in the GFS. The European model (ecmwf) keeps the cut off closer and
further S...and several passing short waves combined with diurnal
heating produce isolated to scattered -shra mainly west and over hir terrain.

The only other feature of note..is as period ends GFS has Bermuda
high backing into East Coast...along with a coastal type front may
result in increasing S flow...dew point and threat of thunderstorms Sat afternoon S tier.

Hpcs overnight package reflects pvs European model (ecmwf) and current GFS. It will
be a period of pc conds...and temperatures 3-5 degree below normal with warm
days and cool nights. Isolated -shra cant be ruled out...particularly
over hir terrain...but for the most part it will be a dry comfortable
period.

&&

Aviation /15z Saturday through Wednesday/...
mainly VFR conditions are expected through the end of the taf period
ending at 12z sun. The exception will be some showers and perhaps a
few embedded thunderstorms late tonight. Otherwise...expect few-scattered
cumulus developing today. Expect batches of cirrus to stream
overhead with middle level clouds moving in late in the afternoon into
the evening. While it is difficult to time the convection overnight
it will generally be after 09z at the taf sites so have added 3sm
rain showers ovc025 to the tafs.

Light to calm winds overnight becoming south to southwest today at 5
to 10 knots...then becoming light and variable again this evening.

Outlook...

Sunday night: high operational impact. Likely rain showers...tsra.
Monday: high operational impact. Likely rain showers...tsra.
Monday night: moderate operational impact. Chance of rain showers.
Tuesday: no operational impact. No sig weather.
Tuesday night: no operational impact. No sig weather.
Wednesday: no operational impact. No sig weather.
Wednesday night: no operational impact. No sig weather.
Thursday: no operational impact. No sig weather.

&&

Fire weather...
high pressure along the Atlantic Seaboard will drift out to sea
today...with a return southwest flow of increasing moisture for
the weekend. Our weather will turn unsettled with bouts of showers
and thunderstorms from late tonight into Monday.

Relative humidity values will recover to 35-45 percent this
afternoon...increase to 90 to 100 percent tonight...the drop to
minimum values of between 55 and 65 percent Sunday afternoon. Relative humidity
values will increase to near 100 percent Sunday night.

Winds will become southwest around 10 miles per hour today...light southwest
tonight and continue southwest Sunday around 10 miles per hour.

&&

Hydrology...
dry weather will persist into this evening. Showers are likely
with scattered thunderstorms late tonight and Sunday morning.
These will become scattered Sunday and Sunday evening...but may be
accompanied by heavy downpours. Showers and scattered
thunderstorms will overspread most the the region Sunday night
into Monday.

Total rainfall of 1 to 2 inches is likely...with locally higher
amounts in thunderstorms between tonight and Monday. Locally
heavy rainfall...especially Sunday...may result in minor flooding
of urban areas...poor drainage locations and low lying area.

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...Snyder
near term...11/jpv
short term...Snyder
long term...Snyder
aviation...11
fire weather...Snyder
hydrology...Snyder

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