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Area forecast discussion 
National Weather Service Albany New York
448 am EST Sat Dec 27 2014

Synopsis...
high pressure over the eastern Seaboard will drift offshore today
as a cold front approaches from the Great Lakes region. The cold
front will cross the region late tonight and Sunday morning with
rain showers and snow showers over some higher terrain. Sunday
evening into midweek a very large Canadian high pressure system
will ridge into the northeast with generally fair and more
seasonable temperatures to end the year.

&&

Near term /through Sunday/...
ridging will shift eastward off the coast today and tonight allowing
a low pressure system to move across the region bringing mainly rain
showers to the area tonight and Sunday.

The surface high centered to our south will shift eastward and off
the southeast coast this afternoon and tonight. Deep southwest flow
will develop between the departing ridge and the advancing trough.
850 mb temperatures will rise today especially this afternoon...so
despite cloud cover today will feature above normal temperatures
ranging from the upper 30s across portions of the southern
Adirondacks into the lower 50s in the middle Hudson Valley. These
values will be up to around 15 degrees above normal.

Chances for showers will increase from northwest to southeast across
the forecast area tonight as the low level jet associated with the
system moves in and across the region. Chances will be greatest
to the northwest of the capital district. It may get cold enough
for some snow across portions of the southern Adirondacks late
tonight...otherwise rain showers are expected. Overnight readings
will be very mild with lows only in the 30s. Normal lows this time
of year are generally from 10 to 20 degrees across east central
New York and western New England.

The cold front's southeast progress will be slowed by parallel flow
aloft. Chances for showers will gradually decrease from north to
south Sunday with chances lingering across south of the capital
district during the afternoon hours. Sunday will again feature above
normal temperatures by is not as mild air as Saturday.

&&

Short term /Sunday night through Tuesday night/...
during this period a flat 500hpa ridge in a very fast flow over
much of the eastern United States will flatten as a series of
short waves knock it down. Much further west in a northwest flow at
500hpa...a massive 1055 surface high center will drop southeast from the
Canadian rockies. This high will also ridge at the surface across the
eastern border regions of both countries. As a result a relatively
shallow layer of cold air will settle over the northeast USA..and
thicken as the week progresses. While overall this will be a
quiet and more or less dry period there are a few modest flies in
the ointment to contend with:

1) sun evening the departing cold front will drift S from the i95 corridor...but
keep clouds over the southeast portions of the fca for several hours and possibly
a scattered evening -shra in the far southeast.

2) sun nt a secondary cold front front will drop south across the
fca..but generally wash out..it may trigger a scattered -snsh overnight
north & west of alb.

3) given the initially shallow cold air mass early in the
period...there will be considerable veering of the flow with north-NE
surface winds becoming west-northwest by h850pa. This along with the passing of an
assortment of jet maxes/vorticity maxes will results in varying degrees
of cloudiness among the model suite...but all in all a partly cloudy
regime with more or less at times.

4) Monday nt into Tuesday the major baroclinic zone lies from the
Carolina Piedmont NE Ward. Early Tuesday a coastal low forms along this
boundary off hat..and moves east-northeast. The GFS/Gem/ECMWF keep this
system any associated precipitation just S of fca although some clouds are
likely across S tier associated with it. The NAM has the whole system
about 100 miles further north with clouds across S half of forecast and
chance -sn across S most areas. The trend among the rest of the models
has been toward a further S track the last two runs...and for now
will keep it S of region.

5) the last item is a 500hpa short WV mvng into Great Lakes Tuesday...and
an east-west Arctic cold front mvng S through fca Tuesday nt. Besides a
reinforcing trend toward cold and near normal temperatures...it will act to
turn the flow to a west-northwest across the Great Lakes and result in a
developing lake response toward the end of the period. This will be
mainly an increasing threat of -shsn Tuesday nt in west fca as well as increase
clouds...but it may becoming more sig in the efp.

Overall a period featuring variable clouds...a return to near normal
temperatures...mainly dry...with a few low chance intervals of -shsn. All an
all a quiet weather period to end the year.

&&

Long term /Wednesday through Friday/...
during the first part of the efp a series of 500hpa short waves
carve a broad trough over the northeast...with a cutoff east of
hudsons Bay. By the end the 500hpa flow becomes zonal yet again.

At the surface a series of cdfnts drop S into the region...acting as a
focus of lake effect response. The first is Wednesday...mainly into the west
adrdks. The second east-west cold front is accomp by a strong 500 hpa short
WV that drops S into the mhwk valley Thursday nt. This will result in yet
another enhanced lake effect period into the west adrdks. While there
will be lake effect -shsn into the west adrdks off and on through the
period...amnts should remain modest.

Elsewhere other than stray -shsn with the frontal passages it
should be dry and with seasonable temperatures...variable clouds north and pc
conds S. By the end of the period the cold front is stalled east-west across
New York state ad begins to become the focus for warm air advection clouds that are spilling
into the state in the fast zonal 500hpa.

European model (ecmwf)/GFS/wpc in agreement during this period and will populate
grids with HPC and adjust for lake effect. However just bynd of they spread
wildly with next system.

&&

Aviation /10z Saturday through Wednesday/...
high pressure will shift eastward with the center of the surface high
shifting offshore the southeast coast this evening as a low pressure
system approaches. The surface low will well modeled to to move
across the Great Lakes region into eastern Canada today a and
tonight while dragging its associated cold front into the region
tonight. The upper ridge will hold fairly steady however the flow
will become southwesterly with time. Overall looking at VFR
conditions through 06z/Sunday with increasing clouds.

Chances for showers will increase from northwest to southeast across
the forecast area tonight as the low level jet associated with the
system moves in and across the region. Chances will be greatest
to the northwest of the capital district.

Surface winds will light...mainly calm overnight with a south-southwest
flow developing today with a more westerly flow at kpsf.

Outlook...
Sun night-Wed: no operational impact. No sig weather.

&&

Hydrology...
river levels are now receding across the region...and will
continue to do so for the next week.

A cold front is expected to bring rain showers with a mix of rain/snow
across higher elevations late tonight into Sun morning. Quantitative precipitation forecast with this
event will be on the order of 0.10 to 0.40 inch...generally
insignificant amounts to river flows.

Generally dry conditions...and colder temperatures...are expected
into at least early next week. By then end of the period with
decreasing flows and normal temperatures ice may begin to form.

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...iaa
short term...Snyder
long term...Snyder
aviation...iaa
hydrology...Snyder

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