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fxus61 kaly 242128 
afdaly

Area forecast discussion
National Weather Service Albany New York
428 PM EST Fri Feb 24 2017

Synopsis...
a strong cold front will cross the region Saturday afternoon
and evening, bringing with it locally heavy rainfall and perhaps
a thunderstorm, gusty winds, and much colder temperatures by
Sunday.

&&

Near term /until 6 am Saturday morning/...
Flood Watch in effect for the western Mohawk Valley, the upper
Hudson, the southern Adirondacks, Lake George Saratoga region and
southern Vermont from tonight through Sunday. See hydrology
section for details...

Clouds have largely shifted north of our region but there is
still evidence of a surface boundary north of the Mohawk Valley
into central Vermont where winds are light north and temperatures
are in the 50s. Satellite and radar imagery would suggest a
mainly clear sky tonight based on upstream conditions and
strengthening south to southwest flow expanding the warm sector
over our region.

However, would like to see evidence of the surface boundary to
the north continue to lift north so that any focus for fog, low
clouds or isolated showers shifts north. Boundary layer flow is
expected to increase and south winds could channel through the
Hudson Valley including the capital district and possibly
points north tonight. If mixing is more limited, increasing low
level moisture cold aid in the development of some fog and low
stratus clouds in some areas but little to any developed the
past couple of nights and what did mixed out quickly in the
morning.

So, lows in the 50s in areas that could see the channeling of
south winds tonight. Lows in the 40s in areas where there could
be less mixing, sheltered by winds and/or where any fog or low
clouds could develop.

&&

Short term /6 am Saturday morning through Monday/...
as low level flow turns more south Saturday morning, maybe even
slightly southeast at the surface, there could be some low level
clouds that could form through the morning. However, again,
upstream conditions are relatively cloud free and if we have
similar conditions ahead of the convection expected along the
cold front Saturday afternoon, then we would see highs well into
the 60s to near 70.

Even if clouds develop and we have more clouds than sun
Saturday, increasing low level flow and mixing should still get
US into the 60s, just closer to the lower to mid 60s and maybe
around 60 northern and western areas. Still, the warmth will
contribute to some marginal instability but maybe enough where
we need to keep a close eye for possibilities for strong
thunderstorms Saturday afternoon and evening.

Even with marginal surface based instability, low level forcing
will be strong, low level wind fields will be very strong and
midlevel lapse rates are quite steep. Granted it is difficult to
get convection deep enough where midlevel lapse rates could make
a difference in updraft intensity of convection. Some guidance
sources suggest low level flow off the ocean could stabilize
the atmosphere over eastern New York and New England, limiting the
chances for strong convection. Will see how convection in the Ohio
Valley and Great Lakes evolves as it tracks east tonight and
through western New York/PA Saturday morning.

The cold front exits Saturday afternoon and evening and west to
northwest winds increase through the night as cold advection
deepens. Lows Saturday night in the 30s but some 20s in higher
terrain. Some lake effect snow is expected to develop and
extend into the western Mohawk Valley, southern Adirondacks and
Schoharie valley.

Northwest winds and strengthening cold advection is expected
Sunday with some wind gusts approaching 40 to 45 miles per hour in some
places. Will have to watch trends to see if gusts will be higher
and if a Wind Advisory may be needed in some areas Sunday. Highs
Sunday in the 30s to lower 40s some mid 40s southern areas. Lake
effect snow showers continue in the western Mohawk Valley,
southern Adirondacks and Schoharie valley.

Upper heights rise Sunday night and Monday as flat upper ridging
and gradual warm advection spreads east. Highs Monday in the mid
40s to lower 50s but around 40 northern areas.

&&

Long term /Monday night through Friday/...
active weather to persist through much of the long term period, with
a gradual transition from above normal temperatures through mid
week, to near normal temperatures by the end of the work week.

The period starts out Monday night with high pressure over the
region Monday evening, gradually shifting eastward off the East
Coast by late Monday night. With a zonal flow aloft, the next low
pressure system will quickly approach from the mid Atlantic and Ohio
Valley regions on Tuesday. The surface warm front associated with
this system will bring precipitation mainly on Tuesday, but will
mention slight chance Monday night to account for wider time window
if the system movement speeds up. Thermal profiles indicate
potential for some mixed snow/rain at the onset, and especially for
areas north of Albany and over the higher terrain. Temps should warm
enough for plain rain by late Tuesday morning or early afternoon. A
brief break in steady rain expected for a time Tuesday night, before
the next chance of rain arrives by Wednesday.

A stronger system is then forecast to track from the upper Great
Lakes northeastward into southeast Canada by Wednesday. Our region
will be on the warm side of cyclone, with the potential for warming
into at least the upper 40s to lower 50s despite rainfall. If breaks
of sunshine can occur, temperatures would be even warmer. The
system's cold front will push through in the Wednesday night time
frame, with a more seasonable air mass filtering in behind the
front. The European model (ecmwf) is showing a greater potential for earlier phasing
or northern and southern stream energy over coastal New England
Wednesday night into Thursday morning, which could result in some
accumulating snow especially in upslope areas. The GFS is more
progressive and depicts later phasing farther east with less
potential for snow.

A colder cyclonic flow regime will then set up from Thursday night
through the rest of the work week, with possible multiple clipper-
type lows track through of near the area. After a stretch of
significant warmth, snow could be on the ground in many areas by
next weekend.



&&

Aviation /21z Friday through Wednesday/...
a warm front has pushed north of the kalb/kpou/kpsf terminals,
with warmer air surging in and lower clouds scouring out.
However, the front remains just south of kgfl, so lower clouds
in MVFR range have lingered but should tend of scour out this
afternoon as the warm pushes northward. So VFR conditions
expected at all terminals the rest of the day. However, as
unseasonably high moisture levels move into the region tonight,
conditions are expected to deteriorate to MVFR this evening,
then IFR overnight. Depending on if thicker fog can form, LIFR
will even be possible.

Low clouds and/or fog will linger through much of the morning
and possibly into the afternoon with the moist air mass in
place. Conditions should improve from IFR to MVFR by late
morning though.

Winds will be southerly around 5-10 kt through tonight,
increasing to 10-15 kt by late Saturday morning with higher
gusts around 20-25 kt at kalb. Some low level wind shear may
develop toward afternoon where surface winds are relatively
light and a southerly low level jet moves overhead. Low level wind shear may
need to be mentioned in subsequent taf issuances.

Outlook...

Saturday night: high operational impact. Windy with gusts to 30.0 likely rain showers...shsn...tsra.
Sunday: moderate operational impact. Windy with gusts to 33.0 no sig weather.
Sunday night: no operational impact. No sig weather.
Monday: no operational impact. No sig weather.
Monday night: low operational impact. Slight chance of rain...sn.
Tuesday: moderate operational impact. Likely rain...sn.
Tuesday night: moderate operational impact. Chance of rain.
Wednesday: moderate operational impact. Likely rain.

&&

Hydrology...
Flood Watch in effect for the western Mohawk Valley, the upper
Hudson, the southern Adirondacks, Lake George Saratoga region and
southern Vermont from tonight through Sunday. Runoff will
result from a combination of snow melt over the next couple days
and heavy rainfall Saturday afternoon/evening.

At this time minor flooding of some main Stem rivers is expected,
including the Upper Mohawk, smaller rivers/streams in areas with
significant snow depth in the southern Adirondacks and southern
Green Mountains of Vermont, and possibly even portions of the upper
Hudson basin. There remains the potential for flooding for areas
south of the watch, but confidence is much lower. So will continue
to mention the threat in the severe weather potential statement for possible expansion of the watch
if conditions warrant.

A warm and increasingly moist air mass will be in place through
Saturday evening. A quick moving, strong cold front is expected
to bring a period of moderate to heavy rainfall Saturday
afternoon and evening. Total rainfall forecast of 0.50 to
around 1.50 inches is forecast through Saturday night, with the
lowest amounts in the Mid-Hudson valley and northwest
Connecticut, and the highest amounts over the western/southern
Adirondacks. The time frame for greatest potential for flooding
is during and after the cold front passage due to heavy
rain/snow melt combination and subsequent runoff.

Drier and colder air will filter in behind the cold front for
Sunday, with some lake effect snow possible across the western
Adirondacks and western Mohawk Valley.

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.

&&

Climate...
all-time February high temperature records set today at Albany
and Poughkeepsie.

Albany reached 74 degrees, which broke the old all-time
February record of 69 set yesterday. Poughkeepsie reached 73
degrees, which broke the all time February record of 72 set
back in 1954.

&&

Aly watches/warnings/advisories...
CT...none.
New York...Flood Watch from 7 PM EST this evening through Sunday evening
for nyz032-033-038>043-082>084.
Massachusetts...none.
Vermont...Flood Watch from 7 PM EST this evening through Sunday evening
for vtz013>015.

&&

$$
Synopsis...NAS
near term...NAS

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