Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 250245
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
945 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 remains 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...

As of 945 PM EST, a nearly stationary frontal boundary was
still evident across the southern Adirondacks and western Mohawk
Valley, with temperatures mainly in the 30S and 40s along with
north/northeast winds on the cooler side of the boundary. To
the south of this boundary, temps are still mainly in the 50s
and 60s.

Also on the north side of this boundary, some areas of fog/low
clouds have developed, with some locally dense fog possible,
especially across portions of the southern Adirondacks, as a
moistening low level air mass cools with the lingering snow
cover.

Latest satellite trends also indicate low clouds expanding
northward from the NYC/LI area into western CT and NJ. We expect
these low clouds to continue expanding northward through the
night, so mostly cloudy skies expected after midnight. Some
areas of drizzle should also form, especially across portions of
the eastern Catskills, Berkshires, Litchfield Hills, and
Helderbergs toward daybreak.

Low temperatures will be tricky overnight, esp for northern
areas where 30s and lower 40s are currently present. We expect
the boundary to slowly lift northward before sunrise, so min
temps likely will occur by midnight, with steady or rising temps
expected thereafter. For areas south of the boundary, lows
should mainly be in the 40s and 50s.

A somewhat gusty south breeze should continue through at least 2
AM within portions of the Hudson River Valley from Albany
southward, and portions of the Housatonic Valley of western New
England, with some gusts of 25-30 mph possible. Winds may
subside slightly after 2 AM as low level moisture deepens,
potentially mitigating low level lapse rates from current steep
levels.

&&

.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 NY and New England, limiting the
chances for strong convection. Will see how convection in the OH
Valley and Great Lakes evolves as it tracks east tonight and
through western NY/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 MPH 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 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 /03Z SATURDAY THROUGH WEDNESDAY/...
Mainly VFR conditions are expected through early this evening.
However, patchy ground fog/low clouds may develop at KGFL
between 03Z-06Z, and may become more extensive through mid
morning Saturday.

Elsewhere, low clouds and/or fog may develop and expand
northward across KPOU/KPSF and KALB between 07Z-11Z/Sat, and
may linger through much of the morning and possibly into the
afternoon with the moist air mass in place. MVFR to IFR
conditions would be likely should this stratus and/or drizzle
occur. Conditions should improve from IFR to MVFR by late
morning though.

A strong cold front will then sweep east across the TAF sites
between roughly 21Z-24Z/Sat. A period of moderate to heavy rain
showers, strong gusty winds, and perhaps even a few rumbles of
thunder will be possible as the leading edge of the front moves
through, with light to moderate rain likely lingering in its
wake.

Winds will be southerly around 5-10 kt through tonight,
increasing to 10-15 kt by late Saturday morning with higher
gusts around 25-30 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. LLWS may
need to be mentioned in subsequent TAF issuances.

Winds will shift into the west with the cold front and increase
to 10-20 KT with gusts of 25-35 KT possible, perhaps even
stronger in any embedded thunderstorms.

Outlook...

Saturday Night: High Operational Impact. Windy With Gusts To 30.0 Likely SHRA...SHSN...TSRA.
Sunday: Moderate Operational Impact. Windy With Gusts To 33.0 NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: Low Operational Impact. Slight Chance of RA...SN.
Tuesday: Moderate Operational Impact. Likely RA...SN.
Tuesday Night: Moderate Operational Impact. Chance of RA.
Wednesday: Moderate Operational Impact. Likely RA.

&&

.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 HWO 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.
NY...Flood Watch through Sunday evening for NYZ032-033-038>043-
     082>084.
MA...None.
VT...Flood Watch through Sunday evening for VTZ013>015.

&&

$$
SYNOPSIS...NAS
NEAR TERM...KL/NAS
SHORT TERM...NAS
LONG TERM...JPV
AVIATION...KL/JPV
HYDROLOGY...NAS
CLIMATE...



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