Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 211147
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
647 AM EST Sat Jan 21 2017

.SYNOPSIS...
Mild and fair weather is expected for most of the weekend.
However, a coastal storm is expected to impact the region Sunday
night into Tuesday bringing mixed precipitation and gusty winds
to the area.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
One isolated patch of sprinkles tracked through the Capital
District and the dried up. Taking the rest of the rain chances
out today and tonight based on radar and satellite trends. Extensive
cloud cover continues across much of the northeastern U.S. but
there are some holes in the clouds in OH and western PA just
approaching western NY that are slowly building east.

Some guidance suggests these holes in the clouds work there way
into the eastern Catskills, mid Hudson Valley, NW CT and the
southern Berkshires later this afternoon and evening. Boundary
layer flow should be west while surface flow turns from south to
southwest. So, some weak downslope flow could help mix out the
cloud cover in some southern areas.

Trends in data are not promising as holes in the clouds are
just so slow to build east and by the time they may get to our
area, more trapped moisture at the boundary layer to our west
could redevelop the cloud cover. So, keeping cloudy to mostly
cloudy through this afternoon with temperatures reaching the
40s. However, temperatures could be a couple to a few degrees
colder than guidance. It may be near 50 in southern areas if
there are some breaks in the clouds.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Upper system in the southwestern U.S. is expected to track to
the Gulf Coast states by Sunday and cut off before tracking
northeast through the TN Valley and southern Appalachians Sunday
night to the mid Atlantic and northeastern U.S. Monday and
Monday night within a negatively tilted mean upper trough. Upper
confluence in eastern Canada Sunday will support fairly strong
low level ridging that builds south into northern and eastern
New England, with some cooler and drier air that is expected to
build west and south into NY Sunday night and Monday. The Low
level ridging will retreat back to the north and east through
the day Monday, allowing some low level warming from the south
into our region.

This chaotic upper pattern and how it affects the evolution of
the thermal profiles from low levels through the atmosphere in
our region leads to considerable uncertainties as to what falls
out of the sky, where and when. The strong upper low and
associated strong forcing and considerable moisture supports
widespread and locally heavy precipitation, of assorted
precipitation types due again to the complex and changing
thermal profiles through the atmosphere.

So, on Sunday, with increasing and thickening cloud cover, highs
in the 40s. There is a chance for the leading edge of the rain
to reach the mid Hudson Valley and NW CT by late Sunday
afternoon. Rain spreads over the entire region Sunday night but
the colder air draining south and west into western New England
and NY will change rain to mixed precipitation in northern areas
to southern VT and the northern Berkshires. The mixed
precipitation should mainly be snow, sleet and rain but pockets
of freezing rain not out of the question Freezing rain should
be isolated enough where it will not be mentioned this far out
but will be watched in future sets of guidance.

Mixed precipitation continues in higher terrain Monday while
rain is the predominant precipitation type in southern areas and
the Hudson Valley, including the Capital District. Highs Monday
in the upper 30s to lower 40s but mid 30s higher terrain. Winds
are expected to be strong early Monday morning and through the
day into southern VT and the Berkshires with very strong east
winds aloft affecting higher terrain and getting channeled
around Bennington and North Adams.

Upper dynamics proximate to the strong upper cut off may enhance
diabatic wet bulb processes and column cooling through a deeper
layer of the atmosphere in our region Monday night. Mixed
precipitation is expected to be more widespread Monday night
with mostly snow in higher elevations. There could be a better
chance for freezing rain in some areas as well and mentioning in
the forecast for Monday night, especially later Monday night and
early Tuesday morning. Snow accumulations at this time look to
be moderate in higher elevations but dustings could occur in
some valleys. There could be some noticeable ice accumulations
in areas that see freezing rain, maybe a tenth of an inch or a
little more.

Again, it should be emphasized that slight changes in the
strength and track of the storm and changes in how much of the
cold air gets anchored in our region could completely change
thermal profiles in the atmosphere and when, where and how much
wintery precipitation occurs. The forecast will change a number
of times as new data and guidance are available through this
weekend.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
At the beginning of the long term period we will still be dealing
with the coastal system and associated wintry mix of precipitation.
Following a GFS/ECMWF compromise, the surface wave should be
tracking northeastward from around Cape Cod to the Gulf of Maine
during the day Tuesday. The 500 mb low center will be displaced to
the west of the surface wave, centered over eastern NY. The heaviest
QPF will likely be over by Tuesday morning, however additional light
to moderate amounts will be possible during the day Tuesday as the
500 mb low and associated cyclonic vorticity advection moves through.

Thermal profiles and resulting precip type continue to be very
challenging to represent for the latter part of the storm on
Tuesday. Used the top-down approach which results in mainly
snow/sleet for the higher terrain of the Adirondacks/Catskills, but
freezing rain for southern Vermont into the Berkshires due to an
expected more pronounced warm nose aloft persisting in western New
England Tuesday morning. Rain possibly mixed with some sleet
expected in valley locations from around the Capital District
southward. Colder air aloft gradually filters in Tuesday afternoon,
which will result in any sleet/freezing rain to become more of a
rain/snow mix. Additional light snow accumulations possible Tuesday
afternoon/evening mainly across higher terrain areas.

The storm system finally pulls away late Tuesday night into
Wednesday morning, with a brief period of dry weather. However, the
next system (upper level trough/surface cold front) will quickly be
approaching from the Great Lakes, bringing a chance of rain/snow
showers Wednesday afternoon and night. Another push of colder air
arrives on Thursday, which will allow for temperatures to gradually
fall into Friday. Any rain/snow shower mix will turn to all snow
showers by Thursday night. Best chance for measurable snow will be
for areas west of the Hudson Valley, where lake effect and upslope
snow showers should develop with sufficient lake induced instability
occurring in wake of Thursday`s cold front passage.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
A ridge of high pressure aloft will be in place over the next 24
hours providing dry conditions. However, there is plenty of
moisture trapped beneath a low level inversion, so OVC skies
will persist through the period ending 12Z Sunday. Conditions
will be mainly in IFR range through much of the morning hours,
with some brief periods of LIFR with some fog at KGFL/KPSF.
VSBYS will improve during the day, with cigs showing some
improvement to MVFR levels through the day and into the
evening. Conditions may deteriorate again to borderline IFR
levels tonight, but it is uncertain at this time.

Winds will be south-southwest around 3-6 kt through the next 24
hours.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Chance of RA.
Sunday Night: Moderate Operational Impact. Chance of RA...SLEET.
Monday: High Operational Impact. Breezy Likely RA...SN.
Monday Night: High Operational Impact. Definite RA...SN.
Tuesday: High Operational Impact. Likely RA.
Tuesday Night: Low Operational Impact. Slight Chance of SHRA...SHSN.
Wednesday: Low Operational Impact. Slight Chance of SHRA...SHSN.

&&

.HYDROLOGY...
Daytime temperatures will be above normal through the weekend,
although overnight lows will fall around or just above freezing
for most areas. As a result, some very minor snowmelt may occur
in a few areas, but it will likely have little impact on rivers
and streams.

Widespread precipitation will occur early next week, but there
are still questions regarding the exact precipitation type and
amounts. The latest MMEFS do not show any flooding on area
rivers and streams, although some river rises are likely to
occur.

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.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...NAS
NEAR TERM...NAS
SHORT TERM...NAS
LONG TERM...JPV
AVIATION...JPV
HYDROLOGY...NAS



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