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fxus61 kaly 231821 
afdaly

Area forecast discussion
National Weather Service Albany New York
121 PM EST Fri Feb 23 2018

Synopsis...
another system will bring a wintry mixed precipitation
today, mainly into the higher terrain. Milder and mainly dry on
Saturday, but another round of mixed precipitation is likely late
Saturday night into Sunday.

&&

Near term /through tonight/...
as of 100 PM, pockets of showers expanding in coverage across
the forecast area, and will continue to do so through mid-
afternoon as isentropic lift continues to increase. P-type has
been mainly liquid with some freezing rain where temps are still
below freezing. Could be some light sleet/snow still over
western New England and the Lake George/Glens Falls area as Storm Prediction Center
mesoanalysis still indicated h850 temps below freezing. As
expected, surface temps have been slow to budge today with even
some valley areas remaining near to below freezing early this
afternoon. An Special Weather Statement was issued for those areas not in the advisory
for the possibility of patchy icy spots. Elsewhere, have
extended the advisory which was set to expire at 1 PM into the
evening for the Mohawk Valley and northern Herkimer County where
temps remain in the upper 20s to low 30s. Will reevaluate if we
can cancel some zones early with the next update around 4 PM.
Still expecting any icing to be around a tenth or less, but a
few higher amounts are possible over the western Mohawk Valley
and southern Adirondacks.

Previous discussion...lift and moisture transport will exit to
the east of the region through the evening hours. A weak thermal
trough lingers as slight chance pops will be kept through most
of the night. Question is precipitation type. Per soundings,
seems we lose the ice nuclei for either a light shower or
drizzle as thermal advection properties will be little hence not
much change to the temperatures from the daytime highs to the
forecast lows tonight.

&&

Short term /Saturday through Sunday/...
Saturday, low-level winds will become west-northwesterly and
usher in slightly drier air as weak high pressure expands into
the area at all levels. We'll start the day fairly mild, and
depending on the amount of clearing that occurs, we could be
looking at a fairly mild day as we will favor the warmer side of
the guidance envelope. Clouds increase late in the day ahead of
the next system, and we could even see light precipitation
beginning in the evening over southern zones as yet another
round of isentropic lift begins. Similar to our current system,
wet bulb processes may result in a period of wintry mixture,
mainly north and east of the capital region as low level
ageostrophic flow will remain from the north for a period of
time. Otherwise, a period of wet weather expected Sunday.

&&

Long term /Sunday night through Thursday/...
throughout the long term period, we will see the upper ridge over
Florida and the Gulf finally break down leading to an unsettled
weather pattern over the northeast Continental U.S..

The period starts out with a low pressure system pushing offshore
with some lingering wintry precip over the eastern third of the
forecast area. This precip should quickly come to and end Sunday
night as drier air and high pressure builds in at the surface.

High pressure will strengthen over the region through the first half
of the work week as the 850mb ridge builds, allowing for a period of
dry weather and slightly above normal temperatures. Through this
period, high temperatures will average in the 40s to low 50s, with
overnight lows in the 20s to low 30s each day.

The next potential storm system develops in the Central Plains and
moves towards the Great Lakes by Thursday. This system is quite
complex and dynamic as it involves an upper level shortwave moving
into the Great Lakes, a surface low pressure and a potential
secondary low that forms out of the southern stream. Global models
are in good agreement with the location of the shortwave but
struggle with the low features and overall strength of this system.
Due to the discontinuities, have bumped pops down from superblend to
maintain chance pops from Thursday Onward into the weekend. A mix of
rain/snow is likely due to the potential prolonged period of
precipitation and diurnal temperature swings each night.

&&

Aviation /18z Friday through Wednesday/...
showers will continue to increase across the terminal corridor
into mid-afternoon, with cigs and vsby dropping to MVFR/IFR.
P-type expected to be mainly liquid, although some brief
sleet/snow cannot be ruled out early this afternoon. With
temperatures near freezing, some light freezing rain is
expected at kgfl/kpsf this afternoon. Showers will diminish
after 00z, but some lingering spotty showers or drizzle could
continue. With a steep inversion developing, low clouds and mist
are a good possibility overnight, at least through 06z, before
low-level winds turn westerly and usher in a bit drier air. Kpou
may remain socked in all night.

Improving conditions Saturday with cigs becoming VFR shortly
after sunrise as high pressure briefly builds in.

Winds will be south to southeast for the rest of the day at
around 10 kt. These winds will gradually shift westerly
overnight while diminishing to around 5 kt, but mainly light
and variable at kpou. Surface winds should be light enough to
support low-level wind shear conditions overnight at at least
kpou/kpsf. West to northwest winds Saturday morning into early
afternoon will increase to around 10 kt with some gusts around
20 kt at kalb/kpsf.

Outlook...

Saturday night: high operational impact. Breezy likely rain.
Sunday: high operational impact. Breezy definite rain.
Sunday night: slight chance of rain.
Monday: no operational impact. No sig weather.
Monday night: no operational impact. No sig weather.
Tuesday: no operational impact. No sig weather.
Tuesday night: no operational impact. No sig weather.
Wednesday: low operational impact. Slight chance of rain...sn.

&&

Hydrology...
main hydrologic concern continues to be flooding due to ice jams
along the Mohawk River in central Schenectady, southern Saratoga and
northeast Albany counties, as well as the Hudson River in a small
area of central Warren County. Flood warnings or flood advisories
are in place for these areas. Refer to the flood statements for
additional details. The main larger ice jam has broken into
small pieces on the Mohawk River, but are scattered between lock
9 and Cohoes Falls. Ice jams appear to be settling in place,
but sudden movement will still be possible tonight into Friday
which could cause fluctuations in water levels.

Outside of ice jam areas, additional wintry precipitation is
expected today into the weekend, with rain as well. Wintry
precip including freezing rain, is expected for mainly high
elevations areas. Current forecasts call for around a three
quarters of an inch to over an inch of liquid equivalent
precipitation during this time, with the greatest amounts west
of the Hudson Valley. Runoff from this precipitation may result
in additional river rises. Temperatures are expected to remain
above normal during this time, but not as warm as earlier this
week.

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...Winter Weather Advisory until 10 PM EST this evening for
nyz032-033-038>042-047-048-051-058-063-082-083.
Massachusetts...Winter Weather Advisory until 10 PM EST this evening for
maz001-025.
Vermont...Winter Weather Advisory until 10 PM EST this evening for
vtz013-014.

&&

$$
Synopsis...bgm/Thompson
near term...bgm/Thompson

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