Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 192123
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
423 PM EST Sun Feb 19 2017

.SYNOPSIS...
An upper level disturbance moves through tonight with high
pressure building back into the region behind it. Another weak
mid-level disturbance approaching from the west will bring
chances for light mixed wintry precipitation Tuesday evening
through Tuesday night. Temperatures will generally be above
average this week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Leading edge of clouds dropping south with more solid cloud
cover just north of the U.S. Canadian border. Tail of band of
clouds north of Lake Huron is eroding already.  Based on
trajectories in satellite imagery and cloud cover forecasts in
guidance, cloud cover forecasts in guidance may be overdone for
tonight into Monday morning.

Based on trends in satellite imagery and the expectation for
deeper cold advection and tightening thermal gradient with the
cold advection, a period of broken clouds should occur at some
point tonight over eastern NY, VT and Berkshires but some doubts
about the extensive cloud cover in western areas to the eastern
Catskills, mid Hudson Valley and NW CT.

Guidance has been struggling to resolve the surface through
boundary layer in the past week, with misrepresented cloud cover
and winds through the low levels. So, with the thought that
there will be a period of partly to mostly cloudy sky and some
steady light winds through most of not all night in many areas,
not straying far from guidance but siding with warmer guidance.
Lows in the 30s with some 20s northern areas and maybe around
30 southern areas where less cloud cover potential.

Boundary layer winds will be quite strong and shifting more to
the north. Winds usually mix down more efficiently in cold
advection. So, the odds are that most areas should see steady
light winds tonight but still not sure if decreasing snow pack
will create enough of an inversion to prevent winds from mixing
down in some areas toward daybreak. Any areas that go calm will
see colder temperatures.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
As said earlier, guidance has had considerable issues resolving
the surface through boundary layer for some time now and with
the tail of the cloud cover north of Lake Huron eroding
already, would like to believe the suggestion from guidance
that most areas will see lots of sun Monday. So, even with
boundary layer temperatures cooling considerably, mixing
potential would support highs at least a couple of degrees
warmer than the warmest guidance, as long as we mix to around
850 hPa. Even if we mix to 925 hPa the highs should be at about
the warmer guidance. So, highs Monday in the 40s, but near 50
southern areas and mid to upper 30s northern areas.

The low level ridging shifts overhead Monday night and with a
clear sky and nearly calm winds, temperatures will have a chance
to fall into the teens to around 20. A quick moving upper
impulse approaches our region Tuesday and some mid and high
clouds should move into our region through the afternoon. There
may be some spotty light rain in western areas by late Tuesday
afternoon. Warmer boundary layer temperatures, west boundary
layer winds and some sun filtered only by mid and high clouds in
the afternoon should help temperatures to warm to the mid to
upper 40s many areas but lower 40s northern areas.

A shot of warm advection and isentropic lift will support
patches of light rain and mixed precipitation Tuesday night.
The mixed precipitation should be confined to the usual colder
spots of northern areas, southern VT and the Berkshires. Since
there are just chances, just mentioning the mix in the Hazardous
Weather Outlook.

The system exits later Tuesday night and with a warmer airmass
and boundary layer temperatures in our region, Wednesday is
expected to be sunny with a more significant warm up. West
boundary layer flow should also help with mixing. Since
guidance has again been struggling with temperature forecasts
showing a cold bias, highs Wednesday solidly in the 50s, but
some mid 40s northern areas and pushing 60 in southern areas.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Highly changeable conditions are expected through the long term,
with the main storm track remaining north and west of the region.
However, toward the end of the week into next weekend, as a stronger
storm tracks from Colorado into the western Great Lakes, there is
some suggestion that high pressure across eastern Canada builds
southward. Depending on how strong and far south any potential sfc
high builds, there could be a bout of wintry precipitation across at
least northern portions of the region sometime between Friday and
Saturday, with rain or showers elsewhere.

A weak system should track north of the region on Thursday, with a
cold front trailing from this system settling southward late
Thursday or Thursday night. Some spotty rain showers or sprinkles
may accompany the front. Before the front passes, a deep
west/southwest flow should allow for very mild/warm temperatures
regionwide, with highs reaching the 40s and 50s for most areas, with
some 60s quite possible across portions of the mid Hudson Valley, if
not even further north in the Hudson Valley.

Gradual cooling spreads south and east Thursday night into Friday
behind the front, with the main uncertainty being how far south this
colder air seeps, again related to the strength of the high across
eastern Canada. Although most global models currently suggest a
fairly weak high, with the brunt of the low level cold air remaining
north of the region, we have seen several instances this cold season
where models are initially too weak/far north with such highs. So,
have gone a bit colder than blended model guidance for Fri-Sat
temperatures, with highs mainly in the 30s and 40s, and nighttime
lows in the 30s. As the low approaches the Great Lakes,
strengthening isentropic lift should allow precipitation to increase
across the region sometime Friday and continue into Saturday,
although there are timing differences among the global models, with
some holding off any precip until Saturday. For now, have indicated
chance pops Fri-Sat, with mainly rain, except for pockets of
freezing rain across portions of the southern Adirondacks, Mohawk
Valley and southern VT. Again, trends will have to be watched
through the week, as the potential for more widespread and
persistent mixed precipitation exists.

The system`s cold/occluded front should move east of the region by
Sunday, with windy and seasonably cool conditions in its wake, in
addition to possible upslope and/or Lake Effect snow showers across
northern areas. High temperatures should mainly be in the 30s and
40s.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
Not much seen on the satellite imagery and looking out our
forecast office windows this early Sunday afternoon. Nearest
stratus was approaching Lake George region with SCT-BKN VFR
deck. As this upstream cold front approaches and migrates
through, a chance for BKN VFR to high end MVFR conditions for
KGFL-KALB-KPSF. VFR conditions should prevail at KPOU with
favorable downsloping winds from the west. Winds will be gusty
at times and slowly veer to a more west-northwest direction.

Tonight, as this front passes through, not enough confidence to
have broken ceilings as we will leave SCT CIGS for all TAF
locations. Wind gusts will subside, as direction becomes
northwesterly to north.

VFR conditions expected on Monday as high pressure settles
across the region.

Outlook...

Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Low Operational Impact. Slight Chance of RA.
Tuesday Night: Moderate Operational Impact. Chance of RA.
Wednesday: No Operational Impact. NO SIG WX.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: Moderate Operational Impact. Chance of SHRA.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Moderate Operational Impact. Chance of RA.

&&

.HYDROLOGY...
No widespread hydro problems are expected into the middle of
next week with limited chances of widespread precipitation.

Milder temperatures are expected into early next week. Although
these warmer temperatures will promote some snow melt during
the day, it won`t be accompanied by any significant rainfall and
strong southerly winds, and overnight temperatures will fall
below freezing. This will allow for a controlled and gradual
diurnal melt of the snowpack in place. Only small and minor
rises can be expected on rivers and streams through the early to
middle portion of next week.

With another approaching storm system, a light mix of
precipitation to rain showers is expected Tuesday night into
Wednesday. This looks fairly light and is not expected to have
a major impact on the hydro service area at this time.

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...KL
AVIATION...BGM
HYDROLOGY...NAS


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