Area Forecast Discussion
Issued by NWS Albany, NY

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351
FXUS61 KALY 280031
AFDALY

Area Forecast Discussion
National Weather Service Albany NY
831 PM EDT Mon Mar 27 2017

.SYNOPSIS...
A cold front will approach from the eastern Great Lakes
region with cloudy and mild conditions ahead of the boundary
tonight. Scattered showers will accompany the front with a weak
disturbance moving along it that will pass to the south of the
region tomorrow. Cooler and drier air will filter back into the
region Tuesday night with high pressure building back in for
Wednesday into Thursday with normal to slightly below normal
temperatures.

&&

.NEAR TERM /THROUGH TUESDAY/...Northern stream s
Northern stream short wave trough will move off to the east
overnight while a southern stream short wave approaches from
the southwest. The local area will be between the two with
little flow with a nearly stationary boundary meandering across
the region. Have abundant low level moisture across most of the
area with areas of fog expected to develop, some locally dense.
Overnight in mid 30s to lower 40s.

For Tuesday, yet another southern stream shortwave currently
tracking across the mid Mississippi Valley will track east/northeast
toward the northern mid Atlantic region. In addition, another
shortwave currently over south central Canada will be driving
east and strengthening.

It appears that rain should overspread southern areas during the
morning, and may expand north northeast in the afternoon, although
the northern extent of the rain shield remains somewhat in question.
For now, have indicated best chance for rain for the I-90 corridor
and points north in the afternoon/evening, as southern stream
moisture combines with the approaching northern stream energy which
may tend to pull the rain shield northward. The steadiest rain,
however, should be mainly from Albany and points south and east
through the day.

Given the expectation for clouds and at least some rain, have
trended high temperatures cooler than blended MOS for Tuesday, with
mainly mid 40s to lower 50s expected. Temps will likely fall in
areas once rain becomes steadier due to wet bulb cooling
processes.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 425 pm EDT...

Tue Night...The cold front continues to move across the region
from northwest to southeast with a period of showers along it.
The latest 12Z NAM/GFS/ECMWF/CAN GGEM are in pretty good
agreement that the majority of the shower activity will be over
shortly before or just after midnight. The highest pops were
kept early in the evening over the southern most zones...mainly
south and east of the Capital Region. Cold advection will kick
in the wake of the system with perhaps a few snow showers or
flurries over the southern Adirondacks and the southern Greens.
Any snow amounts will be very light with a coating to maybe a
couple of tenths. In terms of the low/mid- level cold advection,
H850 temps from the latest 12Z GFS lower to -3C to
-9C north and west of the Capital Region, southern Greens, and
 northern Catskills. South and east of this area H850 temps
 fall to -3C to +3C by daybreak on WED. Lows will generally be
 in the mid 20s to lower 30s north and west of the Capital
 District and mid/upper 30s from the Capital Region/Mid-Hudson
 valley south and east.

Wed-Wed Night...The forecast area will be under the influence of
an upper level trough and cyclonic flow through the day. Cold
advection will be continuing through the afternoon. A few snow
showers/flurries/sprinkles will linger across the upslope areas
of the southern Adirondacks and southern Greens. H850 temps
actually lower to -3C to -10C across the region during the day.
It will be brisk and chilly for a late March day. Mixing depths
may reach H850-825, but model soundings from the NAM indicate a
fairly strong subsidence inversion above H850, so NW to N winds
of 10 to 20 mph are possible with gusts to 25-30 mph at best.
Sunshine will mix with clouds, with more clouds over the higher
terrain. The mixing coupled with downsloping off the higher
terrain should allow for highs in the mid 40s to lower 50s /mid-
Hudson Valley for the lower 50s/ in the valley areas with mid
30s to lower 40s over the mountains. The winds should diminish
to less than 10 mph after sunset with a ridge of Canadian high
pressure building in from south-central Ontario or James Bay. A
cold night is expected with lows mainly in the 20s, except for
teens over southern Adirondacks, southern Greens and the
Catskills.

Thursday...High pressure continues to dominate and build in
form southeast Ontario/southwest Quebec with cool and dry
weather. The mixing depths looks shallow for this day with light
northerly winds. The strong subsidence from the anticyclone
will yield mostly sunny conditions for most the region with
partly sunny conditions north and west of the Hudson River
Valley. The upper low trough shifts downstream with some flat
ridging building eastward ahead of the next trough moving
through the central Plains. Highs will be near normal to
slightly below normal for THU. With the late March sun angle
highs will be in the upper 40s to lower 50s in the lower
elevations with upper 30s to mid 40s over the hills/mountains.

Thursday night...A potent mid and upper trough moves from the
central Plains into the central MS River Valley/Midwest based
on the latest GFS/ECMWF/CAN GGEM. Clouds quickly thicken and
lower ahead of the systems warm front with a mid-level shortwave
approaching in the southwest flow. The ECMWF/GFS both have some
over-running or warm advection pcpn reaching eastern NY and
possibly portions of western New England between 06Z-12Z FRI.
The CAN GGEM is a little slower. We kept slight and low chc pops
across most of the region, except for southern VT. Thermal
profiles are cold enough for some wet snow with the onset of the
warm advection with perhaps a rain/snow mix over the mid-Hudson
Valley. Some light snow accums of a coating to less than an
inch are possible west of the Hudson River Valley. There is
still quite a bit of uncertainty with the track of this system
and thermal profiles, as we head into Friday. Lows Thu night
are expected to be in the 20s to lower 30s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 425 pm EDT...

Guidance is in general agreement a low pressure system should be on
the approach from the southwest late in the week and it should pass
to our south Saturday as a southern stream trough/low moves toward
the southeast coast. What is uncertain is the exact track of the
system and the expected thermal profiles which will determine
precipitation types. Also there is quite a range in expected QPF
however guidance is indicating rather high amounts.

Have enough confidence to run with likely pops Friday into Saturday
however confidence is much lower for precipitation types and their
timing. At this time based on the current forecast, the
precipitation Friday morning would be transitioning from snow to
rain as the boundary layer warms with a transition back to snow
across much of the forecast area Friday night. If guidance trends
colder then more snow would be expected. The bulk of the
precipitation is expected Friday into Saturday with it tapering off
during the day Saturday as the system moves off to our east. A
northern stream short wave trough and associated front is expected
to then sweep across the region in the wake of the system over the
weekend with higher pressure building in as we head into next week.

As for temperatures with clouds and precipitation looking at below
normal during the daytime and near or a bit above at night

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Northern stream short wave trough will move off to the east
overnight while a southern stream short wave approaches from
the southwest. The local area will be between the two with
little flow with a nearly stationary boundary meandering across
the region. Have abundant low level moisture across most of the
area with areas of fog expected to develop, some locally dense.
The southern stream short wave trough will dampen out as it
approaches and an occluded front will gradually move across the
area Tuesday. Chances for showers will increase as we head
through day especailly south of I-90.

Have VLIFR-LIFR at KGFL and expect these conditions to persist
through the overnight. Am improvement to IFR is expected after
sunrise with MVFR developing in the afternoon. At KALB expect
MVFR conditions to lower to IFR then these conditions persist
even when the showers move in by late Tuesday morning. At KPSF
have IFR due to ceilings except visibilities to lower with IFR
conditions persisting even as showers move in by late Tuesday
morning. While at KPOU VFR conditions are expected to lower to
MVFR then IFR as fog and stratus form. Showers move in Tuesday
morning after sunrise with IFR conditions expected through the
day.

Winds will be light and variable to calm.

Outlook...

Tuesday Night: Moderate Operational Impact. Chance of SHRA.
Wednesday: Low Operational Impact. Breezy.
Wednesday Night to Thursday: No Operational Impact. NO SIG WX.
Thursday Night: Moderate Operational Impact. Chance of RA...SN.
Friday-Friday Night: High Operational Impact. Likely RA...SN.
Saturday: Moderate Operational Impact. Chance of SHRA.

&&

.FIRE WEATHER...
Much of eastern New York and western New England continues to
have snow on the ground. Some of the valley areas have bare
patches, but the mountains have a deep snow pack. A moist and
damp air mass will be in place tonight with light winds, as a
cold front and a weak disturbance will bring showers tomorrow
into early tomorrow evening. High pressure will build in for the
mid-week into Thursday with cooler and drier weather.

&&

.HYDROLOGY...
A mild air mass will be over the region tonight ahead of a cold
front, and low pressure moving north of the Saint Lawrence River
Valley with some additional snow melt.

Scattered showers are possible or a period of rain tomorrow
into early tomorrow night with the cold front. Additional
rainfall will range from a tenth of an inch or so over the
northern basins to a third of an inch over the the mid-Hudson
Valley and NW CT. This rainfall, along with the expected
snowmelt, will cause some within bank rises on rivers and
streams. However, this rain and snowmelt is not likely to
produce any concern for flooding at this time.

The latest MMEFS forecasts have a few points getting to the
alert or action stage, but no flooding is forecast. The latest
NERFC forecasts only have Williamstown on the Hoosic River
barely reaching the alert or action stage Tue into early Wed.

Flows will recede Tuesday night through the mid-week with a
colder and drier air mas building in. Temps are expected to go
below freezing Wed night and Thu night with a normal diurnal
melting of the snowpack in spots.

Some additional precipitation in the form of rain and snow is
expected for Friday into Saturday with another storm system.
There is some uncertainty with the track and the amount of
moisture associated with it. It be could be a moderate to heavy
precipitation event, but it is a low confidence forecast 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...Wasula
NEAR TERM...IAA/KL
SHORT TERM...Wasula
LONG TERM...IAA
AVIATION...IAA
FIRE WEATHER...Wasula
HYDROLOGY...Frugis/Wasula



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