Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 260534

National Weather Service Albany NY
134 AM EDT Fri Apr 26 2019

Another storm system brings a widespread rainfall and cooler
temperatures to the region for late tonight into Saturday
morning. Blustery conditions will return for Saturday along with
rain and mountain snow showers. It will remain chilly Sunday,
along with possible rain showers.


As of 115 am, early morning water vapor shows copious northward
deep-layer moisture advection over much of the eastern US ahead
of a digging full latitude trough. As the trough continues
eastward and assumes a negative tilt, the low level jet will
strengthen and back over the local area. Bands of showers are
ongoing on the leading edge of the associated isentropic lift
from central NY back into PA/MD. Expect coverage of these
showers to fill in as they track into the forecast area through
12Z such that categorical PoPs are warranted over most of the
area by 12Z. Some of the lift will be lost to saturating the dry
low levels sampled by the 00Z KALY RAOB. The dewpoint depression
is still 18F at KALB at 05Z.

As the trough continues to dig into the southeastern US and its
negative tilt increases, the forecast area gets into a quasi
warm sector for the morning and into the early afternoon. The
low level jet will be strong but does not have much of a
temperature gradient to operate on. Also, midlevel height falls
are weak for much of the day. As we do not have organized
forcing for ascent, much of the precipitation will be showery in
nature and modulated by the terrain with strong southeasterly
winds of 30-40kt at 925 mb. Midlevel lapse rates steepen and
Showalter values are around zero by the afternoon and evening,
so a rumble of thunder cannot be ruled out. With the strong
southeasterly flow at low levels, winds will likely be quite
strong across the western slopes of the Greens, Berkshires, and
Taconics. A low level inversion is expected to keep mixing from
becoming too deep, so forecast gusts are below advisory level at
this time. We have sided a bit toward the warmer side of
guidance with the forecast temperatures given that it does not
appear to be a steady rain for areas outside of the
southeasterly facing slopes of the higher terrain.

From about 21Z today through 06Z tonight, dynamic forcing for
ascent rapidly increases as the trough and associated height
falls pivot into the area. This should allow for a more
organized area of steady rainfall to arrive from southwest to
northeast. Numerical guidance is depicting a surface wave
spinning up on the approaching thermal gradient. The associated
frontogenetical forcing could result in a period of briefly
heavy rainfall at times during this period, although guidance
has backed off somewhat on this scenario. We are still not
expecting widespread flooding concerns with this system owing to
the brief nature of the stronger forcing for ascent, but some
poor drainage flooding cannot be ruled out (see hydro discussion
below for more). We could see some embedded thunder as well.
Coverage of precipitation diminishes quickly after 06Z, but some
upslope showers over the higher terrain should continue,
possibly mixing with snow toward daybreak.


Much colder air will move into the area behind the front later
Friday night and Saturday morning. Showers will linger in most
areas as the mid level system closes off across southern New
England Saturday morning. The atmosphere will probably become
cold enough for rain showers to mix with or change to snow
showers over the Adirondacks and Green Mountains by Saturday
morning with some light accumulations possible. A few flakes
could even be see in the mid to upper Hudson Valley Saturday
morning before showers end in the afternoon. Temperatures
Saturday afternoon will be hard pressed to get out of the 40s in
many areas, with possibly some lower 50s in the Hudson Valley.
These temperatures will combine with westerly winds gusting to
20 to 30 mph to make for a very chilly spring day.

The second system to affect our area will move quickly eastward
from the Ohio Valley tracking across Pennsylvania late Saturday
night and Sunday. The NAM and ECMWF are in good agreement with a
track that will be far enough north for a swath of light to
moderate precipitation for much of our area, yet far enough
south so that not all of the precipitation will be rain for our
higher elevations. The GFS is a bit farther south. At this point
we will go with low likely pops for Sunday and mention light
rain or snow for the higher elevations outside of the Hudson
Valley. In the Hudson Valley we will just go with rain for now.
Have lowered temperatures on Sunday a few degrees below model
blends as clouds and precipitation could potentially keep
temperatures only in the 40s, with even some highs in the upper
30s possible over higher elevations.


Below normal temperatures will remain in place as we close out April
and head into early May with a few chances for precipitation
(including rain/snow mix in the higher terrain) within the fast
zonal flow. Since our milder than normal April ranging 3-4F degrees
above normal has led to budding vegetation from the Capital Region
south/east, the anticipated cooler temperatures may necessitate
frost/freeze products. Read on for details.

We start the period Sunday night with subsidence and a 1030-1035hPa
Canadian high pressure moving into the Northeast in the wake of a
departing clipper. Northwesterly flow should lead to cold air
advection overnight, advecting in 850mb isotherms between -3C to -
6C. Guidance is in good agreement with plenty of mid-level dry air
moving into eastern NY and western New England which should lead to
clearing skies. Breezy winds may be in place for the first half of
the night due to the pressure gradient between the departing clipper
and building high but winds should relax overnight. Add in dew
points falling into the 20s by Monday morning and this should lead
to a decent radiational cooling set-up with low temperatures falling
into the low to mid 30s for the Hudson Valley, southern Berkshires
and Litchfield County with the surrounding hill towns and higher
terrain dropping into the mid-upper 20s. We will continue monitoring
temperature trends but this may necessitate some frost/freeze
products for the Greater Capital Region and some areas south and

High pressure takes control of the region for Monday which give us a
pleasant day despite temperatures being a few degrees cooler than
normal in the mid-upper 50s. The dry weather does not look to last
long as a shortwave embedded within the fast zonal flow and riding
along a baroclinc zone moves eastward from the Midwest into the
Northeast/mid-Atlantic overnight. As the previous forecast
discussed, there still remains some uncertainty regarding the track
of the low. The global guidance still shows some slight differences
with where the best baroclinic zone sets up which will determine if
the low tracks more into the mid-Atlantic as the CMC-NH shows or a
bit further north into the Northeast as the ECMWF and GFS show. For
now, we have widespread chance POPs Monday night into Tuesday with
temperatures cool enough in the higher terrain of the Adirondacks,
Greens, Berkshires and Catskills to lead to rain/snow mix.

By Tuesday the differences in the guidance become more apparent as
the ECMWF and CMC-NH show a strong nearly 1040hPa Canadian high
sinking southward and shunting our baroclinc zone into the mid-
Atlantic while the GFS keeps it firmly in place across the
Northeast. For now, sided more with the ECMWF and CMC-NH out with
cooler temperatures with highs in the 50s and lows in the 30s
returning for the mid-week period along with decreasing cloud

The next system to monitor will be for the end of the week as a more
organized system from the Midwest heads east potentially leading to
overrunning precipitation.


High pressure will continue to shift south and east of New
England into tonight. A complex storm system will approach from
the lower Great Lakes Region and OH Valley tonight. The warm
front to the system will brings periods of rain into the region
Friday morning into the afternoon. The occluded front will keep
the threat for heavy showers and an isolated thunderstorm into
Friday night.

Mid and high clouds will increase from the south and west across
eastern NY and western New England through this evening with
VFR conditions continuing. The threat for showers or a period of
light to moderate rain increases between 06Z-10Z, earliest at
KPOU then building toward KALB, KPSF and KGFL through 10Z-12Z.

Ceilings and visibilities will lower with the low level
moisture increasing with widespread MVFR conditions setting up.
The rain may become steadier and a bit heavier after 12Z and
some IFR ceilings and visibilities are included at KPOU and
PSF. The rain will likely continue through the morning and only
slowly and gradually decrease in coverage into the afternoon.
So, keeping the ceilings and visibilities steady at MVFR/IFR
through Friday afternoon.

Variable winds at 6 Kt or less will become south to southeast
and increase to 4 to 8 Kt at KALB/KPSF. The winds may increase
towards 12Z Friday at KALB, 8 to 12 Kt by daybreak with some
gusts close to 20 Kt. Winds at all TAF sites will become
southeast at around 10 Kt and some gusts over 15 Kt are
possible Friday afternoon.

The 2000 foot AGL southeasterly winds will increase to 30-35
kts between 08Z-12Z at KPSF and KPOU and LLWS was added to the
TAF sites since the surface winds are expected to be light at 10
Kt or less. The 2000 foot winds will become south at 40 Kt
Friday afternoon. So, LLWS was kept at KPOU and KPSF but added
to KALB, even if southeast surface winds gust to around 15-16


Friday Night: High Operational Impact. Breezy Pds SHRA...RA.
Saturday: Moderate Operational Impact. Windy With Gusts To 35.0 Chance of SHRA.
Saturday Night: Low Operational Impact. Breezy NO SIG WX.
Sunday: Moderate Operational Impact. Chance of SHRA.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: Moderate Operational Impact. Chance of SHRA.
Tuesday: Moderate Operational Impact. Chance of SHRA.


Weak high pressure will bring fair and seasonably mild
conditions today, before another storm system brings widespread
rainfall and cooler temperatures to the region for Friday into
Saturday morning. Blustery conditions will return for Saturday along
with some rain and mountain snow showers. It will remain chilly
Sunday, with another chance for rain showers as a fast moving
upper level disturbance tracks nearby.


Flood Warning remains in effect on the Schroon River at
Riverbank. The Schroon River at Riverbank will continue to
gradually fall and is forecast to go below 8 feet, moderate
flood stage, by later today.

Please visit our Advanced Hydrologic Prediction Service /AHPS/
web page for specific area rivers and lakes observations and

Mainly dry conditions are expected through this evening.

Another storm system is expected to bring widespread rainfall
to the region early Friday morning into early Saturday morning.
Looks like total QPF from this system will average from 0.75
inches to 1.50 inches area wide. This may result in renewed
river rises late Friday into the upcoming weekend, especially
across portions of the Adirondacks into the Mohawk Valley where
river levels are already running high from recent rainfall and
snowmelt. Trends will need to be watched closely, and if this
potential for heavy rain increases further, then a Flood Watch
would be issued. This potential would be greatly enhanced if
total rainfall amounts reach/exceed 2 inches.




NEAR TERM...Thompson
LONG TERM...Speciale
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