Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 221541
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
1141 AM EDT Fri Oct 22 2021

.SYNOPSIS...
Showers and thunderstorms associated with a cold front
will diminish across the region early this morning. After that, just
expecting a few isolated showers over the weekend with temperatures
near to below normal temperatures expected for the weekend behind
the cold front. However, chances for rain increase again by Sunday
evening, and will remain elevated for much of next week thanks to an
upper low that will be nearby. Daytime highs next week will
generally be near or slightly below normal with low temperatures
warmer than normal.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Updated at 11:00 AM EDT. Colder air is gradually filtering
eastward across the area late this morning. Latest satellite
imagery shows strato cumulus clouds covering most of the
forecast area, with some breaks in the Hudson Valley and
especially downstream from the Catskills in the lower and mid-
Hudson Valleys. Temperatures have fallen into 40s across much of
central and western NY per the NY state mesonet, but 60s are
still hanging on in the Hudson Valley from the Capital District
southward. Some light sprinkles have been occurring east and
west of the Hudson Valley this morning, but those appear to be
diminishing as dryer air works into the area. The remainder of
the day looks to be mostly cloudy except down wind of the
Catskills, with near steady temperatures. The current forecast
is on track and we have made just minor tweaks to the grids
based on the latest trends. Previous discussion is below.

.Update...As of 6:40 AM EDT, current surface observations show
an area of low pressure located over southern Quebec moving off
to the northeast. Initial cold front moved through the region
last night/early this morning, but a secondary cold front is
currently draped across central and western NY. While the
upper- level shortwave and associated showers that impacted the
region overnight have moved off to the northeast as well,
another band of showers has developed along the secondary
surface cold front in central and western NY. Current radar
imagery shows some of these showers in Herkimer and hamilton
counties, so tweaked PoPs upward slightly here for the next
couple hours to account for these showers. As we head through
the morning, however, these showers will likely diminish in
coverage as the front slides eastward across our region. Also
increased temperatures a few degrees this morning to be in
better alignment with current observations, as temperatures have
remained rather warm overnight with most areas in the 50s this
morning. Otherwise, no major changes to the forecast, but did
refresh grids to reflect current obs. Cold front should continue
to slide across the region this morning into early afternoon,
ushering in cooler temperatures for the mid/late afternoon and
evening into tonight. Previous discussion below has some
additional details...

.Previous [3:45 AM EDT]...showers and an isolated embedded
thunderstorm are currently tracking across the region. The bulk
of the precipitation has exited to the north at this time,
although some showers remain across mainly to the east of the
Capital District. Did see a few lightning strikes to the
northeast of tech Capital District over the last hour thanks to
some elevated instability, so did include slight chance thunder
for souther VT for the next couple hrs in the grids.

The showers are associated with a surface low tracking across
southern Quebec that developed in response to an upper-level
shortwave rotating around the base of a cosed upper low located
north of the Great Lakes. These showers developed along a pre-
frontal trough/windshift ahead of a surface cold front that is
currently located back over western NY per latest surface obs.
Temperatures did not fall very much tonight except in eastern
areas of the Taconics and Berkshires where skies remained more
clear earlier tonight, so did adjust temperatures upwards a few
degrees over the next couple hours.

As we head into the day Friday, the cold front located to our
west will move towards our area and is expected to move across
the region later this morning into the early afternoon. While
the bulk of the precipitation is moving away from the region at
this time, a few more showers will be possible with the frontal
passage, especially in the Mohawk Valley and Western
Adirondacks. As the surface low pulls away to the northeast,
high pressure will try to build in from the west, which will
result in a tightening of the pressure gradient. This will
result in increasing westerly winds that will help advect cooler
air into the region. A few lake effect showers and some lake
effect clouds will be possible in the Mohawk Valley as the
colder airmass moves over the relatively warmer Great Lakes, but
elsewhere precipitation chances will diminish as cold air
advection and anticyclonic vorticity advection aloft promote
subsidence. Temperatures may briefly rise into the low/mid 60s
ahead of the cold front for areas south and east of the Capital
District late this morning/early this afternoon, but
temperatures will begin to fall later this afternoon and evening
behind the cold front.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
Tonight...The night begins with some partial clearing behind
the cold frontal passage, although some lake effect clouds may
hang around for the Mohawk Valley and western Adirondacks. The
pressure gradient will degrease as surface high pressure tries
to build into the region, but cold air advection will promote
subsidence that may help keep the boundary layer slightly mixed,
so it will not be an ideal night for radiative cooling. Then,
after midnight, another upper-level disturbance will pivot
around the base of the upper low that will be located to the
north of the Great Lakes. Moisture looks limited so any showers
will be rather isolated in nature, but this disturbance will
likely lead to some increasing mid-level clouds towards morning.

Saturday...the day begins with the upper-level shortwave
passing through the region, so skies will be mostly cloudy to
start the day, although some partial clearing is expected for
the afternoon behind the departing upper-level disturbance.
However, with decent mixing to around 850 mb expected tomorrow,
steep low-level lapse rates may yield some more cumulus and
stratocumulus clouds in the afternoon. A few isolated showers
will be possible with steep low-level lapse rates and a
relatively cold air aloft associated with upper-level troughing.
We will remain in a cold air advection regime, so daytime high
temperatures look to stay in the 40s in the high terrain to 50s
for the valleys, which is near or just slightly below normal for
this time of year.

Saturday night, heights rise aloft and we will be under the
influence of surface high pressure. This will result in large-
scale subsidence and partly to mostly clear skies, with the
greatest clearing for southern areas which will be closer to
the center of the surface anticyclone. With a weak pressure
gradient and light winds, conditions will be more favorable for
radiational cooling, so expectation is that temperatures will
fall off quickly after sunset with the development of a
nocturnal inversion. It is not out of the question that some of
the higher elevations of the Adirondacks, southern Greens, and
eastern Catskills could see overnight low temperatures in the
upper 20s. Even the Mid Hudson Valley should see lows in the
upper 30s.

Sunday will start off rather chilly, with partly to mostly
clear skies. During the day Sunday, the closed upper low located
to the north of the Great Lakes will begin to drop
southeastward, but will get sheared by confluent flow aloft as
it does so. At the same time, another upper-level disturbance
will be moving across the center of the country, and will induce
surface cyclogenesis in the lee of the Rocky Mountains. The
cold front that passed through our region Friday will be
stalled to our south Sunday morning, cut cyclonic flow around
the aforementioned surface cyclone will attempt to push the
boundary back northward as a warm front. However, anticyclonic
winds around a surface high located over Ontario (beneath
confluence aloft) will try to counteract this northward movement
of the front.

The resulting deformation in the flow will lead
to an increase in precipitation along this frontal boundary, and
precipitation will be increased by cyclonic vorticity advection
aloft and divergence aloft in the right entrance region of a
300 mb jet streak. However, there is some uncertainty as to how
far northward this boundary gets Sunday evening and Sunday
night. The general trend over the past 24 hours has been for
more shearing out of the upper low, which would keep the upper
low further to the north. This would allow the frontal boundary
to move northward across our region Sunday night as a warm
front, bringing with it increased chances for precipitation. At
this time, will keep most of the day Sunday dry and will bring
chance PoPs for the entire region Sunday night, with likely PoPs
confined to areas south of I-90. However, may need to increase
PoPs further northwards if the northward trend in the position
of the frontal boundary continues over the next couple days.
Highs on Sunday will be a couple degrees warmer than on
Saturday, as will Sunday night lows thanks to increasing cloud
cover with the warm front moving into the region.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Much of the model guidance has been coming better agreement that a
slow moving storm system will be impacting the area during much of
the long term period.

At the start of the period, upper level shortwave and its associated
low pressure area will be moving across the Ohio Valley for Monday.
A stalled or very slow moving surface boundary will be extending off
eastward towards the northern mid Atlantic for Monday.  To the north
of this boundary, warm advection/isentropic lift will be allow for a
large area of steady rain that is expected to last through the
entire area on Monday for all of Upstate New York and into New
England.  While rain intensity looks mainly light, it will be steady
through the entire day, so rainfall totals may reach over a half
inch for much of the region.  With our area on the cool side of the
boundary, along with clouds and rain all day, temps will be held
down.  Have gone on the cooler-side of the blended guidance, with
40s to low 50s for the area for Monday.

The low pressure will be heading towards the mid Atlantic States for
Monday night and lifting towards the Jersey Shore/NYC area for
Tuesday into Tuesday evening.  It will be moving very slowly, as the
upper level shortwave will be cutting off and only slowly sliding
eastward towards the Atlantic seaboard.  As a result, periods of
steady rain look to continue for the area.  While there may be a
break Monday evening, it should pick up for the late night hours and
through the entire day on Tuesday, with the heaviest rainfall for
southern parts of the area closer to the low pressure area.  With
moisture surging in off the Atlantic thanks to a developing low to
mid level jet, some heavier rainfall is possible for southern areas,
especially the higher terrain, where upslope will enhance rainfall.
There are still some differences between the models on the exact
speed/strength of this system, and that will determine just how much
rainfall occurs, so this is still somewhat uncertain. Temps will
still be held below normal with all the rain clouds.  Overnight lows
will be in the upper 30s to mid 40s, with highs only in the mid 40s
to low 50s.

By Wednesday, there may start to be a brief break, as the storm
finally departs and a narrow ridge moves across the area.  As a
result, daytime temps may be a little warmer, with valley high into
the mid to upper 50s.  However, hard to promise a lot of sun despite
the ridging, as plenty of lingering low-level moisture and the poor
sun angle will keep lots of clouds around.

Another slow moving closed upper level low will return the threat
for clouds, rain and cool temps for Thursday.  Will keep chc POPs in
place with temps mainly in the 50s and a mostly cloudy sky.  This
system may also impact the region for a few days, keeping the
cloudy, cool and stormy pattern in place.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
Surface cold front has now moved through the area and a secondary
boundary is making its way across the area at this time. Winds have
become southwesterly and will become westerly behind the secondary
boundary by the mid-morning hours.

Skies have briefly cleared out, but clouds will be returning behind
the secondary boundary as cooler air aloft will promote the
development of stratocu clouds.  Most sites will become bkn-ovc at
3500-5000 ft today.  There may be some borderline MVFR cigs (such as
at KGFL or KPSF) but it should stay VFR most of the time today.
Westerly winds will be about 5 to 10 kts through the day.

While clouds should decrease for KALB this evening, they may linger
into the overnight at KGFL/KPSF.  Some MVFR cigs are possible
overnight, especially at KGFL.  Meanwhile, KPOU may clear out this
evening, but will see clouds start to return for later in the
overnight, although ceilings will be high enough for it to remain
VFR. Northwest winds will decrease to 5 kts or less overnight.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Low Operational Impact. NO SIG WX.
Sunday Night: Moderate Operational Impact. Chance of RA.
Monday: Moderate Operational Impact. Likely RA.
Monday Night: Moderate Operational Impact. Chance of RA.
Tuesday: Moderate Operational Impact. Chance of RA.
Tuesday Night: Moderate Operational Impact. Chance of RA.
Wednesday: Moderate Operational Impact. Chance of RA.

&&

.FIRE WEATHER...
Scattered showers associated with a cold front are exiting the
region early this morning. A cooler and drier air mass will
build in during the day today with partial clearing this
afternoon. Another weak disturbance will increase clouds with
an isolated threat for a shower to open the weekend.

RH values are currently near 100% at this time, and will
decrease to 60-70% this afternoon. The RH values will recover
to 85 to 95 percent tonight and will decrease to 55-65%
Saturday afternoon.

The winds will shift from the south to southwest at 5 to 15 mph
to the west to southwest this morning with the cold frontal
passage. The west to northwest winds will increase to 10 to 20
mph during the afternoon, and then decrease Friday night.

&&

.HYDROLOGY...
Hydro problems are not expected in the ALY Hydro Service Area
through the weekend.

A cold front and some associated showers have brought a light
rainfall to the region overnight. Some minor within bank rises
are possible, but no flooding issues are expected.

Light rainfall amounts are possible on Saturday with no impact
on the waterways.

The next significant pcpn event will be Sunday night into
Tuesday, but QPF is quite variable due to uncertainty in the
position of a warm frontal boundary.

Overall, flows will be steady or slightly fall into early next
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.
NY...None.
MA...None.
VT...None.

&&

$$
SYNOPSIS...Main
NEAR TERM...MSE/Main
SHORT TERM...Main
LONG TERM...Frugis
AVIATION...Frugis
FIRE WEATHER...Main/Wasula
HYDROLOGY...Main/Wasula


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