939
FXUS61 KALY 220821
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
421 AM EDT Sun Sep 22 2024

.SYNOPSIS...
Mainly sunny and pleasant end to the weekend before clouds
increase tomorrow with cooling temperatures. Then, our long
stretch of dry weather ends by the middle of the workweek as a
disturbance from the Midwest directs periods of rain into the
region Tuesday night through Thursday. Unsettled conditions may
continue into Friday but the forecast remains uncertain.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A bit of a challenging cloud and temperatures forecast tonight.
Latest GOES16 night fog channel shows some debris cirrus clouds
spilling into the eastern Catskills, mid-Hudson Valley, and
areas east from Central NY leftover from yesterday`s convection.
It also shows with some mid-level clouds in western New England
rotating inland from our exiting coastal low. In between, radiational
cooling has led to pockets of low-level stratus clouds. Where
skies remain mainly clear temperatures have cooled into the mid
to upper 50s with even upper 40s in the southern Adirondacks.
Where we have stratus or mid-level clouds, temperatures are a
bit warmer in the upper 50s. While fog has yet to develop, with
dew point depressions only 3 to 8 degrees, patchy fog may
develop where skies remain clear towards the pre-dawn hours.
Overnight lows expected to drop into the upper 40s to mid 50s.

Patchy early stratus clouds/fog will give way to clearing this
morning with sunshine mixing with some diurnally driven cumulus
clouds midday into the afternoon as we reach our convective
temperature. Our coastal low off Cape Cod will finally exit out
to sea with high pressure centered in eastern Quebec building
into northern New England. Upper level ridging from western
NY/PA will also slide eastward resulting in subsidence over
eastern NY and western New England. This will effectively
keep our region dry for an 11th straight day (outside of some
innocuous isolated showers in the Upper Hudson Valley and
southern/western Adirondacks last week) and maintain our stretch
of very pleasant weather for this first day of autumn. Easterly
winds sustained 5-8kts will advect in a slightly cooler air
mass that has spread into northern New England; however, a
rather dry atmospheric column will support deep boundary layer
mixing up to 850hPa which, when combined with the insolation,
will allow high temperatures to reach into the low to mid 70s
with upper 60s in the higher terrain areas.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/...

Mainly clear skies tonight as upper level ridging builds
overhead. Expecting radiational cooling to support cooler
temperatures than recent nights with overnight lows dropping
into the mid to upper 40s with around 50 in the immediate
valley. Patchy fog is favored in river valleys and near wet-
lands as temperatures drop towards their respective dew points.

Early sun Monday morning fades behind increasing mid and upper
level clouds as a shortwave trough tracks eastward out of the
Great Lakes into the Northeast. Most of the moisture is in the
500 - 300hPa layer as the sfc high centered in eastern Quebec
expands keeps a strong hold over the Northeast. This high
undercuts most of the low-level moisture that tries to approach
from the west so we only show slight chance POPs in the far
western Mohawk Valley in the southern Adirondacks and far
eastern Catskills. Temperatures will be cooler than recent days
thanks to the clouds and southeast sfc winds advecting a cooler
air mass out of New England but the deep boundary layer mixing
still support seasonably warm temperatures rising into the upper
60s to low 70s.

Initial clouds give way to clearing Monday night as our
shortwave exits to our east and upper level ridging amplifies
overhead in response to a much stronger trough in the Central
CONUS intensifying. Another favorable radiational cooling night
once we scour out the clouds and with a cooler air mass
overhead, temperatures should be similar to the previous night
dropping into the mid to upper 40s with around 50 in a few
valley areas. Some patchy fog again possible in typical valley
areas and near water bodies.

Our Canadian high maintains control of the Northeast into
Tuesday keeping our region dry for yet another day. Upstream,
the amplifying trough in the Central CONUS will lead to a
sfc low tracking through the Corn Belt States with its
associated warm front marching north and eastward. In response,
downstream ridging will remain over much of the Northeast and
undercut the approaching low and mid level moisture. This should
allow much of the day to turn out mostly sunny with high
temperatures warming into the upper 60s to low 70s (cooler low
60s in the higher terrain). Despite the sun, the east-southeast
wind fetch will maintain a cooler/marine influence air mass.

Our ridge axis shifts into New England Tuesday night, resulting
in increasing clouds as the aforementioned sfc low tracks into
Michigan and its associated warm front lifts into western NY. An
incoming 30-40kt southwest jet directs the leading edge of the
mid-level moisture and thermal gradient ahead of the sfc warm
front into eastern NY and western New England after 06 UTC
Wednesday. We thus show slight chance and chance POPs for
showers expanding from west to east as increasing upper level
divergence and strengthening warm air and moisture advection
should allow rain showers to spread eastward after Midnight.
Held off on any thunderstorm mention as elevated instability
remains to our west within the approaching sfc warm sector. Also
capped POPs at just chance for now as the existing Canadian
high may be stubborn to kick out.

Between the increasing clouds and rain showers, temperatures
should be milder than previous nights with overnight lows
dropping into the upper 40s to low to mid 50s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Wet and unsettled weather will likely continue into the latter half
of the workweek with upper-level troughing approaching the region
from the west while an upper shortwave dives south, aiding in the
generation of a closed low somewhere over the Lower MS/OH Valleys.
Numerical guidance continues to struggle maintaining run-to-run
consistency with the evolution of this flow, particularly once a
potential tropical low enters the Gulf of Mexico late in the week.
Despite differences among ensemble members, guidance continues to
favor the development of a second closed low over the Northeast or
Canadian Maritimes by late Thursday into Friday.

Locally, rain showers and potential thunderstorms will spread across
the region from the west ahead of a frontal passage Wednesday into
Wednesday night. Rain showers may linger through Thursday and
possibly into Friday, with more widespread dry weather returning for
the weekend, although isolated showers remain possible within moist
cyclonic flow contingent on the location of the closed low.

Temperatures through the period remain near seasonal norms for late
September. Afternoon highs will reach the mid 50s to mid 60s in high
terrain and mid 60s to mid 70s at lower elevations each of Wednesday
through Saturday, while overnight lows remain in the mid 40s to mid
50s across the region Wednesday through Saturday nights.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Through 06Z Monday...VFR conditions are expected to continue tonight
as enhanced mid-level strato-cu coverage remains to the east over
New England associated with a surface low near Cape Cod. The western
edge of these clouds remains near GFL/PSF, with clearer skies to the
west aside from lingering convective debris pushing east into the
Hudson Valley from Central NY. All told, mixed low and mid-level
clouds are expected through tonight, with a conditional threat for
radiation fog if clearer skies persist, most likely at GFL/POU and
possibly also at PSF. Few-sct strato-cu at 3-5 kft will develop at
all terminals after 12-15Z Sun, before coverage of cirrus at 25 kft
begins to increase late in the period, after 00Z Mon, as a frontal
system approaches from the west.

Calm to light and variable winds tonight will increase out of the
northeast to east at 4-8 kt after 12-15Z Sun, turning out of the
east to southeast late this afternoon into this evening. Speeds
decrease to 5 kt or less after 00-03Z Mon.

Outlook...

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

&&

.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.

&&

$$

SYNOPSIS...Speciale
NEAR TERM...Speciale
SHORT TERM...Speciale
LONG TERM...Picard
AVIATION...Picard