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939
FXUS61 KALY 221054
AFDALY

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

.SYNOPSIS...
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Mainly sunny and pleasant for this first day of autumn 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.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

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Some patchy stratus clouds and a cirrus canopy overhead will
give way to sunny skies this morning with sun 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 13th 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.
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&&

.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 /12Z SUNDAY THROUGH THURSDAY/...
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Through 12Z Monday...VFR conditions are expected through the
majority of the TAF period at all terminals. Brief restricted vsbys
this morning within patchy fog will dissipate by 13Z Sun. Otherwise,
few strato-cu are expected at 3-5 kft across the region through this
evening, 00-03Z Mon. Few-sct cirrus at 20-25 kft will increase from
the west ahead of an approaching frontal system while strato-cu
lowers to 2-4 kft this evening into tonight, after 00Z Mon. Patchy
fog may again develop late in the period yielding restricted vsbys,
most likely at GFL after 09Z Mon.

Calm to light and variable winds this morning will increase out of
the northeast to east at 4-8 kt, turning increasingly out of the
east to southeast at 5 kt or less into this evening. Winds again
diminish to calm or light and variable after 03-06Z 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.
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&&

.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