Area Forecast Discussion
Issued by NWS Albany, NY

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FXUS61 KALY 211529
AFDALY

AREA FORECAST DISCUSSION
National Weather Service Albany NY
1129 AM EDT Mon Sep 21 2020

.SYNOPSIS...
High pressure will control the weather for the upcoming week.
Temperatures will steadily climb with anomalies getting back
to warmer than normal levels later in the week. Dry and mainly
clear weather is expected to continue.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
With a 1030+ hpa high pressure system overhead, dry and tranquil
weather will continue over eastern New York and western New England
through this evening. Plenty of subsidence from the high pressure
system along with a weak pressure gradient will allow for sunny
skies and light northerly winds today. According to the GOES-East
Geocolor satellite imagery and some of the hi-res guidances, smoke
aloft (25-30 kft) from the western U.S. wildfires have moved into
our cwa which could make for a hazy (if not, otherwise blue) sky.
The smoke could make for a picturesque sunset this evening. This is
especially true over western New England where the greatest
concentration of smoke is located.

Differential surface heating will allow for the boundary layer to
slowly warm today giving way for daytime high temperatures to climb
into the low to mid 60s across the valleys, and into the upper 50s
to lower 60s across the higher elevations. Dewpoint temperatures
will remain in the 30s through today.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Low level ridging builds south and southwest while flat upper
ridging builds east into our region. There could be some periods
of smoke aloft by Tuesday and Wednesday that could filter the
sun a little at times in some areas.

The tropical system is expected to track well east of our
region but the pressure gradient between it and the high
pressure tightens on Tuesday and Wednesday, resulting in breezy
conditions. A weak northern stream upper impulse and associated
weak cold front tracks through Wednesday with some potential
intervals of mid and high clouds Tuesday night and Wednesday
morning. There should not be enough moisture for any showers.
Little to no cold advection behind the weak front and warm
advection should return with the departure of the tropical
system and flat upper ridging reasserting itself into our
region from the west.

Lows tonight in the 30s to near 40 and a few areas where the
growing season has not ended could see another threat for some
frost but not as widespread a threat as the past couple of
nights. Highs Tuesday in the 60s to around 70. Lows Tuesday
night in the 40s to near 50 with some potential steady light
winds. Highs Wednesday around 70 to mid 70s but some 60s higher
terrain. Lows Wednesday night in the mid 40s to lower 50s with
potentially steady light winds and gradual warm advection.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Dry conditions with warm temperatures running about 5-10 degrees
above normal temperatures will continue through the end of the work
week before a longwave trough from the western CONUS amplifies as it
digs into the Great Plains. The deterministic global guidance has
captured this longwave trough over the past few models runs.1
Although there remains uncertainties regarding its timing,
intensity and placement among the GFS, ECWMF and CMC solutions, this
feature represents a pattern shift from persistently dry conditions
to one with increasing chance for rain. Read on for details.

Zonal flow ensues Thursday and Friday over eastern NY/western New
England as our region is caught within a split flow regime. While a
weak shortwave passes well to our north, broad ridging settles over
the Southeast U.S. A weak cold front associated with the northern
stream shortwave may brush our northern zones on Thursday but this
feature is moisture starved so we continued a mainly dry forecast,
outside of slight chance POPs in far northern Herkimer and Hamilton
counties. Westerly flow becomes southwesterly on Friday as the
aforementioned cold front lifts northward as a warn front front and
ridging within the southern stream builds northward. With 850mb
isotherms ranging +9C to +12C both days, high temperatures should
reach into the mid to even upper 70s in valley areas (perhaps near
80 in the mid-Hudson Valley) with upper 60s to low 70s in the higher
terrain. The one fly in the ointment could be the effect any smoke
from the wildfires in the western U.S has on our temperatures,
should smoke still be overhead for the end of the week. Overnight
lows should remain mild, only falling into the 50s (upper 40s in
terrain areas).

By Saturday, ridging over the western Atlantic strengthens in
response to our longwave trough digging over the Central Plains. As
a result, the associated surface high pressure that now shifts into
the northern Atlantic looks to build to ~1030mb and maintain
dominance over the eastern seaboard on Saturday. Given that the high
is centered so far out to sea, the clockwise circulation around it
should cause winds to back to the southeast. This would advect in
marine influenced air mass and thus introduce higher humidity and
slightly cooler temperatures compared to previous days but still
remain above normal.

Sunday and Monday feature increasing chances for precipitation as
the longwave trough in the Great Plains progresses eastward and
strong southwesterly flow ahead of it pushes into the Northeast. As
warm air advection increases and directs moisture from the Gulf of
Mexico towards our region, PWAT values should rise as well. The
ECWMF seems to be handling this trough the best of the deterministic
guidance as the GFS and CMC suggest the amplifying trough quickly
becomes a cut off low but this seems too progressive. To capture the
advancing trough and increasing moisture advection, we introduced
slight chance POPs for the entire area on Sunday and increase to
chance POPs Sunday night into Monday. Depending on how this
potentially amplified longwave trough evolves, there could be a
multi-day period with chances for much needed precipitation before
we close the weather books on September.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
Latest GOES16 Nighttime Fog product shows patchy fog has developed
in valley areas which has resulted in MVFR and IFR visibilities at
ALB and PSF with LIFR ceilings at ALB. GFL has remained VFR but we
continued a tempo group through 13 UTC to account for possible brief
MVFR visibilities from patchy fog. Ground fog will likely burn off
by 13 UTC. Then, expect mainly sunny skies and VFR conditions
through the end of the TAF period.

Light and calm winds tonight will become northeasterly by late
morning staying near or less than 5kts. Winds then turn light and
calm tonight.

Outlook...

Tuesday Night through Saturday: No Operational Impact. NO SIG
WX.

&&

.FIRE WEATHER...
Gusty northwest winds to 25 mph possible Tuesday afternoon
from the Hudson River Valley through western New England...

High pressure will control the weather during the upcoming
week. Temperatures will moderate back to above normal, with dry
and mainly clear weather expected to continue.

RH values will fall to 30 to 40 percent this afternoon. Winds
will be light and variable at 15 mph or less. RH values rise to
80 to 100 percent tonight. RH values will fall again on Tuesday
to near 40 percent in the afternoon, with northwest winds
increasing to 15 mph. Areas from the Hudson River Valley through
western New England could see gusts up to 25 mph Tuesday
afternoon. The next chance for rain will not be until late next
weekend.

&&

.HYDROLOGY...
High pressure will be in control through much of this week,
allowing for mainly clear skies and no precipitation. With no
storms systems heading our way, dry weather is anticipated to
continue through much of the upcoming week as well. This will
allow for river and stream levels to hold steady or slowly fall.
Many locations are already seeing below normal stream flows and
this is expected to continue. The next chance for rain will not
be until late next weekend.

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...Evbuoma
NEAR TERM...Evbuoma
SHORT TERM...NAS
LONG TERM...Speciale
AVIATION...Speciale
FIRE WEATHER...NAS
HYDROLOGY...NAS


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