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000
FXUS61 KBGM 091338
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
938 AM EDT Sun Aug 9 2020

.SYNOPSIS...
Today will be fair and seasonably warm. Warmer and more humid
weather will return Monday through Thursday. This warmer and
more humid air will bring mainly afternoon and evening scattered
showers and thunderstorms to the region.

&&

.NEAR TERM /THROUGH MONDAY/...
935 am update...

Forecast remains on track and just made very minor changes to
cloud cover based on latest METSAT and observations. No other
changes needed at this time.

245 am update...
Main concerns in the near term are focused on the patchy valley
fog this morning, the potential for isolated weak showers this
afternoon, the hot and humid conditions expected Monday along
with the threat for isolated thunderstorms in the afternoon.

Synoptic conditions this morning defined by a nearly zonal
upper level flow and weak high pressure at the surface across
much of the Northeast. The air mass is relatively dry overall as
well. Light surface winds and a dry/suppressive air mass will
continue to create favorable conditions for fog this morning.
The presence of a thin layer of high clouds may limit the
amt/extent of fog, but still expecting patchy valley fog through
about 8-9 am this morning.

An upper level short wave is currently tracking east through
the n-central Great Lakes, and will move through nrn NY late
this morning. Large scale lift along this trough axis will sweep
across the Northeast and act to mainly increase cloud cover
over n-central NY, but there is also the potential for a few
light rain showers as well. Temperatures will rise into the 80s
this afternoon, but with limited humidity, the amt of
instability will be low enough to keep thunderstorms from
forming.

Tonight, favorable conditions for fog return with skies
clearing off south of the Finger Lakes, across the upper
Susquehanna and into ne PA. Temperatures will fall into the 60s,
and combine with light surface winds to help with the formation
of valley fog.

The surface high finally shifts to the east on Monday which
will act to create a more robust sw flow into PA/NY, and usher
in a warmer air mass. Temperatures will climb into the lower 90s
for a good portion of the forecast area. Dew points will inch
up into the lower 70s, which will allow heat index values to
reach into the mid to upper 90s in some locations. Areas of
central NY may need a Heat Advisory Monday afternoon. There is
also a threat of thunderstorms Monday afternoon. BL CAPE values
above 1000 J/kg and steep low level lapse rates will allow for a
positive setup for isolated-scattered thunderstorms. The lack
of deep layer shear will keep the severe threat to a minimum,
but weak steering flow and PWATs around 1.5 inches may cause a
few slow-moving thunderstorms with brief heavy downpours to
produce localized flooding issues.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
With the loss of daytime heating, any remaining showers or
thunderstorms end by sunset Monday evening. Skies will be mostly
clear, aside from some patchy valley fog. Lows will likely be in
the mid 60s to lower 70s. With dewpoints remaining in the upper
60s, it will remain quite humid as well.

A slow moving cold front will approach the area on Tuesday
from the Great Lakes. Model guidance has trended considerably
slower and weaker with this front compared to prior runs. As a
result, now expecting Tuesday morning to remain completely dry.
Also reduced PoPs significantly for Tuesday afternoon. Greatest
chance for scattered showers and thunderstorms remains across
Central NY, with a much lesser chance further south and east.

The more noteworthy story for Tuesday will likely end up being
the heat and humidity. Highs will likely range from the upper
80s to lower 90s (mid 80s across the Catskills). Some of the
valley locations may even climb to the mid 90s. Dewpoints look
to be mainly in the upper 60s to lower 70s. This will lead to
widespread heat indices in the 90s. Valley locations and the
northern Finger Lakes/Syracuse area will likely have heat
indices in the mid to upper 90s. If these trends continue,
these areas may end up needing Heat Advisories as we get closer.
The one big question mark is if isolated to scattered afternoon
convection keep temperatures down a bit.

Additional isolated to scattered showers and thunderstorms will
be possible Tuesday evening with the frontal boundary remaining
nearby. However, with the loss of daytime heating, expecting
coverage to gradually diminish overnight. Otherwise, expecting
partly cloudy skies with lows in the mid 60s to lower 70s.
Dewpoints once again remain in the mid to upper 60s.

The above mentioned frontal boundary likely stalls just south of
the area on Wednesday. This will lead to another day of
diurnally-driven scattered showers and thunderstorms, especially
during the afternoon. Greatest chance for this will be closer to
the frontal boundary in Northeast PA and the Twin Tiers. Highs
will likely be a bit cooler on Wednesday, mainly in the 80s.

With the loss of daytime heating, any lingering showers or
thunderstorms taper off overnight Wednesday. Lows will likely be
in the 60s.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
The above mentioned frontal boundary very slowly drifts
southward during during the mid-late week, but remains nearly
stationary. With this boundary around, diurnally-driven showers
and thunderstorms are possible each day, especially across the
southern half of the area (Twin Tiers into Northeast PA). That
being said, no particular day looks to be a washout at this time
since coverage will be isolated to scattered and mainly
concentrated during the afternoon.

Temperatures remain above normal during much of the long term
period, with highs mainly in the 80s. By next weekend, a
slightly cooler airmass moves in, likely bringing temperatures
back closer to normal for this time of the year.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
Patchy fog will lift and mix out between 12-14Z with all sites
going VFR afterward and through the rest of the day. Conditions
will be mainly VFR with only a thin layer of high clouds and a
low-end VFR cumulus deck in the afternoon. Cannot rule out a
brief rain shower, but confidence is not high enough to include
in TAFs. There is a chance of more valley fog again tonight.

Winds will be light west to southwest under 10 knots.

Outlook...

Monday...Mainly VFR with a small chance of an isolated shower or
thunderstorm Monday afternoon.

Tuesday through Thursday...Chances for restrictions in showers
and thunderstorms.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.

&&

$$
SYNOPSIS...BJT
NEAR TERM...BJT/MPK
SHORT TERM...BJG
LONG TERM...BJG
AVIATION...BJT/DJN