641 
FXUS61 KBGM 262331
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
731 PM EDT Sun Aug 26 2018

.SYNOPSIS...
Warmth and humidity increasing during the next couple of days, 
isolated showers and thunderstorms will be possible this evening
and potentially again Monday afternoon. Especially hot and 
humid conditions will occur Tuesday and Wednesday, with peak 
heat indices of at least 95 to 100 degrees. After a cold front 
late Wednesday with showers and thunderstorms, the weather turns
cooler later this week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
400 pm update...
Main concerns this evening and tonight remain focused on the 
potential for a few showers and isolated weak thunderstorms 
through about 10pm...then the possibility of fog developing 
later tonight into early Monday morning.

Upper trough exiting to the east this afternoon with a weak 
surface front lingering behind from NY into PA. Much of the 
region was enshrouded in a broken layer of low-mid clouds this 
morning, but has since lifted and scattered out enough to warm 
much of the region into the upper 70s and lower 80s. Air mass 
has destabilized as well with ML CAPEs above 1000 J/kg. 
Convection has been able to initiate along a Lake Ontario lake 
breeze...and should continue to progress to the e/se through the
rest of the afternoon and into the evening hours...remaining
weak as they track into the nrn Catskills. A lack of deep layer
shear and minimal upper level support will keep any convection 
that does develop on the weak side. 

After sunset this evening, much of the region will likely
stabilize and most of the cloud cover should dissipate. This set
up should lead to fog developing tonight into Monday morning.
The most favorable areas for fog will be in the valley
locations. Temperatures will cool into the lower to mid 60s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/...
400 pm update... 
Hot and humid conditions expected Monday and Tuesday. Heat Advisory 
in effect Monday afternoon and evening...with additional advisories 
and/or warnings likely on Tuesday.

Upper level ridge building over the eastern U.S. on Monday with very 
warm air moving in will create very hot and humid conditions in the 
afternoon and evening. Temperatures will climb into the mid to upper 
80s with dew points in the lower 70s. Heat index values will rise 
into the lower to mid 90s for much of the region...especially along 
the lake plain of the northern Finger Lakes into the Syracuse metro 
area...also into the Wyoming Valley of ne PA.

There will be a weak upper s/w sliding through in the late morning 
and early afternoon, which may trigger a few late morning showers, 
but the presence of large scale subsidence should keep convection to 
a minimum. Precipitation is expected to drop off in the evening with 
the collapse of the boundary layer. Temperatures will likely not 
cool that much...only into the lower to mid 70s Monday night. 

The stage will be set for the hottest day on Tuesday with 
temperatures starting out in the lower to mid 70s in the morning 
and quickly warming through the 80s into the lower 90s. Dew points 
in the lower 70s...potentially inching into the mid 70s...will 
create heat indices in the mid 90s to 100-105. The hottest 
conditions will be across the Finger Lakes into the Chemung and 
Susquehanna basins...and into the Delaware river basin. The presence 
of warm air aloft and at the surface should allow for enough of a 
capping inversion on Tuesday to keep any convection at bay. A layer 
of low-topped cumulus is possible with s/sw winds increasing to 
around 10 to 15 mph in the afternoon.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
400 pm update...
For Tuesday night, we should start to see southwesterly flow 
strengthen as ridging starts to slide east/weaken. Even though the 
odds of seeing at least isolated showers or thunderstorms will 
likely increase over far northern/western areas late Tuesday night, 
most of the region should see a continuation of humid and dry 
weather conditions.

Some flattening of the upper ridge over the Eastern Seaboard is 
expected as we head into mid-week. This should allow a shortwave 
trough to "top the ridge" and push a cold front into and across the 
forecast area sometime in the Wednesday-Thursday time frame.  Before 
the front's arrival, we'll likely see another warm day, with 
temperatures likely again hovering around the 90 degree mark.

Timing of the front remains problematic this afternoon, which is to 
be expected at this stage of the game.  Ensembles suggest upper 
ridging will remain on the stronger side, which implies to me a 
slower, and possibly weaker frontal passage for our area.  The 
latest deterministic model output seems to be leaning toward this 
idea, with the cold front into our area Wednesday afternoon and 
moving through our area before sunrise Thursday.

Values of surface-based CAPE will likely average between 1000-2000 
J/kg across the region Wednesday afternoon.  Other thermodynamic 
fields, such as mid-level lapse rates, are not as impressive 
(probably due to stronger ridging aloft).  Kinematic fields (such as 
the surface to 500mb bulk shear) while not impressive, appear 
sufficient for thunderstorm organization ahead of the front even 
though much of the dynamical support associated with the upper jet 
will likely pass well to our north.  Long and short - we'll likely 
see some thunderstorms Wednesday afternoon and night.  And while a 
few stronger storms with gusty winds can't be ruled out, the overall 
risk of organized severe weather appears minimal.

The front should move through the forecast area Thursday morning. 
Surface high pressure is then expected to quickly move across the 
region for the end of the week and should bring a respite to the 
heat/humidity for much of the region.  A couple of flies remain in 
the ointment, though.  Medium range models continue to suggest a 
couple of weak perturbations will likely top the ridge in a broad 
southwest-west flow aloft.  These features could combine with 
slightly deeper moisture across (mainly) southern areas to yield 
isolated to scattered showers and thunderstorms.

By next weekend, it looks like moisture will likely start to deepen 
as the southwesterly flow strengthens on the back side of the high. 
Discrepancies abound in the Day 6-7 time frame amongst the 
deterministic model output.  NAEFS output suggests the presence of a 
strengthening upper ridge over our region (and amplification of a 
large scale trough out west) as the center starts to retrograde. So, 
we'll likely see a return to warmer and more humid conditions with 
at least some isolated convection as weak disturbances break through 
the ridge.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Terminals all start out VFR as diurnal cumulus in NY and some
stratocumulus in northern and central Pa mixes out and fades
as the day's heating wanes. We expect more stratocumulus and
patchy MVFR to IFR ceilings to form again tonight with net
radiational cooling of the still fairly moist boundary layer. 
At KELM and KBGM we expect conditions to go to LIFR at KELM and 
IFR at BGM between about 08z-09z and 13z-14z. At KRME, KITH, and
KAVP we expect MVFR in ceilings again between 08z-09z to 13z- 
14z. Confidence is medium to high at KELM for IFR to LIFR 
conditions, low to medium at KBGM for IFR conditions and medium
for MVFR at KRME/KITH and KAVP. With strong insolation we expect
the boundary layer to grow enough to lead to few to scattered 
cumulus clouds in the afternoon VFR all TAF sites. This should 
occur after 14z. We do expected isolated showers and a 
thunderstorm or two in the afternoon but too early to mention in
TAFs. 

Outlook...

Monday night through Wednesday morning...VFR, though isolated 
evening thunderstorms will be possible for the NY 
terminals.

Wednesday afternoon through early Thursday...Showers and
thunderstorms likely with associated restrictions.

Thursday and Friday...Mainly VFR.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...Heat Advisory from noon to 8 PM EDT Monday for NYZ016>018.

&&

$$
SYNOPSIS...BJT
NEAR TERM...BJT
SHORT TERM...BJT
LONG TERM...DAB
AVIATION...DJN