289 
FXUS61 KBGM 131522
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1122 AM EDT Mon Aug 13 2018

.SYNOPSIS...
A low moving across southern Pennsylvania will bring showers and
thunderstorms to the area today, some with very heavy rain. The
low will move into eastern New York on Tuesday and bring
additional showers.

&&

.NEAR TERM /THROUGH TUESDAY/...

Unusual August setup as a closed upper low meanders eastward
into Tuesday. Upper low is positioned over eastern Ohio this 
morning and will drift into Pennsylvania over the next 24 hrs. 
Deep tropical moisture lurking over the east coast and western 
Atlantic is set to be tapped by the southeast flow ahead of the 
low, and the upper divergence over eastern NY. This will develop
a surface low that meanders into southwest New England by 
Tuesday morning. SHort term high resolution models are 
exploding precip over northeast PA this morning into central NY
near that low level inflow and under the favorable upper jet. 
With model QPF ranging from a couple to isolated 5 inch 
amounts, and wet antecedent conditions, Flash Flood Watch seems
prudent for the area, especially given the sensitivity to rain 
and the near term history, and the weak steering flow that will 
cause slow moving cells. At this time, most threatened areas are
most of NEPA into the southern tier counties of NY. However,
mesoscale modeling and the 12Z NAM suggest several other areas
of very heavy rainfall setting up later today. The first is over
northeast PA later this afternoon into the evening with new
development of slow moving showers and storms. This activity is
expected to move northwest into the Finger Lakes tonight
resulting in another window for slow moving heavy showers and
thunderstorms. With all that said, the flash flood watch was
expanded into these areas. Also, the watch was expanded in time
throughout the entire night given the expected persistence of
localized heavy rain in the region tonight. 

Rain should taper off a bit this evening as some of the forcing
for the convection is instability and heating related. Showers
will fire again on Tuesday, but tropical inflow will have moved
east by then.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
350 AM Update...
Though not completely rain-free, this period appears to be our
best window for relatively benign weather.

Upper low will start to open up into a wave while exiting
northeast of the region Tuesday night. Lingering activity will
be quick to diminish Tuesday evening, and temperatures will
settle into the lower-mid 60s for lows. Decreasing clouds yet
waterlogged ground could easily lead to temporary areas of
fog Tuesday night-early Wednesday, but Wednesday itself looks
mostly sunny in Northeast PA and at least partly sunny in
Central NY if not indeed also more sun than clouds. Ridging will
also boost temperatures well into the 80s for most of the
region, which combined with still fairly humid dewpoints of mid
to upper 60s will make things feel a bit uncomfortable. Even
this supposedly tamer day could still produce a couple showers 
and thunderstorms in the afternoon, mainly in Central NY where a
shallow boundary will skim by the region. Most of the area, and
time, will be dry.

Things will be quiet Wednesday night, with lows again in lower-
mid 60s, and areas of fog probably forming again.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
350 AM Update...
Forecast adjusted towards latest multi-model blend with little
change overall in the thinking. Confidence is now high enough to
place some of Central New York into likely range for showers-
thunderstorm chances Friday. Also, latest ECMWF for Sunday has 
backed away from its earlier solution that allowed a system to 
approach; thus as with Canadian/GFS models it does appear that 
the second half of the weekend will be generally dry.

Previous discussion...
Thursday and Thursday night: The frontal boundary will be meandering 
over our region with the exact location of the boundary 
differing on operational modeling and the respective ensemble 
guidance. Enough lift and moisture will likely be present for a
few pop up storms in the afternoon and evening. Given some mid-
level ridging ahead of the next front the 12Z GFS looks rather 
overdone with QPF and storm coverage Thursday. Modeling has 
trended slower overall with the timing of the next system 
holding off till almost Friday now. Another day with highs in 
the 80's and lows in the 60's.

Friday through Sunday...A surface low pressure system/upper 
level trough will be approaching from the Great Lakes region and
will head towards extreme southeastern Canada. Associated with 
this system will be a cold front. However, as is usual this far 
out, there are differences between various ensemble members 
regarding the timing of the passage of this front. Models have 
been trending towards most of the action occurring Friday 
afternoon. This will have to be monitored closely as we get 
closer to this period. 

Due to the uncertainty in the timing of the front and how far out 
this still is, decided to cap POPs for showers and thunderstorms to 
high-end chance rather than likely for now. Some lingering showers 
are possible Friday night into early Saturday, but this is once 
again highly dependent on the timing of the front. To account for 
this uncertainty, left in chance POPs for this time period. 
Otherwise, a drying trend should occur for the remainder of Saturday 
and most likely Sunday as well, as high pressure looks to gradually 
build in. The 12Z ECMWF shows another system approaching from the 
Great Lakes for Sunday, but left this out of the forecast for
now since previous runs have not shown this with most other 
models keeping precipitation chances well south of the area 
along a stationary front. 

High temperatures during this period will remain nearly steady in 
the upper 70s to lower 80s. The most noticeable change will be the 
dropping dew points behind the passage of Friday's cold front, 
leading to a less humid weekend. Lows Friday night will be in the 
lower to mid 60s and lows Saturday night will be in the upper 50s to 
lower 60s.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Low moving south of the area with deep moisture will keep
showers over the area with scattered thunderstorms. This will
result in MVFR ceilings and visibilities with spotty IFR 
conditions for much of the day and into the night. The rain is
expected to become lighter after midnight but with the abundant
moisture, IFR conditions are possible late in the period with
light winds and a more stable environment.

Light and variable winds through the period. 

Outlook... 

Tuesday through Tuesday night...Restrictions likely in 
occasional showers/thunderstorms.

Wednesday through Thursday...Primarily VFR although brief 
restrictions possible in isolated convection.

Friday...Restrictions possible due to showers and storms.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Flash Flood Watch through late tonight for PAZ038>040-043-044-
     047-048-072.
NY...Flash Flood Watch through late tonight for NYZ022>025-044>046-
     055>057-062.

&&

$$
SYNOPSIS...DGM
NEAR TERM...DGM/MWG
SHORT TERM...MDP
LONG TERM...BJG/MDP/MWG
AVIATION...DGM/DJN