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173
FXUS61 KBGM 221956
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
356 PM EDT Sun Jul 22 2018

.SYNOPSIS...
A warm and muggy night is expected across the region with
scattered showers and thunderstorms especially over northeast
Pennsylvania, the southern tier and southern Catskills. A deep
southerly flow of very moist air will reside over the region
through Thursday. Showers and thunderstorms are expected through
the period with the activity most widespread during the
daylight hours. The thunderstorms will produce heavy downpours.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
At 330 PM...local radar indicated just isolated to scattered
activity across northeast Pennsylvania and the southern
Catskills. A mid level short wave lifting north from southeast
Pennsylvania will increase the convective coverage in northeast
Pennsylvania, the southern tier and western Catskills through
the early evening hours. Any thunderstorms will be capable of
heavy downpours which could lead to poor drainage and urban
flooding. Late tonight there will be a lull in the activity
before embedded mid level short waves in deep southerly flow
toward daybreak bring more convective activity into northeast
Pennsylvania. Overnight lows will range in the mid 60s to lower
70s.

Monday through Monday night...A deep south/southeast flow of
very moist air will continue over the region as an upper level
low continues dropping south into the Tennessee Valley while an
upper level ridge resides in the western Atlantic. A
combination of embedded mid level short waves and diurnal
instability will increase convective coverage by mid/late
morning through the evening hours. Precipitable water values
increase to around 2 inches by the afternoon and model soundings
indicate tall/skinny CAPE along with warm cloud layer above 10k
feet. This all indicates the potential for very heavy downpours
with any thunderstorms and will include in the forecast from
mid morning through the evening hours. No flood watches planned
yet but if training convection occurs during the next several
days a watch may be needed. Highs on Monday will range in the
upper 70s to mid 80s and with dewpoints around 70 is will feel
rather uncomfortable.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
430 AM Update...
The latest guidance continues to be in excellent agreement for
the overall pattern in the short term period. An upper level low
will remain nearly stationary over the Southeast US during this
timeframe; at the same time a building upper level ridge will
be centered off the New England Coast, out over the North-
Atlantic. The circulation around these two features will pull
deep, tropical moisture northward from the central Caribbean and
Bahamas region. With these features remaining nearly stationary,
a prolonged stretch of tropical moisture transport is progged
to impact the area. As the upper ridge flexes westward a bit
Monday night...this will place the best tropical moisture feed
from eastern North Carolina, to Washington DC, up into Northeast
PA and Central NY. In the heart of this enhanced moisture feed
PWATs are now forecast to be between 2-2.25 inches, along with
dew points around 70...a very humid air-mass. This conveyor
belt of tropical moisture basically waffles back and forth
across our CWA through the short term period, with little
overall movement. The guidance is indicating that waves
/disturbances will move from south to north embedded within this
deep moisture feed...these waves will provide ample lift for
periods of showers and thunderstorms to impact our area. With
confidence growing, bumped PoPs up into the likely category
Monday night through Tuesday night. Exact rainfall amounts are
difficult to forecast this far out, but the potential is
certainly there for showers/storms to produce heavy rain. 12
hour basin average QPF amounts are expected to range from
0.25-0.50" Monday night, 0.33-0.75" Tuesday (highest west) and
0.25-0.75" Tuesday night (highest west)...but there could
certainly be much higher amounts locally. WPC has placed parts
of our forecast area in a slight risk for excessive rainfall
Monday night into Tuesday...indicating a 10-20 percent chance
for rainfall amounts to exceed flash-flood guidance.

The mid-level flow is well aligned from south to north across
the region in the 850-500mb layer, with mean layer winds between
30-40 kts forecast...therefore showers and thunderstorms have
the potential to train over the same areas. This period will
need to be monitored closely for the heavy rain and flooding
/flash-flooding potential. The pattern continues to look very
similar to the end of June 2006...so the heavy rain potential is
certainly there.

Daytime instability parameters are expected to be around 500-1000
J/Kg of MLCAPE, with modest LIs around -4. Deep layer shear
values are higher Monday evening, between 30-40 kts...so cannot
rule out a few stronger storms. By Tuesday 0-6km shear decreases
to between 20-30 kts....so it would seem there is a lower
chance for well organized severe weather Tuesday.

Outside of the showers and thunderstorms expect mostly cloudy
skies, warm and humid conditions through the period. Overnight
lows will be in the mid-60s to lower 70s both nights...with
daytime highs in the upper 70s to lower 80s Tuesday afternoon.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
430 AM Update...
By Wednesday, the latest guidance shows heights falling as an
upper level trough slowly approaches from the Great Lakes. This
will only act to further enhance the sub-tropical moisture
feed, increasing lift and instability across our area. PWATs
remain at or above 2" through the day. Therefore, Wednesday
looks to feature widespread showers and thunderstorms, with
heavy rainfall being the main concern once again. With excellent
model agreement, went ahead and bumped PoPs up into the categorical
range Wednesday into Wednesday night, as the front very slowly
pushed east. It is now looking like Wednesday into Wednesday
night could feature the heaviest rain and greatest potential to
see flooding and/or flash-flooding. Exact details of where the
heaviest rain sets up, and exactly how much rain will fall
remain uncertain...but the pattern is favorable for torrential
downpours.

By Thursday morning, the initial front will be over the far eastern
portion of our forecast area, with showers and thunderstorms
lingering here. PWATs should begin to come down behind this
boundary, as the tropical air-mass shifts east...but showers and
t`storms will still remain likely areawide as instability
increased under the influence of the slow moving upper level
trough. Thursday is looking a bit warmer, as the area perhaps
sees occasional breaks of sunshine. Highs are now forecast to
reach 80-85 in most locations, dewpoints hold in the mid to
upper 60s.Thursday night features just a chance for a shower or
thunderstorm under partly cloudy skies. Lows hold in the 60s.

On Friday, a secondary frontal boundary will work through the area
from west to east during the day. Instability will remain
sufficient out ahead of this front for scattered thunderstorm
development. The amount of convection the area sees on Friday
will be highly dependent on the timing of this front...if it
moves through during the morning there may not be enough time
for much t`storm development...as opposed to if if moves through
during the afternoon or evening. The timing remains uncertain
at this point. PWATs and dew points continue to lower as the
humid air mass moves east. By Friday afternoon look for dew
points in the lower to mid-60s with temperatures reaching the
upper 70s to lower 80s again.

There remains a lot of uncertainty for Saturday and Saturday
night, as the latest GFS stalls the frontal boundary across
northern PA, bringing additional periods of showers and t`storms
to our area. Meanwhile, the 00z ECMWF push the front further
south/east...allowing for drier weather. With the lower
confidence decided to take a blend of the latest guidance for
now, until models can converge on a common solution. Temperatures
look to be very close to the seasonal average, with lows in the
lower to mid-60s Friday night and highs 75-82 Saturday.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
A very moist airmass will reside over the region through this
TAF period. Through early evening MVFR/low VFR ceilings will
continue with a chance for MVFR showers at KAVP/KELM through
early evening. Overnight, ceilings will lower into the
MVFR/Alternate Required category. Monday morning slow
improvement to MVFR/low VFR will occur during the mid/late
morning. Scattered showers and thunderstorms will occur
overnight and into Monday morning but coverage not widespread
enough to include in TAF. By Monday afternoon MVFR/Alternate
Required showers and thunderstorms are likely at all terminals.

East to southeast winds at 10-15 knots with gusts around 25
knots decreasing this evening to 5-10 knots. East/southeast
winds again Monday increasing to 10-12 knots with gusts around
20 knots.

Outlook...

Monday night through Thursday...Occasional restrictions likely,
with periods of showers and thunderstorms.

Thursday night/Friday...Brief restrictions possible in
scattered showers and thunderstorms.

&&

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

&&

$$
SYNOPSIS...RRM
NEAR TERM...RRM
SHORT TERM...MJM
LONG TERM...MJM
AVIATION...RRM