Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 260430
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1230 AM EDT Sat May 26 2018

.SYNOPSIS...
Warm, dry weather will continue into Saturday morning, before a
frontal boundary wavers back and forth across the region,
Saturday afternoon through Monday. As a result, there will be
daily chances for showers or thunderstorms. However, none of
these days is expected to be a washout, with notable periods of
rain free weather.

&&

.NEAR TERM /THROUGH TODAY/...


Mostly clear skies are expected overnight, with the exception of
thicker cloud cover getting as far south as Rome. Thinking
remains that these clouds will be hard pressed to get much
further south overnight. Although surface dew points should
slowly creep up, sounding profiles still look too dry overall
for widespread valley fog formation. Lows by daybreak should
range from the upper 50s-mid 60s.

On Saturday, model guidance continues to suggest the approach
of a back-door type surface cold front from the north later in
the day. However, with weak dynamic support aloft, any
associated convection is expected to stay isolated-widely
scattered in nature.

Meanwhile, down across NEPA and Sullivan county, NY, forced lift
may actually be somewhat better ahead of an approaching short-
wave. Also, somewhat higher dew points/instability and localized
orographic lift will be supporting factors. Thus, we expect
better late afternoon coverage of showers/storms in these areas.

Saturday will be another warm day, with a more muggy feel during
the afternoon. Highs should range in the 80s.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
3 pm update... Saturday night, the best chances for showers and
thunderstorms should remain over NEPA and Sullivan county, NY,
especially during the evening hours. However, showers cannot be
ruled out anywhere, given the proximity of the back-door frontal
zone.

Sunday`s forecast looks tricky, with the exact position of the
above mentioned front a key factor. Model consensus would
suggest that the boundary gets hung up somewhere near the I-81
corridor, with cooler temperatures to the east, and warmer, more
unstable conditions to the west. For now, we centered our
delineation of likely showers/storms near the I-81 corridor,
with more scattered activity possible outside of this corridor,
especially eastward.

Current model projections would suggest ML CAPE of 500-1500 j/kg
along and west of the boundary, along with marginal shear
conditions (0-6 km values of 20-30 kt). Although a few
stronger storms cannot be ruled out, the marginal CAPE/shear
phase space for severe development lowers confidence in such,
and precludes any mention in our hazardous weather outlook at
this time.

As alluded to above, temperatures Sunday are tricky. At this
time, we`ll range Sunday`s highs from the lower 70s over the
Catskills, to the lower 80s across the Finger Lakes region.

Sunday night, convective coverage is likely to diminish
diurnally. However, showers are not expected to disappear
altogether, with the front still hanging around. Lows by Sunday
night will range from the lower 50s-lower 60s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
330 PM Update...On Monday the forecast area will be under a
northwest flow pattern as an upper level ridge builds over the
central Great Lakes region. A weak shortwave disturbance will
cross the top of the ridge moving from Ontario into Central NY
and NE PA during the afternoon hours. Model guidance and
forecast soundings indicate that there will be ample moisture
and instability for shower and t`storm development in our area.
Mixed layer CAPE values on the latest GFS are progged to be
between 600-1200 J/kg with Lifted Indices between -3 and -6. The
12z NAM has the same idea, but is likely too aggressive (high)
with its instability parameters. 0-6km bulk shear values are
marginal, between 20-30 kts....but there could certainly be a
few well developed if not even strong thunderstorms around the
region Monday afternoon. Outside of the scattered showers
/t`storm activity expect partly to mostly cloudy skies and warm
temperatures, with highs in the upper 70s to mid-80s in most
locations. It will be rather humid with dewpoint well into the
60s through the day.

Another weak disturbance drops through the area Monday night,
but without the assistance from daytime heating/instability,
just a few showers are expected. Much drier air moves in behind
this system from the north on Tuesday...especially for our
Central NY zones. The boundary could stall somewhere over
northern or central Pennsylvania...and to the south of this
boundary a fair amount of instability and  moisture will
linger. Therefore, added in a slight chance to low end chance
for PM t`storms over the Poconos and Wyoming Valley region of
NE PA Tuesday afternoon. Outside of this possible activity it
will again remain partly cloudy and warm...with highs in the 70s
to lower 80s.

A weak ridge builds into the area Tuesday night into Wednesday.
This will bring dry weather and clearing skies. Overnight lows
stay mild...in the 50s to near 60. Cannot rule out a stray
shower or t`storm later in the day Wednesday, especially west
as a southerly return flow begins to develop.

The weather pattern looks to turn more unsettled for the end of
next week. The remnants of current Sub-tropical storm Alberto
are forecast to combine with a northern stream trough to bring
periods of rain and possible t`storms to our region. The
remnants of the deeper tropical moisture (PWATS approaching 2")
look to arrive later Thursday night into Friday. As expected,
there remains significant uncertainty in the models as far as
the ultimate track of this system. This will have implications
on just how much rainfall our area receives. With the clouds and
showers around temperatures should be cooler...mainly in the
70s during the day and around 60 at night.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected through the period as the area sits
under a large ridge. Winds will become light tonight as we lose
mixing, and resume from the west Saturday after sunrise.
Isolated showers and thunderstorms are possible after 18Z
tomorrow, but limited coverage does not justify mention in the
TAFs at this time.

Outlook...

Saturday night through Monday...At least scattered showers and
thunderstorms expected, with occasional restrictions foreseen.

Tuesday...A shower or thunderstorm still possible, especially
near KAVP.

Wednesday...Mostly VFR.

&&

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

&&

$$
SYNOPSIS...MLJ
NEAR TERM...DJP/MLJ/MWG
SHORT TERM...MLJ
LONG TERM...MJM
AVIATION...DGM/MLJ


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