Area Forecast Discussion
Issued by NWS Binghamton, NY

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FXUS61 KBGM 261110
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
710 AM EDT Mon Sep 26 2016

.SYNOPSIS...
After a chilly start to the morning, high pressure will shift
east and yield slightly milder temperatures today yet also
increasing clouds. The next front will then sweep a period of
showers from west to east across the region tonight. Generally dry
conditions are expected Tuesday and Wednesday, but an upper level
system may get close enough for a few showers late in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
7 AM Update...
Chenango and Madison counties slipped lower than expected on
temperatures. They likely had a good amount of frost as well like
the Advisory counties further east. Otherwise, forecast for the
coming day and timing of the showers this evening still look good.

Previous Discussion...
Main feature of interest is a front which will sweep west to east
through the region tonight, with a round of showers.

For now, high pressure overnight still dominates our weather.
Temperatures dropped quickly in the dry air and clear sky in the
evening. Our frost advisory counties - Oneida, Otsego, Delaware,
and Sullivan NY - are already mainly mid to upper 30s, with upper
30s to mid 40s elsewhere. However, the high is now centered over
interior New England and will shift offshore today. Meanwhile,
upper ridge aloft is about to pass through the region, and high
thin clouds are already spreading out ahead of the next system.
Light southeast low level return flow is beginning on the back
side of the high, at least immediately above the shallow surface
inversions that exist in the valleys. Thus temperatures will drop
little if any during the remainder of the night, and may even go
up slightly in the Finger Lakes region. Main areas of frost will
be in our current advisory counties, with only patchy frost if any
elsewhere.

Pressure gradient steepens for our region between departing high
and approaching front today. Southeast to south winds will pick up
as a result into a sustained 15-20 mph for Central Southern Tier
to Finger Lakes region this afternoon, and generally 10-15 mph
elsewhere (lightest in lower elevations of Northeast PA). Gusts
could approach 30 mph in the Finger Lakes region, especially
south-southeast to north-northwest downsloping areas. Clouds will
also increase and thicken through the day, which along with the
wind may make our expected highs of 60s to low 70s not feel quite
that mild.

Pretty good agreement in the models for timing of the front. It
will be occluding as it passes through tonight, and our region
will be in the unfavorable right exit region of the jet aloft. So
it makes sense that while rain chances are quite high, the amounts
in the models are generally trending down and it is reasonable to
expect an areal average of only a few tenths of an inch. Triple
point of warm-cold-occluded fronts will slide from the vicinity of
Finger Lakes NY to Wyoming Valley PA. Just enough instability for
a slight chance of non-severe embedded thunder in those areas as
the front moves through, but for the most part our region will
only see a 2-4 hour period of showers out of this system. Timing
will be roughly Finger Lakes-Central Southern Tier 7-9pm,
crossing I-81 corridor 9pm-Midnight, and then Tug Hill-Catskills-
Poconos shortly after. There will only be a few lingering showers
east of I-81 by 4am. With all of the cloud cover and little
difference in air masses ahead of/behind occluding front, lows
tonight will actually be on the mild side - upper 40s to mid 50s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
For Tuesday, the area will get into a massive dry slot with a cold
front well to our east Tuesday and the main upper low near Lake Superior.
A southwest flow of chilly air will support some lake effect rain
showers over far western and northern NY however over central NY
and NE PA expect partly to mostly sunny skies with dry weather.
Highs will be mainly in the middle to upper 60s.

Little change occurs for Tuesday night into Wednesday as the upper low
digs south over the midwest while weak ridging at the surface
extending from a high over eastern Canada pokes south into eastern
NY. This will allow for mostly clear skies with continuing dry
weather. Lows Tuesday night will be in the 40s with highs
Wednesday in the 65 to 70 degree range.

Heading into Wednesday night, the digging upper low over over the
eastern CONUS looks to spawn a developing coastal low to our south
which should eventually affect the area with rain. However
forecast models disagree on how quickly this system moves north
spreading rain into the area with the GFS and ECMWF bringing the
system in beginning Wednesday night while the GEM and NAM keep
area dry. Will mention chance/slight chance showers for Wednesday
night with the highest POPs south.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
230 AM Monday Update...Forecast models continue to trend toward a
solution that involves an upper level low becoming cut off from
the main flow and stalling to our south through much of the long
range period. The result looks to be unsettled weather with mostly
cloudy skies and periods of rain and showers Thursday and Friday
and potentially through a good portion of next weekend as both the
0z GFS and GEM have the upper low still situated close to the
region even by 0z next Sunday. In terms of the gridded forecast,we
loaded in the latest superblend as a starting point but made some
minor adjustments...lowering highs slightly and slightly raising
POPs and sky cover. Still have POPs capped at chance for all
periods through long range however if current trends continue
these may need to be adjusted higher.


Sunday PM Update...Main forecast concern will be the evolution of
the cut off upper level low mentioned above. Previous runs of the
GFS took this system south and eventually to our east, keeping
impacts to our area limited with drying expected by Friday and
Saturday. The EURO has hinted the past few runs that this low
would cause us more headaches and could keep us unsettled into
next weekend! The new 12Z GFS is in and the trend toward a more
unsettled solution continues. IT appears as the upper low drops
south by Wednesday, rain chances will still mainly be to our south
and west, closer to the low itself. However by Thursday and beyond
as the low drifts to our south, the southerly flow of air around
it will slowly drag moisture northward into our area. The latest
SUPERBLEND is a decent depiction showing at least chance pops for
rain through Saturday, versus our dry forecast from before. If
this trend continues however chances for rain will likely need to
be increased.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
VFR through the day, but showers and associated deteriorating
conditions can be expected with a frontal passage this evening-
tonight. High pressure is in charge for now. Very high thin clouds
are increasing along with southeasterly low level flow, which will
prevent valley fog formation at any of the terminals early this
morning. During the day, clouds will continue to thicken yet
easily remain VFR, while southeast to south winds will pick up
into 8-12 knots range with gusts 16-22 knots. Showers, with
degradations to at least MVFR and eventual Fuel Alternate level,
will occur as front moves through the region 00Z-06Z Tuesday, then
gradual improvement yet still lingering post-frontal CIGS for some
terminals 06Z-12Z Tuesday.

OUTLOOK...

Early Tuesday...Lingering CIG restrictions possible in wake of
passing front.

Midday Tuesday-Wednesday...Mainly VFR.

Wednesday Night-Friday...Possible occasional restrictions from
showers associated with upper level system in region.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...Frost Advisory until 8 AM EDT this morning for NYZ009-037-046-
     057-062.

&&

$$
SYNOPSIS...MDP
NEAR TERM...MDP
SHORT TERM...PCF
LONG TERM...Heden/PCF
AVIATION...MDP



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