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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBGM 261420
AFDBGM

Area Forecast Discussion
National Weather Service Binghamton NY
1020 AM EDT Wed Sep 26 2018

.SYNOPSIS...
A cold frontal boundary will move through the region today with
another round of showers and scattered thunderstorms. Some of
the storms may produce heavy rainfall and gusty winds. High
pressure will then build southeast into the region tonight into
Thursday bringing dry weather. A few showers then return Thursday
night through Saturday as weak weather systems move through.

&&

.NEAR TERM /THROUGH TONIGHT/...
1015 AM Update...
Forecast expectations remain generally the same with this
update. Showers driven by mid-level warm advection were passing
through portions of the area this morning and this will be
followed by a relative break during the midday hours, although
our western Southern Tier and Finger Lakes region will remain
with the highest chance for continous shower activity as the
cold front moves in. Mesoscale models continue to advertise an
organized squall line, or broken lines of thunderstorms,
developing this afternoon and evening. Instability is in
question under this blanket overcast, however, deep shear around
50 kts is more than sufficient along and behind the cold front
with the advancing upper trof. Low-topped convection with a
wind signature threat seems to be the mode of the day, if things
get going. Our severe weather analogs support this idea as
well. In addition, a localized flood threat remains a moderate-
high concern as the deep southwesterly flow can support a
thunderstorm training environment. Already seeing hints of this
across SW NY and NW PA. Rainfall amounts have been generally
light this morning, thus still confidence is still not high
enough for a Flash Flood Watch given the forecast progressive
nature of the cold front later today. Will monitor and issue a
short-fused one if necessary.


Previous Discussion...430 AM Update
Complex and unsettled weather expected today. A deep trough of
low pressure is moving slowly across the upper Great Lakes this
morning. A cold front extends across eastern Lower Michigan down
into the Ohio Valley currently. Initial shortwave out ahead of
the front are bringing intermittent showers and isolated
thunderstorms across the western portion of our forecast area
early this morning. The next shortwave and area of
showers/storms is evident across KY/OH and NW PA at this time.
Latest CAMs show this area of convection moving mainly across
western NY through mid to late morning...but it could also clip
our far western zones again. If this area of convection were to
track even slightly further east, we could begin to see issues
with heavy rain and even flash-flooding. The flash-flood
guidance remains very low across much of Central NY/Northeast
PA...generally 0.5-1"/hr....except closer to 1.5"/hr across the
NW Finger Lakes and Mohawk Valley regions. After this round of
showers moves off to the north and east, additional showers and
scattered t`storms will enter our forecast area from the west
during the early afternoon hours. These showers/storms are
associated with the fast moving cold front. Went with
categorical PoPs for a several hour period later this afternoon
as the front tracks east. Added mention of heavy rain and gusty
winds into the forecast grids as well. The front should
approach the I-81 corridor from SYR-BGM between about 1-4
pm...then move into the Catskills and Poconos during the late
afternoon and early evening hours. Our CWA will be under a very
moist air-mass, with high shear and modest amounts of instability
forecast. This equates to some potential for gusty winds as
storms develop this afternoon, which could cause isolated
damage, such as downed trees and power lines. Parameters going
again severe weather include very limited instability (<500 J/Kg
of MLCAPE) and poor mid-level lapse rates. SPC continues the
slight risk for severe t`storms over our entire area this
afternoon. With the extremely wet antecedent conditions another
worry will be for localized areas of flash-flooding...if any
showers or storms end up training over the same areas this could
certainly cause issues. PWATs will rise up to around 1.75"
today, with localized rainfall rates of 0.5-1"/hr possible. Will
continue to evaluate and fine tune the forecast to see if any
portions of our forecast area need to be placed under a flash-
flood watch for this afternoon. For now continued to mention the
threat for heavy rain and gusty winds with t`storms in the HWO.
Otherwise, expect mostly cloudy skies today with south winds
10-20 mph turning west-northwest behind the front in the late
afternoon. High temperatures will be mild, in the upper 60s to
mid-70s most locations.

Tonight: The frontal boundary quickly moves east away from our
area by 8-10pm...leaving dry weather and partially clearing
skies. As a surface high pressure system builds overhead expect
decreasing winds and cool temperatures. Overnight lows dip down
into the mid-40s to lower 50s. Areas of valley fog are also expected.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
430 AM Update
The frontal boundary that moved through our area today will be
well off to the south across the Mid-Atlantic through the day
Thursday. We will be under a deep southwesterly flow in the mid
and upper level, with a 1022mb surface high centered directly
over Central NY and NE PA Thursday morning. As mentioned above
expect valley fog to be around in the early morning, but should
dissipate by mid to late morning. The area of high pressure
quickly slides off to the east by Thursday afternoon. This
should allow some high level cirrus clouds to move into the
region from the south. High temperatures will be in the mid to
upper 60s Thursday afternoon in most areas.

Another weak wave of low pressure will attempt to push the
front back north toward our area Thursday night. As the wave of
low pressure passes by moisture will increase, bringing a chance
of showers to the southern half of the area. Latest model
guidance has come into better agreement that showers will be
across our CWA, especially from the NY southern tier south to NE
PA. With the increased clouds and showers around it will not be
quite as cool Thursday night, with lows in the upper 40s to
mid-50s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
300 AM UPDATE...Old frontal boundary to the south may generate a
few showers on Friday over the southern zones, meanwhile a cold
front racing through the Great Lakes will push through on
Saturday also generating a few showers,especially over the NY
counties. Behind the front, a large and cool high pressure area
will build in and keep dry weather over the area into Monday. On
Tuesday, yet another front moves into the area with another
chance for showers.

Made some adjustments to the grids to align to the latest
guidance and model timing. In general no major changes at this
update. Previous discussion below.

Model uncertainty grows for the weekend into Monday with several
waves moving into the northeast and middle Atlantic through the
period. Models vary on timing and extent of these waves and
potential for light precipitation. So used the superblend and
have slight chance to chance POPs for a few showers through this
period. Temperatures will average close to normal to slightly
above normal.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
Low level moisture around this morning resulting in spotty MVFR
ceilings. A strengthening SW flow ahead of a cold front will
help mix out the moisture and raise the ceilings to VFR. Around
18 Z a cold front will push through the TAF sites with a line of
convection bringing brief IFR conditions and gusty winds. Much
drier air behind the front will result in VFR returning into the
evening. Late night fog is possible, especially at ELM and LIFR
conditions.

Outlook...

Wednesday night...Ceilings lifting during the evening then
patchy valley fog with restrictions around sunrise Thursday.

Thursday...Improving to VFR early, then VFR. Winds under 10
knots.

Thursday night and Friday...More restrictions possible with
showers at KAVP and KBGM. Some possibility the showers reach
KITH, KELM, KSYR and KRME for a time in the morning. Winds
generally 10 knots or less.

Saturday and Sunday...VFR conditions expected. Winds generally
10 knots or less.

&&

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

&&

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