Severe Thunderstorm Warning 85, NWS Binghamton, NY

Area Forecast Discussion
National Weather Service Binghamton NY
703 PM EDT Fri Sep 21 2018

.SYNOPSIS...
A pronounced cold front will cross the area tonight, with
showers and a few thunderstorms, along and ahead of it. Some of
the storms could produce strong winds. Over the weekend and into
early next week, Canadian high pressure will bring dry and
cooler weather.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...

700 PM Update...Squall line approaching our western zones as of
7pm this evening. This line has a history of producing wind
gusts mainly between 40-50 mph across western NY...with a few
storms also showing signs of rotation. This line of thunderstorms
should progressively move off to the southeast through the late
evening hours across our forecast area. The best parameters to
support any severe weather are in place across our western
counties (Steuben, Schuyler, Yates, Seneca, Cayuga and Onondaga)
where a severe thunderstorm watch remains in effect until 11
PM. Further south and east toward Binghamton, Norwich and
Towanda, the line should move through around 10-11pm producing
some lightning, gusty winds and brief downpours. The line of
storms should gradually weaken as it heads east from here,
reaching Monticello, Scranton and Wilkes-Barre around or just
after midnight. Near term forecast update is out, and main
adjustments were to the timing of the highest PoPs and also to
increase southerly winds out ahead of the front early this
evening ...especially across the northern Finger Lakes and
Susquehanna region. In this area downsloping wind gusts have
been up to 40-45 mph early this evening.

145 pm update... Steady as she goes with the current forecast.
The latest runs of the convection allowing models still suggest
a healthy squall line into our far northern/western zones, from
about 23-00z. Thereafter, the line will weaken with eastward
extent, as it crosses the rest of CNY/NEPA during the course of
the evening.

Further details for the rest of the afternoon into the evening
hours are contained in the previous discussion.

1130 am update... The current forecast is in pretty good shape.
Just cosmetic changes to the sky cover/POP/weather grids, based
on the latest satellite, radar, and high resolution model data.

Low stratus deck is holding stubbornly over much of the forecast
area at midday, as expected. Although some erosion at the
western fringes is possible this afternoon, for the most part,
things should remain as they are, with partly sunny skies and
warm temperatures in our far northern/western zones, and
cloudy, much cooler conditions elsewhere. Just subtle changes to
our high temperature grid were made, with maximum temperatures
near 80 where sunshine prevails in the western Finger Lakes/Lake
Ontario plain areas, and only reaching the 60s to lower 70s for
the remainder of CNY/NEPA.

The latest convection allowing models are in very good
agreement, showing a well developed squall line moving into our
far northern/western zones towards 7-8 pm, with just isolated
activity earlier. As expected, a sharp stability gradient
exists, with ML CAPE perhaps into the 500-1000 j/kg range by
later this afternoon where the clouds break, with almost no
destabilization where the clouds hold. Wind fields (especially
in the lower levels) are quite impressive, so any earlier
discrete cells would have to be closely watched, along with
obviously the linear feature itself into the early evening.

We still think convective intensity will quickly wane with
eastward extent after about 8-10 pm, with only a few lingering
showers surviving after midnight.

Please check our latest hazardous weather briefing online for
more specific details on possible severe weather
development/timing.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
340 PM Update...
Saturday and Saturday night: Northwest flow will continue
through much of the day Saturday behind the departing cold
front. Will see some upslope/lake enhance clouds through the
morning and early afternoon hours...with perhaps an isolated
shower as well. Otherwise it will be much cooler with NNW winds
10-15 mph in the morning, decreasing to less than 10 mph by
afternoon. High temperatures only reach the upper 50s to mid-
60s. Surface high builds overhead Saturday night with
strengthening low level inversion, light winds, river valley fog
and very cool temperatures. Low temperatures are forecast to be
in the upper 30s to 40s areawide.

Sunday and Sunday night: Early morning fog burns off giving way to
mostly sunny skies with continued light northerly winds.
Slightly warmer with highs in the mid to upper 60s. Strong
Canadian high to the north for Sunday night, with a northeast
drainage flow over our area. Another strong low level inversion
night, with mostly clear skies and patchy fog possible again.
Remaining chilly with lows in the 40s.

Monday: Upper level ridge builds over the area from the Mid-Atlantic
as the surface high slowly exits off to the northeast. Still
have a dry easterly flow, especially in the low to mid-levels of
the atmosphere. With large dew point depressions suspect it
will take quite a while for any rain showers to move in from the
south. Therefore, expect just gradually increasing clouds, with
cirrus lowering and thickening from south to north through the
afternoon hours. Slight chance of a late day shower across
southern Luzerne/Bradford counties. Southeast winds increasing,
8-15 mph by afternoon. High temperatures reach mid to upper 60s
once again.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
340 PM Update...
A wave with a quasi warm frontal boundary approaches the area from
the south Monday night...PoPs quickly increase from SW to NE as
the atmosphere moistens up. Introduced likely PoPs for much of
the area after 06z Tuesday...with early rainfall forecasts
between a quarter to half inch possible by Tuesday morning. It
remains unsettled on Tuesday with our CWA getting into the warm
sector of a low pressure system passing by well to the north. It
should be mostly cloudy with scattered showers around, and
perhaps enough instability for an afternoon t'storm. The cold
front slowly approaches from the west Tuesday night into
Wednesday. This will keep showers in the forecast, with a chance
of thunderstorms during the day Wednesday.

There are some model discrepancies for Thursday, as the latest
12z GFS now attempts to stall the frontal boundary over Central
NY and Northeast PA leading to additional showers. Meanwhile
most of the other guidance sweeps the front through the area
with drier air moving in. For now, used a blend of the guidance
which gives a chance for a few showers. Early indications are
that yet another frontal system could approach the area toward
next Friday, therefore kept chances for showers in the forecast.
Temperatures through the long term period will be mainly in the
60s to lower 70s during the day...with overnight lows in the 50s.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
18z update... Low clouds will hold tough at KITH, KBGM, KRME,
and KAVP into this evening, with mostly fuel alternate-MVFR
restrictions. KBGM will continue to see IFR for most of the
afternoon, at least. In the meantime, KELM should see MVFR
improve to VFR for a time later this afternoon, while KSYR stays
VFR/unrestricted.

A line of showers and thunderstorms will quickly cross the
region this evening (mostly 01-03z), with additional
restrictions. Also, wind gusts of 25-45 kt may accompany the
squall line, especially at KELM and KSYR.

Later tonight, once a cold front goes through, post-frontal low
clouds could bring at least a few hours of fuel alternate-MVFR
ceilings in the pre-dawn hours over CNY. Improvement to VFR is
foreseen area-wide Saturday morning.

Gusty S-SW winds this afternoon could reach speeds of 25-35 kt
at times. Winds will switch into the NW later tonight behind the
cold frontal passage (generally after 03-05z).

Outlook...

Saturday...Some early ceiling restrictions possible, then
improving to VFR.

Sunday and Monday...Mainly VFR.

Tuesday...Possible restrictions in showers.

&&

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

&&

SYNOPSIS...MLJ/MJM
NEAR TERM...MLJ
SHORT TERM...MJM
LONG TERM...MJM
AVIATION...MLJ

Hazardous Weather Outlook
National Weather Service Binghamton NY
410 PM EDT Fri Sep 21 2018

NYZ009-015>018-022>025-036-037-044-055-PAZ038-222015-
Northern Oneida-Yates-Seneca-Southern Cayuga-Onondaga-Steuben-
Schuyler-Chemung-Tompkins-Madison-Southern Oneida-Cortland-Tioga-
Bradford-
410 PM EDT Fri Sep 21 2018

This Hazardous Weather Outlook is for central New York and
northeast Pennsylvania.

.DAY ONE...Tonight.

This evening a strong cold front will cross the area with showers
and thunderstorms. Some of the thunderstorms could have damaging
wind gusts and brief heavy rain.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

NYZ045-046-056-057-062-PAZ039-040-043-044-047-048-072-222015-
Chenango-Otsego-Broome-Delaware-Sullivan-Susquehanna-Northern Wayne-
Wyoming-Lackawanna-Luzerne-Pike-Southern Wayne-
410 PM EDT Fri Sep 21 2018

This Hazardous Weather Outlook is for central New York and
northeast Pennsylvania.

.DAY ONE...Tonight.

This evening a strong cold front will cross the area with showers
and isolated thunderstorms. Some of the thunderstorms could have
gusty winds and brief heavy rain.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.