Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 211619

Area Forecast Discussion
National Weather Service Buffalo NY
1219 PM EDT Fri Oct 21 2016

Low pressure tracking to our south and east today will keep steady
rain in place across Western and North Central New York. Most
areas will pick up an additional one to two inches of rainfall
through tonight. Generally cool and unsettled weather can be
expected through Saturday night with mainly dry weather holding
off until Sunday.


Nearly textbook cyclogenesis underway this morning over PA with
warm conveyor belt rising NNE from about WV through Central NY,
while a cold conveyor belt is now showing up clearly in satellite
data by poking out toward OH. Deformation NE of the surface low is
starting to develop underneath the baroclinic leaf from OH to
southern Ontario. For the WNY, this will ensure continued light to
occasionally moderate rain for much of the day and night as well.

The main concern continues to lie to the east from about the
Finger Lakes region and North Country which are still under a
tightening baroclinic region forced by the warm conveyor belt
nearly overhead.

A flash flood watch is still in effect for nearly all Central and
North Central NY due storm total/24 hr reports of 2-3+ inches with
an additional 1-2 expected through tonight. The greatest threat
will be on the eastern side of the watch...from about Cayuga
County and northeast into areas east of Lake Ontario where there
still may be some convective elements and enhanced rainfall this
afternoon and evening.

Tonight...the upper level trough to our west will close off and
move overhead as the surface low merges with the remnants of a
tropical disturbance lifting along the east coast. As these two
systems merge, a rapidly deepening surface low will form over
Southern New England by 12z Saturday. Wrap around moisture will
continue to support high POPs but expect coverage and intensity of
rainfall to taper off toward far WNY. A cool and breezy/gusty
north to northwest flow will support overnight temperatures
dropping to the mid 30s and low 40s along with lingering low cloud


Moving into the weekend, a vigorous closed upper low will be
located in the vicinity of New York City with a corresponding
strong surface low centered over western Maine. Abundant wrap-
around moisture within a zone of frontogenesis and enhanced lift
on the west side of the low will continue to generate showers
across the North Country into Saturday evening with lake
enhancement also taking place east and southeast of Lake Ontario
as cooler air begins to filter across the lower Great Lakes and
850mb temps fall below 0C. As surface temperatures fall into low
to mid-30s Saturday night in the North Country, we may see rain
mix with snow inland from Lake Ontario, with snow accumulating to
around an inch across the top of the Tug Hill plateau and along
the Western slopes of the Adirondacks...roughly above 1200ft.

Lake-enhanced rain showers will also be possible on the chilly
northwest flow south of Lake Ontario and across the western Southern
Tier Saturday into Saturday evening, though coverage and intensity
will be limited both by shorter fetch across the lakes and
increasingly dry air aloft as shortwave ridging moves in from the
west. In addition to the precip chances...the tightening pressure
gradient on the back side of the low coupled with the aforementioned
cold air advection may result in possible wind advisory level gusts
to 50 mph south of Lake Ontario and east of the Genesee valley
Saturday into Saturday evening.

Any lingering lake-enhanced precip should taper off Saturday night
into Sunday morning as the upper low lifts away from the region and
is replaced by a transient low-amplitude shortwave ridge. Persistent
cool west-northwesterly flow will still keep a decent amount of lake
effect cloud cover hanging around through Sunday though.

The lull in activity will be short-lived, as a shortwave diving
across the Great Lakes from the Canadian prairies will bring another
chance of rain showers to the region, with lake effect activity re-
developing in the wake of the low on Monday, as cool cyclonic flow
returns to the region.



High pressure returns on to the region once again on Tuesday as
upper level ridging is shunted eastward by another strong storm
barreling into the Pacific Northwest. Guidance is currently in
fairly good agreement on the development of a low in the lee of the
Rockies Tuesday that deepens on Wednesday...ultimately reaching our
forecast area late Wednesday night into Thursday...bringing more
rain showers along with slightly milder temperatures.


IFR to low MVFR ceilings will continue today and into tonight across
the bulk of Western and Central New York as low pressure deepens
from central PA into the Southern New England coast. The low
cloud cover will be accompanied by widespread rain...which will be
heavy at times east of about KROC-KELZ. The steady rain will
combine with areas of fog to produce IFR to MVFR VSBYS at times.
North winds this morning will become northwesterly by this
afternoon as the surface low tracks into New England. Rain will
become more scattered/broken tonight as moisture shifts east with
the low with some improvement to MVFR possible.


Saturday...Improving conditions far west but remaining IFR to MVFR
from KROC to the Eastern Lake Ontario Region.
Sunday...MVFR/VFR. A chance for rain showers SE of the lakes.
Monday...Mainly VFR. A slight chance for a rain/ North Country snow
Tuesday...Mainly VFR with a slight chance for a shower SE of Lake


An area of low pressure will cross just to the south and east of the
eastern Great Lakes region today. Behind this surface low a
northwest, cool flow will cross the Great Lakes through the end of
the week, and this set-up will continue to bring an extended period
of Small Craft Advisories to the lower Great Lakes.

On Saturday and Saturday night the surface low will rapidly deepen
over New England with winds nearing or exceeding gale force on Lake
Ontario Saturday night. A Gale Watch has been issued as confidence
begins to increase in these higher wind speeds.


NY...Flash Flood Watch until 4 PM EDT this afternoon for NYZ003>008-
MARINE...Small Craft Advisory until 8 PM EDT Saturday for LEZ040.
         Small Craft Advisory from 7 PM this evening to 2 AM EDT
         Monday for LEZ041.
         Small Craft Advisory until 8 PM EDT Saturday for
         Gale Watch from Saturday evening through Sunday morning
         for LOZ043-044-062>064.
         Small Craft Advisory until 6 PM EDT Saturday for LOZ043-
         Small Craft Advisory until 11 PM EDT Sunday for LOZ042.
         Small Craft Advisory from 8 PM this evening to 11 PM EDT
         Sunday for LOZ045.



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