Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 211104

Area Forecast Discussion
National Weather Service Buffalo NY
704 AM 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 the be expected
through Saturday night with mainly dry weather holding off until


Regional radars show widespread rain continuing this morning across
much of upstate New York, western PA into eastern Ohio and West
Virginia. There are embedded pockets of heavy rain which as of 700am
includes a strip from north-central PA across the Genesee Valley
and Finger Lakes. 24 hour rainfall totals across our region range
from one to three inches with current bands of rainfall only adding
to these steep numbers.

This rainfall is due to a sharpening mid level trough extending
across the western Great Lakes south to the lower Ohio and Tennessee
River Valleys. This trough will become negatively tilted through the
day today in response to a strong embedded shortwave moving through
the base of the trough over Tennessee. Synoptic scale lift
associated with this trough and the right entrance region of 100-120
knot upper level jet is working to force a plume of anomalously high
Gulf of Mexico moisture driving the rain. At the surface elongated
low pressure over WV and PA will provide low level forcing as it
slowly shifts north and east. Expect steady rainfall to continue
across our region today with model consensus QPF of and additional 1
to 2 inches. With the additional rainfall in mind, have extended and
expanded the Flash Flood Watch. The watch is now in effect until 4pm
today along with adding a single tier of counties to the western
edge to include heavy rainfall expected over the Genesee River
Valley. The clouds and steady rainfall will keep temperatures
steady in the low to mid 50s today.

Tonight...a cut off mid level low is forecast to develop over our
region 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 western NY. 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 cover.


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.


Sunday night into Monday morning a shortwave trough will cross the
region in the northwesterly flow aloft. This will bring a few
showers across the forecast area, while reinforcing the cooler
Canadian source air into the region. Temperatures will remain near
to slightly below normal for the first half of the work week, as
we remain influenced by the troughing over New England and southern
Quebec. After the departing shortwave on Monday, heights aloft
slowly rise through Wednesday brining a mainly dry stretch of
weather. By Wednesday night into Thursday another shortwave trough
should approach from the Midwest and bring the next chance of


IFR to low MVFR ceilings will continue today and into tonight across
the bulk of western and central New York as low pressure pushes by
just to to our south and east. The low cloud cover will be
accompanied by widespread rain...which will be heavy at times. 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.
         Small Craft Advisory from 11 AM this morning to 6 PM EDT
         Saturday for LOZ044.



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