Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 210928

Area Forecast Discussion
National Weather Service Buffalo NY
528 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 southern Ohio and West
Virginia. There are embedded pockets of heavy rain which as of 430am
includes a stripe from northwest PA across western New York. 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.


Saturday the mid level trough will continue to sharpen and move
from the Great Lakes to western New England and Quebec, closing
off into a deep mid level closed low. A secondary surface low will
develop over the Gulf of Maine near the triple point as the mid
level low closes off, with a rapidly deepening low over Maine or
eastern Quebec. The most widespread showers will be found east
and southeast of Lake Ontario by Saturday as the system moves
slowly east. Most of the rain will be light by this time as the
stronger forcing and plume of deep moisture re-organize off the
New England coast. That said, there may be a relatively small
embedded area of moderate rain moving from west to east across the
area Saturday in the comma head of the deepening cyclone as a
weak TROWAL develops.

Saturday night the system begins to move east down the Saint
Lawrence Valley, with deeper wrap around moisture focusing on the
eastern Lake Ontario region. Precip will remain more widespread
there, while Western NY slowly dries out from west to east as a
drier airmass begins to build into the region.

The airmass will grow cold enough for lake enhancement as lake
induced equilibrium levels rise to around 8k feet. Off Lake Ontario,
this will manifest in the form of some lake enhancement within the
slowly departing comma head of the low. Off Lake Erie, some limited
northwest flow lake effect may develop later Friday night and
Saturday across the Chautauqua Ridge, but short fetch will limit the
coverage and intensity.

Temperatures aloft and in the boundary layer will remain warm enough
for all rain through late Friday night. By Saturday morning the
boundary layer should cool just enough to allow a few wet snowflakes
to mix in across the highest terrain of the Southern Tier and Tug
Hill region. A better chance of a mix and change to wet snow will
come Saturday night east of Lake Ontario, as colder air continues to
wrap around the deepening low. The column should cool enough for a
change to all wet snow overnight across the Tug Hill and western
Adirondacks above about 1200 feet in elevation, where some minor
accumulations are possible. Some wet snow may also mix in across
lower elevations with little or no accumulation.

On Sunday the deep surface low and associated mid level low will
move quickly northeast into the Canadian Maritimes. Any lingering
lake effect and upslope rain/snow showers early Sunday morning east
of Lake Ontario will end, leaving mainly dry conditions areawide
through the rest of the day. A fast moving weak wave of low pressure
over the central Great Lakes will approach later in the day, with
clouds increasing in the warm advection pattern ahead of the low.

Temperatures will bottom out on Saturday, with highs only in the
upper 40s on the lake plains and low to mid 40s across higher
terrain. Expect some recovery by Sunday with highs in the mid to
upper 50s on the lake plains of Western NY, and low to mid 50s
across the higher terrain and east of Lake Ontario.


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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