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Area forecast discussion 
National Weather Service Buffalo New York
1013 PM EST Sat Nov 22 2014

the combination of an upper level disturbance and warmer air moving
back into the region will result in intermittent rain showers
tonight. Temperatures will continue to warm Sunday and into Monday
with additional rainfall and windy conditions expected Sunday night
into Monday as a deep area of low pressure passes to our northwest.
This will accelerate melting of recent heavy snows...creating a
significant flooding risk across portions of western and
north-central New York. A cold front will then cross the region
Monday evening...bringing a return of more winter-like temperatures
and a chance of snow by later in the week.


Near term /through Sunday/...
temperatures remain steady in the upper 30s to middle 40s or are
slowly rising. The more important factor to snowmelt is the rising climbing through the lower to middle 30s and even near
or above 40 degrees.

Tonight...expect light rain showers across the region through the
night with area temperatures steady or slowly rising from the upper
30s to the middle or upper 40s.

Sunday...warm air advection will continue as deep southerly flow
continues around the west side of a broad surface high over the
northwest Atlantic. 850 mb temperatures will rise to near +10c
which should boost surface high temperatures into to middle 40s to near
50 with dewpoints climbing above the freezing mark to near 40
degrees. A weak warm front aloft will cross the forecast area but
lack of significant lift should only bring a widely
scattered/scattered showers.


Short term /Sunday night through Tuesday night/...
the main concerns for Monday into Tuesday remain: 1) the warm up
with some rain and the potential flooding and 2) a possible high
wind event on Monday...for which a high wind watch has been issued
for portions of western New York.

Phasing between the subtropical and polar jets over the Midwest will
allow for an amplified upper-level pattern...with deep southwesterly
winds over the forecast area on Monday. A rapidly deepening surface
low will track from the Midwest across the upper Great Lakes and
into Canada. This will advect abnormally warm temperatures across
New York state as a warm front lifts across the state Sunday night.
Precipitation will push from south to north across the area with
this warm front passage. Forecast models are in good agreement with a
very strong low-level jet pushing across New York state...with a
consensus of 70+ knots at 850 mb. The southeasterly component to
this initial low-level jet will bring a strong wind threat along the
Lake Erie shoreline...including Dunkirk...due to downslope winds off
the Chautauqua ridge. The other impact of these southerly downslope
winds will be to eat away at some of the precipitation along the warm
front...which could help to limit quantitative precipitation forecast amounts somewhat. However the
warm front and qg forcing will likely overwhelm the
quantitative precipitation forecast amounts around 0.25 or slightly more still seem reasonable.
Another impact of the warm air advection and increasing winds will
be to keep temperatures from falling much at all Sunday night into
Monday morning...which will help expedite the snow melt process.

During the day Monday the winds aloft veer to the southwest with a
more favorable orientation for a widespread strong wind event as
winds aloft are mixed to the surface. In comparing the forecast
pattern to local research on high wind events across western New York
this event matches very well to the average pattern seen during high
wind events. Temperatures on Monday will also push into the
60s...and likely well into the 60s in the favored downslope
locations from Rochester across the northern Finger Lakes.

The strong cold front will push through the area by Monday
evening...and will likely result in a line of precipitation moving
across the forecast area...bringing an additional 0.10 or so of quantitative precipitation forecast.

Tuesday will be much cooler with high temperatures running in the
upper 30s to lower 40s...and will continue to be fairly windy behind
the Monday nights cold front passage...however winds will likely
remain below high wind criteria.

Snow melt and flooding potential...
the warm up and precipitation events are still on track and appear
favorable to produce flooding from the snow melt. Once surface
dewpoints rise above freezing Sunday the ripening snow pack will
begin to let loose with rapid snow melt across areas which received
last weeks heavy lake effect snowfall. Snow depth measurements from
Friday indicated snow pack has compacted down to between 20 and 40
inches with an average of 4-6 inches of liquid locked up. Snow melt
modeling covering a time range from later Sunday through Monday
indicated 50 inches of snow could melt under forecasted conditions.
Therefore...all of the existing snow pack is expected to melt away
raising the concerns for flooding with finer details highlighted in
the Flood Watch and hydrology section below.

High winds...
added a high wind watch for portions of western New York to
highlight the high wind threat on Monday. The strong southeasterly
850mb jet Monday night is favorable for strong downslope winds along
the Lake Erie shore and along other northward facing slopes in
western New York and The Finger lakes...and possibly the Black River
valley. Following the passage of the warm front the low level jet
veers to southwest which is more favorable for widespread strong
winds as wind energy from 50-60kt 850mb winds mix down.


Long term /Wednesday through Saturday/...
temperatures will return to below average for the bulk of next week
including the Thanksgiving Holiday as a developing ridge over The
Rockies will force a downstream trough to carve into the Great Lakes
and northeast. The airmass looks to be cold enough Tuesday/Wednesday
for a return of chances for lake effect snow as lake induced
equilibrium levels climb to around 10kft. At this point it does not
look unstable enough for a significant event.

The middle level trough and a weak surface low/surface trough may bring
a few snow showers for Thanksgiving Thursday behind a possible
noreaster' lifting along the East Coast. A fresh blast of cold air
behind the weak low/surface trough looks to then again bring renewed
chances of lake effect Friday into Saturday.


Aviation /03z Sunday through Thursday/...
low ceilings will continue this evening as light precipitation
spreads across the forecast area from southwest to northeast as a
warm front lifts north across the region. Low level wind shear will also be an
issue tonight as a strengthening southwesterly low level jet moves
overhead. Otherwise...expect showers to continue overnight with
ceilings lowering to MVFR later tonight as deeper moisture advects
into the region.

Sunday through Monday...periods of IFR/MVFR in rain. Significant
low level wind shear possible Sunday night and into Monday morning.
Tuesday...mainly VFR with a chance of rain/snow showers.
Wednesday and Thursday...mainly VFR/MVFR except IFR possible in lake
effect snow showers east of both lakes.


small craft advisories remain in effect across the majority of
nearshore zones as high pressure moves off the East Coast and the
surface pressure gradient tightens between this departing high and
low pressure well to our northwest across James Bay. South-southwest
flow will continue to be brisk through the weekend with gales
possible by Sunday night into Tuesday as a much deeper area of low
pressure tracks across the upper Great Lakes and a cold front
sweeps across the lakes ushering in an extended period of cold and
brisk west-southwest winds.


a snow survey was completed Friday to get snow depth and snow water
equivalents from the hardest hit areas. The survey came up with a
general 4 to 6 inches of swe in the hardest hit areas. See
bufpnsbuf for the specifics.

Temperatures will rise to near 50 on Sunday...then into the lower
60s on Monday with very mild lows Sunday night. Dew points are
already well above 32 this evening and will continue to steadily rise
into the upper 40s to around 50 by Sunday night and Monday. The
higher dewpoints combined with strong winds will be very efficient
at rapidly melting the deep snow pack. This...along with rainfall
amounts of generally under a quarter inch through Sunday
night...will result in significant rises on local tributaries with
areal flooding expected for the areas in far western New York that
received the two lake effect snow storms this past week.

The flood potential will be two fold. First...there is a general
risk of urban flooding in the towns hardest hit by the snow as
melt water pools in low lying and poor drainage areas. Excessive
snow piles and leaves beneath the snow may block storm drains.
Flooding of some streets and residential basements could begin as
early as this have issued an areal Flood Warning
through at least Monday afternoon to address this threat.

There will also be the risk for the flooding of the various
tributaries across far western New York. The greatest threat is
on the Buffalo creeks which drain the hardest hit areas from this
Weeks Lake effect snow. This includes Cazenovia...Buffalo...
Cayuga...and Ellicott. Individual flood warnings for these creeks
have been all are now forecast to reach at least minor
flood levels. There may also be some flood risk for Cattaraugus
creek and some of the smaller creeks that flow through Dunkirk and
Silver Creek.

There is also a fairly heavy snow pack in the upper reaches of the
Oatka watershed...but not as high as the Buffalo creeks. We will
continue to monitor this basin for possible future inclusion in
the Flood Watch. The Eastern Lake Ontario region had less snow...
with totals of 2 to 2.5 feet on the Tug Hill. This snow pack is not
excessive for that have not included the north country
in a Flood Watch at this time.


Buf watches/warnings/advisories...
New York...high wind watch from Monday morning through Monday evening for
High wind watch from Sunday evening through Monday evening for
Marine...Small Craft Advisory until 1 PM EST Sunday for lez040-041.
Gale watch from Monday morning through Tuesday evening for
Small Craft Advisory until 1 am EST Sunday for lez020.
Gale watch from Monday afternoon through Tuesday
evening for loz042>045-062>065.
Small Craft Advisory until 1 PM EST Sunday for loz043>045.
Small Craft Advisory until 7 am EST Sunday for loz042.



near term...tma/wch

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