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Area forecast discussion
National Weather Service Buffalo New York
702 am EST sun Nov 17 2019

Synopsis...
dry and cold conditions will continue through tonight as high
pressure gradually moves eastward across northern New England. A
coastal storm is expected to bring a wintry mix or rain to portions
of the region Monday through Monday night.

&&

Near term /through tonight/...
surface high pressure over northern Maine will track east and
off the coast of Maine today. A east-southeast wind will
continue across the region while warm air advection moves in.
Temperatures will rebound into the mid to upper 30s with a few
places near the New York and Pennsylvania border seeing 40.
Mostly sunny conditions expected today.

The region will become situated between a coastal low moving north
along the East Coast and a cold front approaching from the upper
Great Lakes tonight. Low-level moisture will be increasing from the
south-southeast and low clouds will likely enter inland portions of
western NY, southern tier to Finger Lakes late tonight. Moisture
ahead of the approaching cold front will stay confined to the west
tonight. Dry conditions expected overnight with lows in the mid to
upper 20s across western New York and low 20s east of Lake Ontario.

&&

Short term /Monday through Wednesday night/...
coastal low mainly impacts eastern New England on Monday but there
is still uncertainty on how much light precip occurs on western
fringe of the system impacting mainly the Eastern Lake Ontario
region. Soundings indicate moisture for those areas on Monday could
extend as high as 7-10kft but with temps at coldest in moist layer
of -6c, there will be minimal chance of seeing any ice nucleation.
Thus, any precip on Monday over the Eastern Lake Ontario region will
be in the form of drizzle/light rain. Since temps will be just below
freezing to start the day, there may be some freezing drizzle or
freezing rain as well. Still not sold on how widespread precip will
be most of Monday during the day, so kept pops less than likely.
Will mention potential for light icing in the severe weather potential statement. Think better
chance of icing occurs late Monday afternoon into Monday evening
before deeper moisture and cooling aloft turns precip to snow
later Monday evening into Monday night.

Meanwhile, over rest of western New York toward Finger Lakes, precip
chances most of Monday look minimal as swath of enhanced precip in
right entrance region of jet streak ahead of upper trough over the
upper Great Lakes. Big differences even amongst the higher res
version of the NAM (4km) compared to nam12 in how much low level
moisture is around much of the day. If low-level moisture is
significant, suppose could see some light precip in the upslope
areas of western New York. Similar to east of Lake Ontario, would be
drizzle or freezing drizzle based on sfc temps. Then Monday evening
into Monday night, slightly better chances for precip occur as upper
lakes trough and associated jet slides across. Ptype could start out
as drizzle/freezing drizzle but eventually transition to light snow
overnight. Based on the potential for mixed precip and some light
icing Monday night, did continue mention in the severe weather potential statement. However, think
all the mixed precip concerns over western New York may end up mainly a
moot point as, by far, the better chances for precip in the forecast
area will occur east of Lake Ontario closer to southern stream
shortwave lifting across the mid Atlantic states and departing
coastal low.

Into Tuesday, ptype all areas will change to rain and snow
showers as deeper moisture with approaching upper trough moves
across. Even with weak cold air advection on Tuesday as 850 mb
temps drop to -4c, water temps on both Lake Erie and Lake
Ontario now into the mid 40s (7-8c) and lack of additional
forcing/lift likely will result in minimal lake responses. As
shortwave embedded in trough slides se across portions of
western New York on Tuesday night, may see uptick in lake responses.
Blyr winds begin Tuesday night from WSW before veering more WNW
by Wednesday morning. Instability remains marginal even with
better forcing, so kept pops less than likely but favored areas
east and southeast of the lakes could see at least some minor
snow accums Tuesday night into Wednesday morning. Timing of
this wetter/greasier type lake effect snow (slr/S less than
10:1) may lead to slippery commute in spots on Wednesday morning.
Temps warm enough through the day though, so any precip left in
the aftn will be mainly in the form of rain/snow showers or even
just rain showers. Upper ridge and warming temps aloft arriving
Wednesday night will shut off any lingering lake effect.

&&

Long term /Thursday through Saturday/...
Thursday will be the warmest day of the next seven with daytime
highs possibly reaching a little above average in the upper 40s,
before the next shot of cooler air sends temperatures back below
average for the tail end of the work week into the start of next
weekend. It will be wet to start the period, with ptype eventually
trending more toward snow or a mix of rain and snow toward the
latter half of the period as colder air moves in. Breezy to windy
conditions can also be expected throughout a good majority of the
period. The details...

Thursday may start out dry across the forecast area, but will become
wet from west to east through the day. As mentioned above,
temperatures will warm to around or just above average. However as
is almost always the case this time of year that will come at a
price, as rain and wind will be on the increase.

A cold front will then sweep across the area sometime Thursday night
into the first part of Friday. Cooler air behind the front will
change the ptype back to mainly snow across the higher terrain
beginning Friday morning, with snow the predominant form Friday
night for all areas. Followed a non-diurnal temp curve late Thursday
night through Friday but even so, surface temperatures at lower
elevations will still be marginal enough to keep a mix of rain/snow
showers for much of Friday. After mainly snow showers on Friday
night, will see mix of rain and snow showers again by Saturday
afternoon as slight warming results in a more typical changeable
Fall like weather pattern (as compared to the more persistent cold
we have seen recently).

Aside from first rain then wintry weather, wind be the other main
story during this time frame. It will become breezy to downright
windy Thursday night, and pretty much remaining that way for much of
the remainder of the period. Low pressure moving northeast across
Michigan and the Central Lakes will be deepening as it passes by to
our west later Thursday and Thursday night, which is one key
component looked at for seeing stronger winds across our area. That
said, despite a 40-50 knot low level jet poised to move across the
area Thursday afternoon/night, it will be difficult to fully mix
this jet down to the surface as it resides ahead of the surface cold
front in the warm air advection regime. There is also upward
vertical motion (lift) in the low levels ahead of the cold front.
Would like to see downward vertical motion and cold air advection in
this layer, which would help to force the stronger winds to surface.
All that said, it will still be quite windy, especially Friday and
Friday night when strong pressure gradient co-incides with cold air
advection/deeper mixing.

&&

Aviation /12z Sunday through Thursday/...
high pressure moving east from the St Lawrence Valley will assure US
of mainly clear VFR conditions with light winds today. Low-level
moisture increases from the south-southeast late tonight. MVFR/IFR
cigs will likely move into the southern tier and Finger Lakes
region. At this time, they should stay east of kjhw through 9z
Monday.

Outlook...

Monday and Tuesday...mainly MVFR/VFR with a chance of showers.
Wednesday...mainly VFR with a chance of showers.
Thursday...MVFR/VFR with a chance of showers.

&&

Marine...
high pressure moving from the St Lawrence Valley to the Canadian
Maritimes during the next 36 hours will result in veering winds
across the lower Great Lakes...with a southeasterly flow through
tonight. The easterly component will direct the highest wave action
and choppiest conditions into Canadian waters.

Winds and waves will remain below Small Craft Advisory levels Monday
and Monday night...as a weak trough will cross the region.

&&

Climate...
an unseasonably cold airmass will remain across our region
tonight. This will not only keep temperatures 20 to 25 degrees
below typical mid-November averages but also bring the
likelihood for additional new low temperature records. This will
especially be the case at Watertown.

Record low minimums for Sunday November 17th...

Buffalo..........13f (1959)
Rochester........15f (1959)
Watertown........13f (1995)

&&

Buf watches/warnings/advisories...
New York...none.
Marine...none.

&&

$$

Synopsis...hsk/SW
near term...hsk
short term...jla

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