Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 190927
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
427 AM EST Thu Jan 19 2017

.SYNOPSIS...
Low clouds and areas of drizzle will persist today with abundant
moisture trapped in the low levels of the atmosphere. A weak trough
will cross the area Friday with a period of rain showers during the
afternoon and evening across Western and Central NY. Mainly dry
weather will then return for the start of the weekend with
temperatures remaining well above average.

&&

.NEAR TERM /THROUGH TONIGHT/...
IR Satellite imagery shows an extensive low stratus deck covering
all of the Great Lakes and New England early this morning. Radar
imagery shows a good amount of drizzle as well, especially east of
Lakes Erie and Ontario where frictional convergence and upslope into
the higher terrain inland is enhancing low level convergence. Some
patchy fog will also continue through this morning, especially east
of the lakes and across higher terrain.

The drizzle will likely continue in place east of Lakes Erie and
Ontario through the first half of today before the moisture becomes
more shallow by this afternoon, allowing most of the drizzle to end.
Temperatures will remain near the freezing mark through mid morning
across the higher terrain of the Tug Hill Plateau, Black River
Valley, and western foothills of the Adirondacks continuing the risk
for some areas of freezing drizzle. Temps will warm to above
freezing there by late morning, with any remaining freezing drizzle
changing to just drizzle at that point.

High pressure surface and aloft will build into the Lower Great
Lakes this afternoon and evening. The building high will do nothing
to eliminate the extensive low level moisture, and will act to
steepen the low level inversion and make it even more difficult to
erode the stratus deck. With this in mind, expect low clouds to last
through today and much of tonight across the region, with some
partial clearing possible later tonight across Western NY. The
extensive low level moisture will also allow some patchy fog to
develop again later tonight into early Friday morning, especially if
any breaks in the stratus develop and allow for better cooling
overnight.

The low clouds will keep diurnal ranges small, with highs today
ranging from the upper 30s at lower elevations to mid 30s higher
terrain. Lows tonight will be in the lower 30s in most areas.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
The trough across the central plains today will become negatively
tilted and track toward the Great Lakes on Friday. The result will
be an area of rain moving into southwestern NY during the day
Friday, on the nose of the best moisture advection and frontogensis
ahead the upper-level trough. This trough and associated area of
frontogensis will become sheared out across central NY Friday
afternoon and evening, thus decreasing forcing and allowing rain to
become more scattered and fizzle out as it tracks toward the North
Country Friday evening. Have increased PoPs some more across the
western Southern Tier to near 100 percent, and brought categorical
PoPs farther north toward the Niagara Frontier. From the northern
Finger Lakes into the North Country, the rain will become much more
scattered, and have maintained chance PoPs there. Temperatures will
remain very mild on Friday with enhanced warm air advection an some
downsloping, bringing daytime highs well into the 40s. The rest of
Friday night, the showers associated with this feature will
gradually end... with skies remaining shrouded under plenty of low
cloud cover. Low temperatures will only bottom out around 40 in the
Lake Plains to mid 30s inland.

A progressive shortwave ridge will amplify over the Lower Great
Lakes on Saturday. This will provide us with a fairly nice day for
outdoor activities...as 850 mb temperatures rise to +5C over western
NY to +2C over North Central NY. This will allow daytime
temperatures to surge to low 50s for those in western NY, the
Genesee Valley and the Northern Finger Lakes, while the North
Country will remain in the low to mid 40s.

Sunday will largely feature more uneventful weather across our
region...as the high amplitude ridge will gradually exit across New
England. High temperatures on 850 mb temperatures fall slightly
ahead of the approaching low, but daytime highs will remain near 50
in western NY to the low 40s in the North Country.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Confidence remains very high in a period of precipitation across the
region from later Sunday night into Tuesday as an anomalous low
pressure system tracks northward through the coastal Atlantic
states. Despite maintaining very high confidence in precipitation,
there is decreasing confidence in the type of precipitation, as the
chance for snowfall across the region increases.

The eastward shift in the track of the low pressure system noted by
yesterday`s forecast discussion remains true with the 00Z model runs
this morning. As was noted previously, the eastward shift places
western and central NY on the cooler side of the system, increasing
chances for wintry precipitation. Since this storm system will lack
a tap to significant cold air, temperatures profiles will be
marginal and dynamical cooling process will be very important. While
the GFS thermal profiles remain overall uninteresting for wintry
precipitation in our area, the ECMWF, along with with ensembles, and
the Canadian are actually much more interesting. These models are
overall a few degrees colder, which makes all the difference near
the freezing mark. Dynamically cooling will play a vital role in the
wrap around precipitation as the low tracks up the coastline,
something the models typically seem to underrepresent. Also
supportive of the idea that the GFS thermal profiles may be too warm
is the CIPS analogs based on the GFS forecast itself. The top
analogs, all produced a swath of significant snowfall through NY
state. All of this points to increasing chances for potentially
significant snowfall, while the possibility of a cold rain remains
solidly on the table at this point as well. This storm system will
need to be watched closely as we move through this weekend, since if
the colder solutions verify, this would bring snowfall impacts to
the beginning of the work week.

A bit more on the daily details:

The mature storm system will drift to the Mid Atlantic region on
Monday. This will establish a deep easterly flow (40-50 kts) of
Atlantic moisture over our region where a strongly coupled H25 jet
will provide lift for increasingly widespread rain. This pcpn could
be moderate to heavy at times with some areas possibly receiving a
half to one inch of rain. High temps will be in the mid 30s to
near 40 for most areas.

The rain will continue and could begin to mix with or change to snow
across the region Monday night into Tuesday, as the storm system
will track north-northeast across New England. This is when things
could get interesting. Because of the more eastward track...colder
air will be able to work in behind the parent low. As mentioned, the
air could be cold enough to allow for a transition to wet snow,
especially across the higher terrain. In a worst case scenario, the
snow would change over at a point where significant accumulations
could occur.

Drier air will then work its way across our region later Tuesday
night and Wednesday...finally bringing an end to the pcpn event.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
Low stratus will remain widespread across the entire region today
into at least this evening. Expect IFR CIGS areawide through the
first half of today, with some improvement to MVFR this afternoon at
lower elevations with IFR continuing across higher terrain. The
stratus will likely continue into tonight with MVFR at lower
elevations and IFR higher terrain. Low level moisture may also allow
for some patchy fog to develop after 05Z Fri, especially in areas
where the stratus begins to thin out.

Outlook...

Friday...Areas of MVFR/IFR in morning stratus and fog, then areas of
MVFR with rain showers in the afternoon.
Saturday and Sunday...Areas of IFR/MVFR in low stratus.
Monday...Areas of MVFR/IFR with rain or wet snow.

&&

.MARINE...
Moderate southwesterlies will continue to produce low end Small
Craft Advisory conditions on Lake Erie through early this morning,
with choppy conditions on Lake Ontario remaining below Small Craft
criteria. Winds and waves will slowly diminish through today as the
pressure gradient relaxes across the Lower Great Lakes. Relatively
light winds will then continue through the end of the week and into
the weekend with mild temperatures and a weak pressure gradient in
place.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 10 AM EST this morning for
     NYZ006>008.
MARINE...Small Craft Advisory until 7 AM EST this morning for LEZ040-
         041.

&&

$$

SYNOPSIS...HITCHCOCK
NEAR TERM...HITCHCOCK
SHORT TERM...CHURCH
LONG TERM...CHURCH
AVIATION...HITCHCOCK
MARINE...HITCHCOCK


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