Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 222327
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
627 PM EST Thu Feb 22 2018

.SYNOPSIS...
Mainly dry weather will prevail through tonight...before another
low pressure system brings another round of milder temperatures and
mainly rain to our area on Friday. Above normal temperatures will
then continue through the weekend...with yet another storm system
bringing another round of widespread rain and windy conditions
Saturday night and Sunday.

&&

.NEAR TERM /THROUGH FRIDAY/...
Our region will lie between systems tonight...as surface high
pressure over southern Quebec will drift eastward across Maine to
the Canadian Maritimes. The high will provide our region with quiet
and mainly dry weather...with an associated incursion of drier air
and subsidence also helping to bring at least some partial clearing
to areas north of the NYS Thruway...while further south lower clouds
will remain intact thanks to a swath of lingering low level
moisture.

Very late tonight chances for precipitation will begin to slowly
increase across the Southern Tier out ahead of an approaching warm
front...though at this point the coverage of such looks to remain
rather limited through daybreak...with surface temperatures across
this also simultaneously rising above freezing...and thereby
resulting in whatever precip does occur likely falling in the form
of plain light rain. Expect mainly evening lows to range from the
teens across the North Country to the 25-30 range across most areas
south of Lake Ontario...with readings then rising overnight as the
low level flow veers to southeasterly and warm air advection
commences.

On Friday...yet another broad and loosely organized low pressure
system will bodily track northeastward across the Central Great
Lakes and to the Ontario-Quebec border...and in the process will
push its attendant warm front northeastward across our region.
Ongoing warm air advection/overrunning out ahead of this system will
result in widespread cloud cover and light precipitation
overspreading our region from southwest to northeast once again...
for which categorical PoPs remain in play.

With respect to ptype on Friday...the combination of the somewhat
slower arrival of the precip and the steady warm air advection
regime should result in the bulk of the precipitation falling in
the form of plain rain across the majority of the region...with
just a brief/localized potential for some spotty light freezing
rain or sleet across interior sections at the onset. At this
point the best potential for such appears to lie across the
North Country...though again even here this should be rather
brief and localized...and therefore not enough for a Winter
Weather Advisory at the present time.

As for temperatures...the ongoing steady warming of our airmass
should result in highs climbing into the lower to mid 40s across
areas east of Lake Ontario Friday...while the remainder of the
region should see readings warm into the mid to upper 40s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
The main large scale feature for the weekend will be the evolution
of the upper level low that is moving south into the Northern
Sierras and Great Basin.  This feature will spawn a surface low in
typical lee cyclogenesis fashion over the Western Plains by Saturday
morning.  The low will continue to deepen as is moves NE across Lake
Superior Sunday morning.  While this will be an impressive system
from a synoptic point of view, it doesn`t appear to have extreme
characteristics worthy of local extreme effects - namely excessive
high winds for WNY.  Here`s a breakdown of timing and impacts for
the weekend:

Friday Night...A low will be moving ENE across S Central Quebec with
any leftover rain quickly moving east into Northern NY and New
England.  This will leave WNY and CNY dry for most if not all of the
night.

Saturday...Expect a dry start as high pressure north of the region
moves east.  From a profile stand viewpoint, there should be some
cirrus and possibly some low clouds overhead with a dry layer in
between at the start of the day.  Warm air advection moving toward
the PA line will increase moisture within the dry layer in the
afternoon. This may may finally saturate the column over the
Southern Tier, perhaps N toward the Thruway by the end of the day.
Will leave a chance of rain in the forecast, although current model
QPF appears to be overdone when considering the profile forecasts.

Saturday night...This is where there is high confidence for
measurable precipitation for all areas, moving in from SW-NE across
all of WNY overnight.  Mixed precipitation or just freezing rain is
a concern for the St Lawrence Valley overnight with at least
initially a supply of subfreezing air from downstream on a NE flow
sneaking in under the warmer air aloft, but this should change over
to rain by Sunday morning. Rainfall amounts should be highest from
about KBUF through KFZY with over 0.5", but less to the south and
east.

Another impact may be downslope winds NW of the Chautauqua Ridge and
Tug Hill.  These winds often have a hard time mixing to the surface
while its raining though.  Localized advisory level winds are at
least possible however.

Finally, on Sunday...the main impact is high wind potential.  The
main surface low is almost too far from WNY to have significant
impacts with is max deepening occuring prior to the trough passage
Sunday morning.  Winds aloft are strongest in the warm advective
pattern (Saturday Night) and decrease with time on Sunday as cold
advection moves in.  The airmass should rapidly dry out with good
mixing after the cold front, but lapse rates don`t compare to
archived model profile forecasts of extreme event from last March
2017.  The NAM in particular, although at the end of the model run,
shows a stout cap down to 2000` for Sunday after which, if it were
to verify, would ensure advisory-only winds.  The GFS is a little
more impressive, but still only grazes warning thresholds via
momentum transfer, and mainly areas closest and NE of Lake Erie.
Current forecasts follow this idea, with high end advisory winds in
the forecast.  As is always the case however, the forecast can,
should, and will change as the event approaches.

Finally of note will be temperatures, which should briefly spike
into the 50s across WNY.  However, unlike the recent warmup, there
will likely only be a tiny window between the ending rain and
imminent winds for one to enjoy the spring conditions.

Sunday night will be uneventful in comparison, with a relaxing wind
field and temperatures dropping back to normal with continued cold
air advection and a drying airmass.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
High pressure will drift across the region to start the work week
with temperatures running above climo(+5F - +10F), with daily highs
in the 40s and nighttime lows in the upper 20s to low 30s.
Precipitation chances will increase into Thursday as a wave ejects
from the Four Corners region to the Great Lakes.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Tonight a mix of IFR to MVFR ceilings will persist across the higher
terrain south of KBUF/KROC. Elsewhere general VFR conditions will
prevail...though some MVFR ceilings may work back northward to
KBUF/KIAG late as the low level flow turns southeasterly out ahead
of an approaching warm front. The front may also bring the chance of
a little light rain to areas near the NY/PA border late
tonight...though at this point it appears that surface temperatures
in this area will be rising above freezing by that time.

On Friday...the aforementioned warm front will lift northward
across our region...while also spreading rain and lower ceilings
across the area from southwest to northeast. This will result in
flight conditions lowering to mostly IFR across the higher terrain...
and to MVFR across the lower elevations. At the onset of the rain...
some very brief/localized freezing rain or sleet cannot be ruled
out away from the TAF sites (with the greatest potential for this
lying across the North Country)...though at this point the chances
for such still appear to be pretty low.

Finally...since the KJHW observation has not been reporting for
several days...we have continued with a rarely used NIL TAF for
KJHW. Safety concerns have played a major role in this decision...
especially given the continued potential for low/erratic ceilings
at this particular site.

Outlook...
Friday night...Gradual improvement to MVFR/VFR with any lingering
rain showers ending. Some LLWS possible.
Saturday...VFR/MVFR with additional periods of rain developing...
which may be mixed with a little snow or freezing rain across the
North Country at the onset. LLWS also becoming likely.
Sunday...Rain ending with improvement to VFR...though also turning
rather windy.
Monday...Mainly VFR.
Tuesday...Mainly VFR...with a chance of rain/snow showers across
the North Country.

&&

.MARINE...
Moderate northeasterlies across the Lower Lakes Region will veer
to easterly and then southeasterly tonight as high pressure over
Southern Ontario/Quebec slides eastward to Maine and the Canadian
Maritimes. At this point...winds and waves are still expected to
remain below advisory levels through tonight.

On Friday winds will veer further to southerly (and increase a bit
on Lake Ontario) as low pressure passes by to our northwest...though
the offshore orientation will help to keep the highest waves confined
to Canadian waters.

In the wake of this system...high pressure will briefly build back
across the Lower Great Lakes on Saturday... before a strong area of
low pressure tracks northeastward across the Great Lakes on Sunday.
This latter system should bring at least a round of higher end
advisory-worthy conditions...with gale force winds possible.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JJR/RSH
NEAR TERM...JJR/RSH
SHORT TERM...ZAFF
LONG TERM...CHURCH
AVIATION...JJR/RSH
MARINE...JJR



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