NWS Area Forecast Discussion

000
FXUS61 KBUF 230627
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
127 AM EST Fri Feb 23 2018

.SYNOPSIS...
Mainly dry weather will prevail early this morning before a warm
front lifts north with a round of milder temperatures and mainly
rain through the daylight hours today. 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 TODAY/...
Surface high pressure is centered over the Saint Lawrence Valley
early this morning. It is providing western and central NY with
quiet and dry weather although also trapping widespread lower clouds
across much of the region. Further southwest, Low pressure over
Missouri is expected to lift north the the central Great Lakes
through today while a warm front pushes north across the Ohio
Valley. This will bring low chances for precipitation ahead of the
front across the Southern Tier. Temperatures in the western Southern
Tier are largely just above freezing. Whatever precip does arrive
will likely fall in the form of plain light rain. Expect
temperatures (L/M 30s WNY, 20s North Country) to rise under
southeasterly flow and warm air advection commences.

After daybreak, the surface warm front will lift further
northeastward into western PA and perhaps the NY Southern Tier
before an occluded front trailing low pressure shifting just north
of the eastern Great Lakes pushes east across our region. widespread
cloud cover and light plain rain will overspread our region from
southwest to northeast through midday with precip tapering off
toward this evening behind the occluded front. Temperatures east of
Lake Ontario will play a key roll in surface p-type when the rain
arrives. There is a chance temps hold below freezing over the Tug
Hill where some freezing rain may occur. Will take a closer look
this morning to evaluate possible winter weather advisory if
confidence for freezing rain increases.

Ongoing steady warming of our airmass should result in high temps
climbing into the lower to mid 40s across areas east of Lake Ontario
today while WNY into the Finger Lakes should see readings warm into
the mid to upper 40s.

&&

.SHORT TERM /TONIGHT 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 will be a high wind
potential. While a deepening...sub 980mb low will be some 500
miles to our northwest and will be taking a more northerly track
than is climatologically favorable for damaging winds across
our region... other parameters will come into play that will
favor strong/damaging winds. To start with...H85 winds in the
wake of a strong cold will be in the neighborhood of 50 knots.
While these winds will be weaker than those found ahead of
front...forecast soundings suggest a three hour window of strong
subsidence and lapse rates exceeding 8 deg c/km that should
allow most of this wind to mix to the surface. Both of these
parameters will come together during the midday hours at the
peak heating of the day...and with the bulk of the guidance
packages suggesting significant clearing...very efficient mixing
should be present. While this scenario is similar to that from
March of 2017...winds will not be as strong aloft when the
parent low was closer to our region. That being said...feel that
the Niagara Frontier will experience AT LEAST advisory criteria
winds...if not low end high wind warning criteria a solid
possibility. Have issued a high wind watch for the four counties
of the IAG Frontier to cover this risk...which should be
exacerbated by a thawed surface (frost depth at KBUF now ZERO).
This would more easily allow for shallow rooted trees to come
down.

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 /07Z FRIDAY THROUGH TUESDAY/...
A mix of ceilings will persist south of Lake Ontario overnight while
VFR will continue at KART and KGTB. KBUF at 06z is reporting VFR but
should lower shortly to MVFR. IFR along the southern Lake Ontario
with an easterly flow. Later this morning a warm front will lift
northward into the western Southern Tier while spreading widespread
rain from southwest to northeast. Expect IFR cigs to lift to MVFR
cigs with winds veering to southeast.

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.

There is a possibility of some patchy LLWS this afternoon/evening
with a 40-50 kt low level jet shifting over our region. Rain will
taper off west to east this evening with an occluded/cold front
shifting east. All precip should be finished by midnight at the
latest. Low MVFR/IFR cigs will linger through tonight however, as
high pressure ridges east over our region.

Finally...since the KJHW observation has not been reporting (or
reporting very inconsistently)...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...

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 overnight with high pressure over
the Saint Lawrence River Valley. This high will slide eastward to
Maine and the Canadian Maritimes. Winds and waves are still expected
to remain below advisory levels through this morning.

After sunrise today, 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...High Wind Watch from Sunday morning through Sunday afternoon
     for NYZ001-002-010-011-085.
MARINE...None.

&&

$$

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

NWS BUF Office Area Forecast Discussion