Forecast Discussion

Forecast Discussion for BUF NWS Office
000
FXUS61 KBUF 142352
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
652 PM EST Wed Nov 14 2018

.SYNOPSIS...
High pressure will build across the lower Great Lakes and New
England overnight. The next system will begin to impact the
region Thursday afternoon and last through Friday. A wintry mix
of snow, sleet and freezing rain will expected before changing
to all snow by Friday morning. Ice and snow accumulations are
likely.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
High pressure will continue to build across the region this
evening. Although it will remain cold aloft with 850mb
temperatures around -14C, the weakening flow will cause any
lingering lake effect activity to taper to flurries and
then end all together later tonight. There still will be
lingering cloud cover from lake effect and high clouds from the
next system which is developing across eastern Tennessee.

High pressure moves overhead tonight and into southern Quebec
and northern New England Thursday morning. This will result in dry
and cold conditions overnight. Temperatures will fall into the
upper teens to low 20s, except single digits and teens east of
Lake Ontario where skies will clear out and provide excellent
radiational cooling conditions.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...
Isentropic ascent centered in the 290-300K layer increases
rapidly during the afternoon on Thursday. This is in advance of
a warm push aloft commiserate with the filling inland low that
will be moving northward west of the Allegheny Front. A secluded
bubble of warm air aloft has been well depicted on several
successive runs of guidance that penetrates up into the Southern
Tier of New York with fairly good run-to-run continuity. Some
higher resolution guidance further advances this elevated warm
bubble toward Buffalo and Rochester, as well. With this in mind,
precipitation type becomes the biggest ball of wax to deal with
Thursday afternoon and evening as the column saturates and
lifting increases.

Warm air aloft looks to get eroded by dynamical cooling as well as
cold air impinging from the the west as the coastal low gradually
takes over into Thursday night. This will allow for the secluded
bubble to erode as it advances eastward toward the northern Finger
Lakes such that it eventually becomes nonexistent. Before that
juncture, however, strong moisture transport in the lifted
layer means several hours of potential mixed precipitation in
the Southern Tier, South Towns, and southern half of the
Rochester area. Farther north, with less certainty on the warm
layer persisting, the forecast was trended more strongly toward
snow/sleet as the GFS/ECMWF both favor colder profiles, even
though higher resolution guidance does not.

Regardless of the profiles followed, this does not look like a very
efficient snow maker in terms of snow-to-liquid ratios. While lift
is strong in the 290-300K layer and does bisect the dendritic growth
layer, substantial riming below that layer will cut back on
ratios. With that in mind, SLRs were capped at about 10:1 and
greatly reduced south of the Thruway due to the influence of
warm air aloft and sleet/freezing rain mixing into the frozen
precipitation spectrum. Regardless, in areas were it remains all
snow, a solid advisory snow seems likely, and in areas where it
doesn`t, advisories will be necessary for icing. The only place
this isn`t the case looks to be Niagara County, which several
successive runs have shown to be just a tad outside of the
northwest fringe of the action from this system.

As the coastal low intensifies on late Thursday night/early Friday
and moves northeast along the coast, a period of enhancement from
the apex of the trowal airstream may allow for a secondary maxima in
snowfall from Allegany County toward Lewis County. This would help
to enhance snowfall amounts there even in the areas that are likely
to see snowfall reduced Thursday evening because of mixed
precipitation. This is the biggest piece of uncertainty in the
forecast. Should these areas remain all snow earlier, it would be
likely that winter storm warnings would be necessary.

Otherwise, drier air in the dendritic layer starts to advect into
the area from the west on Friday. This will allow for a tapering off
of snow into drizzle or freezing drizzle through the late morning
and early afternoon hours. As cold air takes its sweet time
advancing into the area, the boundary layer does not look likely to
cool off enough behind the system on Friday to make this be a
persistent affair.

The next system to affect the area advances eastward on
Saturday. This will bring a round of lake enhanced snow showers
and much colder/drier air behind it. Temperatures will really
take a nosedive Saturday night with persistence of this pattern
into the long term period.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Broad upper level troughing will continue to dominate the Great Lakes
and Northeastern states in the extended portion of the forecast...
resulting in a certainty of continued well below normal temperatures
through the middle of next week. Speaking more specifically...we can
expect daily highs to mostly be in the 30s...while nightly lows range
from the teens and lower 20s across the North Country to the mid and
upper 20s elsewhere. Such readings will be more typical of mid-winter
than of the middle of November.

In terms of precipitation...while the medium range guidance suite is
in general agreement on a couple of weak surface troughs affecting our
region in the Sunday-Monday time frame...considerable discrepancies
still exist with respect to the track and timing of these features.
Consequently...the orientation...strength...and amount of shear in
the low level wind field at any given point also remains much in
question. With both of the above in mind...forecast confidence in
the timing and placement of both synoptically-driven and lake-driven
precipitation during the first half of this period remains on the low
side...and as such have continued with mostly broadbrush snow shower
chances through Monday. After that...there is loose agreement on a
broad warm frontal zone slowly pushing toward/into our region in the
Tuesday through Wednesday time frame...for which lower-end broadbrush
chance PoPs remain in the forecast. Given expected temperatures...
any precip during the latter half of the period should again be mainly
in the form of snow showers...with a little rain perhaps mixing in on
Wednesday as boundary layer temperatures turn more marginal.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
High pressure will build across the lower Great Lakes this
evening, and then slide into New England. There may be a few
lingering flurries, with otherwise just lake effect clouds which
should mainly be in the VFR flight category. These clouds will
dissipate later tonight, leaving just high clouds in advance of
the next system.

The next storm system will spread a wintry mix which will move
into the area Thursday afternoon and evening. This mix will
mainly include snow and sleet, but freezing rain cannot
completely be ruled out either. Expect conditions to lower to
IFR or lower with the arrival of this precipitation.

Outlook...

Thursday night and Friday...MVFR/IFR possible in wintry mix of sleet
and snow.
Saturday and Sunday...Mainly VFR, but IFR possible east of
both lakes in lake rain and/or snow.
Monday...MVFR/IFR with a chance of snow showers.

&&

.MARINE...
Winds will continue to diminish this evening as high pressure
builds across the lower lakes. Another coastal low will bring
the next wintry mix potential Thursday afternoon into Friday. A
mix of snow, sleet and freezing rain is expected before changing
to all snow by Friday morning. The strongest winds will remain
off shore through Thursday night. Westerly winds increase Friday
and small craft conditions will return for the end of the work
week and into the weekend.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 7 PM Thursday to 1 PM EST Friday
     for NYZ004>008.
     Winter Weather Advisory from 4 PM Thursday to 11 AM EST Friday
     for NYZ002-003-010-011.
     Winter Weather Advisory from 1 PM Thursday to 11 AM EST Friday
     for NYZ012>014-019>021-085.
MARINE...Small Craft Advisory until 10 PM EST this evening for LOZ043-
         044.

&&

$$

SYNOPSIS...Apffel/HSK
NEAR TERM...Apffel/HSK
SHORT TERM...Fries
LONG TERM...JJR
AVIATION...Apffel/HSK
MARINE...Apffel/HSK

NWS BUF Office Area Forecast Discussion