Area Forecast Discussion
Issued by NWS Buffalo, NY

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826
FXUS61 KBUF 220943
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
443 AM EST Thu Feb 22 2018

.SYNOPSIS...
A weak storm system passing south of New York will bring some mixed
precipitation to the Southern Tier this morning followed by
some accumulating snowfall through midday today. Another low
pressure system will then bring another round of mainly rain to
our area on Friday. A third storm system will bring more rain
and some wind for Sunday. Otherwise, temperatures will remain
above normal through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Strong high pressure is centered over southwest Quebec but spread
across the Great Lakes early this morning. Further south, a wave of
low pressure is lifting north across the southern Appalachians.
Radar mosaic shows this wave of low pressure is generating
widespread rain across the Ohio Valley into western PA with some
echoes also extending north across western NY. Temperatures in
western NY at 4am are running in the low 30s but the echoes across
WNY remain elevated with drier air remaining near the surface
reflected by temp/dewpoint spreads. Aloft, model soundings indicate
a thin warm layer which will support some mixed wintry
precipitation this morning across the Southern Tier as the lower
levels saturate. We continue with a forecast expecting an initial
mix of freezing rain and sleet early this morning perhaps mixed with
some snow, before the warm layer erodes to support just snow
generally after 9-10am. By midday the wave of low pressure will be
shifting across Central PA with most likely probabilities for light
to moderate snow south and east of a Buffalo-Rochester-extreme
southern Lewis county axis. Only a low chance for some light snow in
the North County closer to high pressure. The high temp for today
should run in the mid 30s with sub-freezing thermal profiles during
the morning daylight hours so not expecting any rain. The wave will
depart to the east through the afternoon with snow tapering off to
chances for some snow flurries except drizzle in the western
Southern Tier where the warm layer looks to surge back north across
the state line.

A Winter Weather Advisory remains in place through 4pm for
Chautauqua, Cattaraugus and Allegany counties to highlight expected
ice accumulation of up to a tenth of an inch followed by snow
accumulations of 1-3 inches. Further north, expect only a chance for
a little light snow of 1-2 inches in Southern Erie and Wyoming
counties eastward across interior portions of the Finger Lakes. Just
a chance for a light coating north of these areas.

Tonight, expect mainly dry weather in the wake of the weak surface
wave pushing off Southern New England. Temperatures should drop into
the upper 20s to low 30s for most. There remains a slight chance of
some drizzle or freezing drizzle with lingering low level moisture
in the western Southern Tier. Late tonight, chances for
precipitation again increase ahead of a warm front shifting north
toward WNY. Low level temperature profiles indicate a chance for
some mainly plain rain for most with surface temps rising back above
freezing near daybreak Friday but and rule out some freezing rain or
freezing drizzle in areas where surface temps hold longer at or
below freezing.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
The prevailing flow aloft Friday and Saturday will feature a SW-NE
oriented jet stream generally stretching from the Desert Southwest
into the Central Great Lakes region. The result at the surface will
be a number of relatively weak troughs/lows.

On Friday, an area of mid-level warm air advection will move from SW-
NE across the region resulting in period of widespread
precipitation. Temperatures should be warm enough for all rain at
most locations with the exception of the North Country where it may
start off as freezing rain. SSW surface winds will result in
downsloping and warmer conditions across the lake plains where
temperatures will climb into the upper 40s.

There may be some light upslope enhanced precipitation behind this
wave Friday evening. After this surface high pressure will briefly
ridge into the region while a frontal boundary remains stalled to
our south. This will provide a period of dry weather late Friday
night into Saturday. Lingering cloud cover associated with the
departing system and frontal boundary will limit radiational cooling
with lows in the 30s.

A more significant synoptic low is expected to develop Saturday
night, with this low expected to strengthen as it tracks across the
Upper Great Lakes and into southern Ontario on Sunday. Overall model
guidance is in good agreement with this system bringing widespread
rain to the region Saturday night into Sunday. Some guidance
develops a weak wave just ahead of this system with rain possible
across the Southern Tier as early as Saturday afternoon.
Temperatures will be warm enough for all rain with the possible
exception of the North Country where some light snow accumulations
are possible at the onset before temperatures warm into the 50s on
Sunday.

This system has the potential to bring a period of strong to
damaging winds for the typical areas northeast of Lake Erie on
Sunday behind the cold/occluded front passage. The consensus track
is less than ideal (a bit too far north and west) but skies are
likely to clear behind the front which would help winds aloft mix to
the surface. There is a risk winds may gust in excess of 60 mph and
this risk will continue to be discussed in the HWO.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
Quiet and drier weather returns Monday with surface high pressure
building over the Ohio Valley. Highs will remain above climo (+5F -
+10F) with the daytime highs in the mid and upper 40s likely for
most locations for the first half of next week.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
Mainly VFR remains in place across our region ahead of some incoming
wintry weather. MVFR cigs showing up at KROC at 9z. The wintry
weather will generally be limited to south of KBUF-KROc line. Expect
IFR to MVFR cigs and vis possible across the Southern Tier this
morning with some mixed wintry precip eventually transitioning to all
snow. Since KJHW observation has not been reporting for several
days, have continued with a rarely used NIL TAF for KJHW. Safety
concerns play a major role in this decision...especially given the
erratic cigs and potential for mixed precipitation at this elevated
site during the first half of the TAF period.

North of the Southern Tier, VFR should remain through today. Some
light snow may edge toward or over KBUF-KROC midday but otherwise
remain dry. VFR expected much of tonight with a possible late
reduction to MVFR with a chance of some rain toward 12z Friday.

Outlook...
Friday...Deterioration to MVFR with rain developing...with a
very brief wintry mix possible at the onset.
Saturday and Sunday...VFR/MVFR with additional periods of rain
developing...which may be mixed with a little snow across the
North Country. Monday...Mainly VFR.

&&

.MARINE...
Light to moderate northeasterly winds in place this morning as high
pressure is centered northeast of the Great Lakes. These winds will
veer to easterly later tonight while remaining below advisory levels.

Southerly winds will veer to westerly Friday as a weak storm
system passes over western NY. This will keep highest waves on the
northern half of Lake Ontario. High pressure will build briefly back
over the Great Lakes Saturday before a strong low pressure cuts
across the Great Lakes Sunday. This should bring a round of higher
end Small Craft Advisory conditons.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 4 PM EST this afternoon for
     NYZ019>021.
MARINE...None.

&&

$$

SYNOPSIS...SMITH
NEAR TERM...SMITH
SHORT TERM...APFFEL
LONG TERM...CHURCH
AVIATION...SMITH
MARINE...SMITH



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