Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 221519
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1019 AM EST Thu Feb 22 2018

.SYNOPSIS...
Weak low pressure passing by to our south will bring some light to
moderate accumulating snow to areas south of Buffalo and Rochester
through the early to mid afternoon hours. Otherwise 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 later on in the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of this writing the forecast is playing out mostly as expected...
with an elongated swath of steady light to moderate precip extending
across our southernmost two tiers of zones...and area surface obs
indicating that ptype changed over to all snow rather quickly early
this morning with the elimination of the layer of above-freezing air
previously in place aloft.

For the balance of the day...we can expect steady light to moderate
snow to continue across the above areas (while also edging a little
further northward) through the midday/early afternoon hours...before
quickly tapering off from northwest to southeast this afternoon as
the responsible wave of low pressure to our south slides eastward
and falls apart. With respect to accumulations...have bumped up snow
amounts a little from continuity owing to current radar trends and
the somewhat faster changeover to all snow...with totals across the
Winter Weather Advisory area expected to range from 1-3" across
Chautauqua county to 3-5" across Allegany county. In the next tier
of zones to the north...totals should range from 2-4" across southern
portions of Livingston and Ontario counties to under an inch across
far northern sections...with little to no accumulation expected along
and north of a rough Buffalo to Rochester line owing to the sharp
northern edge to the precipitation shield. As the precip winds down
this afternoon...we could see a little sleet briefly mix back in
across the Southern Tier as warmer air tries to nose back northward
aloft...however this will be of little consequence.

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. Very late tonight chances for
precipitation will begin to increase again ahead of a warm front
shifting north toward WNY. Low level temperature profiles indicate
a chance for mainly plain rain for most with surface temps rising
back above freezing near daybreak...but still cannot totally rule
out some brief/spotty light freezing rain where pockets of colder
low-level air persist.

&&

.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 /15Z THURSDAY THROUGH MONDAY/...
For the balance of the day...light to occasionally moderate snow
will continue to produce IFR conditions across areas south of a
KBUF-KROC line through midday/early afternoon...before tapering
off and giving way to some lingering IFR/MVFR ceilings. From KBUF-
KROC northward general VFR conditions will prevail...though some
patchy MVFR ceilings will linger in the vicinity of KROC thanks
to the northeasterly flow off Lake Ontario.

Tonight a mix of IFR to MVFR ceilings will persist across the
higher terrain south of KBUF/KROC...with VFR conditions prevailing
elsewhere. Very late tonight...there will be the chance for a
little light rain near the NY/PA border out ahead of an approaching
warm front.

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...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...JJR
NEAR TERM...JJR/SMITH
SHORT TERM...APFFEL
LONG TERM...CHURCH
AVIATION...JJR/SMITH
MARINE...SMITH



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