Area Forecast Discussion
Issued by NWS Buffalo, NY

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000
FXUS61 KBUF 250840
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
440 AM EDT Sat Mar 25 2017

.SYNOPSIS...
A frontal boundary will remain draped across the region today...before
slowly lifting back north across the region as a warm front
Sunday and Monday. Several disturbances sliding along this
boundary will bring frequent bouts of precipitation through the
weekend and early next week... with cooler temperatures
prevailing north of the boundary and milder temperatures to its
south.

&&

.NEAR TERM /THROUGH TONIGHT/...
At 4 a.m. surface observations showed a frontal boundary dividing
temperatures in the 50s from temperatures in the 30s was draped
across the Western Southern Tier. Steadier showers were located
north of the surface boundary along a sharp mid-level thermal
gradient.

The boundary will continue to slide slowly south this morning, with
periods of rain expected to continue along the I-90 corridor, with
lowering chances to the south. There was some thunderstorms last
night due to elevated instability, and a few rumbles cannot be ruled
out this morning though this instability is limited.

Thermal profiles are colder across the Eastern Lake Ontario region,
where there will be some mixed precipitation. The temperature of the
mid-level warm layer will be marginal (0 to +3C) with snow, sleet,
and freezing rain all a possibility. Although any snow or ice
accumulation should be light, this may result in some slick spots
this morning with a winter weather advisory in place. Temperatures
should rise above freezing late this morning.

High pressure near the Ontario/Quebec border will expand southward
and push the boundary to near the NY/PA state line. Model consensus
stalls the front here late this afternoon and evening. The lack
of motion should result in diminishing shower activity along
the boundary, though a stray shower cannot be ruled out.

The front should then lift back northward as the high drifts to the
east, with modest mid-level warm air advection increasing chances
for some light precipitation late tonight. This should mainly fall in
the form of rain, but there is a risk of freezing rain late tonight
across the Eastern Lake Ontario region. Confidence in measurable
precipitation is low, but this may require another round of
headlines for this region.

With most of the area on the cool side of the front, temperatures
will be much cooler than yesterday. Highs will only be in the upper
30s in many areas, rising to the upper 40s near the Pennsylvania
state line. Temperatures will not cool much tonight, before rising
late in the night as the frontal boundary lifts back northward into
the region. The exception is the North Country where skies should
clear out, allowing for some radiational cooling and temperatures to
fall into the upper teens to lower 20s. The forecast hedges
toward high resolution guidance which is better able to resolve
the sharp temperature differences.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Sunday a band of isentropic lift precipitation will lift across the
region, though with neutral temperature advection and ridging aloft
rain showers will likely be scattered in nature. Early morning
temperatures east of Lake Ontario will likely remain near or below
freezing. Expect another period of freezing rain Sunday morning
before surface temperatures rise above freezing. A northeast wind
through the Saint Lawrence Valley may linger freezing rain chances
into the early afternoon.

Sunday night an area of low pressure will advance towards Michigan,
and bring another increase in moisture across the lower Great Lakes.
Increased surface convergence, along with falling heights aloft by a
nearing shortwave of low pressure will bring increasing chances for
rain showers. Ahead of this surface low will be a fair amount of
instability across the Ohio Valley, but waning as it reaches WNY.
Still there will be chances for thunder across SW NYS Sunday
afternoon and evening. As the upper level shortwave passes Sunday
night and into Monday it will carry an area of showers across the
region.

Through the day Monday and Monday night the surface low will slowly
track eastward, just to the north of Lake Ontario. Abundant low
level moisture will maintain chances for rain showers through the
end of the forecast period.

Temperatures Sunday will rise well into the 50s across WNY, though
SE and E of Lake Ontario, highs will remain in the 40s. As winds
become SW Monday milder air will spread across the entire region,
with 50s, and possibly a few Genesee Valley lower 60s for highs.
Sunday night will remain mild with the SE winds and thick cloud
cover allowing for only a 5 to 10 degree drop in air temperatures.
Monday night will remain mild, with overnight lows in the 40s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The lengthy unsettled period will last into Tuesday as the stalled
complex frontal zone remains nearby. Both the GFS and ECMWF based
guidance suggest one more wave moving along the frontal zone and
passing to our north on Tuesday, producing another round of showers.
Temperatures will remain mild given the northerly low track, with
highs at least into the 50s and possibly into the 60s for the
southern half of the area.

Tuesday night and Wednesday a mid level trough will amplify across
Quebec and finally drive the frontal zone well south of our area,
with moisture and showers diminishing from northwest to southeast.
Cold advection associated with the trough will knock temperatures
back a few notches, with highs in the 40s Tuesday.

A slow warming trend should then ensue for the second half of next
week as the trough over Quebec moves offshore of the Canadian
Maritimes and height rises/weak warm advection overspread the
eastern Great Lakes. Model guidance diverges by next Friday with
respect to the track of the next system. The GFS keeps most of the
energy and deeper moisture suppressed well to the south across the
Ohio Valley and southeast States, while the ECMWF takes a much more
northerly track through the Great Lakes and would be a warmer and
wetter solution. Given the time range and inherent uncertainty, have
just included chance POPS for now.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
At 08Z a frontal boundary is across the region, with this front
across the Western Southern Tier near JHW. A northeasterly flow
north of this boundary will advect cooler air which will mix with
the moist air in place resulting in low cigs and some fog. This
pattern is climatologically favorable for IFR or lower cigs at
BUF/IAG/ROC/ART and conditions have been lowering as expected at
these locations. Expect this trend to continue through mid-morning
with a period LIFR conditions likely. There will also be periods of
precipitation and patchy fog, and an isolated thunderstorm cannot be
ruled out through mid-morning just north of the boundary due to
elevated instability. Precipiation may mix with snow or sleet at ART.

Drier air will first build into ART as the boundary pushes further
south, with conditions improving this afternoon and evening.
Elsewhere, expect a prolonged period of mainly IFR conditions as the
northeasterly flow persists.

Later tonight, expect IFR/MVFR conditions will continue south of
Lake Ontario, with VFR conditions at ART.

Outlook...
Sunday through Tuesday...MVFR/IFR cigs with rain likely at times.
Wednesday...VFR.

&&

.MARINE...
A frontal boundary will push further south of Lake Ontario today,
briefly pushing south of eastern portions of Lake Erie. A
northeasterly flow will develop on the cool side of the front
requiring small craft headlines along the south shores of Lake
Ontario from late this morning through Sunday evening. Winds and
waves will also briefly build on Lake Erie southwest of Dunkirk.
Conditions will be marginal, but expect there will be a shorter
period which meets small craft criteria late this afternoon and into
tonight.

After this, expect a benign pattern for the first half of next week
resulting in modest winds with any headlines unlikely.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory until 11 AM EDT this morning for
     NYZ006>008.
MARINE...Small Craft Advisory from 5 PM this afternoon to 2 AM EDT
         Sunday for LEZ040.
         Small Craft Advisory from 11 AM this morning to 11 PM
         EDT Sunday for LOZ042-043.

&&

$$

SYNOPSIS...APFFEL
NEAR TERM...APFFEL
SHORT TERM...THOMAS
LONG TERM...HITCHCOCK
AVIATION...APFFEL
MARINE...APFFEL



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