Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 270550
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
150 AM EDT Fri Apr 27 2018

.SYNOPSIS...
High pressure will build across our region tonight, bringing fair
dry weather that should last through most of the day Friday. A
pair of weak low pressure systems will then bring additional
opportunities for rain showers Friday night and Saturday, before
a shot of colder air leads to chances for some rain and wet
snow showers Saturday night and Sunday. The return to colder
conditions will be short-lived however, as much warmer weather
remains forecast to return for most if not all of next week.

&&

.NEAR TERM /THROUGH TODAY/...
High pressure will build east across our region overnight, bringing
fair and dry weather areawide. A shortwave approaching from the Mid-
Atlantic states will spread some cirrus into our region from the
south, however this will do little more than result in the
development of some partial cloudiness. Overnight lows will be in
the mid to upper 30s.

On Friday the surface ridge will slide eastward and off the Atlantic
coastline, however mainly dry weather should still prevail through
the bulk of the day as we will be caught within the squeeze play/
zone of compensating subsidence between the aforementioned shortwave
lifting northeastward across eastern New York/New England, and a a
second and larger upper level trough and associated cold front
pushing eastward across the Central Great Lakes. With this in mind,
have notably lowered shower chances from continuity for a sizable
chunk of our area. As a result, we now only some widely scattered
activity forecast along our southeastern periphery during the mid to
late afternoon as some very weak instability develops along the
western fringes of the initial shortwave, and then some additional
scattered showers becoming possible across the Southern Tier late in
the day, again with the development of some very weak instability
and the approach of the larger upper level trough. Otherwise the day
should be dry, with somewhat warmer air aloft also supporting
afternoon highs ranging through the 60s away from any lake
influences, with areas immediately east northeast of the lakes
running a bit cooler.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
The weather for this upcoming weekend does not look very spring-like
as winter takes (what is hopefully) its last parting shot for the
season. A closed upper low and the core of cold air aloft will drop
from southern Ontario and into Western New York over the weekend.
This will result in periods of showers, which will mix with snow at
times Saturday night and Sunday. Model consensus is in fairly good
agreement on this overall pattern which increases forecast
confidence.

On Friday night a subtle trough of low pressure will move across the
region during the evening hours. This will then be followed by the
leading edge of an upper level trough and colder air aloft on
Saturday. This will result in two rounds of showers which will move
across the area from west to east. Rainfall amounts will generally
be light and hit or miss in each case, only supporting likely PoPs.
Lows Friday night will average in the lower 40s, then temperatures
will rise slightly Saturday before colder air spreads across the
region from west to east during the afternoon hours.

The core of the coldest air (about -8C at 850mb) will move into the
region late Saturday night and into Sunday morning. This combined
with a cyclonic flow and limited lake enhancement will result in
some showers Saturday night. Thermal profiles suggest it will be
cold enough for snow in many areas, however any accumulation would
be light with a negligible impact.

The closed 500 mb low will move from Western New York on Sunday into
New England Sunday night. This feature combined with diurnal
instability is likely to result in some rain or snow showers during
the day Sunday. Meanwhile afternoon highs will be well below normal,
with temperatures struggling to climb into the lower 40s. The
forecast hedges cooler than MOS based guidance which can struggle to
capture such an anomalously cold air mass. Rain or snow showers may
linger into Sunday evening east of Lake Ontario, but should taper
off in all areas late in the night.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
The closed upper-level low will slowly open up and exit the region
off into the Canadian Maritimes Monday. In its place, building 500mb
heights and surface ridging along the Carolinas will begin a rapid
warming trend with dry conditions for the Lower Great Lakes that
will last through Midweek. However, before that can happen look
for one last chilly start with temperatures in the 20s and low
30s early Monday morning. Temperatures will then begin to
rebound with highs climbing into the L60s with U50s across
higher terrain for Monday. Additional warming will occur through
midweek with highs climbing +15-20F degrees above climo with
mid-upper 70s, even a few 80F readings by Wednesday. Wednesday
night, a frontal boundary will approach Western New York from
the west bringing increasing chances for showers for our region.
This frontal boundary will then serve as a guide for several
waves to ride northeast into and across our region with
additional chances for precipitation through the end of the
week.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
High pressure will build east across our region overnight, bringing
fair and dry weather areawide. Some thin cirrus will continue
to spread into the region from the south.

On Friday the surface ridge will slide eastward and off the Atlantic
coastline, however mainly dry weather and VFR conditions should
still prevail through the bulk of the day as we will be caught
within the squeeze play/zone of compensating subsidence between one
shortwave lifting northeastward across eastern New York/New England,
and a a second and larger upper level trough and associated cold
front pushing eastward across the Central Great Lakes. Any potential
for scattered showers will be limited to interior portions of the
Finger Lakes and North Country from about mid afternoon onward, and
across the Southern Tier late in the day.

Outlook...
Friday night and Saturday...Mainly VFR with scattered to occasionally
more numerous rain showers.
Saturday night and Sunday...VFR/MVFR with a chance of rain and snow
showers.
Monday and Tuesday...VFR.

&&

.MARINE...
High pressure will be across the lower Great Lakes through Friday.
Light winds and minimal wave action is expected through Friday, with
waves perhaps building under an increasing westerly flow on Saturday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JJR/TMA
NEAR TERM...JJR/TMA
SHORT TERM...Apffel
LONG TERM...AR
AVIATION...JJR/TMA
MARINE...JJR/Smith/TMA


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