Area Forecast Discussion
Issued by NWS Buffalo, NY

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813
FXUS61 KBUF 281900
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
300 PM EDT Fri Apr 28 2017

.SYNOPSIS...
A frontal boundary will push towards our region tonight, then linger
over the region through the weekend, with a chance for showers and
a few thunderstorms, although much of the time it will remain
dry and mild.

&&

.NEAR TERM /THROUGH SATURDAY/...
High pressure will slowly lose its influence on the region tonight.
Denser coverage of mid and high level clouds over the Ohio Valley
will continue to work up towards the north over the area through
this evening and early tonight.

Tonight, a frontal boundary over the Ohio valley will return north
as a warm front, with associated showers developing into the
Southern Tier, after midnight. Most models push the warm front north
toward the New York and Pennsylvania border where it stalls during
the day Saturday. Best chance for showers and perhaps a few
thunderstorms during Saturday will be along the Southern Tier, with
a much better chance for a completely dry day closer to Lake Ontario
and the North country.

Rising dew points will help keep temperatures mild tonight, with
most overnight lows in the lower to mid 50s. Temperatures on
Saturday will greatly depend on amount of sunshine or lack of cloud
cover/precipiation, but for the most part still looks mild with most
areas reaching the 60s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Saturday night into Sunday a developing low pressure system over the
central plains will begin to influence the stalled frontal boundary
across the area pushing it northward as a warm front. The warm
frontal boundary aloft will move north of Lake Ontario Sunday,
however the surface warm front will get hung up on on the south side
of Lake Ontario, enhanced by the lake breeze off the relatively
cooler lake waters. The main area of widespread synoptic
precipitation will develop along the frontal boundary aloft north of
Lake Ontario, while enhanced surface convergence along the surface
boundary will continue to support scattered showers across western
NY. There will also be a wide range in temperatures on Sunday with
locations north of the I-90 thruway corridor markedly cooler than
areas south across the western Southern Tier and southern Genesee
Valley. Along the southern Lake Ontario shoreline and the Saint
Lawrence valley temperatures will likely remain in the 40s to low
50s, while temperatures across southern portions of the state could
push into the upper 70s. Rochester and Watertown will likely remain
on the cooler side in the 50s, while Buffalo will be very near the
transition with as much as a 20 degree temperature difference
possible between the Southtowns and Niagara Falls.

By Sunday night into Monday, the surface warm front will finally
push north across Lake Ontario with deep southerly downslope winds
developing across the region in the warm sector of the occluded low
pressure system centered back across Wisconsin. 850 mb temperatures
will again surge to +15 to +18C promoting temperatures reaching at
least the upper 70s to low 80s, depending on cloud cover and timing
of the impinging cold front. Showers will cross the region with
thunderstorms likely Monday afternoon and evening. There will be
ample shear to result in strong to severe thunderstorms; however, the
main limiting factor will be how much instability can be realized
ahead of the approaching front. This will depend on the timing of
the front itself and how much sunshine can break through in the warm
sector to destabilize the atmosphere. Will continue to mention the
potential in the Hazardous Weather Outlook. The cold front and any
associated convection will cross the region through Monday evening
with cooler air filtering in it wake.

A cooler airmass will be in place on Tuesday as the trough crosses
the region. As the upper-level trough crosses the region on Tuesday
enough moisture and ascent from the trough passage could spark some
light showers across the region with the steep lapse rates aloft.
Cloud cover will also linger under the trough, and with 850 mb
temperatures to around 0C, high temperatures will be limited to the
upper 40s/ low 50s in western NY to nearly 60 toward central NY.
Tuesday will be a windy day, with a 45-50 kt 850mb flow potentially
supporting advisory level gusts to 50 mph. Ultimately this will
depend on the track and strength of the surface low, and if there is
any sunshine to help mix these winds aloft to the surface. This
threat of gusty winds is included in the Hazardous Weather Outlook.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
An unseasonably deep surface low passing northwest of our region
will help usher in much cooler weather with below normal
temperatures expected. This airmass will arrive behind the cold
front on Tuesday along with a chance of some scattered showers and
gusty winds. Strong cold air advection with a source region over
central Quebec will lower 850mb temps to around zero. This will
result in highs only in the 50s on Tuesday.

Tuesday will be a windy day, with a 45-50 kt 850mb flow potentially
supporting advisory level gusts to 50 mph. Ultimately this will
depend on the track and strength of the surface low, and if there is
any sunshine to help mix these winds aloft to the surface. This
threat of gusty winds is included in the Hazardous Weather Outlook.

Winds will slacken off Tuesday night with below normal temperatures
then remaining in place Tuesday night through Wednesday and likely
Thursday with continued cold air advection as a mid-level trough
axis shifts east across our region followed by another trough
digging into the central states. Cool air instability showers will
be possible through Wednesday with the coldest core of below normal
air aloft passing by. Have continued low to slight chances of
showers for this. On Thursday medium range models show the digging
trough over the central states will kick off a surface low along the
Appalachians midweek which could lift some showers into our forecast
area from the south by Thursday. Lows Tuesday and Wednesday nights
look to dip into the upper 30s to low 40s then highs on Wednesday
and Thursday only rising into the low to mid 50s.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Denser coverage of mid and high level clouds will continue to work
up towards the north over the area this evening. Widespread VFR
conditions will continue through the evening. A frontal boundary
over the Ohio Valley will allow for some rain showers to work up
into the area later tonight. Most likely timing of showers to start
to work into western New York looks to be after 06z. Some MVFR CIGs
may develop after 08z with some IFR CIGS will possible at KJHW.

Outlook...
Saturday...VFR/MVFR with a chance of showers and thunderstorms.
Sunday...VFR/MVFR with a chance of showers.
Monday...MVFR to locally IFR with showers and thunderstorms likely.
Tuesday and Wednesday...VFR/MVFR with a chance of showers.

&&

.MARINE...
Waves will approach 2 feet on the eastern waters of the Great Lakes
tonight. A frontal boundary will become draped across the lower
Great Lakes to start this weekend, though winds and waves will
remain light and minimal through the day Saturday and Saturday
night.

Strengthening east to northeasterly winds will likely bring
Small Craft Advisory conditions to the western Lake Ontario
nearshores for Sunday. Another, stronger storm system may bring
another round of thunderstorms early next week, with high end
small craft conditions likely returning on the lakes by
Tuesday.

&&

.TIDES/COASTAL FLOODING...
East to northeast winds will increase Sunday, with waves
building across western portions of Lake Ontario. This combined
with already high levels on Lake Ontario has the potential to
result in lakeshore flooding along the shoreline. The highest
waves are expected in Niagara, Orleans and western Monroe
counties. There is still uncertainty concerning the placement of
the highest wave heights since even a slight shift to the more
easterly direction would push the highest waves to the Canadian
shoreline.

&&

.CLIMATE...
The last days of April will finish with above normal temperatures,
warm enough that it will send our climate sites towards a top
10 warmest April on record. The degree of anomalous warmth has
been greater towards the west, where climate site Buffalo may
near the warmest April on record. Below are the warmest Aprils
on record.


Buffalo

Rank....Value (F).....Year

1........51.3.........1921
2........51.1.........2010
3........51.0.........1955
4........50.9.........2008
5........50.8.........1878

Current April average temperature through April 27th: 50.3F


Rochester

Rank....Value (F).....Year

1........52.6.........1878
2........52.5.........1921
3........52.4.........2010
4........52.3.........2008
5........51.4.........1915

Current April average temperature through April 27th: 51.2F


Watertown

Rank....Value (F).....Year

1........49.1.........1987
2........48.7.........1955
3........48.7.........2010
4........48.3.........1968
5........48.2.........2008

Current April average temperature through April 27th: 47.4F

Temperature records for Buffalo and Rochester begin 1871, while
Watertown`s history is a bit shorter, with temperature records
beginning in 1949.

&&

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

&&

$$

SYNOPSIS...TMA
NEAR TERM...TMA
SHORT TERM...CHURCH
LONG TERM...APFFEL/SMITH
AVIATION...TMA
MARINE...TMA
TIDES/COASTAL FLOODING...APFFEL/TMA
CLIMATE...THOMAS



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