Area Forecast Discussion
Issued by NWS Buffalo, NY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS61 KBUF 242018

Area Forecast Discussion
National Weather Service Buffalo NY
418 PM EDT Tue Apr 24 2018

A large...slow moving storm system moving by to our south tonight
and Wednesday will direct copious amounts of Atlantic moisture
across our region. This will result in a rather extended period of
unsettled weather when most areas will pick up at least a half inch
of rain. The showers will taper off on Thursday as weak high
pressure will move across the Lower Great Lakes.


As we work through the remainder of the late afternoon and first
part of tonight...a diffluent flow aloft and weakly coupled H25 jet
will help to lift an ever moistening airmass so that the light rain
will become more widespread over the western counties. Modest hgt
falls overnight will continue to add to the relatively deep lift so
that the widespread rain will make its way across the Eastern Lake
Ontario region as well. Rainfall amounts tonight will be under a
quarter inch...especially east of Rochester. Along with the
increasing coverage of the light rain...there will be some patchy
fog as we push through the wee hours of the morning. This will
especially be the case across the higher terrain (generally >1500`)
where the lowering stratus will intersect ridge tops.

On Wednesday...the southern stream stacked low will continue east to
the Mid Atlantic coast while a robust northern stream shortwave will
approach from the Upper Great Lakes. Earlier guidance suggested that
these two features would phase in time to have an influence on our
weather...but it now appears that they will remain two distinct
features until they move east of our region. In any case...the axis
of the mid level trough between the two will cross our region and
help to focus more light to occasionally moderate rain. The amount
of lift is not forecast to be as significant as that from the
overnight...but there will be more moisture to work with. Will
maintain cat pops with daytime rainfall amounts in the vcnty of a
quarter to a half inch...with the higher amounts expected to be near
and east of Lake Ontario.


On Wednesday night, a closed 500 mb embedded in the northern branch
of the jet will absorb another low across the mid-Atlantic states.
Model guidance differs on the track of this with the 12Z GEM/ECMWF
guidance tracking this low across western New York while the NAM/GFS
guidance is north and faster with its track. The southerly/slower
track would result in more precipitation and have it last a bit
longer. The forecast uses a consensus of guidance with fairly steady
showers Wednesday evening tapering off from west to east overnight.
Consensus 850mb temperatures fall to around 0C which may allow some
wet snow to mix in across the highest terrain in the Southern Tier
but this will not result in any accumulation. Low temperatures will
range from the mid 30s to lower 40s on Wednesday night.

Showers will likely linger east of Lake Ontario into Thursday
morning, but the rest of the area should be mainly dry on Thursday
as a ridge of high pressure builds in from Michigan. As a result the
forecast is a bit warmer with highs in the 50s with a modest lake
breeze developing in the afternoon. High pressure will then briefly
ridge across the region Thursday night with dry weather and lows in
the 30s.

A broad upper level trough axis will gradually shift to the east
coast Friday and Friday night. A broad surface low is forecast to
develop across the mid-Atlantic states on Friday and track into New
England on Friday night. Model guidance differs, but this may clip
especially eastern portions of the cwa on Friday with some light
rain showers possible. Then showers are possible in all areas Friday
night when the upper level trough axis moves across the area.
Rainfall amounts should be fairly light with this, generally under a
quarter inch. Temperatures should be near normal with highs on
Friday in the mid 50s to around 60.


An upper trough dropping through the Great Lakes will leave a spell
of cooler weather in its wake for the weekend, with daytime highs
only in the low to mid 50s.

Forecast models are coming into good agreement about a ridge
building across the region to start next week. Exactly how fast this
happens remains is in question, but we could be looking at mid to
upper 60s by Monday and 70s by Tuesday along with dry and mainly
sunny weather.


VFR conditions at the start of this TAF period will gradually
deteriorate during the course of tonight. MVFR cigs are anticipated
for the Southern Tier by about 21z...for KBUF and KIAG by 06z...for
KROC by about 08z...and for the North Country (KART and KGTB) by
daybreak Wednesday. The lowering cigs will be accompanied by some
light rain and eventually some patchy fog.

On Wednesday...widespread MVFR to IFR cigs will be in place across
the region as light to occasionally moderate rain will continue. The
lowest cigs will be found across the higher terrain.


Wednesday night...MVFR to IFR conditions in showers.
Thursday...Improving to VFR with showers ending.
Friday...Mainly VFR.
Saturday...VFR in scattered showers.


A relatively weak surface pressure gradient will remain in place
across the Lower Great Lakes through a large but
poorly organized storm system will pass by well to the south. This
will keep generally light winds and negligible waves in place.

In the wake of this system...winds will freshen Wednesday night into
Thursday. This could lead to small craft advisory conditions for
sites on Lake Ontario east of Thirty Mile Point.





MARINE...RSH is the U.S. government's official web portal to all federal, state and local government web resources and services.