Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 171044
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
644 AM EDT Tue Apr 17 2018

.SYNOPSIS...
An upper level trough of low pressure will maintain the unseasonably
cold temperatures across the region today, with scattered to numerous
rain and wet snow showers. This system will push eastward tomorrow
with snow showers ending through the morning east of Lake Ontario,
and surface temperatures then rising into the lower to mid 40s
across the region. Another system will bring additional rain and wet
snow to the Eastern Great Lakes region Wednesday night and Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Water vapor imagery this morning displays moist cyclonic flow across
the Great Lakes and Northeast, with an embedded shortwave near the
UP of Michigan. A consolidating area of low pressure is to our north
and west with a cold westerly flow over the Eastern Great Lakes.
Regional radars and surface observations display mainly snow across
the higher terrain east of both lakes.

Under this upper level low snow (and lower elevation rain/snow) will
continue through the day. While activity this morning will favor the
higher terrain...with a little lake enhancement, it should expand
over the region midday. As a well defined shortwave over the Upper
Lakes barrels down upon WNY, lift ahead of the feature should
blossom numerous snow showers across WNY...aided with increased
lapse rates and daytime instability activity.

As this shortwave passes this afternoon precipitation activity will
begin to diminish across WNY. Meanwhile a second, but lower in
amplitude shortwave will near the North Country today. This should
too increase primarily snow activity across the Eastern Lake Ontario
region. While we will be warming aloft (diminishing lake
enhancement) the lift from the shortwave should bring one last burst
of snow to the Tug Hill region late tonight.

Additional snowfall today will be minor across the Lake Plains where
a coating of snow is possible this morning when the airmass, and
surface temperatures are the coldest. The higher terrain could see an
inch or two of additional snow accumulation. Tonight additional snow
across WNY will be minor, while this evening and overnight 2 to 4
inches of snow will be possible on the Tug Hill.

It will also become windy today with cold air advection and a
tightening pressure gradient. Southwest to west winds will gust
upwards to 30 to 35 mph across the Lake Plain, with gusts peaking in
the afternoon hours.

Under this upper level low skies will be cloudy, and with the cool
pool upon us our daytime highs will struggle to rise through the 30s.
Tonight low temperatures will range from the upper 20s inland to
lower 30s closer to the lakes.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Closed low remaining in the vicinity of northern New England as we
start the day Wednesday. The positioning of this feature will
maintain a cold cyclonic flow across the area which will be prime
for lake enhanced/upslope precipitation with ample low level wrap-
around moisture. As we get into Wednesday afternoon, a rather short
period of subsidence develops with the development of ridging aloft.
Model signal is to strip away deep layer saturation allowing for a
short drying out period, with some potential for limit cloud breaks.
Temperatures still remaining solidly below normal with highs in the
40s.

The potential exists for another minor accumulating snowfall event
Wednesday night for at least portions the higher elevations.
Potent shortwave is forecasted to dive into the Great Lakes/Ohio
Valley Wednesday night with the associated surface wave cutting from
the Ohio Valley through northern Pennsylvania/southern New York.
Some uncertainty exists at this point as to how far south the
shortwave will slide, which will impact the sharpness/location of
northern edge to the precipitation shield. Current thinking is that
precipitation will begin in the form of rain early Wednesday night
before mixing with and changing over to snow, especially across
higher elevations. Snowfall amounts likely remaining less than 3
inches on the hilltops.

Snow, mixed with rain showers will lingering Thursday and Thursday
night as the main upper level trough crosses the region. Cold
advection on the backside of this system will fill in and keep
temperatures Thursday only in the upper 30s to lower 40s with brisk
northwest winds making it feel even colder.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Ridging will finally start to edge into the Great Lakes by the
weekend. This will allow for drier conditions to become very common.
The sun should also start to make its cameo across the region. That
said, the ridge axis on basically all ensembles fails to really
advance through the area, thus while moderating temperatures and
clearing will be common, substantiating warming even to values above
normal looks unlikely during the long term period.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
For the 12Z TAFS moist cyclonic flow will rule the next 24 hours
with widespread IFR/MVFR flight conditions this early morning in a
predominately snow p-type.

After daybreak we should see an improvement to the ceilings will a
return to MVFR/VFR flight conditions for all but possibly the higher
terrain (KJHW) where IFR CIGS may linger towards midday. Scattered
to numerous showers of snow, or a snow/rain mix will occur through
the early evening hours before the upper level low exits to our east
tonight, with precipitation diminishing to just snow showers east of
Lake Ontario.

Southwest winds will become gusty this afternoon across
KIAG/KBUF/KROC where gusts up to 30 knots is possible. These
southwest winds will begin to relax tonight.

Outlook...
Wednesday...Lingering rain/snow showers and IFR/MVFR east of Lake
Ontario diminishing...otherwise mainly VFR.
Wednesday night and Thursday...MVFR/IFR in rain...which may initially
be mixed with some wet snow across the North Country.
Friday...Mainly VFR with a chance of rain/snow showers.
Saturday...Mainly VFR.

&&

.MARINE...
A southwest wind will continue across the water bodies today,
generally in the 15 to 25 knot range. Small craft advisories will
continue for the Lakes, as well as the Niagara River. As the upper
level low and its associated cool pool exits to the east tonight the
winds will begin to subside and waves begin to diminish. Small craft
advisories will end, first on the Niagara River late this evening,
and then on the Lakes late tonight and through the day tomorrow.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ020.
         Small Craft Advisory until 5 AM EDT Wednesday for LEZ040-
         041.
         Small Craft Advisory until 11 PM EDT this evening for
         LOZ030.
         Small Craft Advisory until 11 AM EDT Wednesday for LOZ042-
         043.
         Small Craft Advisory until 8 PM EDT Wednesday for LOZ044-
         045.

&&

$$

SYNOPSIS...Thomas
NEAR TERM...Thomas
SHORT TERM...TMA
LONG TERM...Fries
AVIATION...Thomas
MARINE...Thomas



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