Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 221904
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
304 PM EDT Wed Mar 22 2017

.SYNOPSIS...
High pressure will move from the upper Great Lakes, across the
forecast area overnight, and then east of the region on Thursday.
One last very cold night will come tonight before a moderating
temperature trend Thursday into the weekend. A frontal boundary will
then set up across the region this weekend, with several
disturbances moving along the front, which will bring an extended
period of wet weather Friday through early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
Sprawling arctic high pressure will continue to build in across the
Great Lakes late this afternoon through tonight. Already limited
lake effect south of Lake Ontario will diminish to patchy flurries
late this afternoon, and end this evening with strong subsidence and
a very dry airmass in place. The high pressure system will move over
the forecast area overnight setting us up for optimal radiational
cooling with light to calm winds and mostly clear skies. Locations
with lingering snowpack, like the North Country and interior
portions of the western Southern Tier will see low temperature
plummet overnight, with lows bottoming out in the single digits to
near zero. Meanwhile, lake plains locations, those with limited snow
pack and urban areas will temperatures mainly in the low to mid
teens.

The large high pressure system will slide to our east on Thursday,
with some limited return flow developing by mid-day and the
afternoon. This will allow for some moderation in temperatures as
the core of the cold airmass exits the region. High temperatures
will run a fair bit warmer than Wednesday, as temperatures reach the
low 30s in the North Country to near 40 in western NY. It will be a
fair weather day with mostly sunny skies, a very dry airmass in
place, and light winds.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
After a midweek dry spell, the region will enter a prolonged
unsettled and relatively mild period that will last at least through
the weekend as a slow moving upper level low meanders across the
nation`s mid-section. Southerly return flow around high pressure
stationed off the Eastern Seaboard, enhanced by a strengthening low-
level jet will pump moisture and mild air northwards across the
Great Lakes. Meanwhile, a northerly flow of cooler and drier
Canadian air be found just to our north, sharpening a frontal
boundary across the lower Great Lakes. This front will then serve as
the focus for a band of precipitation across the forecast area that
will develop starting late Thursday night as the warm front lifts
across the region. With warm air initially overrunning the initially
sub-freezing surface air, we may see a brief period of mixed
precipitation, particularly across the Southern Tier and North
Country, late Thursday night into Friday morning before the arrival
of much warmer air on southwesterly flow changes precipitation over
to rain. Temperatures Thursday will then warm into the 50s across
Western NY, with low 40s in the North Country.

Currently, the model consensus places the frontal precipitation band
along and north of the Thruway, with around a half to three quarters
of an inch of precipitation possible Friday, heaviest across
the north Country. Temperatures across the forecast area should
hold above freezing Friday night, allowing for ongoing frontal
precipitation to persist as rain, with the possible exception of
the St. Lawrence valley, where a possible backing northerly
flow may bring in some sub-freezing air and result in mixed
precipitation early Saturday morning.

As we move into Saturday, diurnal effect should keep precipitation
mostly rain, however, as the broad surface low wandering across the
Mississippi valley draws closer to the region, increasing
northeasterly flow into this low may draw colder surface air over
Canada back across the forecast area, potentially undercutting the
warm air aloft.  This may result in more substantial sleet and/or
freezing rain across the North Country, and possible as far south as
the Lake Ontario plain. Model guidance differs somewhat in how far
north the warm front travels into Canada Friday, and hence how far
south it will retreat Saturday, so all mixed precip grids are being
left as a chance for the time being.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Unfortunately...there is high confidence that the wet...unsettled
weather will remain in place across western and north central New
York during this period.

The persistent stacked storm system over the mid west will gradually
`open up` and drift across the Lower Great Lakes later Sunday into
Monday. While the baroclinic zone responsible for much of the
previous days pcpn will be shoved out of the region...significant
hgt falls and the introduction of mid level energy will fuel
additional rainfall.

Our region will experience a very brief lull in the inclement
weather Monday night in the wake of what will then be a passing mid
level trough. Will only have chc pops in place for rain and wet snow
showers...although the majority of the night could very well be pcpn
free.

On Tuesday...while the medium range ensembles are not in agreement
as to the strength of the next shortwave...they generally agree that
another disturbance will drop southeast across the Lower Great
Lakes. This will generate a renewed round of shower activity.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
High pressure will build across the region through tonight and will
move to our east on Thursday. This will bring a long stretch of fair
weather and VFR conditions and light winds to the area.

Outlook...

Friday...Deterioration to MVFR/IFR with mixed rain and
snow developing...then changing over to all rain.
Saturday thru Monday...MVFR/IFR with rain likely.

&&

.MARINE...
Northwest winds will maintain small craft advisories on Lake Ontario
late this afternoon. High pressure will build towards the lakes
tonight, allowing for winds and waves to subside, with SCA lingering
longest along the SE Lake Ontario shoreline.

This high pressure will then build across the region Thursday while
bringing a return to light winds and negligible waves.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 2 AM EDT Thursday for LOZ043-044.
         Small Craft Advisory until 5 PM EDT this afternoon for
         LOZ042-045.

&&

$$

SYNOPSIS...CHURCH
NEAR TERM...CHURCH
SHORT TERM...WOOD
LONG TERM...RSH
AVIATION...CHURCH
MARINE...CHURCH


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