Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 181159
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
659 AM EST Sun Feb 18 2018

.SYNOPSIS...
Light snow will end from west to east this morning. Fair weather
will return today as high pressure will pass to our south...then a
dramatic warm up will being for the first half of the work week when
temperatures will soar well into the 60s and possibly to 70. This
will be the warmest weather since last October.

&&

.NEAR TERM /THROUGH TONIGHT/...
A shortwave trough will move across New England while a large area
of high pressure moves south of the Great Lakes this morning.
Widespread light snow has moved east of the forecast area. Snow
showers will linger across the Southern Tier as orographic lift
taps into lingering moisture. Lake snows will also form across
Oswego County/Tug Hill this morning. Additional snow
accumulation of up to an inch across the Southern Tier and 1-2
inches across the Tug Hill are expected before drier air moves
into the region late this morning. High pressure will move to
the south today. As dry air filters into the region, clouds will
dissipate outside of locally driven snow showers. Mostly sunny
conditions expected everywhere by afternoon. Temperatures will
climb into the mid to upper 30s to low 40.

High pressure moves off the Mid-Atlantic coast this evening and
winds become southwesterly across the eastern Great Lakes. Warm air
advection will cause clouds to increase from southwest to northeast
overnight. Temperatures will drop into the 20s this evening before
climbing back into the 30s by Monday morning. Low temperatures will
be reached this evening.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Wet weather still looks likely during this period.

Longwave trough over the western CONUS develops this period with a
gigantic subtropical ridge off the southeast coast. Quasi-stationary
baroclinic zone to set up in between with copious moisture advection
flooding into the Midwest and Great Lakes. Front aligned nearly
parallel to the mean flow and expect several rounds of rain with
slow ejection of western CONUS trough.

Initial theta-e surge arrives Monday afternoon with our first good
shot of widespread rain. Could even see a few elevated thunderstorms
with this initial surge, though instability profiles are a little
too marginal to introduce thunder at this stage. Not expecting much
impact with this initial rain.

Potential problems will arise Tuesday into Wednesday as several
waves ripple along baroclinic zone. At this point, it looks like the
front will move northward across the area setting up across northern
portions of the area Monday night into Tuesday, eventually remaining
in the vicinity of the central Great Lakes into the Saint Lawrence
Valley. Another round of moderate, and possibly heavy rain with
embedded convective elements is expected late Tuesday into Wednesday
as the front sweeps southeast, but there will likely be a
substantial break during this period for a good portion of the
area that emerges into the warm sector.

While the pattern certainly favors heavy rain somewhere, with
precipitable water values exceeding an inch along active quasi-
stationary front, eventual swath of heavy rain is often narrower
than what coarse global models suggest. Certainly worth keeping an
eye on, but confidence in exact rain amounts and locations remains
low.

Unseasonably warm conditions also expected during this period.
Several guidance packages now suggesting temperatures Tuesday
afternoon will likely jump into the upper 60s to lower 70s across
most locations. Coolest readings will remain northeast of the lakes
with a stiff southwest wind in place, which may keep temperatures
along the immediate lake shore areas in the 50s. Both daily record
high temperatures and record warm low temperatures are likely to be
broken during this stretch.

With the increased confidence in large-scale snowmelt due to the
warm temperatures and resultant river rises, ice break-up and/or
potential ice jam flooding remains the greatest threat with this
event and a Flood Watch has been issued Monday night into Wednesday
for Jefferson, Lewis, and Oswego counties where an extensive
snowpack remains. This flood potential will include the Black River.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
Widespread rain shifting east across our region Wednesday night
will likely mixing with and changing to some snow showers.

Strong dry high pressure should then build over the Great Lakes
Thursday/ Thursday night. There is a low chance of some rain and
snow showers on Thursday depending on the speed of the front but
mainly dry weather should be expected. Model consensus then shows
another warm front or surface low crossing our region Friday night
into Saturday likely leading some rain and/or snow showers Friday
night and chance or rain showers Saturday.

Temperatures Wednesday will be highly dependent on the timing of the
cold front but should likely remain above normal. Temperatures will
fall back toward normal Thursday through Saturday but likely
remaining 5-10 degrees above mid-late Feb normals.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Light snow will exit KART early this morning and MVFR cigs/vsbys
will hang on through morning. MVFR cigs will improve to VFR
elsewhere mid/late morning. High pressure moves to the south today
and VFR conditions will continue tonight. Mid-level clouds will
increase from southwest to northeast overnight.

Outlook...

Monday...Deteriorating to MVFR to IFR in rain.
Monday night and Tuesday...Generally VFR to MVFR in showers but IFR
across the North Country in more widespread rain.
Wednesday...MVFR in moderately heavy showers.
Thursday...VFR.

&&

.MARINE...
Winds will freshen in the wake of a passing trough this morning. The
higher winds and waves on portions of Lake Ontario will reach small
craft advisory criteria after daybreak...so have raised a small
craft advisory from Hamlin Beach to Mexico Bay for the bulk of
today.

Winds and waves will subside tonight and Monday...as the next area
of high pressure will pass to the south.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Flood Watch from late Monday night through Wednesday evening
     for NYZ006>008.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for LOZ043-
         044.
         Small Craft Advisory until 1 PM EST this afternoon for
         LOZ042.

&&

$$

SYNOPSIS...HSK
NEAR TERM...HSK
SHORT TERM...TMA
LONG TERM...SMITH
AVIATION...HSK
MARINE...HSK



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