Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 151937
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
237 PM EST Thu Feb 15 2018

.SYNOPSIS...
A warm southerly flow will continue across Western and North-Central
New York into this evening. This warm air will continue to result in
some fog and drizzle ahead of rain tonight. Low pressure passing
along the New York Pennsylvania border will bring widespread rain
overnight. A cold front following the low will cross our region
Friday with rain changing to snow. Cooler weather will remain for
the weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
Mild temperatures continue across western and north-central New York
this afternoon. Temperature range between the low 40s in the North
Country to 60 in Dansville under southwest flow. Much of the fog has
dissipated leaving low clouds and patchy drizzle ahead of an
approaching warm front. Any lingering fog is limited to the eastern
end of Lake Erie right along the lake shore as the warm air moves
over the ice-covered lake and is advected onto the adjoining
lakeshore. Southwest winds are 15-25 and gust to 35 mph east of the
lakes.

Weak low pressure moving over Illinois will shift east through
tonight. A surface warm front with widespread rain extends from this
low east into central OH. The warm front now looks as it will not
lift entirely north across New York tonight but track east along the
NY-PA border ahead of the surface low. Blend of recent meso-guidance
indicates rain will move into western NY late this afternoon before
widespread rain shifts across our region overnight. The northern
edge of rain will run near Watertown with the SLV perhaps not seeing
any rain at all overnight. Warm temperatures and areas of fog will
also linger into the evening until the low center passes east then
begin to slip back through the 40s and into the 30s late. Blend of
12z model QPF will leave the highest rainfall across the western
Southern Tier where around a half inch is forecast. QPF tapers down
further north with a tenth to a quarter of an inch from Buffalo into
the Finger Lakes.

A cold front will drop south across western and north-central NY
Friday morning. This will usher in the return of a colder airmass
with temperatures slipping back below freezing by midday. Any rain
showers in the wake of the surface low will mix with and change to a
chance of some limited snow showers focused mainly in upslope
locations east of the lakes. Any snow accumulations will be
limited to less than one inch. During the afternoon, drier air
and surface high pressure will build in helping to end
precipitation while also scattering out cloud cover. As 850mb
temps drop toward - 10C, there is a chance for some limited lake
effect clouds and snow southeast of Lake Ontario. Continued
cold air advection will yield surface temperatures falling
through the day plunging into the 20s by nightfall. The cold
advection will also support wind gusts to 30 mph.

The warm temperatures and expected rain tonight continue to support
a Flood Watch for potential ice jam development. The watch runs
through mid-afternoon Friday. More details in the Hydrology section
below.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
Friday night, any nuisance lingering lake effect snow showers or
flurries southeast of Lake Ontario will diminish overnight as very
dry air and subsidence spread across the region coinciding with the
surface high sliding eastward across PA. This will also allow for a
cold night as areas of clearing and light winds east of Lake Erie
and in the Saint Lawrence valley provide optimal radiational
cooling. Expect temperatures in the low teens to single digits
there, with upper teens southeast of Lake Ontario where lake cloud
cover will be most persistent.

High pressure then slides to our east Saturday initiating a
moderating temperature trend Saturday into Sunday. Meanwhile, a
shortwave moving through the lower Ohio Valley with a deepening
surface reflection will track off the mid-Atlantic coast Saturday
night. The best forcing with this system will be well southeast of
the forecast area, but cannot rule out some light snow especially
near the PA line and along the CWA boarder with BGM. High pressure
returns Sunday with mainly dry weather. The only exception may be a
few snow showers over the higher terrain in the North Country with
moist upslope flow. Temperatures during this period will be in the
30s Saturday, with some low 40s by Sunday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A significant warm up continues to be on track to start the next
work week. Medium range models remain in good agreement with a broad
trough carving out across the intermountain west Sunday into Monday,
with the downstream amplification of the broad upper-level ridge
anchored off the southeast coast Tuesday into Wednesday. This
pattern is favorable for opening the door to Gulf of Mexico air to
be advected poleward to the forecast area.

Starting Sunday night, we will see warm air advection underway as
the ridge axis builds overhead, with the thermal ridge axis not
crossing the region until Tuesday. The result will be a non-diurnal
temperature trend beginning to overnight Sunday night into Monday
morning, and continuing to warm through Monday and Monday night
before peaking on Tuesday. Monday will see late-day high
temperatures in the mid 50s across WNY and mid to upper 40s in the
North Country as 850 mb temperatures push +5 to +8C. 850 mb
temperatures will then peak near +10C on Tuesday, which, when
combined with the southwesterly flow, will push high temperatures
across inland locations and the Genesee Valley solidly into the 60s.
Locations northeast of the cold lakes, like Buffalo and Watertown
will likely be held slightly cooler in the upper 50s to near 60.
Would not rule out the possibility of setting some daytime high
temperature records, with the best chance being at Rochester, where
Tuesday`s record is 62 degrees.

Periods of rain showers are likely from Monday afternoon through
Tuesday. PW values will increase to near records levels for this
time of year (likely over 1"), along with a baroclinic zone stalled
to our west with a couple waves of low pressure moving along it.
While there remain model differences on timing any of these waves,
and when the exactly the cold front crosses the region later Tuesday
into Wednesday, it will most certainly be an overall wet period. That
said it will likely not be a total washout, with likely some dry
breaks at times. Will need to closely monitor the flood threat on
area creeks and rivers with the expected combination of snow melt
and rainfall.

A return to cooler, more seasonable temperatures and drier weather
returns for Wednesday into Thursday as high pressure is forecast to
build in across the Great Lakes.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
MVFR and IFR cigs with patchy fog and drizzle continue this
afternoon as a warm front sits just south of the area. Southwest
wind gusts 20-25kt will continue through the afternoon before
diminishing this evening. Some Low Level Wind Shear also looks
likely across the Niagara Frontier with a 45kt low level jet
overhead. There may be a brief improvement in ceilings at some sites
ahead of incoming rain this evening into tonight.

Low pressure will track just south of our region this evening into
tonight bringing IFR vis and cigs. A cold front will approach and
cross the region late tonight into Friday. Most of the rain should
end tonight before colder air moves in. VIS should lift before CIGS
Friday with some snow showers possible mainly southeast of the
lakes. Northwest winds will gust again near 25kts Friday.

Outlook...

Friday night and Saturday...VFR.
Saturday night...chance of light snow and IFR.
Sunday...VFR.
Sunday night...chance of snow changing to rain with VFR/MVFR.
Monday and Tuesday...Rain becoming likely with MVFR/IFR.

&&

.MARINE...
Southwest winds have freshened to 15-20 knots this afternoon but
will relax early this evening. Low pressure will pass south of the
eastern Great Lakes tonight followed by a cold front. Behind the
front, elevated winds and waves are forecast Friday under westerly
flow. Small Craft Advisories have been issued along the south shore
of Lake Ontario. Winds/waves are expected to relax this weekend with
high pressure building across the region.

&&

.HYDROLOGY...
A flood watch remains for a portion of Western New York for a
risk of both ice jam flooding and river flooding. Warm
temperatures will last through this evening, which has resulted
in a significant amount of snow melt in the Buffalo Creeks and
the Allegheny River basins. Ice on the Buffalo creeks is
patchy, but probably minimally ample to support some issues.
Gages show some signs that the ice is breaking up this
afternoon. Because the ice is relatively thin it may flush out
quickly given there will be less ice than earlier in the
season. This still poses a risk for ice jam flooding in the
typically vulnerable locations.

Following the warm temperatures, widespread rain will arrive
tonight as a surface low shifts along the NY/PA border. The
latest forecast is for between a quarter and a half inch within
the watch area. Expect any basin averages in excess of a half
inch will push forecast points to above action stage or even
flood stage when combined with run- off from snow melt. This
uncertainty is reflected in MMEFS ensemble guidance which shows
a wide range of crest levels based on differences in the QPF.

For the Genesee River basin the risk depends on how much rain
falls and given the uncertainty there is not enough confidence
to issue a watch at this point. Temperatures in the Black River
basin will be cooler and there will be less rain there so a
watch is unlikely to be needed for that basin.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Flood Watch through Friday afternoon for NYZ010>012-019>021-
     085.
MARINE...Small Craft Advisory from 1 PM Friday to 1 AM EST Saturday for
         LOZ043.
         Small Craft Advisory from 1 PM to 10 PM EST Friday for
         LOZ042.
         Small Craft Advisory from 1 PM Friday to 4 AM EST Saturday
         for LOZ044.

&&

$$

SYNOPSIS...SMITH
NEAR TERM...SMITH
SHORT TERM...CHURCH
LONG TERM...CHURCH
AVIATION...SMITH
MARINE...SMITH
HYDROLOGY...APFFEL/TMA/SMITH


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