Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 182031

Area Forecast Discussion
National Weather Service Buffalo NY
431 PM EDT Wed Apr 18 2018

A large upper-level trough will pinwheel across New England while
keeping a supply of cool air in place across the region through
Friday. Meanwhile a western wave will track from the Rockies to just
south of the Great Lakes while merging with the upper-level trough
tonight and Friday. Expect widespread light snow with minor
accumulations mainly over higher terrain. High pressure will build
across the region this weekend into early next week finally brining
drier weather and moderating temperatures.


An upper level low will slowly move into the Canadian Maritimes this
afternoon while a brief ridge builds across the Great Lakes. Snow
showers have been coming to an end east of Lake Ontario and mostly
dry conditions will continue today. Northwest flow and wrap around
moisture will lead to mostly cloudy conditions for the rest of the
afternoon. An isolated rain shower is possible across the southern
shore of Lake Ontario where a convergence zone may form this
afternoon. Temperatures will top out in the upper 30s to  the low
40s in a few places.

The break of winter-time precipitation will come to an end tonight
when the next low pressure system approaches the Great Lakes. The
associated closed upper level low will be catch up with the broad
upper level low spinning over the Canadian Maritimes tonight. This
system currently in the Mid-West will quickly track from west to
east from the Ohio Valley and eventually to the south and across
Pennsylvania by Thursday morning. Precipitation, already apparent
across the Mid-West will move into the Southern Tier this evening
and spread eastward across the forecast area. Lighter amounts are
expected across the southern shore of Lake Ontario and eastern Lake
Ontario where these areas will be on the northern fringe of the
precipitation shield. Rain and snow is expected to start before
changing to all snow by midnight tonight. There will be a baroclinic
zone across northern PA and sleet may mix in across the Southern
Tier. Confidence is low as profiles look isothermal and will likely
cool to sub-freezing aloft. Temperatures will drop into the
U20s/L30s across higher elevations and L30s at low-lying areas.
Snowfall accumulations of 1 to 3 inches are expected tonight mainly
at higher elevations across the Southern Tier and western Finger
Lakes. An inch or less is expected elsewhere.

The quick moving low pressure system will be off the southern New
England coast by Thursday morning and northwest flow will begin
across the region. Rain and snow will be confined to areas south and
east of the lake shores Thursday. Snow will intensify east of Lake
Ontario especially the Tug Hill Plateau Thursday afternoon as a
shortwave trough drops south from Quebec. Cloudy conditions will
result in a chilly day, with high temperatures in the 30s.


Following the passage of Thursday`s system...lingering upper level
troughing and a cold cyclonic upslope northwesterly flow will help
to produce some additional snow showers and minor accumulations of
another inch or two across the higher terrain Thursday night...
while any accumulations elsewhere remain under an inch. The activity
will then wind down altogether from west to east Friday and Friday
evening as high pressure and drier air build into the region...with
skies also showing a corresponding gradual decrease in cloud cover
through Friday night. With respect to temperatures...these will remain
solidly below average with lows ranging between the mid 20s and lower
30s...and daytime highs on Friday failing to reach above the upper
30s to lower 40s.

After that...sprawling high pressure centered over the Upper Great
Lakes will steadily build southeastward across our region through
the remainder of the period...with plentiful dry air and subsidence
attendant to the high providing our region with fair dry weather
and the beginning of a welcome long-duration day-to-day warming
trend. During the first couple days of this warmup...we can expect
daytime highs to recover first into the mid and upper 40s on
Saturday and then into the lower to mid 50s on Sunday...with
even warmer readings then expected to arrive early next week...
details on which are provided in the long term section below.


Sprawling surface high will slide off the Northeast Coast late
Sunday into Monday. Return southerly flow on the backside of the
surface high and building 500mb heights will continue the warming
trend across the Lower Great lakes through Tuesday. Monday, look for
highs to finally climb above normal with U50s to near 60F then
readings will top 60F everywhere Tuesday with low to M60s across the
region. Although, it will be significantly cooler near the lakes
shores with lake temperatures in the 30s on both Erie and Ontario.

Meanwhile, while we enjoy the nice warmup a cut off low will slowly
tracking across the deep south which overtime will meander northward
along the spine of the Appalachians. Simultaneously, a potent
shortwave is forecast to drop southeast out of the Canadian prairies
across the Upper Great Lakes. Per latest guidance, these two feature
are forecast to phase over the Tennessee Valley and Mid-Atlantic
inducing cyclogenesis with increasing chances for precipitation for
our region by Midweek. However, with the usual track and timing
issue as of right now have added chance POPs and increasing cloud
cover for Wednesday with slightly cooler daytime highs U50s/L60.


A lull in precipation will continue today before the next wave moves
across the terminals tonight and Thurday. MVFR cigs will hold on
this afternoon. As low pressure moves to the south of NYS tonight,
-SN will move across the terminals. SN will taper off across
 KIAG, KROC and KART as they are on the northern fringe of the
 snow shield. IFR conditions are expected tonight and into
 Thursday due to snow. Temperatures will slowly warm Thu
 afternoon and SN may mix in with RA with the exception of KJHW.
 Did not want to keep terminals at IFR all day Thursday even
 though -SN may be ongoing. Think it will be intermittent and
 TEMPOs may be the best action with a prevailing MVFR vsby/cig.
 -SN will taper off late Thursday afternoon and into Thu
  evening.  -SN will likely persist the longest at KJHW and


Friday...Mainly VFR with a chance of rain/snow showers.
Saturday...Mainly VFR.


A southwest wind will continue to taper off from west to east into
this evening. Tonight winds will turn to the north while increasing
into Thursday morning. Winds will reach SCA levels Thursday
afternoon across the southern shore of Lake Ontario. SCA levels may
be reached along Lake Erie however it looks marginal at this time.

A period of more tranquil conditions will likely come this weekend
into early next week as high pressure moves over the lower Great


MARINE...Small Craft Advisory from 2 PM Thursday to 9 PM EDT Friday for
         Small Craft Advisory from 11 AM Thursday to 2 PM EDT
         Friday for LOZ042.
         Small Craft Advisory until 11 PM EDT this evening for



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