Area Forecast Discussion
Issued by NWS Buffalo, NY

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118
FXUS61 KBUF 191454
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1054 AM EDT Thu Apr 19 2018

.SYNOPSIS...
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 wave will track just south of the Great Lakes
while merging with the upper-level trough Friday, producing periods
of snow showers and minimal accumulations through Friday. High
pressure will build across the region this weekend into early next
week finally brining drier weather and moderating temperatures.

&&

.NEAR TERM /THROUGH TONIGHT/...
Snow showers have blossomed across the eastern Great Lakes
this morning as cold air advection increases today. The
influence of moist cyclonic flow will continue under the upper-
level mean trough today and will support snow showers this
afternoon and evening with some lake enhancement. The best
chance of some minor snow accumulations of a half to 1 inch will
be in the typical snow prone higher terrain locations of the
western Southern Tier and the Tug Hill. Otherwise, outside of
the lake enhanced/upslope prone locations, expect a cloudy and
cool day, with high temperatures in the 30s.

Tonight, snow showers will likely maximize in sticking power this
evening over the higher terrain with the loss of solar insolation,
then diminishing into early Friday morning. This weakening will
occur as the 500 mb vort max on the back side of the mean trough
crosses the forecast area, with the attendant height rises and drier
air weakening and eventually ending the showers. Snowfall tonight
will likely be around 1 to 2 inches for the higher terrain
locations, while the lake plains locations see little if any snow
accumulation.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
On Friday a deep trough will begin to exit New England and move east
into the Canadian Maritimes. Cold northwest flow will be maintained
across the eastern Great Lakes, with synoptic scale low level
moisture slowly decreasing from west to east. 850mb temps of around
-9C will still support some modest lake effect snow showers in the
morning, aided by northwest upslope flow. The limited depth of
moisture and shallow inversion will keep the lake effect snow light,
with scattered snow showers and little accumulation in most areas.
There may still be a little better coverage of upslope snow showers
across the Tug Hill and western foothills of the Adirondacks in the
morning, with an inch or less of additional accumulation. The snow
showers will gradually taper off and end from west to east through
the day. Temperatures will remain well below normal, with highs in
the lower 40s on the lake plains and mid to upper 30s for higher
terrain.

High pressure will build into the western Great Lakes Friday night
as the trough in the Canadian Maritimes continues to move away from
the area. Cold northwest flow will continue to support some lake
effect clouds south of the lakes, but this should scatter out late
Friday night as drier air arrives. It will be a cold night, with
lows in the 20s everywhere except the immediate lakeshores.

Saturday through Sunday high pressure will bring dry weather with
abundant sunshine both days. High pressure overhead and weak
northerly flow at 850mb will prevent any bonafide warm advection,
but day to day airmass moderation will allow temperatures to trend
steadily upward. Expect highs in the mid to upper 40s Saturday, and
lower 50s on Sunday in most areas. Light north to northwest winds
will keep the south shores of Lake Ontario and Lake Erie cooler.
Lows Saturday night will still be chilly with good radiational
cooling conditions. Expect lower 30s on the lake plains and mid 20s
in some of the cooler interior valleys and east of Lake Ontario.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
High pressure surface and aloft will remain in control Sunday night
through Tuesday as the center of the high slowly drifts off the New
England coast. This will maintain dry weather into early next week,
with just some modest increase in clouds by Tuesday as southerly
flow increases. That same southerly return flow will bring more
robust boundary layer warm advection by early next week, allowing
highs to warm into the 60s in many areas Monday and Tuesday away
from any lake influences.

Later Tuesday night and Wednesday the GFS and ECMWF are in
reasonable agreement in moving a weak cutoff low over the southeast
states slowly northward towards the Carolina coast. Another northern
stream trough is forecast to evolve into a cutoff low over the
western Great Lakes by Wednesday, and will begin to interact with
the weak east coast low. The net effect will be to advect increasing
moisture northward into our region, with increasing chances of
showers by Wednesday. It will remain quite warm, with highs in the
60s again Wednesday away from lake influences.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Mainly MVFR conditions expected this morning with brief light snow
possible at the terminals. Snow showers will become fairly
widespread this afternoon, especially in upslope regions south of
the lakes with vsby occasionally below 2SM, with mainly MVFR
conditions outside of these.

Outlook...

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

&&

.MARINE...
Winds will increase today as a low pressure system moves off the New
England coast. Small craft conditions will develop from west to east
across the lakes today and linger well into Friday.

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

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 2 AM EDT
         Friday for LEZ040-041.
         Small Craft Advisory from 2 PM this afternoon to 8 PM
         EDT Friday for LOZ043-044.
         Small Craft Advisory until 2 PM EDT Friday for LOZ042.
         Small Craft Advisory from 5 PM this afternoon to 5 PM EDT
         Friday for LOZ045.

&&

$$

SYNOPSIS...Church
NEAR TERM...Church/HSK
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...Church
MARINE...Church



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