Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 161443
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1043 AM EDT Tue Oct 16 2018

.SYNOPSIS...
Cool and brisk conditions will continue today with some limited lake
effect showers east of Erie and Ontario. Another cold front will
bring more widespread rain showers on Wednesday, with it turning
cold enough for some wet snow across higher elevations Wednesday
night. Lake effect showers are then again expected Thursday with
cool temperatures then temperatures return back toward normal Friday
with mainly dry weather.

&&

.NEAR TERM /THROUGH TONIGHT/...
Expansive surface high pressure extends across much the western and
central states this midday with ridging extending across the Ohio
Valley and eastern Great Lakes. A surface low is tracking across
Ontario Province with a sharp cold front extending south over the
Upper Midwest states. This front will be the source of our next
chances of widespread rain showers later tonight. Until then, cold
air advection continues under a brisk westerly flow with 850mb
temperatures falling to around -4C. Although moisture continues to
diminish behind yesterdays cold front, models and radar trends
continue to support better development of some lake enhanced/effect
rain showers east Lakes Erie and Ontario as the airmass cools.

The surface high pressure will remain ridged across the Lower Great
Lakes today while the aforementioned surface low and cold front will
advance east across the Upper Great Lakes. The airmass will be quite
dry ahead of this next cold front with best moisture limited to
around 5kft, but there may still be just enough to combine with lake
induced instability to support a few scattered lake effect rain
showers. Off Lake Erie, any scattered showers that do develop would
move from the lakeshore of Chautauqua County late this morning to
near Buffalo by early afternoon as boundary layer flow backs to the
southwest ahead of the front. Off Lake Ontario, any scattered
showers over Oswego County will lift to near Watertown by afternoon.
Outside of these lake effect areas, the rest of western and north-
central New York will be dry, with some sunshine away from the lake
effect clouds. Highs will reach the lower 50s at lower elevations,
and mid to upper 40s across higher terrain. Southwest today and
continue to be brisk, with gusts of 20-35 mph.

Tonight, the aforementioned cold front will likely become occluded as
it approaches far WNY late. Forcing ahead of this front will both
enhance any on-going lake effect showers to the east of the lakes
while it should also bring chances for more widespread showers.
Lake effect showers will be directed on a southwest flow, before the
low level flow veers quickly to westerly. Once the flow becomes
westerly, expect the lake effect showers to become well organized,
with lake induced equilibrium levels rising above 10kft before 12z.
Low temperatures will dip into the lower 40s in most locations, with
some upper 30s across higher terrain. It will remain quite windy
overnight, especially across the Niagara Frontier and along the
lakeshores where winds will continue to gust in the 30-40 mph range.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The mid level trough axis will cross the eastern Great Lakes
Wednesday, with associated large scale ascent producing a few
scattered showers outside of lake effect areas. Lake effect rain
will be ongoing at daybreak Wednesday, and will continue through the
day with veering wind profiles forcing the most persistent rain to
be mobile through the day. Cold temperatures aloft will support deep
lake induced instability, with the best moisture, convergence, and
fetch in play for the Lake Ontario band.

Off Lake Ontario...expect an organized east/west band of rain across
the Tug Hill early Wednesday morning on westerly flow. A secondary
cold front will cross Lake Ontario during the morning, with veering
flow during the midday and afternoon taking the band of rain
southward across Oswego County and into Wayne/northern Cayuga
counties by mid to late afternoon. The band will be strongest during
the morning across the Tug Hill and Oswego County when moisture is
deepest, and convergence is enhanced by the approach and passage of
the secondary cold front. Lake effect rain showers will also
increase farther west across portions of Niagara/Orleans/Monroe
counties through the day as boundary layer flow veers to the WNW.

Wednesday night boundary layer flow will continue to slowly veer to
the NW. This will carry the main band of lake effect precipitation
slowly westward across Wayne county and the Finger Lakes and into
the Rochester area. It should be noted that many mesoscale models
take this band all the way to the west of Rochester by late
Wednesday night, but this is a commonly seen systematic bias in
mesoscale modeling and we don`t expect the main band to get that
far west. Model guidance continues to support a strong upstream
connection to Georgian Bay with this one dominant band, which will
support better organization and higher precipitation rates than in
other lake effect bands that develop. Other multiple bands will also
continue along much of the south shore of the lake to the west and
east of this one dominant band, producing scattered showers
overnight. Lake effect showers will continue through Thursday
morning southeast of Lake Ontario before diminishing in the
afternoon as warm advection rapidly lowers the inversion.

Off Lake Erie...East/west oriented lake effect rain showers
Wednesday morning will evolve into more of an upslope scenario as
boundary layer flow veers to the northwest by Wednesday afternoon.
This will focus most of the lake effect showers across the higher
terrain of the Chautauqua Ridge by Wednesday afternoon, where they
will remain through Wednesday night. The fetch off Lake Erie will be
much shorter than Ontario, and the overall synoptic scale moisture
and support will also be a little less favorable. With that in mind
expect a little less coverage of lake effect showers and lower
precipitation amounts as compared to Lake Ontario. There may be a
brief period of upstream connection to Lake Huron Wednesday night,
which may locally enhance the Lake Erie activity across Chautauqua
County. Any lake effect showers that remain Thursday morning will
quickly end as warm advection begins and inversion heights rapidly
lower.

As far as precipitation type goes, it will remain all liquid through
late afternoon or early evening Wednesday. Some wet snow will first
mix in across the higher terrain later Wednesday evening, with the
high terrain going to all snow overnight into early Thursday. The
boundary layer will be more stubborn to cool on the lake plains
given the strong flow off the warm lakes, but even here expect wet
snow to mix in late Wednesday night and Thursday morning away from
the immediate lakeshores. Any accumulation will be minimal, with a
nothing more than a spotty light coating on the grass across the
higher terrain and possibly in the more dominant band southeast of
Lake Ontario.

Thursday night will be dry as ongoing warm advection brings in
temperatures too warm to support any lake response.

As far as temperatures go, it will remain very chilly through the
midweek period. Expect highs Wednesday to reach the upper 40s to
around 50 on the lake plains, with low to mid 40s across higher
terrain. These highs are likely to be reached by midday, with slowly
falling temperatures in the afternoon. Lows Wednesday night will be
in the mid 30s on the lake plains and lower 30s across higher
terrain, with some 20s possible east of Lake Ontario. Windy
conditions and flow off the warm lakes will likely keep the majority
of the area where the frost/freeze program remains active just above
freezing with no frost. Highs Thursday will stay in the 40s, with
some 30`s across the higher terrain east of Lake Ontario.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
There will be a brief warm-up Friday and Saturday as the trough
reloads across the Upper Midwest, with a brief period of height
rises and warm advection spreading into the eastern Great Lakes.
Friday will be dry as high pressure moves east across the Mid
Atlantic with a ridge extending northward into our region. Warm
advection will push temperatures back into the mid to upper 50s,
with some lower 60s possible in the warmer spots from the Genesee
Valley into the western Finger Lakes.

Friday night and Saturday the next shortwave and associated cold
front will approach and cross the eastern Great Lakes, with
increasing chances of rain showers. Cold advection behind the cold
front will then set the stage for more lake effect rain showers east
of the lakes by Saturday afternoon, focusing southeast of the lakes
Saturday night as boundary layer flow becomes northwest.

A deep trough will again become established later Saturday night
through Sunday across the eastern Great Lakes and New England. This
will support more northwest flow lake effect, with some wet snow
again mixing in as temperatures drop to below normal. Another
clipper will cross the Great Lakes Monday with a chance of a few
showers, which may mix with wet snow in the morning.

Highs Sunday and Monday will be back into the 40s, with lows in the
30s both days in most areas and 20`s across the North Country.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
VFR lake effect clouds will continue streaming east/southeast of
Lakes Erie and Ontario late this morning. Radar is only showing some
scattered light showers southeast of Lake Ontario but we continue to
expect better shower development during the midday. This will
initially be south of KBUF/KART but backing flow to the southwest
will bring chances for some lake effect showers to those terminals
around 18z. Patchy MVFR ceilings are possible for a time this
morning as the airmass further cools. The west flow will back to the
southwest this afternoon in advance of an upstream cold front
forecast to drop southeast out of Ontario Province for late tonight.
Expect gusts of 20 to 30 knots through the daylight hours today then
increasing a bit higher tonight as the front further approaches.

The approach of the front will enhance lake bands east of the lakes
tonight with showers likely across KART and perhaps KBUF while also
bringing a chance for more widespread showers away from the lake
effect toward 12z Wednesday. Cigs tonight will generally be mainly
VFR but some MVFR or even IFR is possible in the higher terrain
including KJHW especially towards 12z Wednesday.

Outlook...

Wednesday...Mainly VFR except east of Lake Ontario where lake effect
rain showers will be accompanied by MVFR cigs.
Thursday and Friday...Mainly VFR.
Saturday...MVFR to VFR with some showers likely.

&&

.MARINE...
Strong cold air advection and deepening surface low tracking well to
the north of Lake Ontario continues to support gusty winds on the
lower Great Lakes this morning where Small Craft Advisories are in
place. Lake Effect clouds and rain showers will be found on the
lakes today and tonight.

Westerly winds will support lingering Small Craft Advisory
conditions on the lower Great Lakes through much of this week.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 8 AM EDT Thursday for LEZ040-041.
         Small Craft Advisory until 8 PM EDT Wednesday for LEZ020.
         Small Craft Advisory until 8 PM EDT Thursday for
         LOZ043>045.
         Small Craft Advisory until 8 AM EDT Thursday for LOZ042.

&&

$$

SYNOPSIS...Smith
NEAR TERM...Smith
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...Smith
MARINE...Smith


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