Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 141421

Area Forecast Discussion
National Weather Service Buffalo NY
1021 AM EDT Sat Oct 14 2017

A broad ridge dominating the eastern half of the country will help
to supply our region with fairly nice weather today...although a
shower or two cannot be ruled out across the Niagara Frontier and
east of Lake Ontario. Temperatures will climb well above normal
today and stay there through most of Sunday. A strong cold front
will then bring a dramatic end to this bout of warmth late
Sunday...with strong winds and possibly some thunderstorms. The
notably colder air in the wake of the front will then set the stage
for some lake effect rain showers on Monday.


It will be a fairly pleasant day across the region a
broad ridge over the eastern half of the country will supply us with
weather more typical of early September rather than mid October. The
only potential fly in the ointment will be a weak baroclinic zone
that will extend from the Canadian shores of Lake Ontario to the
Thousand Islands region. The corresponding surface boundary could
strengthen during the course of the day...high pressure in the vcnty
of the Canadian maritimes will move further out to sea...thus
allowing stronger warm advection between H925 and H7. Will continue
to carry low chance pops for the afternoon across the North Country,
and also across the Niagara Frontier in closer proximity to the
stalling boundary.

It will be pleasantly mild this H85 temps that will
climb to between 10 (North Country) and 12c will support high
temperatures that will range from the upper 60s to lower 70s. These
readings will be 10 to 15 degrees above normal mid October values.

Tonight...a robust shortwave will cross the Upper Mississippi Valley
and energize an inverted surface trough that will already be in
place from the central plains to the Upper Great Lakes. In fact...
disorganized low pressure within this surface trough will become
organized overnight...eventually deepening to under 1000mb in the
vcnty of Lake Huron by Sunday morning. This is several millibars
`weaker` than previous model runs with the track being further to
the southeast...thus closer to our forecast area. Meanwhile...the
approaching storm system will lead to a northward bulge in the mid
level ridge...and this will help to provide us with a dry night.
Again...the exception could be during the evening hours when a
shower or two will be possible north of the Tug Hill.

The scenario outlined above will result in winds that will veer to
the south and freshen during the course of the night...thus
encouraging a non diurnal temperature trend as the mercury should
bottom out before midnight. Mins will range from the upper 50s
across parts of the Southern Tier and over Lewis County to the mid
60s across the lake plains. These temperatures will average 20
degrees above normal. The unfortunate thing about this is that when
we experience such anomalous temperature departures (esp at
night)...we usually find ourselves just ahead of a deep storm system
with a strong cold front...with threatening winds at our doorstep.
This case will be no different.


Sunday will be an active weather day, with most of our issues
stemming from strong winds. The day will start off with the region
solidly in the warm sector. There may be a few breaks of sunshine
through early afternoon before clouds increase ahead of an
approaching cold front. Temperatures will soar again, with highs in
the mid to upper 70s in most areas, with the I-90 corridor
from Rochester to Syracuse likely to reach 80.

A strong cold front associated with a vigorous shortwave and
strengthening low pressure across southern Ontario will enter
Western NY early to mid afternoon and then race to the Eastern Lake
Ontario region by early evening. There will be a strong SSW flow
ahead of this front with a 50 kt LLJ, however in the warm air
advection flow this is not likely to mix fully to the surface with
pre-frontal gusts of around 40 mph. The bigger concern is that there
will likely be a brief period of stronger winds immediately behind
the front which will last only an hour or so. This is because of
steepening low level lapse rates and subsidence just behind the
front, especially near the lakeshores where water temperatures are
still in the 60s. 00Z model guidance has slightly stronger winds
with BUFKIT profiles showing gusty winds just behind the front. The
strongest winds will be east and northeast of the lakes, including
the Niagara Frontier and Eastern Lake Ontario regions. In these
locations peak gusts in excess of 50 mph are possible behind the

In addition to the wind, strong convergence along the advancing cold
front, strong mid level DPVA from the approach of a strong mid level
trough, and strong upper level jet dynamics will come together to
produce a band of strong ascent along the cold front. This should
result in a fairly solid band of showers moving from west to east
across the area, entering Western NY by early to mid afternoon, then
racing to the eastern Lake Ontario region by early evening.

Model guidance continues to develop 300-500J/kg of SBCAPE just ahead
of the cold front. This may allow a few scattered thunderstorms to
develop along the cold front. With or without thunder, there may be
a band of convective showers along the cold front. Given the very
strong wind fields aloft, downdrafts and precip loading in any line
of heavy showers may transport gusty winds to the surface at a
minimum, with damaging winds a low, but non-zero possibility.

The cold frontal showers will end quickly from west to east Sunday
evening. A dry slot initially will give way to some limited wrap
around moisture late Sunday night. Increasing lake induced
instability will bring a chance of lake effect rain showers
overnight southeast of the lakes. It will turn sharply cooler, with
temperatures falling into the low to mid 40s by daybreak Monday.

On Monday lake effect rain showers will continue southeast of the
lakes. Despite the very chilly airmass, a relatively dry synoptic
scale background and short northwest fetch will keep coverage and
amounts limited. Highs will only be in the lower 50s at lower
elevations with mid to upper 40s across higher terrain. Any rain
showers will end by Monday night when a high pressure ridge builds
from the Appalachian mountains into Western New York. This will also
result in good radiational cooling conditions Monday night with
chilly (and possibly below freezing) temperatures.


The period will feature a rather pleasant fall pattern with mainly
dry weather and gradually warming temperatures. Model consensus
tracks a shortwave trough across Quebec on Tuesday which is likely
to keep any showers to our north with only a slight chance showers
will clip the Saint Lawrence Valley. This will result in a breezy
day on Tuesday with temperatures topping out in the upper 50s to
lower 60s.

After this high pressure across the mid-Atlantic states will ridge
into the region with dry weather and slightly warmer temperatures
for Wednesday. Model guidance diverges after this, with the 12Z GGEM
digging a trough across the region while the ECMWF/GFS guidance
strengthen a broad Atlantic ridge into the region. Given continuity
and model track record the forecast favors the latter solution which
would result in a return much above normal temperatures for the end
of the week. By Friday, temperatures should warm into the upper 60s
to lower 70s in most locations.


While high pressure extending back across our region from the
Canadian maritimes will maintain generally fair weather across our
region today, a good amount of cloud cover will remain. CIGS will be
VFR for the bulk of the area with a few exceptions. Across the
western Southern Tier, low stratus will continue to bring IFR
through at least early afternoon before slow improvement late. Some
MVFR will be found east of Lake Ontario through early afternoon. A
few light showers may move into the Niagara Frontier and North
Country late today, but VSBY will remain VFR.

Tonight...mainly VFR conditions will be found across western and
north central New York as a strong cold front will approach from the
Upper Great Lakes. The only issue could be some low level wind shear
across the Southern Tier.


Sunday...VFR in the morning, then MVFR conditions in the afternoon
and evening with strong winds and the potential for thunderstorms.
Monday...MVFR/VFR. A chance -SHRA SE of the lakes.
Tuesday and Wednesday. VFR with local AM valley fog.


Gale warning now in effect for Lake Ontario.

A southerly flow over the Lower Great Lakes this morning will weaken
during the midday and afternoon...becoming variable in nature for a
few a the surface pressure gradient will continue to
relax. This should allow for fine late season conditions for
recreational boating...although residual southerly winds early this
morning will result in some choppy conditions for the Lake Ontario
nearshore waters north of Mexico Bay. Otherwise...conditions today
will be favorable for late season boaters.

Conditions will deteriorate over the Lower Great Lakes late tonight
and particularly on a deepening storm system will track
from the Upper Great Lakes to western Quebec. A cold front extending
south from this relatively strong storm system will plow across the
region Sunday afternoon. While there will be the chance for gusty
thunderstorms with the frontal is a guarantee that
winds will dramatically increase to near gale force. This will
especially be the case on Lake Ontario where a gale watch has been
upgraded to a gale warning. After collaborating with the CLE
office...will maintain the gale watch for Lake Erie.

The strongest winds are forecast to be over the region Sunday
afternoon and the first half of Sunday night. High pressure over the
southern plains late Sunday night will then extend northeast to the
Lower Great Lakes...and this will result in a steady weakening of
the winds through Monday night.


A strong cold front will cross Lake Ontario late Sunday
afternoon. Southwest winds will increase ahead of the front
through the day Sunday, then become west and increase further to
near gale force early Sunday evening, bringing significant wave
action to the entire NY shoreline. Winds will then become
northwest and quickly diminish late Sunday night and Monday

The Lake Ontario level is several feet lower than late spring,
and is about a foot above normal for the month of October. The
lower lake level reduces the risk of flooding along the
lakeshore even on windy days. However, the lakeshore is still
very fragile and unstable in many areas following the heavy
erosion from earlier this year. With this in mind, a Lakeshore
Flood Watch is still needed due to the potential for more
shoreline erosion Sunday night from the period of high wave


NY...Lakeshore Flood Watch from Sunday evening through Monday
     morning for NYZ004>007.
     Lakeshore Flood Watch from Sunday evening through late Sunday
     night for NYZ001>003.
MARINE...Gale Warning from 6 PM Sunday to 2 AM EDT Monday for
         Gale Warning from 4 PM to 11 PM EDT Sunday for LOZ042-062.



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