Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 210548
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1248 AM EST Tue Feb 21 2017

.SYNOPSIS...
High pressure will continue to provide our region with fair weather
through early afternoon Tuesday. A weak front will then cross the
area late Tuesday and Tuesday night with a period of rain showers.
Mainly dry weather will then return for Wednesday and Thursday
before low pressure moves into the Great Lakes Friday with the next
period of rain. Temperatures will remain well above average through
the week before colder air arrives next weekend.

&&

.NEAR TERM /THROUGH TODAY/...
Surface analysis this morning shows high pressure centered over
eastern Quebec extending south into New England and the Mid Atlantic
States. Satellite imagery showing clear skies across Central NY and
the North Country, with thin high clouds now moving into Western NY.
Thicker high clouds are poised just upstream across the central
Great Lakes.

Tonight the center of the surface high will shift further east
toward New England and the Canadian Maritimes while the axis of mid-
level ridging shifts across western NY. Mid/upper level warm
advection will increase overnight as the mid level ridge moves east
of the area, allowing high cirrus level cloudiness to increase from
west to east. Good early radiational cooling in this dry airmass
will allow temperatures to drop steadily this evening. Expect lows
to range from the upper 20s to lower 30s in far western NY to the
mid 20s for the Genesee Valley, and teens east of Lake Ontario. The
lows across far Western NY will occur by around midnight, with
rising temps late tonight as southerly winds increase.

The mid-level ridge and surface high will shift off the East Coast
on Tuesday making way for a weak cold front and mid level trough to
work its way toward western NY. Ongoing mid level warm advection
ahead of this system will bring thickening and lowering mid level
clouds during the day. There remains some timing differences in
model guidance, with the NAM and Canadian GEM several hours slower
with the arrival of showers than the GFS. Continued to go with a
timing between the GFS and higher resolution guidance, with showers
entering Western NY during the mid to late afternoon then spreading
quickly east through the rest of the area during the early evening.
Rain amounts will be light, with a tenth of an inch or so in most
places.

Southerly winds will increase ahead of the front on Tuesday,
boosting 850mb temps to around +8C. The warm advection and added
boost from southerly downslope flow will likely push temperatures to
well above guidance across the lake plains of Western NY, with upper
50s along the Lake Erie shore and Niagara Frontier east to Rochester
and the Genesee Valley. Increasing clouds will be the only thing
holding temperatures from going even warmer. Expect low to mid 50s
for the higher terrain of the Southern Tier, with mid to upper 40s
across the North Country.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
For those that have enjoyed the recent stretch of mild weather...
you are going to LOVE this period. A parade of Colorado lows...
otherwise referred to as `cutter storms`...will track by to our west
and keep a very mild (if not warm) flow in place across the Lower
Great Lakes. The airmass will originally be Pacific in nature...but
as if that were not enough...the mild air will be further modified
by an injection of warmth out of the Gulf of Mexico. This will
especially be the case as we head towards the end of the work week.
As a result of this scenario...temperatures will average at least 20
degrees f above normal. As for the day to day details...

An elevated front will push through our forecast area Tuesday night.
While the overall dynamics with this `frontal` passage will be weak
(little frontogenetic or jet induced forcing)...there will be a rich
plume of moisture in place immediately ahead of the boundary. This
should allow for a fairly widespread coverage of showers...but with
little QPF. Basin average rainfall will average under a tenth of an
inch...and will be focused over the first half of the night.
Meanwhile...temps will be above freezing...with lows ranging from
the low to mid 40s over the western counties to the mid/upper 30s
east of Lake Ontario.

There will be no real airmass change in the wake of the front...so
temperatures on Wednesday will be every bit as mild...if not
milder...than those from Tuesday. H85 temps in the vcnty of 8c will
support afternoon highs of 60 to 65 for the western counties. It
will be cooler east of Lake Ontario where highs will be closer to
50. The warmth will be assisted by weak mid level ridging and
clearing skies...which will allow for at least partial sunshine by
the afternoon.

The first of two `cutter` lows will pass by to our west Wednesday
night...while the weak ridging over our region will make its way to
New England. This will place our region within a region of deep
southerly flow...so temps will only settle into mid the 40s (nr 40
Ern Lake Ont region). Its conceivable that parts of the Srn Tier may
not fall below 50.

On Thursday...it will remain mild across our region despite the
presence of a weak cool front. The various guidance packages are in
disagreement as to whether the boundary will actually make it south
through our forecast area or will stall to our north...but given
the steady or subtle height rises...its possible that the boundary
will get hung up in the vcnty of Lake Ontario. Either way...H85
temps in the vcnty of 6/8c will once again support afternoon max
temps that will be in the 50s to near 60. This will especially be
the case over the Finger Lakes and Genesee Valley. Given the low
confidence of the frontal placement by Thursday afternoon...will
have to include low chc pops for widely separated shower activity.

A very robust shortwave working out of the southern Rockies late
Thursday and Thursday night will lead to significant cyclogenesis
over the central Plains. The consolidating and deepening surface low
will track to Missouri by daybreak Friday before moving to near
Chicago by Friday evening. A warm front extending east from this
deepening storm system will push north across our forecast area
during the course of the day Friday. This should generate scattered
showers at the very least..if not the likelihood for a two hour
period of rain. Will raise pops to high chc across the Srn Tier and
to likely for the counties near-east of lake Ontario. The bulk of
the rain should come during the morning and midday...then as the
warm front pushes north to Lake Ontario...H85 temps across the
western counties should soar to 10c! This would easily support
afternoon temps in the 60s...well above most guidance packages. If
skies were to clear enough to allow for some afternoon sun...some
Srn Tier bank thermometers could tickle 70...but that would be
assuming ideal mixing and insolation. In any case...it will be a
very mild afternoon for the wrn counties.

Friday night...the still deepening cyclone will track to Lake Huron
while its strong cold front will plow across southern Ontario to to
the Niagara River. Strong southerly winds ahead of the front will
keep very mild conditions in place across all of the forecast
area...with some sites form the Genesee Valley eastward probably
not falling below 50 for an overnight low. Any showers that will be
found over the region early in the night will become more common as
the front approaches...especially over the far western counties.

This should set the stage for a very windy day on Saturday.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
It will certainly be notably colder during this period as
temperatures will return to more seasonable levels. The change back
to winter will include some snow showers...especially in the
snowbelts east of the lakes where mesoscale processes (ie. lake
effect) will contribute to potentially significant accumulations.

As so often happens here during the cold season...the passage a deep
surface low to our west and north will mark the change in the
overall pattern across the country. Rather than having a trough in
the west and ridging in the east...a broad trough full of Canadian
air will dominate the Great Lakes region. Unfortunately...these
pattern changes are also usually marked by significant/damaging
weather events. This case may be no different.

When we open this period Saturday morning...a strengthening sub
990mb low will be pushing northeast from Lake Huron while its
powerful cold front will be bulldozing across western and north
central New York. The accompanying rain showers will be accompanied
by winds of at least 25 to 40 mph with the frontal passage...then
after a couple hours where winds will subside a bit...winds will
ramp back up...possibly as high as 50 mph. The storm track...
negative tilt to the supporting mid level trough...and suggested
subsidence all favor at least advisory criteria winds. The only
thing missing is a significant low level jet. Stay tuned.

Strong cold advection on the backside of the exiting cyclone will
send H85 temps to as low as -15c Saturday afternoon into MOnday.
This will be more than cold enough to promote lake effect snow
showers east of both lakes..with significant accumulations possible
east of Lake Ontario where an upstream connection and full fetch
will be likely. Outside of the lake effect areas...Sunday and Monday
will feature partly to mostly cloudy skies and scattered light snow
showers.

After temperatures fall from 50 Saturday morning in the wake of the
front...max temps will be in the mid 30s on Sunday and close to 40
for most areas on Monday. Mins through the period will be in the
20s.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
For the 06Z TAFS VFR flight conditions were found, and these flight
conditions should prevail through at least 21Z. At that time a line
of rain showers will be nearing the western TAF sites, with mainly
VFR flight conditions continuing through the light rain, though a
brief period of MVFR flight conditions is likely. Rain showers will
likely reach KART between 22Z and 01Z.

This cold front will cross the region this evening, with rain
showers tapering off late this evening, and early morning Wednesday.
There may be some IFR CIGS developing later tonight across the
Southern Tier, with patchy MVFR CIGS elsewhere behind the cold
front.

Light easterly winds this morning will become southwesterly this
evening, with speeds generally remaining 15 knots or less through
the TAF cycle.

Outlook...

Wednesday and Thursday...Mainly VFR.

Friday and Saturday...Periods of rain showers with MVFR and local
IFR. Windy on Saturday.

&&

.MARINE...
Northeast flow will remain in place this evening with some mild chop
along the south shores of Lake Ontario, but winds and waves will
remain well below small craft advisory criteria. While winds will
gradually freshen with a continued veering flow tonight, the flow
will be offshore and this will limit the risk for small craft
advisory conditions. A weak cold front will cross the lakes later
Tuesday with some rain showers. The lower lakes will be between
systems on Wednesday, with a light southwesterly flow expected.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...SMITH
NEAR TERM...HITCHCOCK/SMITH/THOMAS
SHORT TERM...RSH
LONG TERM...RSH
AVIATION...THOMAS
MARINE...SMITH



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