Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 161454
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
954 AM EST Mon Jan 16 2017

.SYNOPSIS...
After a mostly sunny morning, clouds will begin to increase through
the afternoon from west to east as a warm front lifts northward
through the Ohio Valley. Light precipitation will reach Western New
York this evening, spreading eastward across the Eastern Great Lakes
region tonight; and with surface temperatures around the freezing
mark there will likely be a period of light freezing rain. As the
warmer air floods northward Tuesday and Tuesday night the
precipitation will change over to plain rain.

&&

.NEAR TERM /THROUGH TONIGHT/...
This morning an area of high pressure is centered over the DELMARVA
and expanded along the eastern seaboard. Low pressure is found over
southern Kansas.

A milder southerly flow develops on the back side of the area of
high pressure today. The flow will remain weak, though the southerly
direction to the winds will begin to bring milder air northward,
with our highs this afternoon reaching into the mid to upper 30s
with MOS consensus suggesting a few spotty readings of 40/41. Cirrus
clouds will increase this afternoon from southwest to northeast.

Tonight, temperatures will begin to dip, especially across the
Finger Lakes region and east of Lake Ontario where clouds will not
be as thick initially. Look for overnight lows to drop to around 30F
across the So. Tier/Niagara Frontier...upper 20s Genesee Valley and
trending downward into the low 20s east of Lake Ontario. These
temperatures will pose a problem as the developing storm system over
the plains lifts northward to the Central Great Lakes region
tonight.

Moisture ahead of this storm system will lift isentropically across
our region tonight, with precipitation reaching the Southern Tier
this evening. Models are in good agreement that the low level dry
air should diminish pretty quickly this evening, allowing for
falling precipitation to reach the ground. The low level jet will
not be overly strong, and the weaker forcing will limit the overall
precipitation tonight, but we should still see several hundreds of
an inch of freezing rain, and possibly up to a tenth of an inch in
spots before warmer air noses northward and changes the
precipitation to plain rain late tonight with additional rain
accumulation through the event. The ground has a shallow frost depth
which could linger freezing rain at the surface for a few hours,
even after temperatures rise above freezing.

With the threat of freezing rain across WNY tonight we have issued a
freezing rain advisory. The North Country will likely remain dry
tonight.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Low pressure will slowly track from Eastern Michigan on Tuesday to
the Saint Lawrence Valley on Wednesday. For most areas in Western
New York this will result in a brief period of freezing rain Tuesday
morning with generally light icing. More significant icing is
possible across the Saint Lawrence Valley which will be just north
of the track of the surface low.

Precipitation will spread from southwest to northeast on Tuesday.
Expect surface temperatures to be near freezing when precipitation
starts in most areas. Temperatures should rise quickly in downslope
regions across the lake plains adjacent to the Chautauqua Ridge
during the day Tuesday. The wave is relatively weak with guidance
only showing 850mb winds increasing to about 40 kts. As a result
temperatures will probably be very slow to rise on Tuesday, with
highs on Tuesday cooler than most guidance, especially MOS based
guidance. Even with the slow rise in temperatures, expect any ice
accumulations should be less than a tenth of an inch in most areas
with temperatures starting off very close to freezing at the onset
of precipitation and then slowly rising as rain persists. One other
factor to consider is that the ground is frozen in most areas so
precipitation may freeze on contact even as surface temperatures
rise a degree or two above freezing. Precipitation amounts will
average between a quarter and a half of an inch.

The forecast is a bit more complex for the Saint Lawrence Valley
where surface temperatures are likely to remain below freezing much
longer with the track of the surface low likely to maintain a
northeasterly flow of below freezing temperatures well into Tuesday
night. However, the mid-level warm layer will only be +2 to +4 so
precipitation may fall as sleet at times which will limit icing some.
Expect ice accumulations up to a quarter inch, with the most
significant icing across northern portions of Lewis and Jefferson
counties and less ice in and south of Watertown.

A second shortwave originating from the northern branch of the jet
stream is forecast to cross the region late Tuesday night into
Wednesday. This will help push the surface low to the east and will
establish a southwesterly flow across the region Wednesday and
Thursday. Mid-level temperatures will still be quite warm, with
BUFKIT thermal profiles showing cloud tops beneath areas cold enough
to support dendritic snow growth. Meanwhile QPF is mainly generated
by low level lift which is likely due to upsloping. This typically
results in drizzle or just low cloud cover, with patchy fog possible.
Temperatures should generally be in the 30s on Wednesday, probably
just above freezing though some freezing drizzle cannot completely
be ruled out.

Model consensus tracks another shortwave to our north late Wednesday
night and Thursday, with a chance of rain or snow showers across the
North Country. Latest guidance suggests most other areas should be
dry, with some lingering cloud cover as moisture remains trapped
beneath an inversion. Temperatures will remain above normal, with
highs Thursday in the upper 30s to lower 40s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
There is very high confidence that temperatures will average well
above normal across our forecast area during this period...and for
that matter...into the final days of the month. An unusually strong
190kt H25 Pacific East Asian jet will continue to help flood the
Lower 48 with Pacific modified air. This powerful jet will be a
product of a highly anomalous tropical ridge centered near the
Hawaiian Islands and a closed low that has been persistent over
Alaska. For what its worth...a collection of ensembles even suggests
that the strength of the Hawaiian ridge has a once in a generation
return interval for this time of year.

This overlying pattern will keep a split flow in place over North
America...where a dominate sub tropical jet will be part of
amplifying ridge over the eastern third of the country. While
this impressive ridge will support very mild and relatively benign
weather for our region through this time frame...there will come a
time when the proverbial pendulum is going to swing the other way.
That will come as we come out of the weekend when the much discussed
ridge will move to our east. A gaping...wide open feed of tropical
moisture out of the Caribbean will make its way in from the
southeast ahead of a dynamic negatively tilted trough will then set
the stage for what will likely be a very rainy event for our region
Monday into Tuesday...but that is getting a little ahead of
ourselves.

As for the details of this Friday to Sunday period...
Ridging over the Great Lakes Thursday night and Friday will promote
mainly fair dry weather with temperatures Friday afternoon climbing
well into the 40s.

A weakening mid level trough is forecast to push north across our
region Friday night into Saturday. While this trough is not expected
to generate a lot of lift as it fills...feel that there should be
enough to raise pops to low chc. Given the weak thermal gradient and
forcing aloft...near sfc temps Friday night may lower enough for a
little more freezing rain...mainly for areas east of Lake Ontario.
What little forcing will be present during the nighttime hours should
further weaken on Saturday...so will only carry slgt chc pops while
keeping a fair amount of clouds in place. The mercury will climb a
few degrees higher for Saturday afternoon...with highs approaching
50 F over the western counties. These temps will be more than 15 deg
F above normal.

An amplifying ridge will pass across our region Saturday night and
Sunday. Once this feature passes...the door will be wide open for
GOMEX moisture to stream northwards to the Lower Great Lakes. While
dry weather be featured to end the weekend...some showers late
Sunday cannot be ruled out...especially over the far western
counties. Some widespread rain will then be possible Sunday night
into the start of the new work week.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
VFR flight conditions will remain in place today thanks to high
pressure centered over the DELMARVA. Expect light southerly winds
across the region and increasing high clouds from the southwest.

Tonight a storm system will track from the Plains to the southern
Great Lakes region, sending a period of precipitation northeast
across our region, with a start time between 06Z and 09Z across the
Southern Tier...and 15Z and 18Z across the Eastern Lake Ontario
region. Below freezing surface temperatures at the onset may allow
for several hours of freezing rain before surface temperatures warm
above freezing. Quickest change over will likely be across
KBUF/KIAG/KROC while KJHW/KART may hang onto the freezing rain a bit
longer. Expect flight conditions to deteriorate to MVFR and then IFR
at KJHW within the precipitation but hold until after 12z for other
sites.

Outlook...

Tuesday...Deterioration to MVFR/IFR with rain developing...and
possibly beginning as a brief period of freezing rain.

Wednesday...IFR with drizzle and fog.

Thursday...Mainly MVFR/VFR with a chance of rain and snow showers
east of the lakes.

Friday...Mainly VFR.

&&

.MARINE...
High pressure centered over the DELMARVA will continue to advance
off the east coast through the day. A light south to southwest flow
will develop to around 10 to 15 knots. A warm front will cross the
lakes Tuesday, and south to southeasterly winds will increase to 15
knots or so through the day. Higher waves will remain off shore of
both Lake Erie and Ontario through the day.

&&

.CLIMATE...
The main story for next week and beyond will be the extended
period of above normal temperatures not only in our region, but
for much of the eastern 2/3 of the nation. Over the next two
weeks, a strong closed low will remain parked over the Bering
Straits, forcing a strong Pacific East Asian jet to extend farther
east than normal. This will continue to bring a parade of Pacific
systems into the western United States, while also supporting
zonal flow and a flat ridge downstream across the central and
eastern part of the country. The westerly flow across the
continent will support strong Chinook warming off the Rockies,
with warmth spreading to the east coast and even well north into
southern and central Canada.

The warmth will last for another 12 days or so, but there is a
significant pattern change brewing beyond that. A Sudden
Stratospheric Warming event has just occurred in the northern
hemisphere. These events occur when planetary waves propagate
vertically into the stratosphere, with wave breaking and dampening
processes acting to rapidly warm the stratosphere over the high
latitudes and greatly distort the Stratospheric Polar Vortex.

This warming and disruption in the stratosphere has been shown in
numerous studies to slowly feed back into the troposphere, with a
strong tendency for high latitude blocking to increase about 2
weeks after the warming takes place. High latitude blocking
increases the ability of polar air to spread southward into the
mid latitudes, and increases the chances of cold and wintry
weather locking in for a longer period of time.

It appears the long range guidance is beginning to capture this
idea, with the GEFS and NAEFS ensembles suggesting a more highly
amplified flow starting late this month, with a ridge developing
over Alaska and the West Coast while a deep longwave trough
begins to establish across central and eastern North America. The
developing ridge in Alaska may also promote a period of cross
polar flow, draining frigid Siberian air into northern Canada.
GEFS ensembles also support a more negative NAO and AO pattern
towards the end of the month. Putting all this together, it
appears the pattern should become much colder and more wintry
around January 27-29. Past stratospheric warming events suggest
this cold pattern may last for quite some time, and may support
the potential for periods of well below normal temperatures by the
end of the month and first half of February. Stay tuned.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Winter Weather Advisory from 7 AM Tuesday to 4 AM EST
     Wednesday for NYZ007-008.
     Freezing Rain Advisory from 4 AM to 4 PM EST Tuesday for
     NYZ005-006.
     Freezing Rain Advisory from 1 AM to 1 PM EST Tuesday for
     NYZ003-004-013-014.
     Freezing Rain Advisory from 8 PM this evening to 10 AM EST
     Tuesday for NYZ001-002-010>012-019>021-085.
MARINE...None.

&&

$$

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



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