Special Weather Statement, NWS Buffalo, NY

Area Forecast Discussion
National Weather Service Buffalo NY
700 PM EDT Thu Apr 20 2017

.SYNOPSIS...
Showers and thunderstorms will continue through the night, ahead of
a cold front that will track eastward across the region. Some storms
may become strong to severe across the Southwestern New York State.
Behind this cold front, mainly dry conditions will persist across the
Eastern Great Lakes into the beginning of next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
Early this evening a warm front extends across the region with
notably warmer temperatures south of a Buffalo to Dansville
line. North of this boundary there are some showers and elevated
convection, with scattered showers and thunderstorms south of
this where surface temps are in the 60s with dew points in the
50s. The severe weather threat appears mainly confined to the
Western Southern Tier, where there is more surface based
instability in the warm sector. Wind profiles will briefly
support some stronger storms with gusty winds and small hail,
but this window will be narrow lasting roughly between 7pm and
10pm across the Western Southern Tier.

There is higher confidence that another round of moderate to
heavy rain will move across the entire area this evening.
Mesoscale guidance is in good agreement, with radar trends
supporting this guidance. Expect a general half inch to inch of
rainfall with locally higher amounts possible. This will result
in ponding of water on roadways in some areas, with a limited
risk for flooding in locations where heavier rain has already
fallen. Probably the greatest area of concern is the Buffalo
metro area, where rainfall amounts have already reached an inch.
Surface obs show a convergence boundary extending up Lake Erie
which has helped focus rainfall. It probably will not take much
more rainfall this evening to cause flooding in the typically
vulnerable areas in the Buffalo metro area. Area creeks will
also rise, but at this point are expected to remain below flood
stage since basin averages will be less than locally higher
totals.

A cold front will cross the region tonight, sending storms eastward.
As the storms end, and cooler air begins to push eastward into the
region some patchy fog will be possible. In total rainfall today and
tonight will range from a half to an inch across the So. Tier, and
North Country, with an inch to inch and a half along the thruway to
the Lake Ontario shoreline. Due to the convectiveness of this
activity, rainfall amounts will vary. Creeks and rivers should
remain in bankfull through this rain, but any outlier of heavier rain
could produce minor flooding.

For Friday a few rain showers will start the day across the Eastern
Lake Ontario region. This activity will end through the day as
colder and drier air pushes eastward behind the cold front. Clouds
will likely remain tough across the region, though some breaks of
sunshine will be possible. The clouds and cooler air aloft will only
yield highs in the 50s tomorrow, though some early morning lower
60s are possible across the northern Finger Lakes.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
Low pressure over Quebec will lift northeast with limited low level
moisture lingering across the north country. High pressure centered
over the Upper Mississippi Valley Friday night will begin to
build across western New York.

While a mid level trough within the northern branch of the split
flow will sweep across our forecast area on Saturday...surface high
pressure and relatively dry air in the mid and upper levels will
continue to promote dry uneventful weather. Model guidance continues
to hold precipitation associated with a low over the Southeast/mid-
Atlantic to our south across central Pennsylvania on Saturday and
Saturday night.

Temperature-wise look for a cool start to the period. Lows Friday
night within a few degrees of 40 with the interior southern tier and
north country seeing lows into the mid 30s. Cloud cover should
preclude any frost issues. Highs on Saturday will struggle to reach
the 50 degree mark.

High pressure will still dominate on Sunday/Sunday night with some
milder air beginning to overspread the region. Highs Sunday return
to more normal readings around the 60 degree mark. Temperatures
Sunday night fall back into the 30s. With clearing skies...patchy
frost could be possible across the interior sections of the western
southern tier.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Medium range models continuing to advertise a progressive zonal flow
pattern during this period. Surface ridging will continue the dry
but cool weather pattern as we start out Monday and Monday night.
After highs only in the 50s Monday, another cool night is expected
for the interior southern tier and north country Monday night with
lows in the 30s and possible frost issues.

The progressive pattern will send an initial wave over top the
southern ridge by Tuesday which looks to minor out and should
have little impact on our weather. A more vigorous system looks
to develop later in the period which will bring chances for
showers and possible storms back into the forecast for Wednesday
and Thursday. Substantial temperature moderation will bring
temperatures well above normal during the mid week period.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
At 21Z showers and isolated thunderstorms continue across WNY,
with fairly widespread IFR and an easterly wind along the
southern Lake Ontario shore, and spotty IFR elsewhere within
heavier shower activity.

Thunderstorms this afternoon will weaken across WNY, impacting the 4
TAF sites south of Lake Ontario. This activity will extend towards
KART and the north country late this afternoon and evening.

A more significant line of showers and thunderstorms will move
from Eastern Michigan and Ohio into Western New York this
evening. These should weaken, but still may result in a periods
of heavy rain and lightning at our terminal locations as it
moves through

Some patches of fog will form behind the convection tonight, that
will bring additional IFR flight conditions. This fog and rain
showers will end through the later portion of the night as high
pressure noses eastward towards the region tomorrow, with flight
conditions slowly improving.

Outlook...

Friday night...mainly VFR, some patchy fog/IFR across the So. Tier.

Saturday...VFR.

Sunday through Tuesday...Mainly VFR.

&&

.MARINE...
Easterly winds will maintain waves 3 to 5 feet on the western half
of Lake Ontario, with small craft advisories continuing. These winds
will shift to southerly tonight, ending the threat for SCA.

On Friday westerly winds will then flow across the eastern Great
Lakes. This will bring winds to 15 to 20 knots, with waves building
towards SCA levels.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...Small Craft Advisory until 2 AM EDT Friday for LOZ042-043.

&&

SYNOPSIS...THOMAS
NEAR TERM...APFFEL/THOMAS
SHORT TERM...LEVAN
LONG TERM...TMA
AVIATION...APFFEL/THOMAS
MARINE...THOMAS

Hazardous Weather Outlook
National Weather Service Buffalo NY
430 AM EDT Thu Apr 20 2017

NYZ001>003-010>013-019>021-085-210830-
Niagara-Orleans-Monroe-Northern Erie-Genesee-Wyoming-Livingston-
Chautauqua-Cattaraugus-Allegany-Southern Erie-
430 AM EDT Thu Apr 20 2017

This Hazardous Weather Outlook is for portions of western New York.

.DAY ONE...Today and Tonight.

Widespread showers and thunderstorms will move into western NY later
this afternoon and evening. Conditions will be favorable for a few
embedded strong to severe thunderstorms capable of producing damaging
wind gusts. This threat will be greatest across the Western Southern
Tier.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

This product, along with other watches, warnings, advisories, and
statements issued by the National Weather Service office in Buffalo
can be found on the internet at http://www.weather.gov/buf

NYZ004>008-014-210830-
Wayne-Northern Cayuga-Oswego-Jefferson-Lewis-Ontario-
430 AM EDT Thu Apr 20 2017

This Hazardous Weather Outlook is for portions of western and north
central New York.

.DAY ONE...Today and Tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

This product, along with other watches, warnings, advisories, and
statements issued by the National Weather Service office in Buffalo
can be found on the internet at http://www.weather.gov/buf

LEZ020-040-041-LOZ030-042>045-062>065-SLZ022-210830-
Upper Niagara River and Buffalo Harbor-
Lake Erie nearshore waters from Ripley to Dunkirk-
Lake Erie nearshore waters from Dunkirk to Buffalo-
Lower Niagara River-
Lake Ontario nearshore waters from the Niagara River to Hamlin Beach-
Lake Ontario nearshore waters from Hamlin Beach to Sodus Bay-
Lake Ontario nearshore waters from Sodus Bay to Mexico Bay-
Lake Ontario nearshore waters from Mexico Bay to the Saint Lawrence
River-
Lake Ontario open waters from the Niagara River to Hamlin Beach-
Lake Ontario open waters from Hamlin Beach to Sodus Bay-
Lake Ontario open waters from Sodus Bay to Mexico Bay-
Lake Ontario open waters from Mexico Bay to the Saint Lawrence River-
Saint Lawrence River from Cape Vincent to Ogdensburg-
430 AM EDT Thu Apr 20 2017

This Hazardous Weather Outlook is for portions of Lake Erie, Lake
Ontario and Saint Lawrence River.

.DAY ONE...Today and Tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

This product, along with other watches, warnings, advisories, and
statements issued by the National Weather Service office in Buffalo
can be found on the internet at http://www.weather.gov/buf

Special Weather Statement
National Weather Service Buffalo NY
459 PM EDT THU APR 20 2017

NYZ020-021-202130-
Cattaraugus-Allegany-
459 PM EDT THU APR 20 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN CATTARAUGUS AND
WEST CENTRAL ALLEGANY COUNTIES...

At 458 PM EDT, a strong thunderstorm was located near Allegany, or 8
miles northwest of Olean, moving east at 25 mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Olean, Allegany, Weston Mills, St. Bonaventure, Hinsdale, Portville,
Ischua, Humphrey, Vandalia and Haskell Flats.

This includes Interstate 86 between exits 24 and 27.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 4206 7862 4220 7862 4229 7830 4204 7830
TIME...MOT...LOC 2058Z 254DEG 24KT 4214 7857

Reynolds

Special Weather Statement
National Weather Service Buffalo NY
636 PM EDT THU APR 20 2017

NYZ019-202330-
Chautauqua-
636 PM EDT THU APR 20 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN CHAUTAUQUA
COUNTY...

At 635 PM EDT, a strong thunderstorm was located near Union City, or
18 miles southeast of Erie, moving northeast at 40 mph.

Winds in excess of 40 mph and half inch hail are possible with this
storm.

Locations impacted include...
Jamestown, Lakewood, Clymer, Long Point State Park, Jamestown West,
Busti, Celoron, French Creek, Sherman and Panama.

This includes Interstate 86 between exits 6 and 10.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4210 7976 4223 7937 4205 7921 4200 7923
      4200 7976
TIME...MOT...LOC 2235Z 243DEG 36KT 4192 7990

TMA

Special Weather Statement
National Weather Service Buffalo NY
637 PM EDT THU APR 20 2017

NYZ010-085-210000-
Southern Erie-Northern Erie-
637 PM EDT THU APR 20 2017

...AN AREA OF STRONG THUNDERSTORMS WILL AFFECT NORTHEASTERN ERIE
COUNTY...

At 634 PM EDT, strong thunderstorms were clustered over the Buffalo
metro area. These will produce heavy rainfall which will result in
ponding of water and localized flooding in low-lying areas.

In addition, more rainfall is expected later this evening which may
result in additional ponding and potentially more widespread
flooding. Motorists should exercise caution, and be alert for water
ponded on area roadways.

Locations impacted include...
Buffalo, Cheektowaga, West Seneca, Clarence, Lackawanna, Kenmore,
Depew, Amherst, Tonawanda and Lancaster.

This includes Interstate 90 between exits 57 and 49.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 4280 7887 4286 7890 4293 7890 4294 7891
      4297 7892 4297 7888 4306 7853 4280 7851
      4272 7894
TIME...MOT...LOC 2234Z 248DEG 3KT 4285 7879

Apffel

Special Weather Statement
National Weather Service Buffalo NY
741 PM EDT THU APR 20 2017

NYZ003-011>013-210030-
Livingston-Wyoming-Genesee-Monroe-
741 PM EDT THU APR 20 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN WYOMING...
NORTHWESTERN LIVINGSTON...SOUTHWESTERN MONROE AND SOUTHEASTERN
GENESEE COUNTIES...

At 741 PM EDT, a strong thunderstorm was located near Attica, or near
Batavia, moving east at 30 mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Chili, Batavia, Geneseo, Le Roy, Avon, Attica, Pavilion, Caledonia,
Scottsville and Churchville.

This includes the following highways...
 Interstate 390 between exits 8 and 10.
 Interstate 90 between exits 48 and 47.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 4283 7830 4301 7833 4314 7771 4280 7767
TIME...MOT...LOC 2341Z 266DEG 25KT 4290 7816

Reynolds