Area Forecast Discussion
Issued by NWS Buffalo, NY

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FXUS61 KBUF 011559
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1059 AM EST Wed Mar 1 2017

.SYNOPSIS...
Unseasonably mild air will remain across the region
today, with temperatures peaking in the mid 60s to lower 70s in most
areas this afternoon. Low pressure crossing Southern Ontario and its
trailing cold front will bring widespread showers and scattered
thunderstorms this afternoon. Following the cold front, much more
typical late winter temperatures and some limited lake snows will
return for the end of the week, before another warmup arrives in
time for Sunday and early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface analysis shows a 992mb low centered near Lake Huron late
this morning with a trailing cold front extending southwest to
Southern Michigan and into Indiana. An unseasonably warm and moist
airmass is in place across New York State within the warm sector of
the area of low pressure. Temperatures are running into the upper
50s to low 60s with dewpoints in the low 50s. Only a few scattered
showers remain on the radar for much of western and central NY in
the wake of earlier more widespread showers and thunderstorms. More
shower activity will shift into the western Southern Tier late this
morning from western PA. A tight pressure gradient has also brought
gusty south to southwest winds. This strengthening of the low level
flow will resulting in good mixing and should allow temperatures to
surge into the mid and upper 60s across most of the area by this
afternoon, with highs in the lower 70s more likely from the Genesee
Valley eastward across the Finger Lakes. These temperatures will be
at or above record levels. The gusty southwest winds will however
also bring onshore flow to the Niagara Frontier off the cold lake
waters will help keep highs confined to the upper 50s and lower
60s.

By mid to late afternoon, the surface cold front and its parent mid
and upper level shortwave will be approaching our region. Increasing
large-scale forcing attendant to these features will interact with
our warm and moist airmass, with mesoscale models showing a second
round of convection likely initiating along a lake breeze boundary
east of Lake Erie, then intensifying and spreading northeastward
across the remainder of the region through the early evening hours.
The previously mentioned lake breeze shadow should help keep much
of the thunderstorm activity south and east of the Niagara Frontier.
Dependent upon the exact degree of destabilization realized prior to
its development, this second round of convection could well prove to
be our best chance for some stronger to potentially severe storms,
which will certainly remain possible given the very strong wind
fields with SPC mesoanalysis showing 0-6km Shear to 70kts. Mesoscale
guidance shows MUCAPEs will run less than 1000 j/kg resulting in a
High Shear/Low CAPE environmental with storms being dynamically
forced. With this in mind, SPC has a marginal to slight risk of
severe in place across much of our forecast area mainly south of
Lake Ontario, with strong damaging wind gusts the primary severe
weather threat.

Tonight, the surface cold front will cross western and central
New York. Incoming cold air will steepen low level lapse rates
in the presence of a lingering 50+ knot low level jet. This will
allow for gusty winds to reach Advisory levels of 50-55 mph
overnight. A Wind Advisory is therefore in effect for all
counties in the forecast area overnight. Will evaluate the 12z
guidance for potential of reaching High Wind Warning criteria on
the dayshift today. The incoming cold air will also increase
lake induced equilibrium levels briefly to around 7kft which
will help to develop some lake effect snows east of the lakes
overnight. Accumulations from these snows will range 1-2 inches
mainly on the higher terrain. Temperatures will sharply
overnight with Lows bottoming out in the low to mid 20s. The
combination of these low temperatures and the gusty winds will
bring wind chills around the single digits above zero by
daylight Thursday.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The strong surface low over eastern Quebec Thursday morning will
quickly move east into the Canadian Maritimes through the day. Wrap
around moisture and weak ascent associated with the mid level trough
will still be in place early, but will quickly pull away by late
morning. Expect snow showers in most areas at daybreak, with the
best coverage across the higher terrain of the Chautauqua Ridge and
east of Lake Ontario from modest lake enhancement and upslope flow.
This may produce up to an inch of accumulation across higher terrain
in the morning, with a dusting elsewhere. All of this quickly ends
by afternoon with a return to at least some sunshine as a much drier
airmass quickly builds into the Lower Great Lakes.

Winds will remain strong in the morning with around 50 knots aloft
in the cold advection in the wake of the departing surface low. By
Thursday morning boundary layer flow will be veered westerly or even
WNW, which typically brings the strongest wind gusts to the
southeast corner of Lake Ontario, and also across the higher terrain
of the Finger Lakes and interior Southern Tier. A wind advisory will
remain in place in these areas through 18Z before winds taper off in
the afternoon as the pressure gradient and winds aloft relax.
Temperatures will be dramatically colder than today, with highs in
the lower 30s on the lake plains and upper 20s higher terrain.

Thursday night and Friday a deep longwave trough will take up
temporary residence across the Great Lakes and Northeast. A weak
clipper low will pass by to our south through PA. The 00Z NAM seems
way overdone with the intensity of this system, and have sided with
the much weaker GFS/ECMWF solutions. This may bring a few light snow
showers to the western Southern Tier, with a few snow showers
elsewhere possible in weak northwest flow lake effect. All of this
should remain very light, with any accumulations generally an inch
or less. Expect lows Thursday night in the lower 20s, with teens
across the North Country. Highs Friday will be in the mid to upper
20s in most areas.

Friday night the weak clipper moves off the east coast. Cold
northwest flow may support a few scattered snow showers, especially
southeast of the lakes but again amounts will be very light with the
dry nature of the airmass preventing a significant lake response.
Temperatures will be colder than we have seen in quite some time,
with lows in the lower teens in most areas and single numbers for
the North Country.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
A northwest flow will keep temperatures cold into Saturday and aid
in the continuation of some lingering light lake effect snow
southeast of Lakes Erie and Ontario. Temps will continue below
normal, with highs in the 20s for most.

Warm advection will increase Sunday as the mid level trough moves
east into the Canadian Maritimes and a ridge progresses east across
the Ohio Valley and Great Lakes. Light scattered snow showers are
possible in advance of a weak warm front that will cross the area on
Sunday, and snow will transition to rain as temps rise with passage
of the front. Another stronger warm front will bring a better chance
of rain showers by later Monday. Temperatures will warm to above
normal again for Sunday afternoon through Tuesday.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
A break in precip is in place late this morning behind earlier
showers and thunderstorms. This break has allowed conditons to
improve back to VFR. Low pressure near Lake Huron has brought a
tight pressure gradient to western and central NY with gusty south
to southwest winds.

A second round of showers and scattered possibly strong storms is
expected to develop east of Lake Erie in advance of an approaching
cold front this afternoon. This is then expected to expand
northeastward impacting KJHW to KROC then KART as the line of storms
shifts east through early evening. Expect that KIAG and KBUF largely
stay north and west of the storms due to a strong flow off Lake
Erie. MVFR/IFR is possible with heavy rain/locally gusty winds in
the storms. Tonight, there will be an overall improvement to VFR
across the the forecast area behind the cold front but winds will
become very gusty overnight to around 40kts as cold air moves in
behind the cold front. This colder air will bring some developing
Lake Effect snow showers east of the Lake which is expected to
impact KJHW late tonight with lower VSBY.

Outlook...

Thursday and Friday...Scattered to numerous snow showers with areas
of MVFR/IFR.
Saturday...VFR/MVFR with a chance of snow showers southeast of Lake
Ontario.
Sunday...VFR/MVFR with a chance of rain and snow showers.

&&

.MARINE...
As low pressure tracks east across Southern Ontario province this
afternoon, southerly winds will become westerly following the
passage of an attendant cold front by tonight. The cold air on these
west winds will increase wind speeds to gale force range on both
Lakes Erie and Ontario this evening through the late overnight on
Lake Erie, and from this evening through Thursday afternoon on Lake
Ontario. Winds will slacken on Thursday night, go through a cycle of
light night winds and brisk afternoon winds during Friday and
Saturday, then southeast to east on Sunday in anticipation of the
next low pressure system.

&&

.HYDROLOGY...
The Black River will maintain high levels through the weekend. No
flooding is expected through this afternoon with the river expected
to steadily fall even though it will remain above action stage.

After this, low pressure will again track to the north and bring
more much above normal temperatures and a period of rain. Although
the previous system melted a lot of the snow pack, there is still a
significant snow pack in place across the Tug Hill and the Western
Adirondacks. Run-off from snow melt will combine with rain from this
system to cause the Black River and its tributaries to rise again
late this week. The Boonville and Watertown forecast points are of
greatest concern, where there is a potential for flooding starts
late Wednesday night through Friday. Based on this, have issued a
Flood Watch for Lewis and Jefferson counties, with river flooding
the primary concern.

&&

.EQUIPMENT...
The KBUF radar is down due to equipment issues and will remain so
through at least late today and quite possibly through the end
of the week...depending upon how quickly replacement parts arrive
and how well repair efforts go.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Wind Advisory from 4 PM this afternoon to 7 AM EST Thursday
     for NYZ001>003-010>012-019-085.
     Flood Watch from 7 PM EST this evening through Friday morning
     for NYZ007-008.
     Wind Advisory from 7 PM this evening to 1 PM EST Thursday for
     NYZ004>008-013-014-020-021.
MARINE...Small Craft Advisory until 6 PM EST this evening for LEZ040-
         041.
         Gale Warning from 6 PM this evening to 4 AM EST Thursday
         for LEZ040-041.
         Small Craft Advisory until 6 AM EST Thursday for LEZ020.
         Small Craft Advisory until 6 AM EST Thursday for
         LOZ030.
         Gale Warning from 7 PM this evening to 10 AM EST Thursday
         for LOZ042>045-062>065.

&&

$$

SYNOPSIS...SMITH/WCH
NEAR TERM...RSH/SMITH/WCH
SHORT TERM...HITCHCOCK
LONG TERM...HITCHCOCK/SW
AVIATION...RSH/SMITH/WCH
MARINE...RSH/SMITH/WCH
HYDROLOGY...APFFEL
EQUIPMENT...JJR



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