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Area forecast discussion
National Weather Service Buffalo New York
115 PM 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 New York 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 Storm Prediction Center 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, Storm Prediction Center 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 Saturday 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 40-50 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 and
the Eastern Lake Ontario region.

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. 12z model
consensus keeps the majority of quantitative precipitation forecast with this system to our south,
perhaps just clipping the western southern tier on Thursday night
and into Friday morning. In addition to this, expect that the
moisture with the clipper low will help generate some lake effect
snow southeast of Lake Ontario. 850mb temps will fall to around -17c
which should support lake induced instability when combined with the
limited synoptic moisture. This is not captured well by guidance, so
pop/quantitative precipitation forecast grids were modified to show two areas of precipitation
Thursday night...one with the clipper low and one due to lake
effect. Lows on Thursday night will be in the lower 20s across the
lake plains with teens elsewhere.

On Friday, moisture from Lake Huron may bring some general snow
showers to the region, though model guidance differs considerably
concerning the details of this. Snowfall amounts will be light, with
uncertainty in location resulting in mainly chance probability of precipitation except
southeast of Lake Ontario where snow showers should be more
widespread due to lake enhancement.

Colder air will build into the region behind this system Friday
night through Saturday night. This will result in generally light
lake effect snow southeast of the lakes Friday night and Saturday
until a surface high finally builds across the region on Saturday
night. Following record warmth, it will feel especially cold going
into the weekend. Model guidance is in good agreement, with little
doubt that temperatures will be well below normal. Highs on Saturday
will only be in the lower to mid 20s in most areas, with highs in
the teens possible across the north country where the core of the
cold air will drop across. Slightly warmer mid-level air will build
in from the southwest Saturday night, but the high should allow for
good radiational cooling conditions. Most areas should drop well
into the teens, with single digits across and even some below zero
temperatures expected across the Eastern Lake Ontario region.

&&

Long term /Sunday through Tuesday/...
during Sunday and Monday...surface-based ridging initially over our
area will slide eastward and off the Atlantic coastline...while low
pressure develops over the northern plains states...then lifts into
western Ontario province. The resulting warm air advection regime
across our region will drive our temperatures back up to well above
normal levels by early next week...and will also help to generate
a general chance of some light precipitation...with scattered snow
showers or a rain/snow shower mix changing over to all rain by Monday
as temperatures steadily warm.

Better chances for rain showers will then arrive for Monday night
and Tuesday as the aforementioned low moves to the vicinity of James
Bay and sweeps its trailing cold front toward...and eventually across...
our region. Much warmer than normal temperatures will continue up
until the passage of the cold front...with readings then falling
back closer to (but still remaining a bit above) seasonal averages
through the rest of the period as a cyclonic flow of colder air
overspreads our region. With the cyclonic flow and at least some
wraparound moisture likely to be in place...somewhat lower chances
of rain/snow showers will also persist across the region Tuesday night
into Wednesday.

&&

Aviation /18z Wednesday through Monday/...
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 New York 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 visibility.

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 evening, but temperatures are
well above normal, and will remain so through this evening as
an area of strong low pressure tracks to the north of the area.
Although a 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 late tonight and through Thursday.
The Boonville and Watertown forecast points are of greatest
concern, where there is a potential for flooding starts late
tonight through Friday. Crests are expected to be close to flood
stage. A Flood Watch remains in effect for the Black River
basin.

&&

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...
New York...High Wind Warning until 7 am EST Thursday for nyz001>004-
010>012-019-085.
High Wind Warning from 10 PM this evening to 7 am EST Thursday
for nyz007.
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
nyz005-006-008-013-014-020-021.
Marine...Small Craft Advisory until 6 am EST Thursday for lez020.
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
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...apffel/Hitchcock
long term...jjr

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