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Area forecast discussion 
National Weather Service Buffalo New York
948 PM EST sun Dec 28 2014

high pressure will build across the Great Lakes through Monday. This
will bring cooling temperatures which will help it feel much more
like middle-winter through the coming week with mainly dry conditions
outside of a chance of some weak lake effect snow showers. Better
chances for lake effect snow arrive by late week.


Near term /through Monday/...
skies are clearing in the west with some middle level clouds moving
through the Eastern Lake Ontario counties. Expect most locales in
the forecast area to experience some clear early tonight...only to
see a return of cloudiness with the passage of a secondary cold
front later tonight.

A continued slow cooling process continues tonight as southern
extent of Ontario wave passes across the region. Models continuing
to show a subtle secondary cold front sliding across the lower lakes
overnight. Initially marginally supportive lake surface to 850 mb
temperature gradient slowly increases as the cold air advection
continues...with simple Delta ts eventually yielding better
instability across the lake tonight. However...a vast amount of dry
air above shallow inversion will greatly limit lake processes. This
should limit precipitation potential to just scattered snow
showers/flurries with little if any accumulation...perhaps even some
freezing drizzle with moisture profiles showing shallow moisture
displaced well below the prime dendritic snow growth zone.

850 mb temperatures dropping to near -15c Monday. This will result
in a cold day Monday...but with air mass rather dry and low
inversion heights...looking for at least partial sunshine with a few
flurries within any pockets of stratocu with a cloud layer residing
around -12c. High temperatures generally in the middle to upper 20s.


Short term /Monday night through Wednesday/...
the first 24 hours or so of this period will be characterized by a
progressively colder but also fairly dry northwesterly to west-
northwesterly flow across the Great Lakes and northeast. Coupled
with the rather low capping inversion that will be in place...this
should merely translate into partly to mostly cloudy skies and some
scattered flurries for much of the region. The one exception to this
will be across areas east-southeast of Lake Ontario during
Tuesday...where a somewhat more favorable moisture and a slightly
higher cap should allow for at least some scattered nuisance-type
lake effect snow showers.

Tuesday night and Wednesday...the low-level flow across our region
will slowly back to westerly and then west-southwesterly as high
pressure initially situated along the Front Range of The Rockies
builds southeastward into the Southern Plains...and as broad low
pressure slides from north central Canada into Hudson Bay. At the
same time...850 mb temperatures will remain plenty cold enough for a lake
response and synoptic-scale moisture will also increase a little.
Coupled with a bit of bump in inversion heights and an increasing
fetch across the lakes...this should allow for a somewhat better
opportunity for lake effect snow showers east and eventually east-
northeast of the lakes...particularly downwind of Lake Ontario where
lake effect parameters now appear favorable enough for a likelihood
of snow along with some accumulations of a couple inches or so about
every 12 hours. Outside of the Main Lake effect areas...conditions
should just be dry and cold with a few flurries.

Temperature-wise...slow but steady cold air advection will result in
850 mb temperatures initially in the -12c to -16c range at the start of the
period falling to between -16c and -18c by Tuesday night and
Wednesday. Under this regime...daytime highs initially in the middle to
middle to upper 20s on Tuesday will fall back to the lower and middle 20s
by Wednesday...while nighttime lows dip into the middle and upper teens
south of Lake Ontario by Tuesday night...with even colder readings
of around 10 above found across the north country.


Long term /Wednesday night through Sunday/...
the Wednesday night through Thursday night time frame will be
characterized by a continued west-southwesterly to southwesterly low
level flow across our region as low pressure over Hudson Bay shifts
into northern Quebec and swings an attendant weak surface trough
toward and eventually into New York state...while sprawling high
pressure over the Southern Plains slides east to the Carolina
coastline. Under this pattern...temperatures aloft will slowly warm but
will still remain cold enough to support a lake response...with
these only recovering to the vicinity of -12c by Thursday night.

Under such conditions...the consequent lake response east-northeast
and northeast of the lakes will be greatly influenced by the degree
of synoptic-scale moisture well as the height of the
capping inversion. As has been the case the past couple of days...
these latter factors look to be considerably more favorable over and
downwind of Lake Ontario...where the large-scale environment now
looks favorable enough to warrant a lower-end likelihood of lake
effect snow/snow showers throughout...along with the potential for
at least some modest accumulations. Meanwhile over Lake Erie...more
limited moisture and a notably lower cap should keep any lake effect
snow showers much more scattered and lighter in nature...with just
some minor nuisance-type accumulations appearing possible at this
juncture. Outside of the lake effect areas...conditions should just
be cold and dry...with temperatures remaining a little below
seasonal averages.

On Friday...any lake effect activity downwind of the lakes should
weaken and eventually fall apart altogether as moisture diminishes
and the capping inversion crashes following the surface trough
passage...and as the low level flow becomes lighter and increasingly
sheared. Elsewhere...conditions should again remain dry.

As we head into next weekend...our focus will then turn back to the
synoptic scale as another developing cutter-type low pressure system
over Texas and the Gulf Coast states lifts northeastward and toward
our region. While the medium range guidance remains in general
agreement on this overall pattern...there is also much disagreement
on the forward speed of this system and exact track it will take...
with this likely arising from continued run-to-run and model-
to-model variations in the degree of phasing between the incipient
parent southern stream shortwave and the northern branch of the jet

Given the resultant forecast uncertainty...have elected to stick
closer to wpc guidance and our existing continuity for the latter
portions of the extended period...with a general warmup accompanied
by broadbrush chance probability of precipitation Friday night through Saturday night...
along with a broad transition from snow to rain and back again...
followed by a return to drier weather and more seasonable temperatures to
close out the period.


Aviation /03z Monday through Friday/...
high pressure and drier air will continue to spread into the region
with an improvement in ceilings back into the VFR range through tonight.
East of Lake Ontario just a chance of some weak lake effect snow
showers tonight as a weak surface trough crosses the lower Great
Lakes. Shallow moisture and weak lift may bring some pockets of
freezing drizzle tonight but confidence too low for tafs at this

Monday through Tuesday...VFR/MVFR ceilings.
Wednesday through Friday...possible IFR in west-Southwest Lake effect
-shra...MVFR/VFR elsewhere.


brisk westerly winds will continue this afternoon under a cold
air advection regime...maintaining Small Craft Advisory level
winds and waves. The gradient will slacken tonight with gradual
improvement on the lakes.

Arctic high pressure to our west will result in relatively light
northerly winds for the first part of the coming week before winds
back to the southwest again and strengthen again ahead of another
low dropping out of the Canadian Arctic. This will potentially bring
another round of small craft advisories by Wednesday.


Buf watches/warnings/advisories...
New York...none.
Marine...Small Craft Advisory until 4 PM EST Monday for loz043>045.
Small Craft Advisory until 7 am EST Monday for loz042.



near term...tma/wch
short term...jjr
long term...jjr

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