An interesting lake effect event will be unfolding tonight through
Wednesday night. Confidence in timing and location is fairly high,
but amounts and intensity is not quite as high.
Weak lake effect processes are now underway generally as expected
downwind of Lake Erie with low-topped convection capped at ~7000`
with very dry air above that level. This is resulting in light
accumulations toward the Chautauqua Ridge this afternoon.
Temperatures at cap level will continue to slowly drop through the
night but with little or no increase in available moisture as seen
by numerous but lackluster upstream horizontal convective rolls over
MI.
East of Lake Erie...
Early this evening, westerly flow along the Chautauqua Ridge
and sufficient lapse rates supportive of lake effect processes
will result in a period of lake effect snow through the evening
hours. An advisory is in effect for traditional westerly flow
regions (portions of Chautauqua and Cattaraugus counties), but snow
rates overnight may be somewhat unimpressive due to the initial lack
of available moisture and still cooling airmass, followed by backing
winds overnight that will begin to disrupt any nocturnal
consolidation. Do not expect much more than an inch or two in these
areas.
The more interesting event will occur near sunrise as the band heads
north (during the commute) across the Southtowns, and then into
Metro Buffalo during the morning. Some strengthening of the mostly
singular band is expected during this time with full lake fetch. The
band should reach its northern extent by midday, probably just
clipping SE Niagara County and part of Orleans County before heading
back to the south as the main upper level trough finally moves in.
There remains uncertainty on the strength and duration of the band
while it lingers over/north of Metro Buffalo and into the
Northtowns. But, once it starts to move, it should quickly head
south, with the entire lake band swinging south (and/or being pushed
into the shoreline), blowing past the Southtowns, and back into the
Southern Tier. The band may be briefly strong during the
midday/full fetch time period with aided lift from the upper level
trough. The band should then begin to weaken later Wednesday evening
after losing adequate fetch while the airmass aloft continues to dry
out.
The lower confidence in amounts is compounded by the possibility of
blowing snow. This should may help keep snow amounts down some, but
it will also result in a relatively impactful day in terms of
travel. While not a banner event by any means, this event should
still be troublesome for some. As such, a fairly strongly worded
advisory remains in place.
Most areas should end up with a an inch or two as the band moves
north, followed by another inch or two as the band moves south.
Highest amounts should be over Northern Erie County where the band
lingers the longest. It`s possible some areas could exceed 7" if
the band lingers before heading south, but the emphasis for this
event should be focused more in impact from blowing snow rather than
amounts.
East of Lake Ontario...
A lake banding will probably have a hard time getting established
until late tonight ESE of Lake Ontario due to the above noted
limited moisture availability. Some consolidation is expected
during Wednesday as flow backs, with a better defined lake band
forming by afternoon with Lake Erie serving as its upstream
connection. Once this is established, a lake band should be roughly
over the St Lawrence Valley. But with continued limited moisture
and less than ideal fetch, snow rates and corresponding snow amounts
should be low, at least until the band starts moving back south
toward the more traditional/long fetch east of Lake Ontario in the
afternoon. An upstream multi-lake connection should then be
established ESE of Lake Ontario by Wednesday evening together with
the coldest air aloft. This may result in the best opportunity for
snow rates of 1-2"/hr, but only for a relatively short duration
Wednesday evening. Increasingly dry air aloft should weaken lake
bands overnight.
Similar to downwind of Erie, areas east of Lake Ontario will be
under an Advisory with blowing snow possibly leading to as much of
an impact as snow amounts. In general, expect snow amounts to be
fairly tame over this traditionally hard-hit region, with most
locations staying under 7". Highest amounts should be over the Tug
Hill and toward Oswego County (mainly late Wed-->Wed eve), with
less, possibly much less elsewhere