Heading into Friday night, 850mb temperatures will drop into the mid
negative teens which will fully support lake induced instability
with lake equilibrium levels over 7kft. Meanwhile, ample moisture
will be added to the area through the passage of a mid-level
shortwave trough. This combination and fact that all the lake
convective layer is in the DGZ, will support a period of heavy lake
effect snows northeast of both Lake Erie and Lake Ontario Friday
night through Saturday evening. In addition to the snow, a well
mixed blyr is present as cold air advection occurs. Net result,
strong and gusty winds. Forecast soundings indicate at least
sustained 20-25 mph with gusts at least over 30 mph. In the heart of
the strongest lake convection, think these numbers end up to 30 mph
with gusts to 40 mph. That spells trouble as temps will be dropping
into the lower 20s or even upper teens and thus blowing and drifting
snow will be MUCH more of an issue than we saw with the last Metro
Buffalo lake snow event the day after Christmas. The strong winds
may hold down total snow amounts (higher winds crush the dendrites
and lower the SLRs other than what would be given the thermal
profile shown), but for now have starting point of over a foot in
many areas within the lake plumes off Lake Erie and Lake Ontario.
Bullseye at least right now would be Buffalo Metro off Lake Erie and
Watertown/Fort Drum off Lake Ontario. Winter storm watches have been
issued for this potential high impact event in terms of snow and
wind.
Lake snows will diminish on Saturday night as first leading stronger
shortwave exits east. General synoptic snow will begin to spread
into western NY after midnight, but winds will shift enough to
prohibit lake enhancement as the wave arrives.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
The core of arctic air will drop across western portions of the
Ontario province on Sunday. As its associated trough axis dives
across the Great Lakes, a surface low will pass to our south, with
some model disagreement on its track and strength. This could bring
a light general snow on Sunday, but in its wake it definitely will
be colder heading into next week. GFS/GGEM both drop 850mb
temperatures to around -25C, with the `warmer` ECMWF down to around
-19 C. This will support highs in the teens for Monday and Tuesday,
and even that may be optimistic in some areas if the colder guidance
verifies. Bitterly cold wind chills can also be expected.
In addition to the cold, this will establish a pattern favorable for
lake effect snow. Wind direction and moisture will be key, and it
remains too far out to pin down the details. In general, a
prevailing WSW flow will place the traditional snow belts east of
the lakes at the greatest risk. Does seem at least initially early
next week, better focus for the lake effect may be just south of
where the weekend event is expected to occur. However, bands will
meander, with the potential to impact the cities of Buffalo and
Watertown at times. Overall, this WSW flow will diminish the risk
for heavy snow for counties immediately south of Lake Ontario,
including the Rochester area. Though if winds are strong enough at
least advisory level snows could reach into western portions of
Monroe county.