Tonight will become bitterly cold with lingering lake effect
snow showers. 850mb temperatures will fall to around -20C, but
moisture will be very limited. As a result, QPF consensus of model
guidance is limited, with the greatest amounts south of Lake Ontario
where there is the longest fetch and potentially brief a Georgian
Bay connection. Additional snowfall amounts should mainly be light,
but considering the fluff factor localized accumulations of a few
inches cannot be ruled out even though many areas will remain snow-
free. Cooling will mainly be through advection with lingering lake
effect clouds, but even so temperatures will fall into the single
digits to mid-teens. A late clearing should allow for even lower
temperatures east of Lake Ontario where some below zero readings are
possible.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
The long awaited warm-up will arrive this weekend with several days
of near or a little above normal temperatures as the pattern across
North America temporarily re-aligns, with a trough focusing on the
Northern Plains and forcing downstream height rises across the east.
A deep shortwave will cross the region Saturday and Saturday night
on the leading edge of the warm-up, producing periods of showers.
Warm advection ramps up well ahead of the precip, so this should be
all rain by the time it arrives later Saturday morning.
The rain will taper off from west to east later Saturday night and
Sunday morning as the system moves into New England. Weak high
pressure will then bring a mainly dry Sunday. High temperatures will
be in the 40s both Saturday and Sunday, with overnight lows Saturday
night staying above freezing.
Another potent Pacific shortwave will emerge onto the Central Plains
by early Sunday morning, with the resulting system moving into the
Ohio valley and eastern Great Lakes by Monday. This will bring
increasing rain chances to our region later Sunday night and Monday.
Temperatures will continue to be warm enough through Monday to
support all rain at the surface. This system is forecast by the GFS
and ECMWF, and most of their ensembles, to evolve into a closed low
over the Northeast States By Tuesday and Wednesday of next week.
This will keep unsettled weather across our region, with colder air
filtering back into the Great Lakes and forcing rain to mix with and
change to wet snow by later Monday night and Tuesday.