LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
300 pm update...
The major concern with this period continues to be the
transition over to snow Wednesday night as temperatures
quickly fall through the 30s behind the cold front.
Precipitation remains likely even after the front passes through
with a surface low deepening over New England, helping to
reinforce cold air advection over our region, and another
shortwave rippling through. Guidance continues to agree on a
potential for a few inches of snow especially southeast of Lake
ontario, where there will be some lake enhancement as snow
showers continue through Thursday. The previous discussion
330 am update...
By Wednesday evening temperatures will fall into the 30s. This
drop in surface temperatures will be accompanied by rapidly
falling temperatures aloft, which is should allow the rain
showers to mix with and change to snow showers during the
evening hours. The changeover will continue into ne PA during
the overnight hours, with the entire area cold enough for snow
by late Wed night/early Thur morning.
The challenge with the cold side of this storm system will be
attempting to determine how much precipitation develops post-
frontal as a surface low forms and deepens over New England.
At this time there is a signal on the latest ECMWF and CMC...and
has been there consistently through the past several
runs...showing an enhanced band of snow aligned with an area of
Q-vector convergence, strong PVA ahead of a sharp embedded short
wave, and an area of strong divergence aloft in the entrance
region of a 130 kt jet. There is also support from several EC
ensemble runs as well...which increases confidence in
accumulating snow across portions of the forecast area on
Thursday. Will need to keep a close eye on the evolution of this
system as it could have some significant impacts...mainly snow.
We are also watching the potential for a short period cold blast
Thursday night through Friday night with overnight lows
bottoming out in the teens and highs on Fri afternoon only into
the lower to mid 30s. The combination of gusty northwest winds
and cold temperatures will make it feel even cold...and a lot
more like January than April. The cold air pouring into the
region will be Canadian in origin and relatively dry, but still
be cold enough to interact with the warm lake waters and trigger
lake effect snow showers through this period. There is a
concern for additional accumulating lake effect snow southeast
of Lake Ontario through Friday night. The amounts may be limited
by the warm surface temperatures and potentially some sun
during the day. But, still cannot completely rule out
accumulations during the overnight hours.
Any lake effect snow showers should be ending Saturday morning
and conditions remaining dry through most of the day. However,
there is the potential for a weak wave to move in from the w/nw
later Saturday with another shot of very light rain with
temperatures climbing into the 40s and lower 50s by the