Solid AFD from BTV... noting a few spots may approach Ice Storm Warning criteria.
.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 655 PM EDT Friday...Based on crnt sfc obs and radar trends
have delayed arrival of steadier precip by 1 to 3 hours,
otherwise rest of fcst in good shape. Crntly still pretty dry in
the llvls with sfc dwpts in the single digits to mid teens,
while cloud hghts are btwn 7000 and 12000 feet agl. Initial
returns on radar have only resulted in a few flakes in the
Potsdam area per webcams. However, expect deeper moisture and
better lift over central NY to converge with additional moisture
angling east/southeast over the Great Lakes to quickly enhance
precip returns from west to east acrs our cwa btwn 9 PM and
midnight.
Guidance continues to support favorable parameters for
narrow band of enhanced heavier qpf btwn midnight and 9 AM Sat,
associated with strong 850mb fgen forcing with quasi stationary
west to east boundary draped acrs our fa. Also, pretty
impressive lightning display associated with elevated
instability and embedded s/w energy upstream over the
central/northern Great Lakes, which wl push into our cwa,
helping to enhance hourly precip rates on Saturday morning.
Have noted the HREF hrly ensemble mean snowfall rates of 0.50 to
0.75" btwn midnight and 10 AM acrs northern NY into
central/northern VT. This correlates well with GFS/NAM/RAP/HRRR
all showing a 4 to 8 hour window of 0.60 to 0.80 QPF mostly in
the form of snow mainly along and north of a Malone to BTV to
MPV line, while a messy mix of snow/sleet and freezing rain is
expected south. Generally 2 to 6 inches of snow anticipated by
sunrise north with a dusting to 2 inches south, along with ice
accumulation of 0.05 to 0.15".
By midday, better forcing and axis of enhanced qpf should drop
south over our central/southern cwa, where additional ice
accumulation is likely thru Sat night. Always a little
concerning for additional snowfall accumulation during the
daytime hours in the valleys if the strongest forcing/best lift
and associated heavy precip rates are not directly overhead and
the old 540DAM thickness line is hovering near the International
Border. This could result in sleet/mixed precip a bit further
north and at the same time we wl have to watch drier air
advecting into our northern zones, which can uncut the better
moisture, especially on Sat aftn.
Its extremely challenging to determine ice accumulation/impacts
with late March sun angle, marginal temps in the 28-33F range,
and heavy precip rates at times, which can limit ice accretion.
With that said, I feel given the impressive qpf expected acrs parts
of central/southern VT and Dacks (Eastern Rutland, Eastern
Addison, Orange, and Windsor Counties and Western Essex, NY),
a few areas could approach ice storm warning criteria by 15z
Sunday with localized ice amounts >0.50" especially above 800
feet. We wl continue to monitor and pass along potential to
midshift for potential upgrades if necessary.
