part of Ricky writeup
A look at the 12z GEFS and ECMWF (EPS) ensemble mean and members
certainly stands out for increasing confidence in a significant
winter event for part of if not much of the CWA despite the rather
extended lead time. 4-day (10:1) snowfall means up in 5-9" range,
along with 30-40% probabilities of 6"+ totals and 60-90% probabilities
of 3"+ totals highlights the high % of members with significant
snow swaths. Can`t rule out the outlier members with everything
shunted a bit south, though with that said, felt comfortable even
slightly adjusting PoPs upward a bit from NBM initialization due
to likely to categorical probabilities of measurable precip.
Regarding the wintry mix threat, should a more amplified wave
shunt elevated baroclinic zone back north a bit (such as on 12z
operational GFS and several ensemble members), this would
increase risk of a zone of freezing rain and sleet given northerly
cold air drain. Added in slight chance wintry mix mention for
areas south of US-24 Wednesday through Wednesday evening.
Timing wise, looking at a late Tuesday night/Wednesday morning
start, though there`s certainly wiggle room on this element 5 days
out. Accumulating snow could potentially continue into or through
Thursday per some of the slower solutions, ending as a window of
favorable lake effect parameters Thursday night into Friday. If we
do add to the already extensive snow pack, both Thursday night and
Friday night could be exceptionally cold as the high pressure
transits our area.
Castro