CTP:
Biggest challenge with the forecast today is the digging trough
pressing down from the Upper Great Lakes Thursday night and Friday.
The forecast is very consistent from run to run, and gives high
confidence in a widespread (plowable) snowfall for the entire area.
Did bump PoPs to 100s and SF numbers up just a little based on an
upward trend in the SLRs and ensemble member trends. Even though it
will be falling during the daylight hrs, it is a cold airmass and
dewpoints start out pretty low. The SLRs should be higher than climo
(12-14:1) and may be closer to 20:1 in the NW third of the area.
We`re about 70% confident in the eventual need for an advy for
almost all, if not all, of the CWA for late Thursday night and
Friday. The place with the potential for the highest snowfall totals
is going to be the Laurels, especially when lumping the snow which
will occur after the main slug of forcing and broadest area of snow
passes and upslope snow kicks in Fri night. Therefore, we`ve posted
a winter storm watch for the Laurels for that time frame.
However, we`d like to avoid some confusion and allow confidence to
get to 80% before posting an advisory for the bulk of the area for
Friday. The confusion may come for those who are going to get some
snow later tonight (Wed PM) into Thurs. The certainty in SF numbers
is lowest in the Ridge and Valley region (between UNV-MDT-IPT).
Another shift or so with similar numbers should help boost
confidence.
With plenty of clouds around Thurs night and Fri, we`ll likely see a
decreased diurnal swing. Mins in the 15-25F range are good, and
everyone should hold in the 20s on Friday. One or two spots in the
SErn valleys could get over 30F
