Wednesday into Thursday maybe? Afternoon discussion from LWX
LONG TERM /MONDAY THROUGH FRIDAY/...
The extended forecast will be defined by a large upper trough
centered over eastern Canada with axis extending into the southern
US. A series of potent shortwaves are expected to pivot around the
trough. The finer details of these features have been variable run-
to-run, but as of now one shortwave is expected Monday into Tuesday
and then a stronger shortwave Wednesday into Thursday.
The deep trough over the eastern CONUS will put the region squarely
in a frigid cold air mass, with high temperatures topping out in the
low 40s for most of the area through Wednesday, 20s to 30s in the
mountains. Wind chills could knock an additional 10-20 degrees off
that. With forcing and cold temperatures present, the main
uncertainty lies then with available moisture. The deep cold air
mass is also expected to be starved of moisture, with less than
1.00in PWATs throughout the extended. The most likely scenario for
next week is a burst of upslope mountain snow with each shortwave.
However, probabilities of snow east of the mountains have trended
higher for the Wednesday/Thursday wave. Recent runs have
strengthened this second disturbance, and moisture has trended
higher as well, with ensembles showing a range of 0.30-0.50 PWATs.
Snow probs for measurable snow east of the mountains, including the
I-95 corridor/DC metro, are now around 40-50% for 12z Wed to 12z
Thu.
If this materializes, not much accumulation is expected given
the lack of moisture, but even so the main concern will be timing.
Given the extended period of bitter cold, surface temperatures could
be near or just below freezing. Currently the better timing for
precip is Wednesday afternoon when temperatures are warmer, but a
slower system could mean wintry precip coinciding with colder temps
and Wednesday`s morning commute. Even light accumulation in these
conditions could present significant traveling hazards. As such, we
will continue to monitor closely for this potential.
For beyond Wednesday, a strong upper low is progged to swing into
southeast Canada/the Northeast near the end of the week. While
expected to dunk the NE CONUS into another bitter cold air mass, the
air mass is also likely to be very dry. Some upslope snow could
continue Thursday into Friday, but the better forcing also appears
to stay to our north.
