Shortwave trough moving into the western U.S. tonight will cross
into the Central Plains this weekend. Through 48 hours, the spread
seen in the deterministic guidance has lessened with overall above
average agreement at 500 mb. The NAM is a tad more amplified with
its trough axis as the wave takes on a negative tilt. At the
surface, there is still some latitudinal spread with the ECMWF and
ECENS members showing a northern/northwest favor compared to the
CMCE members further south/southeast. The GFS/GEFS members lie in
the middle and probably provide a good approach for beyond 48
hours. The 00Z UKMET is also a good proxy. So, with the NAM being
a bit amplified and the CMC too far south/southeast, will lean on
a non-CMC, non-NAM blend.
Day 3...
...Great Lakes/Northeast/Mid Atlantic...
Low pressure will slide east across the Upper Great Lakes on
Saturday. As the system moves into the St Lawrence Valley, models
show a coastal low beginning to develop near Downeast Maine Sunday
morning. This has the potential to produce a stripe of
significant snows across portions of northern New England.
Meanwhile, as the low passes to the north, strong westerly flow
will support lake effect snow showers east of Lake Ontario, with
heavy accumulations possible across the Tug Hill region. To the
south, snow changing to a wintry mix is expected to produce some
light snow and ice accumulations from the southern and central
Appalachians into the Mid Atlantic on Saturday.