Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 PM EDT Sun Oct 29 2023

Valid 00Z Mon Oct 30 2023 - 00Z Thu Nov 02 2023

...Southwest to central Texas...
Day 1...
Some additional light precipitation is expected as a broad upper
trough continues to move across the region.  Shallow cold air
behind a cold front that is now moving into portions of southern
Texas will support mixed precipitation this evening into tomorrow,
with some minor ice  accumulations possible across portions of
southwestern into central Texas, with WPC guidance showing some
pockets of higher probabilities for accumulating ice (0.01 inch or
greater) across this region.

...Northern New England...
Day 2...
A shortwave moving through the base of a long wave trough centered
over the central U.S. is forecast to move across the Midwest,
supporting the development of a surface wave over the Mid Atlantic
later today that will then track along the Northeast coast on
Monday.  Thermal profiles continue to indicate mostly rain across
the Northeast, with little threat for significant snow
accumulations except across northern Maine.  WPC guidance
continues to show high probabilities (70 percent or greater) for
snow accumulations of 4 inches across the higher elevations of
northern Maine, where precipitation is expected to start as snow
tonight and remain mostly to all snow before diminishing late
tomorrow. 

...Upper Great Lakes...
Days 1-2...
West-northwesterly flow and colder air aloft associated with the
passage of the previously noted shortwave are expected to support
an increase in lake effect activity across the U.P. of Michigan
beginning later today and continuing into tomorrow, with some
potential for locally heavy accumulations, especially for areas
near the Keweenaw Peninsula.  WPC guidance continues to show high
probabilities (70 percent or greater) for accumulations of 4
inches or more centered across this region for the Sunday night
into Monday period.

A more amplified shortwave is forecast to dive through central
Canada and move across the northern Plains, upper Midwest and the
upper Great Lakes Monday night and Tuesday.  This very dynamic
system is expected to produce a stripe of at least light snow from
central Minnesota to southwestern Michigan, with WPC probabilities
indicating probabilities around 30-40 percent for accumulations of
2 inches or more along this axis.  Steepening lapse rates will
reinvigorate the threat for lake effect activity, with flow
favoring the western U.P. Monday night into early Tuesday before
shifting the focus farther east during the day.  Areas near and
east of the Keweenaw are most likely to see the heaviest
accumulations.

Pereira