Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
324 PM EDT Tue Oct 18 2022

Valid 00Z Wed Oct 19 2022 - 00Z Sat Oct 22 2022


Days 1-3...
...Great Lakes to the central Appalachians...
Cyclonic flow revolving around the upper low tracking through
southern Ontario tonight will send embedded shortwave disturbances
through the eastern Great Lakes. Persistent northerly flow over
Lake Superior will keep lake effect snow bands oriented over the
eastern U.P. of Michigan with several more inches of snow possible
as far east in the U.P. as Sault Ste. Marie. The latest WPC PWPF
features >4" probabilities of close to 10% in the eastern U.P. for
Day 1. Farther south and east, there will be lake enhanced bands
emanating off of Lake Erie within WSW flow at low levels. Similar
to the setup in northern Indiana yesterday (marginal boundary
layers, low SLRs), look for heavy/wet snow to fall at times within
the most intense bands. The 12Z HREF does show 40-60%
probabilities of >1"/hr snowfall rates from from far northeast
Ohio and northwest Pennsylvania into western New York between
~05-13Z. WPC PWPF shows up to ~30% probabilities for >2" of snow,
and while PWPF is not hinting at >4" probabilities currently, the
strongly mesoscale-driven environment and the heavy snowfall rates
depicted by most HREF members could lead to localized amounts up
to ~4". Farther south, upslope snow is on tap in the higher
elevations of the central Appalachians. Similar to their neighbors
up north, probabilities for >4" of snowfall are near zero, but
localized amounts up to 4" cannot be fully ruled out. More likely,
totals will reside closer to 1-2" in the higher elevations where
PWPF shows >2" probabilities of 20-30% in the higher terrain of
western Maryland and east-central West Virginia. By Day 3, all
lingering snow showers will have dissipated and milder
temperatures return to close out the work-week.

Lighter snow showers are anticipated downwind of Lakes Superior,
Erie, and Ontario for Day 2 with probabilities for snowfall >4"
falling below 10 percent. The next area of interest, by Day 3,
will be the Pacific Northwest as a robust Pacific storm system
arrives and bring the next round of wintry weather to the higher
elevations of the Intermountain West this upcoming weekend.

The probability of significant icing is less than 10 percent.

Mullinax