Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
314 AM EST Sun Feb 13 2022

Valid 12Z Sun Feb 13 2022 - 12Z Wed Feb 16 2022


...Great Lakes...
Days 1-3...
Longwave troughing persistent over the Great Lakes will continue
through much of the next 3 days. A few embedded shortwaves
pivoting through the flow will provide episodes of light snow and
LES, the first of which crosses the Lakes today/tonight. Here the
northerly flow supports the best chances of 4 inches or more off
Lake Michigan across southwest Michigan where 4 inch probabilities
near 40-50 percent along the coast. Lighter snows of a couple
inches are expected off Lake Superior while the flow isn't as
favorable for Erie or Ontario. Another shortwave trough passing
through day 2/3 will result in a more westerly flow that will
become very favorable for Lake Ontario (the iced over Erie will
limit heavy snow potential) such that localized 4"+ totals on day
3 will be possible during day 3.

...Mid-Atlantic/Northeast...
Day 1...
Shortwave trough moving through within the broader trough over the
eastern CONUS today will continue to lead to height falls across
the Mid-Atlantic and Northeast. Intensifying poleward arcing jet
streak will place the region within the favorable RRG diffluence
and this combination will deepen a surface low off the Carolina
coast that then tracks north/northeast to off Cape Cod late
tonight. Precipitation breaking out within the cold airmass on the
NW side of the low and associated frontal boundary will transition
from rain to snow early this morning and then lift north/northeast
through the I-95 corridor and reach southern New England late this
morning through tonight. The best forcing and lift within the DGZ
lies across portions of western VA into west-central MD early this
morning then later in the day 1 period across southern New England
where the proximity to the surface low and enhancement from ocean
effect could bring localized 4-6" totals for southeast MA and
portions of Cape Cod. The latest WPC probabilities for 4 inches
ore more reach near 60-70 percent for southeast MA with a near
30-40 percent chance of 6 inches or more. 

...Pacific Northwest through Northern Rockies...
Days 2-3...
Very compact and potent closed upper low will dive south/southeast
from the Pacific Northwest toward the Desert Southwest during the
forecast period. Widespread and robust height falls will push a
cold front through the region with a few waves of low pressure
along the boundary. The combination of modest ascent and moisture
and upslope enhancement will produce snowfall accumulations that
could reach 6-12" over the highest terrain of the WA/OR Cascades.
The latest WPC probabilities for 6 inches or more on day 2 are
highest above 5000 ft and reach 60-80 percent for the OR Cascades.
The threat for moderate to locally heavy snow then spreads
eastward into the central/northern Rockies. Again, the snowfall
will be confined to the higher elevations where isolated 4-6"+
totals will be possible.


For Days 1-3, the probability of significant icing is less than 10
percent.


Taylor