Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
326 AM EST Wed Feb 16 2022

Valid 12Z Wed Feb 16 2022 - 12Z Sat Feb 19 2022

...Rockies...
Day 1...

Potent closed upper low currently over southern California and
northern stream energy over British Columbia will phase together
later today into tonight over the Four Corners region giving way
to larger upper troughing over the southern to central Rockies.
The southern stream shortwave jet streak's left exit region is
well positioned over the central Rockies while in the northern
stream the developing jet over British Columbia favors strong
vertical ascent downwind over the central to northern Rockies. All
told, the combination of these features and modest upslope
enhancement due to the terrain and a trailing cold front will
favor locally heavy snowfall for the higher elevations today into
tonight. The latest WPC probabilities for 4 inches are high across
the taller ranges of north-central Idaho, southwest Montana,
through central Wyoming and much of the Colorado Rockies and even
as far south the Mogollon Rim and White Mountains of Arizona.
Localized amounts greater than 10 inches will be possible for the
highest peaks of the Colorado Rockies.


...South-Central Plains to Great Lakes...
Days 1-2...

The aforementioned southern stream shortwave energy ejects into
the southern Plains late tonight and opens up into a negatively
tilted trough over the Central Plains. Meanwhile, another
shortwave energy through southern Canada will help create
confluent flow over the Upper Midwest. Cyclogenesis across the
southern Plains takes place and this low quickly tracks to the
northeast, reaching the Northeast and New England by Friday
morning. Moisture ahead of this system is impressive with PW
anomalies nearing +2 sigma and the deepening low and tightening
baroclinicity will result in a narrow but intense area of
frontogenesis Thursday. This lift lies within the DGZ and this
should lead to some very intense snow rates within the deformation
band northwest of the low track where the latest HREF shows strong
signals for 2"+/hr rates. Combined with the tightening pressure
gradient, significant blowing snow will be possible. A quick
hitting but very intense snow setup across portions of Kansas
through Illinois, northwest, and southern Michigan.

Forecast spread this cycle has lessened and confidence continues
to increase for significant snow totals greater than 6 inches
along a swath from KS to MI including portions of the KC and
southern Chicago metros. The latest WPC probabilities for 6 inches
are above 60-70 percent with a slight to moderate signal for 8"
totals. Some isolated amounts over 12" will be possible, possibly
from eastern KS to northern MO where the best overlap between
duration and strong forcing exists.

To the south of the heavy snow, a stripe of freezing rain is
expected as a warm nose aloft overruns subfreezing temperatures at
the surface. The greatest signal for ice accumulations greater
than 0.10" lie across central MO toward central IL toward southern
Michigan.


...Upper Midwest to Great Lakes...
Days 2-3...

Shortwave energy quickly dropping southeast out of northwest
Canada reaches southern Manitoba by early Friday morning. This
quick moving clipper system then tracks through the Great Lakes
Friday into Friday night. Ample cold air pulled southeastward into
the region in the wake of the aforementioned storm system combined
with modest forcing for ascent within the left exit region of the
130+ kt jet should yield a few fluffy inches of snow. As the
shortwave passes, some lake effect snows are likely with the
highest amounts likely off Lake Superior and northern L.P. of
Michigan where the latest WPC probabilities for 4 inches are
slight to moderate.


Key Messages for the Feb 17-18 Winter Storm:

- A strong winter storm will impact the Central U.S. from Thursday
to early Friday, producing a variety of hazards including heavy
snow, sleet, and freezing rain.

- Heavy snow is most likely from northern Oklahoma, eastern
Kansas, and northern Missouri into north-central Illinois,
northwest Indiana, and southern Michigan. Snowfall rates are
likely to exceed 2 inches per hour at times.

- The combination of heavy snow and strong, gusty winds may lead
to severely reduced visibility and hazardous travel conditions on
Thursday and Thursday Night.

- A mixture of freezing rain, sleet, and snow is most likely just
to the south, from central Missouri and central Illinois into
northern Indiana and northern Ohio. Impacts to travel are also
possible in these areas.



Taylor