Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
347 AM EDT Wed May 10 2023

Valid 12Z Wed May 10 2023 - 12Z Sat May 13 2023

...North Central & Colorado Rockies...
Days 1-2...

A potent 500mb low tracking through the Lower Colorado River Basin
Wednesday morning will move east and into the Four Corners region
Wednesday evening, taking on a negative tilt as it does. Strong
upper level divergence out in front of the upper low and beneath
the left exit region of a 100 knot 250mb jet streak will coincide
with increasing 700mb moisture flux from the Colorado Rockies on
north to the north-central Rockies. The 500mb heights within the
upper low will be below the 10th climatological percentile and its
track places the Colorado Rockies on the northern flank of the
500mb low track Wednesday night into Thursday morning, which is
ideal placement for heavy snowfall. That being said, if the
calendar read "April 10" rather than "May 10" as it will Wednesday
morning, this would be a far more impactful winter storm. While
the upper low and strong synoptic scale forcing aloft is certainly
in place, there remains a noticeable lack of sufficiently cold air
required for a more widespread snow event for early-mid May. Snow
levels from the Colorado Rockies, on north to the Wind River,
Absaroka, and Bighorn Ranges of Wyoming, and as far north as the
Red Lodge area of Montana will be around 9,000ft. Latest Day 2 WPC
snow probabilities for >6" are up to 50-80% for elevations
>10,000ft over the CO Rockies and moderate for the WY Ranges. WPC
probabilities even show some of the highest elevations of the
central Colorado Rockies with 10-20% odds for >12" of snowfall.
Periods of snow will linger into Friday morning as the upper low
drifts northeast through the central Plains, but not quite as
heavy as Thursday morning. Snow should taper off by Friday evening
as the upper low heads for the Upper Midwest by the start of the
weekend.

The probability of ice accumulations greater than 0.25 inch is
less than 10 percent.

Mullinax